Single pull macgregor type hatch cover.pdf - Cochin University of ...
Single pull macgregor type hatch cover.pdf - Cochin University of ...
Single pull macgregor type hatch cover.pdf - Cochin University of ...
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SINGLE PULL MACGREGOR TYPE HATCH<br />
COVER<br />
A PROJECT REPORT<br />
Submitted by<br />
MANU SHARMA<br />
MUHAMMED ASIM M T<br />
NASIR ALI<br />
NIRAJ KUMAR<br />
NITHIN GOPAL<br />
NITHIN XAVIER<br />
In partial fulfilment for the award <strong>of</strong> the degree<br />
<strong>of</strong><br />
BACHELOR OF TECHNOLOGY<br />
IN<br />
MARINE ENGINEERING<br />
K M SCHOOL OF MARINE ENGINEERING<br />
COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY<br />
COCHIN-682022<br />
JULY 2011<br />
i
CERTIFICATE<br />
This is to certify that the seminar project entitled “SINGLE PULL<br />
MACGREGOR TYPE HATCH COVER” submitted by MANU SHARMA,<br />
NASIR ALI, MUHAMMED ASIM M T, NIRAJ KUMAR, NITHIN<br />
GOPAL S A, NITHIN XAVIER to the department <strong>of</strong> Kunjali Marakkar School<br />
<strong>of</strong> Marine Engineering towards the partial fulfilment <strong>of</strong> the requirements for the<br />
VIII semester <strong>of</strong> the B.Tech Degree course in Marine Engineering <strong>of</strong> <strong>Cochin</strong><br />
<strong>University</strong> <strong>of</strong> Science and Technology, is a bonafide record <strong>of</strong> work carried out<br />
by him.<br />
Head <strong>of</strong> the Department Project guide<br />
K M School <strong>of</strong> Marine Engineering Pr<strong>of</strong>. Dr. Sasikumar P.V.<br />
<strong>Cochin</strong> <strong>University</strong> <strong>of</strong> Science and Technology<br />
ii
ACKNOWLEDGEMENT<br />
First <strong>of</strong> all we helmed in all humbleness and gracefulness to acknowledge our depth<br />
regards to all who helped team to put this topic, well above the level <strong>of</strong> simplicity<br />
and into something concrete.<br />
We express our deep sense <strong>of</strong> gratitude to Director Pr<strong>of</strong> K.A Simon for providing<br />
necessary facilities.<br />
We are very thankful to our project guide Pr<strong>of</strong>. Dr.Sasikumar P.V who was always<br />
there to show us the right track when team needed the help and guided us in<br />
different matters regarding to project. He gave us moral support and guide in<br />
different matters regarding to project report and presentation and is very kind and<br />
patient while suggesting us the outline and structure <strong>of</strong> project report. .<br />
We are equally thankful to our project coordinator Pr<strong>of</strong>. N.G. Nair for his valuable<br />
help.<br />
We record our sincere thanks to course coordinator Pr<strong>of</strong>. Roy.V.Paul for his<br />
valuable suggestion<br />
Last but not least, we would like to thank our parents and friends and all others who<br />
helped us a lot in gathering different information, collecting data and guided us<br />
from time to time in making the project despite <strong>of</strong> their busy schedule.<br />
iii
ABSTRACT<br />
Hatch <strong>cover</strong>s are used to <strong>cover</strong> and protect the cargo in the cargo spaces. Hatch<br />
<strong>cover</strong>s close <strong>of</strong>f the <strong>hatch</strong> opening and makes it water tight. In the days <strong>of</strong> wooden<br />
ships, the <strong>hatch</strong> <strong>cover</strong>s were made <strong>of</strong> wooden planks, beams and boards and were<br />
<strong>cover</strong>ed with tarpaulins. Wooden <strong>hatch</strong> <strong>cover</strong>s had many drawbacks. Mainly, they<br />
used to get spoilt due to continuous exposure to the moisture laden sea winds. Rain<br />
and sea water also used to produce detrimental effects on the wooden <strong>hatch</strong> <strong>cover</strong>s.<br />
But with the advent <strong>of</strong> steel, the wooden <strong>hatch</strong> <strong>cover</strong>s started disappearing.<br />
Nowadays, mostly steel <strong>hatch</strong> <strong>cover</strong>s are used. The most common <strong>type</strong> <strong>of</strong> <strong>hatch</strong><br />
<strong>cover</strong> used today consists <strong>of</strong> a number <strong>of</strong> steel <strong>cover</strong>s linked together. The design <strong>of</strong><br />
a <strong>hatch</strong> <strong>cover</strong> changes according to the size and design <strong>of</strong> the ship, but most <strong>of</strong> the<br />
designs are made to make the opening and closing <strong>of</strong> the <strong>cover</strong>s as quick as possible<br />
in order to facilitate faster cargo handling process.<br />
One such <strong>type</strong> <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> is a MacGregor, single <strong>pull</strong> <strong>hatch</strong> <strong>cover</strong>. In<br />
this <strong>type</strong>, the <strong>hatch</strong> <strong>cover</strong> moves on rollers attached to tracks fixed on the <strong>hatch</strong><br />
coaming. The <strong>hatch</strong> <strong>cover</strong> is not one steel structure but a series <strong>of</strong> steel <strong>cover</strong>s<br />
linked together by chains. When the <strong>cover</strong> is opened, the individual steel <strong>cover</strong>s<br />
ride up and tip onto a stowage tank at the <strong>hatch</strong> end. Most <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong>s<br />
found on board ships are controlled hydraulically by a hydraulic power unit<br />
operated from a control box fixed near the <strong>hatch</strong> <strong>cover</strong>. .<br />
iv
TABLE OF CONTENTS<br />
v<br />
Page no.<br />
CERTIFICATE ii<br />
ACKNOWLEDGEMENT iii<br />
ABSTRACT iv<br />
TABLE OF CONTENTS v<br />
LIST OF FIGURES ix<br />
LIST OF TABLES xii<br />
CHAPTER 1 - INTRODUCTION 1<br />
1.1 Hatch Cover and Their Function. 2<br />
1.2 Early Hatch Cover. 3<br />
1.3 Failing <strong>of</strong> Wooden Hatches. 5<br />
1.3.1 Safety and Security 5<br />
1.3.2 Maintenance 6<br />
1.3.3 Cargo Working 6<br />
1.4 Steel Hatches After 1927 6<br />
CHAPTER 2 - TYPES OF STEEL HATCH COVERS 9<br />
2.1 <strong>Single</strong> Pull. 11<br />
2.2 Side Rolling. 12<br />
2.3 Folding and Multi Type 13<br />
2.4 Lift Away 14<br />
2.5 Piggy Back. 15<br />
2.6 Stacking Covers 16<br />
2.7 Reefers Hatch Covers. 17<br />
2.8 Spring Loaded Covers. 18<br />
CHAPTER 3 - GENERAL REQUIREMENT 19<br />
3.1 Regulatory Requirements. 19<br />
3.1.1 Rule Governing Access Equipment 19<br />
3.1.2 International Load Line Convention, 1966. 19<br />
3.1.3 Freeboard. 20<br />
3.1.4 Freeboard Deck. 21<br />
3.1.5 Weather-Tightness and Water-Tightness. 22
3.1.6 Statutory Regulations. 23<br />
3.2 General Considerations for Access Equipment. 23<br />
3.2.1 Coaming Height 23<br />
3.2.2 Cover Stowage 25<br />
3.2.3 Deck Opening 25<br />
3.2.4 Drainage 26<br />
3.3 Specific Design Requirements for Hatch Covers. 27<br />
3.3.1 Hatch Covers 27<br />
3.3.1.1 Structural Regulations. 27<br />
3.3.1.2 Cleats. 29<br />
3.3.1.3 Loads. 30<br />
3.3.1.4 Scantling. 30<br />
3.3.1.5 Deformation. 31<br />
3.3.2 Seals 34<br />
3.3.2.1 Gaskets Material 35<br />
3.3.2.2 Compression Bar. 35<br />
3.4 Construction Materials. 35<br />
3.4.1 Higher Tensile Steel (HTS) 36<br />
3.4.2 Aluminium 36<br />
3.4.3 Glass Reinforced Plastic (GRP) 37<br />
3.4.4 Wood 37<br />
CHAPTER 4 - OPERATIONAL AND SAFETY ASPECTS 38<br />
4.1 Basic Advice 38<br />
4.2 Monitoring and Inspection 40<br />
4.3 Heavy Weather Precaution 42<br />
4.4 Safety when Working with Hatch Covers 43<br />
4.5 Procedure to Open and Close Hatch Covers 48<br />
4.6 Maintenance and Repair 50<br />
CHAPTER 5 - SINGLE PULL MACGREGOR TYPE HATCH COVER<br />
DESIGN 54<br />
5.1 Parts Design 56<br />
5.1.1 Hold Design. 56<br />
5.1.2 Hatch Opening Dimensions. 56<br />
5.1.3 Hatch Coaming Design. 57<br />
vi
5.1.4 Hatch Covers Design. 58<br />
5.1.5 Track 1 Design. 59<br />
5.1.6 Rising Track Design (Track 2). 60<br />
5.1.7 Jack Design. 60<br />
5.1.8 Crane Space Design 61<br />
5.1.9 Motor Casing 61<br />
5.1.10 Motor Specifications 62<br />
5.1.11 Pulley Design 62<br />
5.1.12 Rope 63<br />
5.1.13 Reduction Gear Design 63<br />
5.1.14 Ladder Design 63<br />
5.1.15 Bulwark Design 64<br />
5.2 Material Selection 65<br />
CHAPTER 6 - FABRICATION 67<br />
6.1 Fabrication <strong>of</strong> Cargo Hold 67<br />
6.2 Fabrication <strong>of</strong> Hatch Way 68<br />
6.3 Hatch Coaming Fabrication 69<br />
6.4 Hatch Stay Fabrication 70<br />
6.5 Fabrication <strong>of</strong> Side & End Dog 70<br />
6.6 Fabrication <strong>of</strong> Hatch Cover. 71<br />
6.7 Sliding Track Fabrication. 73<br />
6.8 Fabrication <strong>of</strong> Rising Track. 75<br />
6.9 Fabrication <strong>of</strong> Crane Space 76<br />
6.10 Motor Reduction Gear Pulley Fabrication 77<br />
6.11 Fabrication <strong>of</strong> Bulwark 77<br />
6.12 Fabrication <strong>of</strong> Ladder 78<br />
CHAPTER 7 - ASSEMBLY OF FABRICATED PARTS 79<br />
7.1 Assembly Between Cargo Hold and Hatch Coaming 80<br />
7.2 Assembly <strong>of</strong> Hatch Stay on Coaming 80<br />
7.3 Assembly <strong>of</strong> Side Dogs and End Dogs on Coaming 81<br />
7.4 Assembly <strong>of</strong> Sliding Tracks 82<br />
7.5 Assembly <strong>of</strong> Rising Track 82<br />
7.6 Assembly <strong>of</strong> Hatch Cover 83<br />
7.7 Assembly <strong>of</strong> Crane Space into Cargo Hold. 84<br />
vii
7.8 Assembly <strong>of</strong> Motor Pulley Gear Arrangement into Cargo Hold 84<br />
7.9 Assembly <strong>of</strong> Bulwark 84<br />
7.10 Assembly <strong>of</strong> Ladder 85<br />
7.11 Assembly <strong>of</strong> Locking Arrangement 86<br />
7.12 Assembly <strong>of</strong> Wire Rope 86<br />
CHAPTER 8 - TESTS AND TRIALS 88<br />
8.1 Water Hose Leak Detection Test 88<br />
8.2 Ultrasonic Leak Detection Test 88<br />
8.3 Putty or Moulding Clay Test 89<br />
8.4 Chalk Test 89<br />
8.5 Tolerance Test for Hatch Covers 89<br />
8.6 Results 90<br />
CHAPTER 9 - CONCLUSION 91<br />
REFERENCES 92<br />
viii
LIST OF FIGURES<br />
Figure no: Title Page no:<br />
Figure 1.1 Simplified arrangement <strong>of</strong> a traditional <strong>hatch</strong> 4<br />
Figure 1.2 Arrangement <strong>of</strong> an early Mege folding steel <strong>hatch</strong> <strong>cover</strong> 8<br />
Figure 2.1 <strong>Single</strong> Pull Hatch Cover 11<br />
Figure 2.2 Side Rolling 12<br />
Figure 2.3 Folding and Multi –<strong>type</strong> 13<br />
Figure 2.4 Lift Away 14<br />
Figure 2.5 Piggy Back 15<br />
Figure 2.6 Stacking Covers 16<br />
Figure 2.7 Reefers Hatch Cover 17<br />
Figure 2.8 Spring Loaded Cover 18<br />
Figure 3.1 Deck Opening with Coaming 26<br />
Figure 3.2 Beam is treated as a Uniformly Loaded simply<br />
Supported Structure 27<br />
Figure 3.3 Detailed Analysis <strong>of</strong> the Structure <strong>of</strong> a 20,000 tdw<br />
bulk carrier 32<br />
Figure 3.4 Hydrostatic Pressure 33<br />
Figure 3.5 Torsional Distortion <strong>of</strong> Hatch Ways 34<br />
Figure 4.1 Hatch Panel 40<br />
Figure 4.2 Vessels in Rough Weather 43<br />
Figure 4.3 Check the Lock-Back Mechanism 44<br />
Figure 4.4 Do Not Use Damaged or Unsecured ladders 44<br />
Figure 4.5 Never Smoke in a Hold 45<br />
Figure 4.6 Never Climbs On Top Of Bulk Cargo Without A Lifeline. 45<br />
Figure 4.7 Never Carry Tools or Equipments While Descending or 46<br />
Ascending a Ladder<br />
Figure 4.8 Never stand on the coaming top when the <strong>hatch</strong> <strong>cover</strong>s are open 46<br />
Figure 4.9 Always wear protective headgear when working. 47<br />
Figure 4.10 Inspect wire 47<br />
Figure 4.11 Always takes precautions when fumigating. 48<br />
ix
Figure 5.1 <strong>Single</strong> Pull MacGregor Type Hatch Cover 54<br />
Figure 5.2 Hold Design 56<br />
Figure 5.3 Hatch Opening Dimensions 57<br />
Figure 5.4 Hatch Coaming Design 57<br />
Figure 5.5 Hatch Cover Design 58<br />
Figure 5.6 Track Design 59<br />
Figure 5.7 Rising Track Design 60<br />
Figure 5.8 Jack Design 60<br />
Figure 5.9 Crane Space Design 61<br />
Figure 5.10 Ladder Design 64<br />
Figure 5.11 Bulwark Design 64<br />
Figure 6.1 Cargo hold 67<br />
Figure 6.2 Hatch way 68<br />
Figure 6.3 Hatch Coaming 69<br />
Figure 6.4 Hatch Stay 70<br />
Figure 6.5 Side and End Dog 71<br />
Figure 6.6 Pantoons 72<br />
Figure 6.7 Pantoons and wheels 73<br />
Figure 6.8 Metallic Wheels on A Pantoon 73<br />
Figure 6.9 Sliding Track 74<br />
Figure 6.10 Hydraulic Jack and Sliding Track 74<br />
Figure 6.11 Rising Track 75<br />
Figure 6.12 Crane Space 77<br />
Figure 6.13 Bulwark 78<br />
Figure 6.14 Ladder 78<br />
Figure7.1 Assembly <strong>of</strong> fabricated parts 79<br />
Figure7.2 Cargo hold and Hatch coaming 80<br />
Figure7.3 Hatch stay on coaming 81<br />
Figure7.4 Side dogs and end dogs on coaming 81<br />
Figure7.5 Sliding track 82<br />
Figure7.6 Rising track 82<br />
Figure 7.7 Hatch <strong>cover</strong>s 83<br />
Figure7.8 Hatch <strong>cover</strong>s 83<br />
Figure7.9 Cargo spaces into cargo hold 84<br />
x
Figure7.10 Bulwark 84<br />
Figure7.11 Bulwark 85<br />
Figure7.12 Ladder 85<br />
Figure7.13 Locking arrangement 86<br />
Figure7.14 Wire rope 86<br />
xi
LIST OF TABLES<br />
Table no: Title Page no:<br />
Table 2.1 Operating mode <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> <strong>type</strong>s 9<br />
Table 2.2 summarizes the most important characteristics <strong>of</strong> 10<br />
each major <strong>type</strong><br />
Table 3.1 Freeboard for different ships length 20<br />
Table 3.2 Increase in freeboard 21<br />
Table 3.3 Summary <strong>of</strong> 1966 Load Line Convention <strong>hatch</strong> 28<br />
Cover regulation<br />
Table 3.4 Access equipment strength calculations 31<br />
xii
CHAPTER 1 - INTRODUCTION<br />
The classic modern <strong>hatch</strong> <strong>cover</strong> is the ‘single <strong>pull</strong>’ which remains the most<br />
common <strong>of</strong> the all the various forms now in service and may rightly be described<br />
as the natural successor to traditional beams and boards. This <strong>cover</strong> derives its<br />
name from its immediate predecessor, the ‘multi-<strong>pull</strong>’ <strong>cover</strong>, which consisted <strong>of</strong> a<br />
series <strong>of</strong> individual panels similar to those <strong>of</strong> the single <strong>pull</strong>, but unconnected.<br />
Each panel had to be rigged before being <strong>pull</strong>ed one at a time into stowage.<br />
The complete <strong>cover</strong> consists <strong>of</strong> a number <strong>of</strong> narrow panels which span the<br />
<strong>hatch</strong>way and are linked together by chains. In the closed position, the panel sides<br />
sit firmly which takes the weight <strong>of</strong> the <strong>cover</strong>. Rubber gasket was attached to the<br />
side and end dogs over which weight <strong>of</strong> panel comes forming a watertight seal.<br />
Extending from the side coamings at the end <strong>of</strong> the <strong>hatch</strong>way where the <strong>cover</strong>s<br />
are stowed are steel rails which the individual <strong>hatch</strong> panels to be transferred to<br />
their stowage location when the <strong>hatch</strong> is opened.<br />
To open a <strong>hatch</strong> hold <strong>cover</strong>, the securing cleats are first freed and each<br />
panel is raised onto its wheel by portable jacks. Entire <strong>cover</strong> is free to move in a<br />
fore and aft direction with its wheel rolling between guides on the top <strong>of</strong> the<br />
coaming. It is set in motion by means <strong>of</strong> a wire (sometimes called a bull wire) led<br />
from a motor wheel and attached to the centre <strong>of</strong> the furthest edge <strong>of</strong> the leading<br />
panel i.e. the panel which goes into stowage first and comes out <strong>of</strong> stowage last.<br />
As the wire is tightened, the panels are each pushed beyond the end coaming. On<br />
reaching the end <strong>of</strong> the <strong>hatch</strong>way; the weight <strong>of</strong> each panel is transferred from its<br />
wheels to balancing rollers situated near its mid length which engage with the rail<br />
extensions <strong>of</strong> the side coaming. The centre <strong>of</strong> gravity <strong>of</strong> each panel is slightly<br />
towards the stowage end <strong>of</strong> the panel from the rollers so that once the panel is<br />
supported from them, it tips into vertical position. It is then pushed further<br />
towards the end <strong>of</strong> the stowage space by the next panel to arrive at the <strong>hatch</strong>way<br />
end. When the <strong>hatch</strong> is completely open, each panel stands vertically in the<br />
stowage space, and all are kept in place with retaining chains.<br />
To close a single <strong>pull</strong> <strong>cover</strong>, the direction <strong>of</strong> rotation <strong>of</strong> motor is reversed.<br />
This cause the first panel to leaves its stowage position, its tip through 90 degree<br />
1
about its roller to land horizontally with its wheels resting on the coaming. It is<br />
then <strong>pull</strong>ed further over the <strong>hatch</strong>way and the chain linking it to the next panel<br />
becomes taut with the result it too is set in motion.<br />
On reaching the end <strong>of</strong> the stowage space, the second panel tips lie<br />
horizontally on the coaming behind the first and together they <strong>pull</strong> across the<br />
<strong>hatch</strong>way. The process is repeated with the third and fourth panels, ending only<br />
when all are lying flat on the coamings and the <strong>hatch</strong> is completely <strong>cover</strong>ed.<br />
1.1 HATCH COVERS AND THEIR FUNCTION<br />
The purpose and function <strong>of</strong> a <strong>hatch</strong> <strong>cover</strong> and its coamings is to prevent ingress<br />
<strong>of</strong> water into a cargo hold after a large opening has been cut in the deck for cargo<br />
access. Hatch <strong>cover</strong>s are a moveable structure designed to a weather tight<br />
standard.<br />
1.1.1 Hatch Cover Construction<br />
Typically <strong>hatch</strong> <strong>cover</strong>s are lightweight steel grillages. Modern design methods<br />
using finite element technology enable more efficient material distribution which<br />
results in lighter (thinner) structures.<br />
Construction from high tensile steel results in even thinner plate being<br />
used. For this reason these lightweight structures must be ‘handled with care’.<br />
Prevention <strong>of</strong> corrosion is essential – safety margins are finite.<br />
1.1.2 Hatch Cover Function<br />
Hatch <strong>cover</strong>s provide a primary structural and weather tight barrier to prevent<br />
water ingress into cargo holds. Rigorous inspection, regular maintenance and<br />
prompt repair <strong>of</strong> damaged <strong>cover</strong>s, securing’s and supports are essential to<br />
maintain fitness for purpose and, in particular:-<br />
� To maintain sufficient strength to resist green seas landing on <strong>hatch</strong>es in<br />
extreme weather;<br />
� To maintain a barrier against ingress <strong>of</strong> water during normal seagoing<br />
weather conditions.<br />
Failure to maintain <strong>hatch</strong> <strong>cover</strong>s correctly can lead to physical loss <strong>of</strong> a<br />
<strong>cover</strong> in extreme weather and hold flooding and possible foundering. Minor<br />
2
leakage can cause cargo damage and, if over a prolonged period, damage to the<br />
ship’s internal structure. Long-term structural decline can lead to structural<br />
collapse and total loss.<br />
1.2 EARLY HATCH COVERS<br />
The upper deck <strong>hatch</strong>es <strong>of</strong> early steamships, in common with those <strong>of</strong> sailing<br />
ships, were small by present standards: four meters by two would not have been<br />
untypical <strong>hatch</strong>way dimensions, even for ocean going vessels in the mid-19 th<br />
century. Deck openings were bounded by vertical coamings and spanned by<br />
wooden boards usually laid athwart ships: water tightness was maintained by<br />
tarpaulins spread over the boards and secured by wedges and cleats at the<br />
coamings, an arrangement which had then been in use for centuries. Web beams<br />
were sometimes placed across the largest <strong>hatch</strong>ways but it was not until 1879 that<br />
their use became mandatory for all vessels classed with Lloyd’s Register <strong>of</strong><br />
Shipping having <strong>hatch</strong>ways more than 12 feet long. Coamings were required to be<br />
<strong>of</strong> iron constructions. No minimum height was specified and it was not until forty<br />
years later that they appeared in Lloyd’s Rules. Hatch boards were made <strong>of</strong> solid<br />
woods 63 mm thick and <strong>of</strong> such an overall size that they could be handled<br />
manually. Since they were laid transversely across the <strong>hatch</strong>way it was necessary<br />
to use ‘fore and afters’ to reduce their unsupported span. These were the heavy<br />
baulks <strong>of</strong> timber placed longitudinally across the <strong>hatch</strong>way, on the top <strong>of</strong> the<br />
transverse iron beams and supported at each end by brackets attached to the<br />
coamings. The <strong>hatch</strong> boards, in turn, were placed across the fore and after which<br />
were so spaced that the unsupported span <strong>of</strong> the boards did not exceed the<br />
maximum allowed.<br />
After the turn <strong>of</strong> the 20 th century, the practice <strong>of</strong> arranging <strong>hatch</strong> boards<br />
longitudinally began to be adopted. There were sound reasons for this change. A<br />
typical cargo ship <strong>hatch</strong>,7.5m(25 ft) long and 5 m(16 ft) wide, with athwart ship<br />
<strong>hatch</strong> boards, would have been fitted with two transverse web beams and three<br />
fore afters which, because <strong>of</strong> their overall length would each have been made up<br />
in three pieces, one for every beam space as shown in figure 1.1. With<br />
longitudinal <strong>hatch</strong> boards the same <strong>hatch</strong> would have required no more than four<br />
transverse beams space 1.5 m apart each <strong>of</strong> lighter construction than the two webs<br />
3
in previous arrangement. Thus the number <strong>of</strong> heavy components to be lifted<br />
every time the <strong>hatch</strong> was opened and closed would have been reduced from<br />
eleven to four.<br />
Figure 1.1 Simplified arrangement <strong>of</strong> a traditional <strong>hatch</strong><br />
Source: Cargo Access Equipment for Merchant Ships.<br />
This arrangement also had the advantage <strong>of</strong> being safer than the earlier<br />
one. As <strong>hatch</strong>es became longer it becomes increasingly necessary to fit force and<br />
afters in several actions. These were more difficult to ship when battening down<br />
that those modes in one piece, since at least one end <strong>of</strong> each section had to be<br />
positioned on a seat attached to a traverse web before the <strong>hatch</strong> board could be<br />
put on. This meant that the man had to sit astride the web, over the open hold, to<br />
guide into place a very dangerous practice.<br />
Atharwdship <strong>hatch</strong> boards and fore and afters continued to be used well<br />
into 20 th century although the longitudinal arrangement gradually replaced them.<br />
After the implantation <strong>of</strong> the 1930 international load line conventions fore and<br />
after were only found in ships with very small <strong>hatch</strong>es.<br />
4
All <strong>type</strong>s <strong>of</strong> wooden <strong>hatch</strong> were made watertight by means <strong>of</strong> tarpaulins<br />
and this method is still employed in those ships with traditional <strong>hatch</strong>es that<br />
remain in service. The use <strong>of</strong> wooden <strong>hatch</strong> <strong>cover</strong> has declined throughout much<br />
<strong>of</strong> this century to the extent that it is now almost unthinkable that they should be<br />
fitted in modern vessel <strong>of</strong> any size. It is interesting therefore, to consider the<br />
reason for their demise. These fall into three broad categories, namely safety and<br />
security, cargo working and maintenance.<br />
1.3 FAILINGS OF WOODEN HATCHES<br />
1.3.1 Safety and Security<br />
It is impossible to exaggerate the importance and secure <strong>hatch</strong> <strong>cover</strong>s; there can be<br />
no question that a ship’s survival may depend upon having them. But how<br />
efficient are wooden <strong>hatch</strong> <strong>cover</strong>s?<br />
Tarpaulins are the most vulnerable component <strong>of</strong> traditional <strong>hatch</strong> <strong>cover</strong>s.<br />
There are several common reasons for tarpaulin failure. Slackening <strong>of</strong> wedges is<br />
one <strong>of</strong> the most important factor. Chaffing is another serious source <strong>of</strong> weakness,<br />
especially at the coamings. Tarpaulins are also liable to suffer damage every time<br />
that they are removed for working cargo.<br />
Security <strong>of</strong> the wooden <strong>hatch</strong>es also arose as a result <strong>of</strong> the comparatively<br />
large size <strong>of</strong> the <strong>hatch</strong>ways <strong>of</strong> many <strong>of</strong> the ships, especially colliers, then entering<br />
service. Not only were the <strong>hatch</strong>ways longer and wider than had been the customs<br />
up to that time, but the ratio <strong>of</strong> <strong>hatch</strong> width to overall beam was <strong>of</strong>ten greater too.<br />
This was particularly apparent in ships employed in the carriage <strong>of</strong> bulk cargoes<br />
and some <strong>of</strong> the most extreme examples were to be amongst self-trimming<br />
colliers where <strong>hatch</strong> width/ship beam ratios <strong>of</strong>ten exceed 0.6.<br />
Individual <strong>hatch</strong> boards were laid loosely on top <strong>of</strong> the beams in a normal<br />
<strong>hatch</strong>way and they could easily be shipped accidently. In order to prevent this,<br />
interlocking boards were developed. These could be handled manually in the<br />
usual manner but once landed on the beams; they were retained in place by a<br />
simple locking device which was claimed by its manufacturer to enhance the<br />
safety <strong>of</strong> a ship, should it lose its tarpaulins, by preventing the boards from being<br />
washed away by the sea.<br />
5
1.3.2 Maintenance<br />
The maintenance <strong>of</strong> the wooden <strong>hatch</strong>es is expensive in both labour and materials.<br />
Although individual components were simple and inexpensive, there were so<br />
many <strong>of</strong> them in a typical <strong>hatch</strong> and they were so easily damaged through<br />
continued hard use that the total cost <strong>of</strong> replacement so <strong>of</strong>ten substantial. Wedges<br />
which are vital to the security <strong>of</strong> the <strong>hatch</strong>es were individually very cheap but they<br />
were frequently lost or misused.<br />
Hatch boards too had to be replaced frequently. Tarpaulins used for<br />
traditional <strong>hatch</strong>es were easily chafed and in some ships one man could well have<br />
been employed continuously for their repair.<br />
1.3.3 Cargo Working<br />
Time spent in port affects the overall economics <strong>of</strong> operating ships. Attention was<br />
given for higher cargo handling rates and faster turnaround times, and time spent<br />
for opening and closing <strong>hatch</strong>es. This become increasingly apparent as <strong>hatch</strong>ways<br />
became larger. Every <strong>hatch</strong> component had to be handled separately; tarpaulins<br />
had to be folded back, each <strong>hatch</strong> board had to be removed manually, each beam<br />
had to be lifted from its seat by derrick and winch or shore crane, and the larger<br />
the <strong>hatch</strong>way, the more items there were to be handled.<br />
1.4 STEEL HATCHES AFTER 1927<br />
The earliest satisfactory <strong>hatch</strong> <strong>cover</strong> produced by the brothers Joseph and Robert<br />
MacGregor, two naval architects from Tyneside, was <strong>of</strong> the hinged <strong>type</strong>. It<br />
consists to two large steel slabs, each spanning half the <strong>hatch</strong>way and hinged at<br />
the side coamings. When opened by winch and derrick, the slabs rotated through<br />
180 degree so that they rested on the bulwarks to form a convenient platform for<br />
working cargo (although obstructing the gangway along the deck). Like other slab<br />
<strong>hatch</strong>es they were kept secure and watertight in the conventional manner and their<br />
hinges were cunningly built into the coamings so as not to impair the<br />
effectiveness <strong>of</strong> their tarpaulins. However, it was the announcement in 1928 <strong>of</strong> a<br />
horizontal rolling <strong>cover</strong> which did not require tarpaulins that marked the real<br />
beginning <strong>of</strong> the long association <strong>of</strong> the Macgregor name with steel <strong>hatch</strong> <strong>cover</strong>s,<br />
which continues to this day.<br />
6
The first horizontal rolling built to the design patented by MacGregor &<br />
king Ltd. Was installed over the aftermost <strong>hatch</strong>way <strong>of</strong> the 9000tdw motor ship<br />
sheaf holme which left the Sunderland yard <strong>of</strong> her builder, Wm. Pickersgill, in<br />
August1929 amid rather more publicity than she would otherwise have merited.<br />
The event was important because it was not the first time that a <strong>hatch</strong> <strong>cover</strong> had<br />
been put into service that was easily operated manually, yet depended on<br />
tarpaulins for water tightness nor did it forgo any <strong>of</strong> the strength with which<br />
previous steel <strong>cover</strong>s had been endowed.<br />
The earliest horizontal rolling <strong>cover</strong>s produced by Macgregor and king<br />
(subsequently known as Macanking) came in two forms, although both were<br />
basically similar. The first was fitted in fairly small <strong>hatch</strong>ways and consists <strong>of</strong> two<br />
moveable sections fabricated out <strong>of</strong> steel plate stiffened by channels bars or bulbs<br />
angles, with a skirt around their perimeters which rested on the coaming when the<br />
<strong>cover</strong> was closed. They revolved about eccentric bushes which could be rotated so<br />
that the clear height <strong>of</strong> the lower edge <strong>of</strong> the <strong>cover</strong> above the coaming could be<br />
varied.<br />
In the closed position, with the <strong>hatch</strong> secured for sea, the bushes were<br />
aligned so that the perimeter <strong>of</strong> the <strong>cover</strong> rested on the coaming throughout its<br />
entire length. To open the <strong>hatch</strong>, the bushes were rotated through half a turn with<br />
a marlin spike, thus raising the <strong>cover</strong> so that it could be easily <strong>pull</strong>ed along on its<br />
wheels. This arrangement has become a feature <strong>of</strong> many MacGregor <strong>hatch</strong>es<br />
since.<br />
In France in 1934, Captain Mege, <strong>of</strong> Louis Dreyfus Cie, patented folding<br />
steel <strong>hatch</strong> <strong>cover</strong>s which were first fitted in the cargo ship Louis L.D. two years<br />
later. They considered <strong>of</strong> double panels hinged together and to the end coamings,<br />
but, unlike the von Tell <strong>cover</strong>s, they were opened by lifting the panel nearer the<br />
coaming hinge. As it was raised, the second panel was <strong>pull</strong>ed towards the end <strong>of</strong><br />
the <strong>hatch</strong>way, supported on two trailing wheels which ran along the coaming,<br />
until both panels were stowed together vertically. In this way a folding <strong>hatch</strong><br />
<strong>cover</strong> could be opened in one operation instead <strong>of</strong> two. Fig 1.2 shows an early<br />
Mege folding steel <strong>hatch</strong> <strong>cover</strong>. Closing was carried out by simply allowing the<br />
fold hinge to open under the combined weight <strong>of</strong> the two panels until both were<br />
in position resting flat on coaming to which they were secured by bolts. In long<br />
7
<strong>hatch</strong>ways, Mege <strong>cover</strong>s were fitted to both end coamings. The folding principle<br />
that was incorporated into their design has become widely adopted, for both wire<br />
operated and hydraulically operated folding <strong>cover</strong>s. More than thirty ships were<br />
fitted with Mege <strong>cover</strong>s before MacGregor & Co. Became the sole licensee for<br />
their construction in 1949.<br />
Figure 1.2 Arrangement <strong>of</strong> an early Mege folding steel <strong>hatch</strong> <strong>cover</strong><br />
Source: Cargo Access Equipment for Merchant Ships.<br />
8
CHAPTER 2 - TYPES OF HATCH COVERS<br />
Many <strong>type</strong>s <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> are now available and the principal ones are listed in the<br />
below table where they grouped according to their mode <strong>of</strong> operation. Table 2.2<br />
shows the most important characteristics <strong>of</strong> each major <strong>type</strong>s.<br />
Table 2.1 Operating mode <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> <strong>type</strong>s<br />
Rollin and tripping <strong>Single</strong> <strong>pull</strong><br />
Lifting Pontoon<br />
Rolling End rolling<br />
Side rolling<br />
Lift and roll(piggy-back)<br />
Telescopic<br />
Roll stowing Roll stowing(rolltite)<br />
Flexible rolling<br />
Folding Hydraulic folding<br />
Wire operated folding<br />
Direct <strong>pull</strong><br />
Sliding/nesting Tween-deck sliding<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
9
.<br />
Table 2.2 Summarizes the most important characteristics <strong>of</strong> each major <strong>type</strong><br />
NNo Cover <strong>type</strong> Usual<br />
ship<br />
<strong>type</strong>s<br />
Decks<br />
applicable<br />
Approxima<br />
te %<strong>of</strong><br />
<strong>cover</strong>s<br />
fitted to<br />
recent new<br />
ships<br />
Guide to<br />
minimum<br />
coaming<br />
height<br />
1 <strong>Single</strong> <strong>pull</strong> (D) Weather 41 Depends<br />
on<br />
section<br />
lengths<br />
but more<br />
than(A)<br />
2 Hydraulic (D) Weather/Tween 25 (A),(B)<br />
folding<br />
3 Wireoperated<br />
folding<br />
4 Direct <strong>pull</strong> All ships<br />
with<br />
cargo<br />
5<br />
Roll<br />
stowing<br />
6 Side and<br />
end rolling<br />
or(C)<br />
(D) Weather/Tween 10 (A),(B)<br />
or(C)<br />
gear<br />
Drive<br />
system<br />
Electric,<br />
hydraulic<br />
or ship’s<br />
cargo<br />
gear<br />
10<br />
Cleating<br />
system<br />
(E)<br />
Hydraulic (E)<br />
Weather 3 (A) Or(B) Ship<br />
crane or<br />
derrick<br />
(D) Weather 2 Depends<br />
on drum<br />
diameter<br />
but<br />
usually<br />
more<br />
than (A)<br />
All, but<br />
mainly<br />
large<br />
bulkers<br />
and<br />
OBOs<br />
7 Lift and roll All, but<br />
mainly<br />
8 Tweendeck<br />
sliding<br />
9 Pontoon<br />
(F)<br />
bunkers<br />
Multideck<br />
cargo<br />
ships<br />
Containe<br />
r ships,<br />
Multideck<br />
cargo<br />
ships<br />
or(B)<br />
Winch Screw or<br />
quickacting<br />
Electric or<br />
hydraulic<br />
Weather 4 (A) or (B) Electric or<br />
hydraulic<br />
Weather 2 (A) or (B) Electric or<br />
hydraulic<br />
Tween and Car<br />
decks<br />
Automatic<br />
(E)<br />
(E)<br />
(E)<br />
2 (C ) Electric Token<br />
Weather/Tween 11 (A), (B) or<br />
(C)<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
Ship or<br />
shore<br />
crane<br />
(E)
2.1 SINGLE PULL<br />
2.1.1 Description<br />
Figure 2.1 single <strong>pull</strong> <strong>hatch</strong> <strong>cover</strong><br />
Source: - Walter Vervloesem – IMCS<br />
The classic modern <strong>hatch</strong> <strong>cover</strong> is the ‘single <strong>pull</strong>’ which remains the most common<br />
<strong>of</strong> the all the various forms now in service and may rightly be described as the natural<br />
successor to traditional beams and boards. This <strong>cover</strong> derives its name from its<br />
immediate predecessor, the ‘multi-<strong>pull</strong>’ <strong>cover</strong>, which consisted <strong>of</strong> a series <strong>of</strong><br />
individual panels similar to those <strong>of</strong> the single <strong>pull</strong>, but unconnected. Each panel had<br />
to be rigged before being <strong>pull</strong>ed one at a time into stowage.<br />
The complete <strong>cover</strong> consists <strong>of</strong> a number <strong>of</strong> narrow panels which span the<br />
<strong>hatch</strong>way and are linked together by chains. In the closed position, the panel sides sit<br />
firmly which takes the weight <strong>of</strong> the <strong>cover</strong>. Just inside the side plate is a rubber gasket<br />
attached to the <strong>cover</strong>, which rest on a steel compression bar forming a watertight seal.<br />
Extending from the side coamings at the end <strong>of</strong> the <strong>hatch</strong>way where the <strong>cover</strong>s are<br />
stowed are steel rails which the individual <strong>hatch</strong> panels to be transferred to their<br />
stowage location when the <strong>hatch</strong> is opened. Although single <strong>pull</strong> <strong>cover</strong>s rarely exceed<br />
16 m in width, larger sizes can be manufactured.<br />
11
2.2 SIDE ROLLING<br />
2.2.1 Description<br />
Figure 2.2 side rolling <strong>hatch</strong> <strong>cover</strong><br />
Source: - Walter Vervloesem - IMCS<br />
Rolling <strong>cover</strong>s usually consist <strong>of</strong> two large panels at each <strong>hatch</strong>way. They are fitted<br />
with wheels which roll along a track at both sides <strong>of</strong> the coaming top. Stowage rails,<br />
which may be portable, extend this track via pillars welded to the deck. In some<br />
installation, the wheels are not attached to the <strong>hatch</strong> <strong>cover</strong> but to the coaming and to<br />
fixed pillars on the deck, and the <strong>cover</strong> rolls across them. Apart from stowage<br />
location, the principal difference between side end rolling <strong>cover</strong>s is that the joint in<br />
between side rolling panels is longitudinally and between end rolling panels is<br />
athwatships.<br />
These <strong>cover</strong>s are usually fitted to large ships. They are <strong>of</strong>ten extremely heavy<br />
owing to their large dimensions and require hydraulic pot lifts (rams) to raise them<br />
into the rolling position. These hydraulic lifts are fitted to the coaming below the<br />
wheels (in their closed position) and are illustrated in fig. There is no limit to the size<br />
<strong>of</strong> the <strong>cover</strong>s, and panels 20 metres square (20 m*20 m) have been installed in ships.<br />
12
2.3 FOLDING & MULTI-TYPE<br />
2.3.1 Description<br />
Figure 2.3 folding <strong>type</strong> <strong>hatch</strong> <strong>cover</strong><br />
Source: - Walter Vervloesem - IMCS<br />
Folding <strong>cover</strong>s may be fitted at both weather deck and tween deck <strong>hatch</strong>ways. In its<br />
simplest form, this <strong>type</strong> <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> consists <strong>of</strong> two flat topped panels, similar in<br />
basic construction to those <strong>of</strong> the single <strong>pull</strong> system. Complex configuration may have<br />
three or more panels at each end <strong>of</strong> the <strong>hatch</strong>way, although installations with an<br />
uneven number <strong>of</strong> panels are rare. Wire-operated <strong>cover</strong>s having more than two panels<br />
require special rigging and their operation is therefore slow.<br />
A typical hydraulic operated <strong>cover</strong> is shown below. Adjacent panels are<br />
hinged together so that they can fold as shown. The panel at the stowage end is hinged<br />
to a plinth welded to the deck and hydraulic rams are usually arranged as illustrated.<br />
The ram rod is withdrawn into the cylinder to prevent corrosion when the <strong>hatch</strong> is<br />
closed at sea. Covers up to 26 m wide have been installed in ships.<br />
13
2.4 LIFT AWAY<br />
2.4.1 Description<br />
Figure 2.4 Lift away <strong>type</strong> <strong>cover</strong>s<br />
Source: - Walter Vervloesem - IMCS<br />
Lift-away <strong>hatch</strong> <strong>cover</strong>s for use on the weather deck are divided into two<br />
categories as follows: .<br />
SINGLE-PANEL COVERS: MULTI-PANEL COVERS:<br />
single-opening abreast with longitudinal joints .<br />
multi-opening abreast with transverse joints .<br />
<strong>Single</strong>-Panel <strong>type</strong>s comprise one <strong>cover</strong> for each opening i.e. there are no joints. They<br />
are normally specified for bulk carriers in the case <strong>of</strong> single opening abreast, and for<br />
cellular containerships in the case <strong>of</strong> multi-opening abreast configurations.<br />
Multi-Panel <strong>cover</strong>s comprise several separate panels for each <strong>hatch</strong> opening.<br />
They are used for cellular containerships in the case <strong>of</strong> longitudinal joints, and for<br />
multipurpose cargo ships and heavy cargo tonnage in the case <strong>of</strong> transversal joints<br />
14
2.5 PIGGY BACK<br />
2.5.1 Description<br />
Figure 2.5 Piggy <strong>type</strong><br />
Source: - Walter Vervloesem - IMCS<br />
Lift and roll <strong>cover</strong>s are a development <strong>of</strong> rolling <strong>cover</strong>s and example is illustrated in<br />
fig. Each <strong>cover</strong>s consists <strong>of</strong> two panels, one <strong>of</strong> which has powered wheels. In the way<br />
<strong>of</strong> the ‘dumb’ panel, four hydraulic rams which act vertically upwards are fitted with<br />
the coaming. These engage in lugs on the side <strong>of</strong> the panel to lift it high enough above<br />
the coaming for the motorized panel to roll underneath. The dumb panel is then<br />
lowered onto the motorized panel so that both can be moved together. The side<br />
coaming can be extended so that the two panels can be stowed beyond the <strong>hatch</strong> end.<br />
Alternatively these <strong>cover</strong>s can be side rolling, stowing abreast the <strong>hatch</strong>way. There is<br />
in the theory no limit to the size <strong>of</strong> these <strong>cover</strong>s composed <strong>of</strong> two 100-tonne panels<br />
for 26m by 23m <strong>hatch</strong> ways have been supplied for forest product carriers.<br />
15
2.6 STACKING COVERS<br />
Figure 2.6 Stacking <strong>type</strong> <strong>cover</strong>s<br />
Source: - Walter Vervloesem - IMCS<br />
16
2.7 REEFERS HATCH COVERS<br />
Figure 2.7 Reefers <strong>hatch</strong> <strong>cover</strong>s<br />
Source: - Walter Vervloesem - IMCS<br />
17
2.8 SPRING LOADED COVERS<br />
Figure 2.8 Spring loaded <strong>cover</strong>s<br />
Source: - Walter Vervloesem - IMCS<br />
18
CHAPTER 3 - GENERAL REQUIREMENTS<br />
3.1 REGULATORY REQUIREMENTS<br />
3.1.1 Rules Governing Cargo Access Equipment<br />
Cargo ships exist to transport goods from one port to another to accomplish this; they<br />
must have some means <strong>of</strong> getting cargo into and out <strong>of</strong> their holds. Thus ships must<br />
have opening either in the weather deck, as in vertically loading vessels, or in the<br />
bow, stern or side, as in horizontally loading vessels. These areas are all vulnerable to<br />
damage at sea. Thus cargo access equipment must provide access in port while<br />
keeping water out, during voyage. One <strong>of</strong> its prime functions is to ensure the safety <strong>of</strong><br />
ship, personnel and cargo. In order to maintain acceptable standards <strong>of</strong> safety at sea,<br />
rules and regulations have been introduced over the years, many <strong>of</strong> which directly<br />
concern access equipment.<br />
3.1.2 International Load Line Convention, 1966<br />
Probably the most important regulations that affect access equipment are those arising<br />
from the 1966 load line convention which replaces the first international load line<br />
convention in 1930 for determining the freeboard. It provides for two categories. It<br />
provides for two categories <strong>of</strong> ship for freeboard purpose-Type. A ships which are<br />
those designed to carry liquid cargoes in bulk and whose tanks have small access<br />
openings and Type B which includes all other ships. Among Type B ships are certain<br />
bulk carriers and ore carriers which are further sub-divided as follows:<br />
(a) Ships <strong>of</strong> over 100 m length having steel <strong>hatch</strong> <strong>cover</strong> on all exposed <strong>hatch</strong>ways<br />
and which can remain afloat in satisfactory equilibrium with any one<br />
compartment flooded. When the length exceeds 225 m, the machinery space is<br />
also treated as a floodable compartment. These ships can have table B<br />
freeboards given in table B and A summarized in table; such freeboard is<br />
referred to as B-60.Tables A and B referred to the minimum freeboard laid<br />
down by the Convention for <strong>type</strong> A and Type b ships.<br />
(b) Ships which can withstand flooding <strong>of</strong> two adjacent compartments may be<br />
assigned B-100 freeboard, virtually equal to <strong>type</strong> A ships.<br />
19
Type B ships which are fitted with portable <strong>cover</strong>s, e.g. beams and boards in<br />
position 1 <strong>hatch</strong>ways are required to have their freeboard increased above<br />
those given in table B.<br />
3.1.3 Freeboard<br />
Table 3.1 shows freeboard from the full tables and compares freeboard for different<br />
ships length as required by Load Line Conventions <strong>of</strong> 1930 and 1966.Corrections are<br />
made to cater for non-standard length depth ratios, block coefficient, extent <strong>of</strong><br />
superstructure etc. The standard ratios block coefficient, extent <strong>of</strong> superstructure etc.<br />
The standards freeboard applies in salt water.<br />
Ship length,<br />
metres<br />
Table 3.1 Freeboard for different ships length<br />
Tanker<br />
Freeboards<br />
1930,<br />
mm<br />
Table ‘A’<br />
Freeboards<br />
1966,<br />
mm<br />
Steamer<br />
Freeboards<br />
1966<br />
mm<br />
30 - 250 250 250<br />
60 570 573 570 573<br />
90 1015 984 1070 1075<br />
120 1550 1459 1775 1690<br />
150 2170 1968 2540 2315<br />
180 2710 2393 3230 2915<br />
210 (3080) 2705 3810 3430<br />
240 (3370) 2946 (4310) 3880<br />
300 (3830) 3262 (4755) 4630<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
Table ‘B’<br />
Freeboards<br />
1966,<br />
mm<br />
In designated summer zones throughout the world; slightly different values in<br />
winter or tropical zones in fresh water, or when timber deck cargoes are carried, as<br />
laid down and in the corresponding national legislation, in the United Kingdom. The<br />
merchant shipping (Load line) Rules, 1968. It can be seen that increasing maximum<br />
draft and therefore cargo deadweight. Table 3.2 is derived from the full tables and<br />
shows the increase in freeboard required for Type B ships having portable <strong>cover</strong>s<br />
20
secured by tarpaulins and battening devices, e.g. beams and boards .Position 1 <strong>hatch</strong><br />
board are defined as those on exposed freeboard decks, raised quarter decks, and<br />
exposed superstructure decks within the forward quarter length <strong>of</strong> ship, while position<br />
2 <strong>hatch</strong>ways are those on exposed superstructures deck is regarded as the deck<br />
immediately above the freeboard deck.<br />
Length,<br />
metres<br />
Table 3.2 Increase in freeboard<br />
Freeboard<br />
Increase,<br />
mm<br />
30 50 300<br />
60 50 623<br />
90 50 1125<br />
120 84 1774<br />
150 228 2543<br />
180 313 3228<br />
3.1.4 Freeboard Deck<br />
Resultant<br />
Freeboard,<br />
mm<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
Regulation 3, paragraph 9 <strong>of</strong> 1966 LLC defines the freeboard deck and is quoted here<br />
in full as it has an important bearing on all aspects <strong>of</strong> equipment used for closing<br />
cargo openings.<br />
The freeboard deck is normally the uppermost complete deck exposed to<br />
weather and sea, which has permanent means <strong>of</strong> closing cargo openings in the side <strong>of</strong><br />
the ship are fitted with permanent means <strong>of</strong> watertight closing. In a ship having a<br />
discontinuous freeboard deck,<br />
The lowest line <strong>of</strong> exposed deck and the continuation <strong>of</strong> that line parallel to the<br />
upper part <strong>of</strong> deck is taken as freeboard deck. At the option <strong>of</strong> the owner and subject<br />
to the approval <strong>of</strong> the Administration ,a lower deck may be designated as the<br />
freeboard deck provided as it is complete and permanent deck continuous in a fore<br />
and aft direction at least between the machinery space and peak bulkheads and<br />
continuous athwart ships. When this lower deck is stepped the lowest line <strong>of</strong> the deck<br />
and the continuation <strong>of</strong> that line parallel to upper part <strong>of</strong> the deck and is taken as the<br />
21
freeboard deck. When a lower deck is designated the freeboard deck, the part <strong>of</strong> hull<br />
which extend above the freeboard deck is treated as superstructure so far as concerns<br />
the application <strong>of</strong> the conditions <strong>of</strong> the assignment and the calculation <strong>of</strong> freeboard. It<br />
is from this deck that the freeboard is calculated.<br />
It should be noted that the requirement for a lower deck to complete and<br />
permanent in order to be designated the freeboard deck, does not mean that any<br />
openings need to be weather tight, only that the structure <strong>of</strong> a deck is present. Tween-<br />
deck <strong>hatch</strong>es may be <strong>of</strong> steel or wood, but are only required to be watertight if fitted<br />
to deep tanks or compartments containing water ballast.<br />
The ‘Administrations’ referred to include the Department <strong>of</strong> Trade in the<br />
United Kingdom, the us coast guard in the united states and equivalent in other<br />
countries.<br />
3.1.5 Weather-Tightness and Water-Tightness<br />
Regulation <strong>of</strong> the 1966 LLC which <strong>cover</strong>s the mean for securing weather-tightness <strong>of</strong><br />
steel weather-tight <strong>cover</strong>s states that ‘The means for securing and maintaining<br />
weather-tightness shall be to the satisfaction <strong>of</strong> the Administration. The arrangement<br />
shall ensure that the tightness can be maintained ain any sea conditions, and for this<br />
purpose test for tightness shall be required at initial survey ,and may be required at<br />
periodical survey and at annual inspections or at more frequent intervals.<br />
Regulation defines ‘weather-tight’ as meaning that water will not penetrate<br />
into the ship in any conditions. ‘Weather-tight’ is not defined into 1996 LLC but is<br />
generally regarded as higher standard than weather-tight.it is usually taken to require<br />
the closure to be capable <strong>of</strong> preventing the passage <strong>of</strong> water through the structure in<br />
any direction, under the head <strong>of</strong> ships margin line, which is line drawn at least 76 mm<br />
in below the upper surface <strong>of</strong> bulkhead deck at the side <strong>of</strong> ship.<br />
In practice the <strong>hatch</strong> <strong>cover</strong>s <strong>of</strong> B-60 and B-100 ships must be <strong>of</strong> steel and<br />
made weather-tight by means <strong>of</strong> special gasket devices. Less commonly, <strong>hatch</strong> may<br />
be made weather-tight by means <strong>of</strong> tarpaulins and battening devices over wooden or<br />
portable steel pontoon <strong>cover</strong>s.<br />
3.1.6 Statutory Regulations<br />
The 1966 load line convention came into force in 1968 after it had been ratified by<br />
required number <strong>of</strong> maritime nations. In UK the convention was brought into the<br />
22
force by the 1967 Merchant shipping Act from which the merchant shipping (load<br />
line) rules 1968 were made the rules for the constructions <strong>of</strong> ship laid down by<br />
Lloyds register <strong>of</strong> shipping are consistent with the convention, as are those <strong>of</strong> other C<br />
classification societies.<br />
3.2 GENERAL CONSIDERATIONS FOR ACCESS EQUIPMENT<br />
3.2.1 Coaming height<br />
Minimum coaming height, derived from the 1966 LLC, is laid down by Classification<br />
Societies. Height are measured above the upper surface <strong>of</strong> the deck, and any sheathing<br />
that may be fitted, and for <strong>hatch</strong>way closed by portable <strong>cover</strong>s secured water tight by<br />
tarpaulins and battening devices, they must not be less than:<br />
600 mm (23.5 in) for Position 1;<br />
450 mm (17.5 in) for Position 2,<br />
Coaming <strong>of</strong> <strong>hatch</strong>ways closed by steel <strong>cover</strong>s fitted with direct securing<br />
arrangements are usually as indicated above, taking into account any sheer or camber<br />
when assessing minimum height. They may, however, be lower, or even omitted<br />
entirely, if the safety <strong>of</strong> the ship is not impaired by doing so, provided the<br />
Administration <strong>of</strong> the country concerned consents.<br />
The scantling and securing arrangements <strong>of</strong> flush <strong>hatch</strong> <strong>cover</strong>s or those having<br />
less than standard height coamings are treated as special cases. Such arrangements<br />
have been approved in the past. Dock safety regulations generally require a minimum<br />
coaming height <strong>of</strong> about 760 mm (2 ft 6 in), otherwise additional fencing must be<br />
fitted to prevent personnel falling through the <strong>hatch</strong>way.<br />
It is rare for ship to have coamings <strong>of</strong> lower height than those stipulated,<br />
unless they are completely flush. Flush weather decks are required in a variety <strong>of</strong><br />
circumstances. For instance, vehicles, wheeled cargo, or containers must sometime be<br />
stowed over the full deck area including the <strong>hatch</strong> <strong>cover</strong>s, and clear decks for<br />
recreation are desirable in passenger ships. Satisfying the flood ability requirement for<br />
B-100 and B-60 ships may result in coaming being increased in height on such ships<br />
to meet loadline and subdivision regulation.<br />
23
In practice one <strong>of</strong> the principal determinants <strong>of</strong> coaming height is the operation<br />
<strong>of</strong> the <strong>hatch</strong> <strong>cover</strong>. Other <strong>type</strong>s that are affected in this way are rolling stowing <strong>cover</strong>s<br />
where the drum height must be sufficient to allow the stow <strong>cover</strong>s to fit between the<br />
drum axis and the deck and single <strong>pull</strong> <strong>cover</strong>s whose panels stow in an upright<br />
position standing clear <strong>of</strong> the deck.<br />
The coaming may also be increased in height to obtain additional cargo<br />
capacity. As a result <strong>of</strong> these considerations, the majority <strong>of</strong> the ships have in the<br />
range 1.0-1.8 m. It is useful if crew and stevedores can see readily into the holds<br />
during port operations. Thus if the coaming is higher than about 1.4 m, a step or a<br />
narrow platform should be fitted at the suitable height. While the top <strong>of</strong> the coaming<br />
is nearly always at the same level on all its sides, it need not be parallel with the deck.<br />
Neither is it essential that the coaming plates be vertical, if by sloping them inwards, a<br />
larger opening at deck level can be obtained.<br />
Another factor influencing coaming height is the nature <strong>of</strong> particular deck<br />
cargoes. Packaged lumber, for example, is usually stowed abreast <strong>hatch</strong>ways until it<br />
reaches the height <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> top, when it is distributed over its whole width <strong>of</strong><br />
the ship. Lumber is usually banded into packages, each 660 mm high, which are<br />
stowed with a 25 mm batten between them. Coamings should therefore be designed<br />
with a height from deck to <strong>hatch</strong> <strong>cover</strong> top which is a multiple <strong>of</strong> 685 mm (27 in). In<br />
heavy lift cargo liners, the coaming height and bulwark height are <strong>of</strong>ten the same so<br />
that awkward loads like barges may be easily supported across the entire ship.<br />
In some ship the internal volume bounded by the coamings needs to be a<br />
greater proportion <strong>of</strong> the total hold volume than the minimum 600 mm coaming<br />
height allows. In the past certain ships engaged in the grain trade were required to<br />
have coamings enclosing 4 percent <strong>of</strong> the total hold volume to allow for settling, but<br />
this requirement have now been suppressed by the provisions <strong>of</strong> the Safety <strong>of</strong> Life at<br />
Sea Conventions 1974(SOLAS 74). These new provisions do not stipulate a minimum<br />
or maximum coaming volume, although it may be necessary to arrange a coaming<br />
height in excess <strong>of</strong> 600 mm in a particular ship so as to meet the stability requirements<br />
for the carriage or grain. These assume that the cargo ships in to void spaces below<br />
side decks, so producing a heeling moment which depends on the resulting ‘free<br />
surface’ <strong>of</strong> the grain.<br />
24
3.2.2 Cover Stowage<br />
Where a designer is attempting to obtain the largest possible <strong>hatch</strong>way openings, the<br />
question <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> stowage is especially important. The width <strong>of</strong> the stowage<br />
space is fixed by the <strong>hatch</strong>way width if the <strong>cover</strong>s are stowed at the end <strong>of</strong> the<br />
<strong>hatch</strong>way, but the height and length <strong>of</strong> the space can be varied. If the <strong>hatch</strong>ways are to<br />
be the longest possible in a given deck length, the length <strong>of</strong> the stowage space must be<br />
kept to a minimum; this can be accomplished in a various ways depending on the <strong>type</strong><br />
<strong>of</strong> <strong>hatch</strong> <strong>cover</strong> employed. No special stowage space is required for simple pontoon<br />
<strong>cover</strong>s since these are usually stowed on adjacent <strong>hatch</strong> <strong>cover</strong>s or on the quayside<br />
when the <strong>hatch</strong> is open. Alternatively side rolling <strong>cover</strong>s may be used if the <strong>hatch</strong>way<br />
is not too wide in relation to the ships breadth.<br />
3.2.3 Deck Openings<br />
As deck opening becomes larger, the problem <strong>of</strong> ensuring adequate hull strength<br />
becomes more complex. The necessary longitudinal strength <strong>of</strong> the hull girder can be<br />
readily achieved, even for ships with <strong>hatch</strong> widths 80 percent <strong>of</strong> the breadth <strong>of</strong> the<br />
ship, by the use <strong>of</strong> high tensile steels. But the provision <strong>of</strong> the adequate torsion<br />
strength may require very detailed design and stress analysis, since the torsional<br />
deflection <strong>of</strong> a ship with large <strong>hatch</strong>ways give rise to high stress concentration at the<br />
corners <strong>of</strong> the openings and to deformation <strong>of</strong> the <strong>hatch</strong>way.<br />
25
Figure 3.1 (a) Rounded deck opening with coaming<br />
(b) Coaming plate following deck opening<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
To avoid high stress concentration in deck plating, the corners <strong>of</strong> deck<br />
openings should be elliptical or parabolic. As the corners <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong>s are<br />
usually rectangular, provision has to be made to accommodate the <strong>hatch</strong> coaming.<br />
This can be done in two ways: either a square coaming can be built with the rounded<br />
deck plating protruding into the coaming space shown in fig3.1 (a) and (b) or the<br />
coaming can follow the shape <strong>of</strong> the deck opening with a filling-in plate welded to its<br />
top. In both cases the clear opening for rectangular cargoes like containers will be<br />
appreciably smaller than the maximum dimensions to the inside <strong>of</strong> the coamings.<br />
3.2.4 Drainage<br />
As mentioned earlier, an important function <strong>of</strong> access equipment is to prevent water<br />
entering the ship through the openings in its hull. If the hull is flexing in heavy<br />
weather, it is almost inevitable that some water will penetrate the seals <strong>of</strong> closing<br />
devices, especially if they are worn. Thus there must be a second line <strong>of</strong> defence, such<br />
as drains, for removing any water before it can damage the cargo.<br />
Drainage facilities must be built into all terms access equipment. Here water<br />
which seeps past the peripheral seal <strong>of</strong> a <strong>hatch</strong> <strong>cover</strong> runs along a channel and is<br />
discharged onto the weather deck through a hole in the coaming. Where the drain is<br />
below the freeboard deck, as in flush weather deck <strong>cover</strong>s, it must be connected to the<br />
bilge, or overboard via a scupper and non return valve.<br />
26
It is also necessary to provide drainage for the vehicle deck in Ro-Ro vessels.<br />
Any scupper which drains a space within an intact superstructure on the free board<br />
deck (usually the main vehicle deck) is led overboard through a pipe fitted with a<br />
screw-down non return valve having open/shut indicators and capable <strong>of</strong> being<br />
operated from accessible positions above the freeboard deck. Alternatively the<br />
scupper may be led down to the bilges or to a drain tank. In an enclosed tween deck<br />
space with a continues centre-line casing, additional scuppers must be installed<br />
adjacent to the casing on the main vehicle deck. Where the inboard end <strong>of</strong> a deck<br />
scupper would be below the load waterline at an angle <strong>of</strong> heel less than 15 degree, it<br />
should be led to a separate drain tank, which may be pumped overboard.<br />
3.3 SPECIFIC DESIGN REQUIREMENTS FOR HATCH COVERS<br />
3.3.1 Hatch Covers<br />
The <strong>hatch</strong> <strong>cover</strong> structure consists in essence <strong>of</strong> steel beams or grinders spanning the<br />
shorter <strong>hatch</strong>way dimension, plated over on top completed by steel side and end<br />
plates. The top plate provides the top flange <strong>of</strong> the beams and grinders. For the<br />
simpler <strong>type</strong>s <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> panel, e.g. pontoon or single <strong>pull</strong>, the design and analysis<br />
assume a uniformly loaded simply supported beam as shown in the fig 3.2.<br />
Figure 3.2 Beam is treated as a uniformly loaded simply supported structure<br />
3.3.1.1 Structural regulations<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
The construction <strong>of</strong> exposed <strong>hatch</strong> <strong>cover</strong>s is governed by regulations 14 to 16 <strong>of</strong> the<br />
1966 Load line convention (1966 LLC). Regulation stipulates that exposed coamings<br />
and <strong>hatch</strong>way <strong>cover</strong>s above the superstructure deck shall comply with the<br />
requirements <strong>of</strong> the appropriate national administration, which means in effect, that<br />
27
such equipments must be design in accordance with the current practice <strong>of</strong> the<br />
administration.<br />
Table 3.3 below summarizes the other requirements <strong>of</strong> these regulations for<br />
beam and board portable <strong>cover</strong>s, and steel pontoon <strong>cover</strong>s secured by tarpaulins and<br />
battening devices, and steel <strong>cover</strong>s fitted with direct securing arrangements. In this<br />
context steel pontoons are plated, <strong>cover</strong>ed having interior webs and stiffeners,<br />
extending the full width <strong>of</strong> the securing arrangements. Classification society rules<br />
embrace these regulations but are more detailed and include non statutory non<br />
exposed cargo <strong>cover</strong>s; they vary slightly between societies. Some important aspects <strong>of</strong><br />
<strong>hatch</strong> <strong>cover</strong> design are not the concern <strong>of</strong> the 1966 LLC, such as increase scantling for<br />
special cargo loads.<br />
Table 3.3 Summary <strong>of</strong> 1966 Load Line Convention <strong>hatch</strong> <strong>cover</strong> regulation<br />
Hatch <strong>cover</strong> <strong>type</strong>s Materials<br />
Portable <strong>cover</strong>s secured watertight<br />
By tarpaulins and battering devices<br />
Wood board<br />
and mild steel<br />
beams<br />
Steel pontoons<br />
28<br />
requirements<br />
Minimum<br />
thickness <strong>of</strong><br />
wooden boards<br />
assumed load<br />
ship length<br />
under 24m ship<br />
length over<br />
100m ship<br />
length 24m-<br />
100m<br />
load factor<br />
maximum<br />
deflection<br />
Assumed load
Other steel <strong>hatch</strong> <strong>cover</strong> secured weather<br />
tight with gaskets and clamping devices<br />
1) With maximum span <strong>of</strong> 1.5m. thickness increased<br />
proportionately for large spans.<br />
2)Maximum stress to be less than<br />
(minimum ultimate strength <strong>of</strong> steel)/(load factor)<br />
3)The strength and stiffness <strong>of</strong> <strong>cover</strong>s<br />
made <strong>of</strong> materials other than mild steel must<br />
be equivalent to those <strong>of</strong> mild steel to the satisfaction<br />
<strong>of</strong> administration<br />
3.3.1.2 Cleats<br />
mild steel<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
load factor<br />
maximum<br />
deflection<br />
minimum<br />
29<br />
platethickness<br />
assumed load<br />
load factor<br />
maximum<br />
deflection<br />
minimum plate<br />
thickness<br />
The 1966 LLC requires that satisfactory means for securing weather tightness be<br />
provided, and gives requirements for <strong>cover</strong>s secured by tarpaulins and battens. For<br />
gasket <strong>cover</strong>s, details are usually agreed between the <strong>hatch</strong> <strong>cover</strong> designer and<br />
classification society.
An important aspect <strong>of</strong> the gasket <strong>type</strong> securing arrangement, whatever its<br />
form is that the pressure between the sealing gaskets and compression bars is correctly<br />
maintained. Manual cleats are <strong>of</strong>ten over tightened despite the steel to steel contact <strong>of</strong><br />
the <strong>cover</strong> skirt plates on the coaming bar, with the result that gasket. Life is severely<br />
shortened. This problem is overcome by the introduction <strong>of</strong> resilient and quick acting<br />
cleats which means that the correct sealing pressure is consistently and uniformly<br />
applied. Cleats on steel <strong>cover</strong>s are generally spaced about 1.5-2 m apart, closer<br />
adjacent to the corners, and no more than 0.6 m apart for wooden <strong>cover</strong>s. With the<br />
advent <strong>of</strong> larger and heavier <strong>hatch</strong> <strong>cover</strong>s, the classification societies have, in some<br />
cases, approved <strong>cover</strong>s with greater than usual cleat spacing.<br />
3.3.1.3 Loads<br />
The <strong>hatch</strong> loading laid down by the 1966 LLC and summarized in table shown take<br />
account <strong>of</strong> the forces exerted on exposed <strong>cover</strong>s by heavy seas breaking over the deck.<br />
Once again however, these are mandatory minimum values and the classification<br />
societies may require that they are increased in certain cases. Thus for <strong>hatch</strong> <strong>cover</strong>s on<br />
which deck cargoes are rarely if ever carried, the loading laid down are adequate,<br />
typically 1.75 tonnes/ . This is equivalent to the cargo stowed 2.45 m high at 1.39<br />
/tonnes. Loading for the <strong>cover</strong>s in the foremost quarter <strong>of</strong> the ship’s length may be<br />
increased to counter the severe sea water forces likely to be experienced in this region.<br />
3.3.1.4 Scantling<br />
Minimum scantling (thickness and dimensions <strong>of</strong> steel plating and stiffeners) and load<br />
factors for steel <strong>cover</strong>s respecified in the 1966 LLC, so that the load factor multiplied<br />
by the maximum stress in the <strong>cover</strong>s is less than or equal to the minimum ultimate<br />
strength <strong>of</strong> the steel. Corresponding minimum scantling depending on loading are<br />
given in classification society rules, alternatively direct calculations <strong>of</strong> required<br />
structural strength may be made using maximum design stress levels.<br />
Table 3.4 below shows the requirements <strong>of</strong> Lloyd’s Register with respect to<br />
steel <strong>hatch</strong> <strong>cover</strong>s or other access equipments constructed <strong>of</strong> grade A mild steel<br />
having a minimum ultimate tensile strength <strong>of</strong> 4100Kgf cm square.<br />
30
Table 3.4 Access equipment strength calculations<br />
Factor Weather deck Tween-deck<br />
Maximum bending stress,<br />
kgf/cm square<br />
Maximum shear stress,<br />
kgf/cm square<br />
965 1200<br />
700 700<br />
Maximum deflection 0.0028 * span 0.0035*span<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
The top plate <strong>of</strong> a typical <strong>hatch</strong> <strong>cover</strong> panel may be from 6-13 mm thick<br />
depending on the spacing <strong>of</strong> the beams (generally, thickness=spacing/100). This plate<br />
is stiffened by beams spanning the <strong>hatch</strong> <strong>cover</strong>, usually fabricated ‘tee’ beams having<br />
a depth <strong>of</strong> about 4 percentage <strong>of</strong> the span and spaced 500-1000 mm apart. The panel is<br />
completely by side and end plates which may be from 8.20 mm thick.<br />
3.3.1.5 Deformation<br />
As the ship become larger and <strong>hatch</strong>ways take up a greater percentage <strong>of</strong> the deck<br />
area, so the question <strong>of</strong> <strong>hatch</strong>way deformation becomes more important. Traditionally<br />
ships have fairly small <strong>hatch</strong>ways and so have derived a considerable amount <strong>of</strong> their<br />
strength from their decks. As <strong>hatch</strong>ways have increased in width, so the deck’<br />
contribution to the longitudinal and the torsional strength <strong>of</strong> the hull girder has<br />
declined, being limited to the strips <strong>of</strong> deck outboard <strong>of</strong> the coaming and between the<br />
<strong>hatch</strong>es. A ship with <strong>hatch</strong>ways more than 70 percentage <strong>of</strong> the beam in width has<br />
approximately half the torsional rigidity <strong>of</strong> a similar ship with <strong>hatch</strong>ways which are<br />
only 40 percentage <strong>of</strong> the ship’s beam. Compensation in the form <strong>of</strong> thickened plating<br />
and/or box girders may be required.<br />
Fig 3.3 indicates the extent <strong>of</strong> <strong>hatch</strong>way deformation that may be encountered<br />
in a large bulk carrier loaded in alternate holds. Although the deformation is not<br />
excessively large and is not permanent, they can be sufficient to allow sea water to<br />
enter and parts <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> to fracture.<br />
31
Figure 3.3 Detailed analysis <strong>of</strong> the structure <strong>of</strong> a 120,000 tdw bulk carrier<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
It has been suggested that, since <strong>hatch</strong>ways are always closed by <strong>hatch</strong> <strong>cover</strong>s,<br />
the latter ought to be designed to contribute to the strength <strong>of</strong> the hull girder. This is<br />
however not practical as the devices securing the <strong>cover</strong> to the coamings would have to<br />
be excessively robust, and any deformation due to the loading <strong>of</strong> the vessel in port<br />
could lead to the <strong>cover</strong>s becoming jammed and thus impossible to open. Moreover, to<br />
make a significant contribution to vessel’s strength, the <strong>cover</strong>s would have to be<br />
considerably stronger and heavier than at present, and this could introduce operational<br />
difficulties.<br />
Hatch coamings can be designed to contribute to the longitudinal strength <strong>of</strong><br />
the ship but there can be problems associated with this. If it is decided to use the<br />
coaming in this way, they must be continuous over the midship portion <strong>of</strong> the ship and<br />
properly tapered at the forward and after into account in calculating the midship<br />
section modulus, according to classification society requirements.<br />
32
Longitudinal deformation <strong>of</strong> the top <strong>of</strong> the coaming is due to the hogging or<br />
sagging <strong>of</strong> the vessel. It depends on <strong>hatch</strong>way length and may be as much as 7-8 mm<br />
at each end. Longitudinal deformation is compensated for by fitting at the ends <strong>of</strong> the<br />
<strong>hatch</strong> <strong>cover</strong> with wide gaskets whose rubber absorbs the relative movement <strong>of</strong> the<br />
compression bars as the sip works. Hatch end cleats must allow such movements,<br />
which would otherwise be taken up at the cross joint with attendant risk <strong>of</strong> leakage.<br />
Steel to steel contact is must. The purpose <strong>of</strong> this is to prevent the over compression<br />
<strong>of</strong> the gaskets. However, it gives rise to a frictional force whose magnitude depends<br />
on the pressure <strong>of</strong> the <strong>cover</strong> on the coaming bar and their relative movement.<br />
Transverse deformation is caused mainly due to the vessel’s changes in draft<br />
as cargo is worked, but also by hogging and sagging. Deformation <strong>of</strong> as much as 15-<br />
25 mm over the width <strong>of</strong> long <strong>hatch</strong>ways is possible. Relative movement between the<br />
<strong>cover</strong> and the coaming is allowed for in a similar way to longitudinal deformation, by<br />
providing the <strong>cover</strong> with wide gaskets, and by ensuring that the wheels on one side <strong>of</strong><br />
the <strong>hatch</strong> <strong>cover</strong> panels are free to move laterally as shown in fig 3.4<br />
Figure 3.4 Hydrostatic pressure<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
Torsional deformation is caused by the combination <strong>of</strong> non symmetrical<br />
loading <strong>of</strong> the vessel and hydrodynamic forces when the ship heads diagonally into<br />
waves. It can rack the midships <strong>hatch</strong>way diagonal <strong>of</strong> a large container ship by as<br />
33
much as 30 mm. Fig 3.5 shows the torsional distortion and the resultant movement<br />
between the <strong>hatch</strong> <strong>cover</strong> and coaming. By fitting resilient cleats at the ends <strong>of</strong> the<br />
<strong>hatch</strong> <strong>cover</strong>s, some movement between <strong>cover</strong> and coaming takes place, thus reducing<br />
the relative movement between panels.<br />
3.3.2 Seals<br />
Figure 3.5 Torsional distortion <strong>of</strong> <strong>hatch</strong> ways<br />
Source: Cargo Access Equipment for Merchant Ships.<br />
The 1966 LLC requires cargo access openings to be weather tight which is generally<br />
achieved by an arrangement <strong>of</strong> sealing gaskets and drainage channels.<br />
The main requirements <strong>of</strong> sealing system are as follows:<br />
(i) It must prevent any transfer <strong>of</strong> water from outside the ship to the cargo<br />
space,<br />
(ii) On combination carriers, it must be oil tight to prevent any transfer <strong>of</strong><br />
liquid from the inside <strong>of</strong> a cargo space to the outside, when subjected to<br />
the pressures.<br />
(iii) It must be able to maintain the weather tight integrity <strong>of</strong> the cargo space in<br />
all sea states and thus, it must be able to accommodate the deformation<br />
discussed earlier.<br />
(iv) It should be resilient and able to accommodate normal irregularities in the<br />
mating surfaces,<br />
(v) The gasket should be abrasion resistant as it may rub against the mating<br />
surface. It must also be resistant to cargo contact,<br />
(vi) It should be easy to maintain,<br />
34
(vii) It should retain all the above properties throughout a long service life,<br />
exposed to climate extremes.<br />
3.3.2.1 Gaskets material<br />
Gaskets material must be <strong>of</strong> a suitable quality; it should not harden excessively when<br />
subjected to neither sub-zero temperature nor s<strong>of</strong>ten in tropical conditions.<br />
Particularly important in this respect are gaskets fitted to refrigerated vessels.<br />
Most gaskets used for seals on dry cargo ships are <strong>of</strong> natural, synthetic or<br />
neoprene rubber, while combination carriers requires a nitrile composition, resistant to<br />
chemical attack by oil. In general neoprene synthetics have good heat, ageing, weather<br />
and flame resistance, but only moderate oil and chemical resistance but worse cold<br />
temperature properties. General construction <strong>of</strong> seal steel work, welding and painting<br />
needs careful attention.<br />
3.3.2.2 Compression bars<br />
The usual arrangement <strong>of</strong> compression bars is shown. It is <strong>of</strong> rectangular section mild<br />
steel welded to the coaming bar. After several years <strong>of</strong> service, these bars can become<br />
badly corroded and require replacing. Moreover, they may then have sharp corners<br />
which press into the gaskets so that the rubber takes on a permanent set earlier in its<br />
life than would be the case for a sealing arrangement employing either a round<br />
compression bar, as shown or rectangular one with rounded corners. The latter<br />
produces an element <strong>of</strong> ‘knife edge’ loading which gives the good seal with the<br />
rubber. When such compression bars are fitted, they are <strong>of</strong>ten <strong>of</strong> stainless steel, which,<br />
although initially expensive, <strong>of</strong>ten worthwhile as it is not usually necessary to replace<br />
the bar during the life <strong>of</strong> the corners<br />
3.4 CONSTRUCTION MATERIALS<br />
In general, Grade A mild steel is used for the construction <strong>of</strong> all cargo access<br />
equipment. Grade A is the ‘ordinary’ mild steel used for most ship building purposes.<br />
Certain application requires Grades D and E steel. Grade D is notch-tough steel with a<br />
chemical composition largely chosen by the steel producer provided that it retains<br />
good weldability. Grade E steel is the highest grade and is also notch-tough but its<br />
manufacture and composition are strictly controlled. Grades D and E steel are<br />
specified for coaming bars on refrigerated ships where low temperature brittle fracture<br />
35
must be guarded against. As these steels have low corrosion resistances, special<br />
coating, e.g. epoxies, are <strong>of</strong>ten used on the underside <strong>of</strong> <strong>hatch</strong> <strong>cover</strong>s where sweating<br />
can cause accelerated corrosion. Other materials such as higher tensile steel and<br />
aluminium are acceptable to the Classification Societies.<br />
3.4.1 Higher Tensile Steel (HTS)<br />
If the stress level within a structure were the only factor governing its scantlings, the<br />
use <strong>of</strong> higher tensile steel instead <strong>of</strong> mild steel would result in weight savings <strong>of</strong> up to<br />
15 percent. However stress is not the only governing factor. Deflection, minimum<br />
thickness, ease <strong>of</strong> construction, initial and maintenance costs must all be taken into<br />
account. Higher tensile steel (HTS) can sometimes be used for the beams <strong>of</strong> <strong>hatch</strong><br />
<strong>cover</strong>s, with their top plates made from mild steel. This reduces the weight <strong>of</strong> the<br />
<strong>cover</strong>s, without incurring the extra cost <strong>of</strong> using all HTS construction. Thus, HTS is<br />
sometimes used on <strong>hatch</strong> <strong>cover</strong>s where, by reducing the <strong>cover</strong> weight slightly, it may<br />
be possible to install less powerful operating mechanism. Construction entirely in<br />
HTS is sometimes used in pontoon <strong>cover</strong>s for container ships, to keep their weight<br />
below the maximum lifting capacity <strong>of</strong> container cranes.<br />
3.4.2 Aluminium<br />
Aluminium structures can be 55-60 percent lighter than equivalent mild steel<br />
structures. Most <strong>of</strong> the problems associated with higher tensile steel are not present<br />
with aluminium. Since it is not as strong as steel, thickness have to be increased,<br />
thereby alleviating problems associated with minimum regulatory deflection, buckling<br />
etc., unless the design is such that deflection is significant. Welding aluminium does<br />
however require special skills and equipment. Corrosion is less <strong>of</strong> a problem if the<br />
correct grade <strong>of</strong> material is used and if precaution are taken where steel and<br />
aluminium meet, e.g. at coamings. The spacing <strong>of</strong> stiffeners can be increased in an<br />
aluminium structures this has the added advantage that the number <strong>of</strong> stiffeners and<br />
hence the weight and cost <strong>of</strong> the structure can be further reduced. The major<br />
disadvantage <strong>of</strong> aluminium is that a suitable grade <strong>of</strong> material for access equipment<br />
costs approximately eight times as much per tonne as mild steel, with the overall<br />
effect <strong>of</strong> increasing the cost <strong>of</strong> the <strong>cover</strong> by upto three times.<br />
Aluminium <strong>cover</strong>s have been fitted to deep tanks because they are so much<br />
lighter. Since deep tank <strong>cover</strong>s are <strong>of</strong>ten made in one piece, aluminium <strong>cover</strong>s are<br />
36
easier to handle without power assistance. Aluminium single <strong>pull</strong> weather deck <strong>cover</strong>s<br />
have occasionally been fitted in the past, sometimes experimentally. Aluminium can<br />
be used for Ro-Ro vessel access equipment but it is usually limited to small ramps and<br />
car decks. It is less resistant to fire damage than steel.<br />
3.4.3 Glass Reinforced Plastic (GRP)<br />
GRP structures are light but the modulus <strong>of</strong> elasticity <strong>of</strong> GRP is only 7 percentages <strong>of</strong><br />
that <strong>of</strong> mid steel and excessive deflection is a problem which invariably accompanies<br />
its use. Additional stiffening is thus necessary, making the structure heavier and more<br />
expensive to manufacturer. For this reason GRP has not as yet found wide application<br />
in the construction <strong>of</strong> cargo access equipment, although development work is in<br />
progress. GRP in ‘sandwich’ construction could be particularly suitable for <strong>cover</strong>s in<br />
refrigerated ships because insulation can be built into them during the manufacturing<br />
process at very little extra cost, whereas the present system <strong>of</strong> insulating steel <strong>cover</strong>s<br />
is expensive and time consuming.<br />
3.4.4 Wood<br />
Wooden <strong>cover</strong>s no longer supplied to weather decks <strong>of</strong> new cargo ships, although on<br />
rare occasions, they are fitted in tween decks. Classification society rules lay down<br />
scantling for beam and boards <strong>cover</strong>s because <strong>of</strong> LLC requirements; in practice they<br />
care now mainly for the benefit <strong>of</strong> repair to older ships.<br />
37
CHAPTER 4 - OPERATIONAL AND SAFETY ASPECTS<br />
4.1 BASIC ADVICE<br />
There are procedures which will help to keep ship’s <strong>hatch</strong> <strong>cover</strong>s in good condition.<br />
The following advice can be considered best practice.<br />
4.1.1 Always<br />
� Carry out regular examination <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong>s, <strong>hatch</strong> beams and coamings<br />
to identify:<br />
o General levels <strong>of</strong> corrosion (check with your classification society for<br />
corrosion allowances);<br />
o localised corrosion at welded connections (grooving);<br />
o Cracks in joints and weld metal;<br />
o Permanent distortion <strong>of</strong> plating and stiffeners;<br />
� Call a Class Surveyor and carry out repairs as soon as possible when there are:<br />
o Indications <strong>of</strong> excessive corrosion e.g. holes or local buckling <strong>of</strong> the<br />
top plate;<br />
o Cracks in main structural joints;<br />
o Areas <strong>of</strong> significant indentation, other than localised mechanical<br />
damage;<br />
� Be particularly vigilant after heavy weather;<br />
� Rectify any steel-to-steel fault before renewal <strong>of</strong> rubber packing. Renewal will<br />
not be effective if steel-to-steel contact points are defective, and expensive<br />
rubber packing will be ruined after only a few months <strong>of</strong> use;<br />
� Replace missing or damaged <strong>hatch</strong> gaskets (rubber packing) immediately. The<br />
minimum length <strong>of</strong> replaced gasket should be one metre;<br />
� Keep <strong>hatch</strong> coaming tops clean and the double drainage channels free <strong>of</strong><br />
obstructions. (Open <strong>hatch</strong> <strong>cover</strong>s to clean coaming tops and the double<br />
drainage channels after loading bulk cargo through grain or cement ports);<br />
� Keep cleats and wedges in serviceable condition and correctly adjusted;<br />
� Keep hauling wires and chains adjusted correctly;<br />
� Attach locking pins and chains to open doors and <strong>hatch</strong>es;<br />
38
� Keep wheels, cleats, hinge pins, haul wires, and chain tension equipment well-<br />
greased;<br />
� Test hydraulic oil regularly for contamination and deterioration;<br />
� Keep hydraulic systems oil tight;<br />
� Ensure the oil tank <strong>of</strong> the hydraulic system is kept filled to the operating level<br />
and with the correct oil;<br />
� Clean up oil spills. If the leak cannot be stopped immediately, construct a<br />
save-all to contain the oil and empty it regularly;<br />
� Engage tween deck <strong>hatch</strong> <strong>cover</strong> cleats when the panels are closed;<br />
� Give notice that maintenance is being performed so that no one tries to<br />
open/close the <strong>hatch</strong>;<br />
� Remember that continuing and regular maintenance <strong>of</strong> <strong>hatch</strong>es is more<br />
4.1.2 Never<br />
effective and less expensive than sporadic inspection and major repair.<br />
� Treat temporary repairs as if these were permanent. The strength <strong>of</strong> the <strong>cover</strong><br />
and ultimately the ship will depend on the quality <strong>of</strong> repairs carried out;<br />
� Ignore serious corrosion, cracking or distortion in the <strong>cover</strong>s and supports.<br />
These are signs <strong>of</strong> weakness and are potentially hazardous;<br />
� Allow grooves to form in the coaming top, especially where the <strong>hatch</strong> side or<br />
end panel rests when the <strong>hatch</strong> is closed;<br />
� Apply petroleum-based grease or paint to rubber packing;<br />
� Remove the rubber ball from a non-return drain valve;<br />
� Use anything other than the recommended hydraulic oil;<br />
� Leave cleats unfastened when proceeding to sea;<br />
� Attempt to open or close any <strong>hatch</strong> that has a load or cargo on it;<br />
� Open <strong>hatch</strong> <strong>cover</strong>s at sea unless absolutely essential;<br />
� Leave open <strong>cover</strong>s unattended when at sea;<br />
� Tighten down the cleats so that the <strong>hatch</strong> <strong>cover</strong> is unable to move on the<br />
coaming top.<br />
39
4.2 MONITORING AND INSPECTION<br />
Hatch <strong>cover</strong>s and their fittings should be inspected at the end <strong>of</strong> every cargo voyage<br />
and all findings recorded. Inspections should be planned and held in time for repairs<br />
to be completed before the next cargo voyage. Empty cargo spaces <strong>of</strong> all cargo and<br />
combustible material if welding torches are used.<br />
4.2.1 Inspect and Check:<br />
� Condition, Covers and coamings should be well painted and free from<br />
significant corrosion, cracks and distortion. During an inspection look for:<br />
o Holes and permanent distortion in the plating<br />
o Distortion <strong>of</strong> beams and/or stiffeners on the underside <strong>of</strong> the top plate<br />
o Corrosion around welded connections <strong>of</strong> beams or stiffeners<br />
o cracking <strong>of</strong> connecting joints and welds<br />
� Hatch movement. This should be smooth. If violent movement is observed,<br />
investigate and remove the cause.<br />
� Towing and backhaul wires. These should be free <strong>of</strong> kinks or broken strands.<br />
Repair or replace damaged or worn wires. Use extreme care when handling<br />
wires to avoid injury.<br />
� Hydraulic system for leakage.<br />
� Hinge pins. Look for wear, particularly at cross-joints and hydraulic cylinders.<br />
Worn hinge pins can cause <strong>hatch</strong>es to slew and misalign at the cross-joint(s).<br />
Misaligned <strong>hatch</strong> panels will leak.<br />
� Drive chain tensioners. Check their condition and adjustment.<br />
� Cleats and wedges. Check for physical damage, corrosion and tension when<br />
locked.<br />
Figure 4.1 panel should be in line with next panel<br />
Source: Lloyd’s Register- A Master’s Guide to Hatch Cover Maintenance<br />
40
4.2.2 Drive Chains; Check their Length<br />
Drive chains and associated equipment are fitted in pairs, opposite one another. The<br />
side towing chains, sprockets and hydraulic cylinders on opposite sides should match.<br />
Adjust the tension <strong>of</strong> chains between panels so that the chains on both sides are<br />
exactly the same length. Do this by removing or adding chain links. If the entire<br />
length <strong>of</strong> chain needs to be replaced, then replace the chains on both sides at the same<br />
time. Always consult the <strong>hatch</strong> <strong>cover</strong> manufacturer for details <strong>of</strong> chain length. As a<br />
rule, chain sag, measured from the assumed horizontal at mid-point along the chain,<br />
should be a fist wide.<br />
4.2.3 Steel Landing Pads; Check for Wear<br />
Worn landing pads will damage <strong>hatch</strong> gaskets and cause <strong>hatch</strong> leakage. When newly<br />
fitted and closed in the sea position, the top plates <strong>of</strong> adjacent <strong>hatch</strong> panels should be<br />
level. Any deviation from level is an indication <strong>of</strong> landing pad wear or permanent<br />
distortion. If noted, investigate fully and repair immediately.<br />
4.2.4 End Stop Pads; Check for Damage<br />
End stop pads prevent <strong>hatch</strong> panels from overrunning when <strong>hatch</strong>es are fully open.<br />
Look for physical damage.<br />
4.2.5 Hatch Wheels; Check for Alignment<br />
Hatch wheels should align squarely with the <strong>hatch</strong> track way. If the wheel axle is<br />
worn the wheel will loll. If it does, repair immediately.<br />
4.2.6 Rubber Seals; Check for Elasticity, Mechanical Damage and Permanent<br />
Deformation<br />
When <strong>hatch</strong>es are opened, rubber seals should regain their original shape. If they do<br />
not, check for ageing. Permanent deformation should not exceed 75 percent <strong>of</strong> the<br />
design compression.<br />
4.2.7 Locking Devices and Hydraulic Cut-Outs; Check that they Operate<br />
Locking devices are <strong>of</strong>ten pins or hooks, these should engage when the <strong>hatch</strong> is open.<br />
Look for physical damage, rusting and seizure. Hydraulic cut-outs should move<br />
freely.<br />
41
4.2.8 Spares<br />
Rubber packing and adhesive has a limited shelf life, so check the date stamp and<br />
discard if beyond the use-by date. There should be sufficient spare parts (cleats,<br />
wedges and gaskets) to complete planned routine maintenance. Always use<br />
manufacturers’ approved spare parts.<br />
4.3 HEAVY WEATHER PRECAUTIONS<br />
The following precautions should be taken if rough or heavy weather or when high<br />
swells are expected or when it is likely that water will be shipped on deck.<br />
4.3.1 Prior To Rough Weather:<br />
� Check that <strong>hatch</strong> cleats are properly secured and adjusted. In rough weather,<br />
hulls are subjected to high racking forces, so it is essential that <strong>hatch</strong> <strong>cover</strong>s<br />
are held in place but allowed to flex.<br />
� Check that all drain valves are operating correctly and that they are open.<br />
Drain valves are the last defence against water entering the cargo space. The<br />
drainage system will be needed during heavy weather, so it must be fully<br />
operational.<br />
� As a precaution, briefly pressurise the hydraulic system to ensure that it is<br />
fully charged and that the piping is filled with oil. This has two benefits, first,<br />
it prevents the possibility <strong>of</strong> seawater entering loose couplings or seals, and<br />
secondly, it eliminates any creep which may have occurred.<br />
4.3.2 After Rough Weather:<br />
� Inspect all cleats, drain valves, guides and hydraulic components for damage.<br />
If hydraulic components have been damaged, do not attempt to open the<br />
<strong>cover</strong>s. The emergency opening procedure should be followed until the<br />
hydraulic components have been checked and tested.<br />
� Check <strong>hatch</strong> <strong>cover</strong>s for buckling or distortion.<br />
� When opening the <strong>hatch</strong> <strong>cover</strong>s check for uneven movement and any unusual<br />
noises that may indicate damage.<br />
� Check all grease points and re-grease.<br />
42
Figure 4.2 Vessel in rough weather<br />
Source: Lloyd’s Register- A Master’s Guide to Hatch Cover Maintenance<br />
4.4 SAFETY WHEN WORKING WITH HATCH COVERS<br />
The avoidance and prevention <strong>of</strong> injuries is <strong>of</strong> paramount importance. Before working<br />
on a <strong>hatch</strong>, a risk assessment should be completed to identify all hazards. Control and<br />
safety procedures should be examined and modified so that hazards are reduced to<br />
minimal levels.<br />
The following points should be borne in mind:<br />
� If entering the hold alone, always ensure someone else knows you are there<br />
and leave a prominent notice at the hold entrance.<br />
� Check the lock-back mechanism on the hold access door or manhole is<br />
operational figure 4.3.<br />
43
Figure 4.3 Check the lock-back mechanism<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
� Do not use damaged or unsecured ladders, accept in emergencies and then<br />
only with a secured safety harness (figure 4.4).<br />
� Check lighting is adequate particularly at the bottom <strong>of</strong> the ladder. If the hold<br />
is unlit, use a powerful torch attached to a sling or strap across the shoulder.<br />
Figure 4.4 Do not use damaged or unsecured ladders<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
44
Figure 4.5 Never smoke in a hold.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
Figure 4.6 Never climbs on top <strong>of</strong> bulk cargo without a lifeline<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
� Always have both hands free for climbing up or down ladders; lower or haul<br />
tools and equipment by rope.<br />
45
Figure 4.7 Never carry tools or equipments while descending or ascending a ladder.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
Figure 4.8 Never stand on the coaming top when the <strong>hatch</strong> <strong>cover</strong>s are open.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
� Always wear protective boots or shoes for working on deck.<br />
� Do not stand under openings.<br />
46
Figure 4.9 Always wear protective headgear when working.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
� Always clean up oil spills. If the leak cannot be immediately stopped, build a<br />
save-all around and regularly empty it.<br />
� Exercise extreme care when handling wires.<br />
Figure 4.10 inspect wire for wear, kinking or broken strands at regular intervals.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
47
Figure 4.11 Always takes precautions when fumigating.<br />
Source: A.Bilbrough & Co. Ltd., Holds and Hatch Covers<br />
4.5 Procedures to Open and Close Hatch Covers<br />
Prior to opening or closing a <strong>hatch</strong>, the watch <strong>of</strong>ficer should be informed and the<br />
condition <strong>of</strong> the hauling wires or chains checked; the hydraulic system should be<br />
topped up. Never open or close more than one set <strong>of</strong> <strong>hatch</strong> <strong>cover</strong>s at a time.<br />
4.5.1 Opening Procedures<br />
� Check that the <strong>hatch</strong> <strong>cover</strong> panel stowage area is clear <strong>of</strong> people, equipment<br />
and dunnage;<br />
� Disengage all cleats;<br />
� Attach towing or hauling wires; switch the power on and ensure the controls<br />
are in neutral;<br />
� Ensure that all personnel are clear <strong>of</strong> the <strong>hatch</strong> and its tracking. Position<br />
crewmembers to observe both sides <strong>of</strong> the <strong>hatch</strong>;<br />
� Raise <strong>hatch</strong> <strong>cover</strong>s to the roll position by jacks or by raising the lifting system.<br />
(The panels need to clear the <strong>hatch</strong> guides);<br />
� Check that towing chains are free and do not foul tracks or the coaming top;<br />
� Start to open the <strong>hatch</strong>, slowly at first, then at normal operating speed until the<br />
<strong>hatch</strong> is almost open and then reduce to slow speed until fully open. Care must<br />
48
e taken when opening <strong>hatch</strong> <strong>cover</strong>s especially when the speed <strong>of</strong> opening can<br />
be only partially controlled;<br />
� When fully open, secure the <strong>hatch</strong> with the safety hook or pin before the<br />
power is switched <strong>of</strong>f.<br />
If applicable, remove the towing and hauling wires;<br />
� Install portable safety rails, if supplied.<br />
4.5.2 Closing Procedures<br />
� Check that the coaming top is clear <strong>of</strong> cargo or debris;<br />
� Check and clear drain channels and entrances to the drain valves;<br />
� Check that any damaged wheel tracks, compression bars and landing pads<br />
have been repaired;<br />
� Ensure that the hold is clear <strong>of</strong> people and that access <strong>hatch</strong>es or entrance<br />
doors are open. Check towing chains are free;<br />
� Attach towing or hauling wires, switch the power on and ensure the controls<br />
are in neutral;<br />
� Remove portable handrails;<br />
� Release <strong>hatch</strong> locking pins or hooks;<br />
� Avoid injuries by ensuring that all personnel are clear <strong>of</strong> the <strong>hatch</strong>. Position<br />
crewmembers to observe both sides <strong>of</strong> the <strong>hatch</strong>;<br />
� Check that towing chains are free and do not foul tracks or the coaming top;<br />
� Start to close the <strong>hatch</strong>es slowly at first with the speed <strong>of</strong> closure being<br />
gradually increased to the normal operating speed. As the <strong>hatch</strong> reaches the<br />
closed position the speed should be gradually reduced. Great care must be<br />
taken when closing <strong>hatch</strong> <strong>cover</strong>s;<br />
� Lower <strong>hatch</strong> <strong>cover</strong>s into guide pockets using jacks or lifting cylinders. Some<br />
<strong>hatch</strong>es are lowered automatically;<br />
� Attach cleats before removing the towing wire or switching power <strong>of</strong>f;<br />
� Finally, check no one is in the hold before closing hold access <strong>hatch</strong>es or other<br />
hold entry points.<br />
49
4.6 Maintenance and Repair<br />
Poor maintenance <strong>of</strong> <strong>hatch</strong> <strong>cover</strong>s causes leakage leading to cargo damage and<br />
represents a hazard to the ship and its crew. Although <strong>hatch</strong> <strong>cover</strong>s are simple and<br />
durable, their sealing gaskets are easily damaged. The quality <strong>of</strong> sealing is affected by<br />
lack <strong>of</strong> alignment and poor gasket compression. When <strong>hatch</strong> <strong>cover</strong>s are opened at the<br />
end <strong>of</strong> an ocean voyage, look for signs <strong>of</strong> leakage such as rust staining or drip marks.<br />
Regular adjustment and repair, by ship’s staff, will reduce the overall cost <strong>of</strong><br />
maintenance. Painting double drainage channels will help to prevent corrosion.<br />
Always keep a detailed record <strong>of</strong> maintenance. Take care during extensive<br />
<strong>hatch</strong> <strong>cover</strong> repair to avoid <strong>cover</strong> distortion.<br />
4.6.1 Rubber Gaskets<br />
Keep clean and free from paint. If physically damaged, permanently set-in or aged,<br />
replace with minimum 1 metre lengths. Always follow the manufacturer’s instructions<br />
when renewing gaskets.<br />
4.6.2 Gasket Channels<br />
If gasket channels are badly corroded, causing the <strong>hatch</strong> packing to hang loose, the<br />
packing should be removed and the channel repaired by welding new metal strips<br />
which should be painted before fitting new rubber. Always follow proper fire<br />
prevention safety procedures. Make sure that cargo spaces are free <strong>of</strong> cargo and<br />
combustible material. When conducting extensive structural repairs, remove the <strong>hatch</strong><br />
<strong>cover</strong>s to shore.<br />
4.6.3 Hatch Cover Structure<br />
Repair or replace any damaged, worn or defective <strong>hatch</strong> <strong>cover</strong>s or coamings. Consult<br />
with the ship’s classification society before commencing repair. Paint new structure<br />
immediately.<br />
4.6.4 Compression Bars<br />
Effective sealing is only possible with a straight, undamaged and non-corroded<br />
compression bar. Compression bars which are not in this condition should be repaired<br />
or replaced, taking care to align the bars properly.<br />
50
Remember to carry out a chalk test to check alignment, both during and after repair.<br />
4.6.5 Landing Pads<br />
Hatch sealing is arranged by design to give the correct compression <strong>of</strong> the gasket<br />
when there is metal-to-metal contact on the <strong>hatch</strong> landing pad, side plate, or inter-<br />
panel block. If landing pads are reduced in height (check with manufacturers’<br />
drawings) because <strong>of</strong> wear, repair is essential.<br />
4.6.6 Hatch Wheel Track Ways<br />
Track ways can corrode. They are weakened by abrasive wear and tear. When<br />
weakened, track ways can distort and break, affecting <strong>hatch</strong> movement and alignment.<br />
Deterioration is visible to the naked eye. Repair by replacing the worn or damaged<br />
material with sufficient new material to restore strength. Always keep <strong>hatch</strong> wheel<br />
track ways clean and painted.<br />
4.6.7 Hatch Coamings<br />
Look for cracks at coaming corners. If any are found, consult the ship’s classification<br />
society before commencing repairs in case the coaming needs to be reinforced.<br />
Examine coaming support brackets for corrosion where they connect with the<br />
ship’s deck. Make sure coamings and their support brackets are painted.<br />
Coamings can be damaged by cargo equipment during loading or discharge.<br />
Look out for damage and repair if found.<br />
4.6.8 Hatch Cleats and Wedges<br />
It is important for compression washers to be adjusted correctly. A locking nut for<br />
adjusting compression is situated at the base <strong>of</strong> the cleat. The procedure to alter<br />
compression (see illustrations) is as follows:<br />
� Close <strong>hatch</strong> and secure for sea;<br />
� Place the cam <strong>of</strong> the cleat in the <strong>hatch</strong> socket as if to lock it, but leave it<br />
unlocked (the cam should move freely and fit snugly in its housing);<br />
� Adjust the locking nut until the compression washer touches the underside <strong>of</strong><br />
the <strong>hatch</strong> coaming or its steel washer;<br />
� Turn the locking nut one full turn to achieve the desired tension;<br />
51
� Do not over-tighten;<br />
� Protect the thread on completion.<br />
When closing and securing a <strong>hatch</strong> for sea passage, check the tension in side<br />
cleats. Cleats should never be adjusted in isolation, adjust all cleats along the <strong>hatch</strong><br />
skirt at the same time.<br />
4.6.9 Hatch Cross-Joints<br />
It is essential for the cross-joint to be in good condition and properly aligned.<br />
Maintenance and repair should focus on:<br />
� Examination <strong>of</strong> the cross-joint structure for corrosion.<br />
� Examination <strong>of</strong> joint hinges for pin wear, blade cracking or weld failure.<br />
(Re-grease the hinge pin bushes making sure grease reaches the hinge pins).<br />
� Examination <strong>of</strong> the steel-to-steel inter-panel blocks and locators for wear.<br />
(Check the top plate <strong>of</strong> <strong>hatch</strong> panels, they should be level when closed).<br />
� Checking the gap between panels when they are closed. Misalignment could<br />
be caused by an incorrectly adjusted cylinder or the wheel tracks could be<br />
worn.<br />
4.6.10 Hatch Wheels<br />
Hatch wheel spindles and bearings (where fitted) need to be greased regularly. Check<br />
the wheel spindle for wear and the wheel housing for physical damage. Repair if the<br />
spindle is worn or if the wheels are out <strong>of</strong> alignment.<br />
4.6.11 Drain Channels and Non-Return Valves<br />
Clean coaming tops and cross-joint channels by removing any loose scale or cargo<br />
residue by brushing or hosing. Clean coaming drain holes and check that the non-<br />
return valve is functioning.<br />
4.6.12 Greasing<br />
Wheel spindles, cleat spindles, hinge pins, hydraulic cylinder protective sheaths, cleat<br />
wedges, drive chain sprockets, toothed rack and cylinder spherical bearings need to be<br />
kept well-greased. Re-grease every month if necessary, and always apply new grease<br />
after the ship has passed through heavy weather.<br />
52
4.6.13 Painting<br />
Corrosion occurs mainly at the panel ends along the cross-joint or where access is<br />
difficult, but it can also occur on the underside <strong>of</strong> a panel, especially along <strong>hatch</strong><br />
beams. Regular painting will be necessary.<br />
4.6.14 Inert Gas<br />
Hatch <strong>cover</strong>s with a double skin, in the form <strong>of</strong> a closed box, are filled with inert gas.<br />
After structural repair, the inner spaces must be re-inerted. This is done by inserting<br />
special tablets (available from the <strong>hatch</strong> <strong>cover</strong> manufacturer) into the space and<br />
welding shut. Never allow water to penetrate the box construction.<br />
4.6.15 Hydraulic Systems and Components<br />
The cleanliness and viscosity <strong>of</strong> hydraulic oil must be checked. Samples <strong>of</strong> the oil<br />
should be sent to a chemist for testing (use the same company that checks and tests<br />
your fuel and lubricating oil). The hydraulic system is provided with bleed points<br />
from which samples can be taken.<br />
Hydraulic oil should be changed every five years or after there have been<br />
significant repairs, such as piping or cylinder replacement.<br />
Hydraulic oil filters should be changed every twelve months. Do not<br />
contemplate repairing the hydraulic system without the proper components and skilled<br />
fitters.<br />
4.6.16 Use <strong>of</strong> Sealing Tape and Foam Fillers<br />
The use <strong>of</strong> sealing tape and foam fillers should be limited to:<br />
� Emergency use. When <strong>hatch</strong>es are known or thought to be leaking and there is<br />
insufficient time to complete permanent repairs;<br />
� Charterers’ requirement. Charterers may require owners to apply sealing tape<br />
when highly water-sensitive cargoes are carried;<br />
� Fumigation tape is usually applied to <strong>hatch</strong> <strong>cover</strong>s during fumigation. The tape<br />
is not heavy duty and should be removed when fumigation has finished.<br />
Foam fillers can be used to fill the air space which is formed along the cross-<br />
joint <strong>of</strong> two closed panels. In heavy weather foam fillers may be washed away, their<br />
use should never be solely relied upon to prevent water ingress.<br />
53
CHAPTER 5-SINGLE PULL MACGREGOR TYPE<br />
HATCH COVER DESIGN<br />
The <strong>hatch</strong> <strong>cover</strong> must be safe to operate, and it must be cost effective, both as an<br />
initial investment and in service, i.e. the maintenance cost has to be low and the<br />
service lifelong. Furthermore, the design <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> must suit the various<br />
general arrangements <strong>of</strong> vessels.<br />
<strong>Single</strong> <strong>pull</strong> <strong>cover</strong><br />
1. Rising track.<br />
2. Panel side chains.<br />
3. Falling track (behind coaming).<br />
4. Balancing roller.<br />
5. Eccentric wheel.<br />
6. Screw cleat.<br />
7. Wheel guide rail.<br />
8. Compression bar.<br />
9. Coaming bar, Coaming stiffener.<br />
10. Coaming <strong>hatch</strong> stay.<br />
Figure 5.1: <strong>Single</strong> Pull MacGregor Type Hatch Cover<br />
Source: Internet<br />
54
11. Coaming.<br />
12. Sheave.<br />
13. Cross joint cleat.<br />
14. Panel top plate.<br />
15. Backhaul wire.<br />
16. Wire to winch or crane hook; bull wire.<br />
17. Rubber gasket.<br />
18. Stowage bay.<br />
The model <strong>of</strong> MacGregor single <strong>pull</strong> <strong>hatch</strong> <strong>cover</strong> is obtained from the ship<br />
named M V IRAN owned by Islamic Republic <strong>of</strong> Iran Shipping. This was a bulk<br />
carrier which was used to carry sacks <strong>of</strong> cement in bulk .There were 4 cargo holds in<br />
this ship using MacGregor single <strong>pull</strong> <strong>hatch</strong> <strong>cover</strong>. Team selected the first cargo hold<br />
and its dimensions and reduced to a convenient ratio <strong>of</strong> 1:25 to make the project.<br />
DESIGN BASIS<br />
NAME : M V IRAN<br />
OWNER : ISLAMIC REPUBLIC OF IRAN<br />
GENERAL CHARACTERISTICS<br />
SHIPPING<br />
CLASS AND TYPE : BULK CARRIER<br />
TONNAGE : 44,468 DWT<br />
LENGTH : 199.50 METER<br />
BEAM : 30 METER<br />
DRAUGHT : 11 METER<br />
DEPTH : 16.0 METER<br />
INSTALLED POWER : 8238 KW<br />
PROPULSION : ONE FIXED PROPELLER<br />
SPEED : 15.25 KNOTS<br />
CAPACITY : 54237M³<br />
NO OF HOLDS 4<br />
HOLD DIMENSION IN METERS<br />
HOLD NO 1 : 37.5 × 30 × 16<br />
HOLD NO 2 : 32.5 × 30 × 16<br />
HOLD NO 3 : 32.5 × 30 × 16<br />
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HOLD NO 4 : 37.5 × 30 × 16<br />
HATCH OPENINGS IN METER : 18.65 × 11<br />
NO OF PANTOONS : 4<br />
TYPE : SINGLE PULL MACGREGOR TYPE<br />
NOTE : SACK CARRIER<br />
5.1 PARTS DESIGN<br />
After studying all the <strong>hatch</strong> <strong>cover</strong>s and their safety and operational aspects, team<br />
which comprise <strong>of</strong> six persons decided to design a working model <strong>of</strong> a single <strong>pull</strong><br />
MacGregor <strong>type</strong> <strong>hatch</strong> <strong>cover</strong>. The various design aspects are given in this chapter.<br />
5.1.1 Hold Design<br />
The hold design was selected from the cargo hold no 1 <strong>of</strong> the M V IRAN ship. The<br />
model was made in a convenient ratio 1: 25.<br />
Length <strong>of</strong> the hold: 150cm<br />
Width <strong>of</strong> the hold: 120cm<br />
Depth <strong>of</strong> the hold: 63.3cm<br />
Plate thickness: 1.5cm<br />
5.1.2 Hatch Opening Dimensions<br />
Figure 5.2: Hold Design<br />
Source: Team<br />
The <strong>hatch</strong> opening dimension was exactly followed from cargo hold no 1.<br />
Length: 74.6cm<br />
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Breadth: 44.5cm<br />
5.1.3 Hatch Coaming Design<br />
Figure 5.3: Hatch Opening Dimensions<br />
Source: Team<br />
The <strong>hatch</strong> coaming design is made from the ship after looking the minimum<br />
requirements stated in the load line convention.<br />
Height: 10.3cm<br />
Height <strong>of</strong> <strong>hatch</strong> coaming stay: 8.3<br />
Width <strong>of</strong> <strong>hatch</strong> coaming stay: 2cm<br />
Thickness <strong>of</strong> <strong>hatch</strong> coaming stay: 1cm<br />
Supported area: 14.3cm<br />
Figure 5.4: Hatch Coaming Design<br />
Source: Team<br />
57
Number <strong>of</strong> coaming <strong>hatch</strong> stay in end coaming: 3<br />
Number <strong>of</strong> coaming <strong>hatch</strong> stay inside coaming: 4<br />
Support for coaming (inside): 7.6×7.6 cm square<br />
Number <strong>of</strong> supports in end coaming (inside): 3<br />
Number <strong>of</strong> support in side coaming (inside): 4<br />
Thickness <strong>of</strong> the support: 2cm<br />
Length between supports: 20cm<br />
Thickness <strong>of</strong> rubber gasket: 1cm<br />
5.1.4 Hatch Cover Design<br />
The model consists <strong>of</strong> four Pantoons whose design was taken from the ship Pantoons<br />
design.<br />
Length: 58cm<br />
Width: 23cm<br />
Thickness at middle: 3cm<br />
Thickness at edge: 2cm<br />
Figure 5.5: Hatch Cover Design<br />
Source: Team<br />
58
Slope: 1cm<br />
Total number <strong>of</strong> panels: 4<br />
Numbers <strong>of</strong> sliding wheels: 4 in each panel<br />
Diameter <strong>of</strong> sliding wheels: 2cm<br />
Wheel to wheel length: 19cm<br />
Numbers <strong>of</strong> balancing rollers: 2 in each panel<br />
Diameter <strong>of</strong> balancing rollers: 3cm<br />
Length between balancing roller: 20.3cm<br />
Type <strong>of</strong> connection in between two panel: Chain<br />
Chain length between two panel: 20.3cm<br />
Chain size: 0.7cm<br />
Size <strong>of</strong> chain connector: 4.5cm<br />
5.1.5 Track 1 Design<br />
The tracks design was taken from the Design features <strong>of</strong> the MV IRAN ship.<br />
Length: 85cm<br />
Width: 2.54cm<br />
Figure 5.6: Track Design<br />
Source: Team<br />
59
5.1.6 Rising Track Design (Track 2)<br />
The rising track design was taken from the ships track design <strong>of</strong> MV IRAN.<br />
Overall length: 66.5cm<br />
Slanting height: 14 cm<br />
Straight length: 46.5 cm<br />
Peak height from the deck: 16cm<br />
5.1.7 Jack Design<br />
Figure 5.7: Rising Track Design<br />
Source: Team<br />
Since the eccentric wheel is not available for the model size, alternate arrangement for<br />
lifting the track was made using hydraulic jack. Since the team were not designing the<br />
hydraulic jack, the same <strong>of</strong> appropriate size and adequate power was brought from the<br />
market as per the instructions from project guide and team decision<br />
Figure 5.8: Jack Design<br />
Source: Team<br />
60
Height <strong>of</strong> jack while normal condition: 15cm<br />
Height <strong>of</strong> jack while lifted condition: 18cm<br />
Lift <strong>of</strong> jack: 3cm<br />
Capacity <strong>of</strong> jack: 2000kg<br />
5.1.8 Crane Space Design<br />
The design <strong>of</strong> the crane space was taken directly from the ship.<br />
Height: 35.5cm<br />
Length: 50cm<br />
Breadth: 12.3 cm<br />
Pulley height from weather deck: 32.5cm<br />
Figure 5.9: Crane Space Design<br />
Source: Team<br />
Angle <strong>of</strong> <strong>pull</strong>ey fitted related to base: 40 degree<br />
5.1.9 Motor Casing<br />
The motor casing was designed according to the motor dimensions.<br />
Length: 24.5cm<br />
Height: 25cm<br />
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Breadth: 10.7cm<br />
5.1.10 Motor Specifications<br />
The motor was selected according to the power required to roll the pantoons over the<br />
track and to <strong>pull</strong> the pantoons back to position. The motor selection was made after<br />
several trials.<br />
Voltage: 240 V<br />
Current: 12mA<br />
Phase: single phase<br />
Frequency: 50 Hz<br />
Power: 0.003 HP<br />
Torque: 3.5cm<br />
Capacitor: .82 K<br />
Shaft diameter: 1cm<br />
Forward reverse switch: 240 V; 5 Ampere<br />
Push button: 240 V; 5 Ampere<br />
5.1.11 Pulley Design<br />
The <strong>pull</strong>ey was selected according to the dimension <strong>of</strong> wire rope and the power<br />
required for opening and closing the <strong>hatch</strong> <strong>cover</strong>.<br />
Pulley fitted to the motor:<br />
Diameter: 8cm<br />
Numbers: 2<br />
Width: 3cm<br />
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Pulley for rope<br />
Diameter: 2cm<br />
Width: 1cm<br />
Numbers: 2<br />
5.1.12 Rope<br />
The rope was selected according to the safe working load <strong>of</strong> the model.<br />
Length: 300cm<br />
Diameter: 3mm<br />
5.1.13 Reduction Gear Design<br />
The selected motor was 60 rpm speed and for the correct working <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong>,<br />
the team designed the reduction gear to reduce the speed into 13 rpm.<br />
Number <strong>of</strong> teeth in bigger gear: 66<br />
Number <strong>of</strong> teeth in smaller gear: 13<br />
Actual speed: 60 rpm<br />
Reduced speed:<br />
5.1.14 Ladder Design<br />
×60=11.81(12rpm)<br />
The ladder design was taken from the MV IRAN Ship.<br />
Height: 36cm<br />
Width: 4.7cm<br />
Numbers <strong>of</strong> steps: 11<br />
Gap between steps: 3.5cm<br />
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5.1.15 Bulwark Design<br />
Figure 5.10: Ladder Design<br />
Source: Team<br />
The design <strong>of</strong> the hand rail was taken according to the convenience.<br />
Figure 5.11: Bulwark<br />
Source: Team<br />
64
Height from the deck: 7.2cm<br />
Height to the first cross bar: 3.2cm<br />
Gap between bars: 4cm<br />
Cross bar diameter: 0.4cm<br />
5.2 MATERIAL SELECTION<br />
The material was selected according to the availability in the market and for the easy<br />
fabrication process. The material was also chosen by considering economic limits.<br />
After all discussions with the team members and project guide, for the successful<br />
fabrication <strong>of</strong> the model the team decided to choose the following materials:<br />
Cargo hold : Ply Wood<br />
Hatch Coaming : Wood<br />
Hatch Stay : Wood<br />
Pantoons : Wood<br />
Sliding Wheels : Plastic<br />
Balancing Wheels : Mild Steel<br />
Chain : Metallic<br />
Chain Connector : Galvanised Sheet<br />
Track : Aluminium<br />
Rising Track : Mild steel<br />
Rope : Iron<br />
Track Support : Cast Iron<br />
Motor Casing : Ply Wood<br />
Pulley : 2 Plastics, 2 Copper<br />
Supports : Steels & Aluminium<br />
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Hand rail : Galvanised Iron<br />
Ladder : Galvanised iron<br />
Hold supports : Ply woods<br />
Side dog : Wooden<br />
Gaskets : Rubber<br />
Gear : Harden steel<br />
Motor shaft : Polished steel<br />
66
CHAPTER 6 - FABRICATION<br />
The design was made with the specific dimensions and was submitted to project guide<br />
for approval. After making necessary changes as directed by the project guide, the<br />
design was approved. After the approval, team started the fabrication work which is<br />
explained in this chapter.<br />
6.1 FABRICATION OF CARGO HOLD<br />
Ply wood material dimensions brought into workshop:<br />
8 ft×6 ft: One piece<br />
6 ft×4 ft: Two pieces<br />
4 ft× 4 ft: One piece<br />
Figure 6.1: Cargo Hold<br />
Source: Team<br />
Placed on the work table and marked the dimensions as follows:<br />
120 cm×63.3 cm (bulkhead separation forward)<br />
120 cm×63.3 cm (bulkhead separation aft)<br />
150 cm×63.3 cm (side plate starboard)<br />
150 cm×63.3 cm (side plate port)<br />
67
150 cm×120 cm (weather deck plate)<br />
150 cm×120 cm (bottom plate)<br />
Marked dimensions were cut accordingly.<br />
These parts were joined together in the shape <strong>of</strong> cuboid with the help <strong>of</strong> nail and gum.<br />
Sander machine was used to get the surface finish.<br />
The final hold dimensions:<br />
150 cm×120 cm×63.3 cm<br />
6.2 FABRICATION OF HATCH WAY<br />
Hold space was marked and removed using wood cutter from the cuboid made above.<br />
The dimensions were:<br />
74.6 cm along the longitudinal axis <strong>of</strong> the hold.<br />
44.5 cm vertical to the longitudinal axis.<br />
Edges were well polished with sander machine.<br />
Figure 6.2: Hatch Way<br />
Source: Team<br />
68
6.3 HATCH COAMING FABRICATION<br />
Brought the wooden piece to the work table which having the dimensions:<br />
Length: 300cm<br />
Breadth: 12cm<br />
Thickness: 2.8cm<br />
Length <strong>of</strong> 300 cm was divided into four parts as follows:<br />
80cm: Two piece<br />
50cm: Two piece<br />
All the four pieces were planed and polished. New dimensions <strong>of</strong> pieces were:<br />
Length: 80cm Length: 50cm<br />
Breadth: 11.8 cm Breadth: 11.8cm<br />
Thickness: 2.6 cm Thickness: 2.6cm<br />
All the four pieces were joined together with the help <strong>of</strong> nails and <strong>hatch</strong> coaming was<br />
made.<br />
Figure 6.3: Hatch Coaming<br />
Source: Team<br />
69
6.4 HATCH STAY FABRICATION<br />
Brought wooden reaper <strong>of</strong> dimension:<br />
Length: 400cm<br />
Breadth: 2cm<br />
Thickness: 1cm<br />
14 pieces were made having length 7.6 cm each and<br />
28 pieces were made having length 3cm each.<br />
These pieces were made into the shape (14 pieces) as shown below:<br />
Figure 6.4: Hatch Stay<br />
Source: Team<br />
6.5 FABRICATION OF SIDE & END DOG<br />
Dimensions <strong>of</strong> wooden piece which was used:<br />
Length: 320cm<br />
Width: 10cm<br />
Thickness: 2cm<br />
70
Using wood cutter length <strong>of</strong> 320 cm were cut into four pieces<br />
Length: 88 cm (two pieces) Length: 66cm (two pieces)<br />
Breadth: 10cm Breadth: 6cm<br />
Thickness: 2cm Thickness: 2cm<br />
Length <strong>of</strong> 80cm and breadth <strong>of</strong> 2.7cm was removed from the 88cm pieces as shown in<br />
the figure 6.5.<br />
Figure 6.5: Side and End Dog<br />
Source: Team<br />
All the parts were plain with planner machine and dog was fabricated.<br />
6.6 FABRICATION OF HATCH COVER<br />
Dimension <strong>of</strong> the cylinder wooden piece which was taken to the mill:<br />
Length: 70cm<br />
Diameter: 38cm<br />
71
Figure 6.6 Pantoons<br />
Source: Team<br />
From the above, four pieces <strong>of</strong> similar dimensions were made which having the<br />
dimensions:<br />
Length: 7cm<br />
Width: 25cm<br />
Thickness: 3cm<br />
The pieces obtained were taken to the work table. After the plaining and chisel work<br />
the final dimensions <strong>of</strong> <strong>hatch</strong> <strong>cover</strong> were:<br />
Length: 58cm<br />
Width: 22cm<br />
Thickness at middle 3cm<br />
Thickness at the edge: 2cm<br />
For keeping all four <strong>hatch</strong> <strong>cover</strong>s in line with each other, locking arrangement were<br />
made throughout the length by using wooden reaper.<br />
Hatch <strong>cover</strong> 1: Locking arrangement at the aft end.<br />
Hatch <strong>cover</strong>s 2 & 3: Locking arrangement at both ends.<br />
Hatch <strong>cover</strong> 4: Locking arrangement at the forward end.<br />
72
Plastic wheels (16 pieces), metallic wheel (8 pieces) and the fitting arrangement were<br />
brought to the working table.<br />
Plastic wheels were fitted at each corners <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> as shown in figure 6.7.<br />
Figure 6.7 : Pantoons and wheels<br />
Source: Team<br />
Metallic wheels were also fitted according to the balancing dimensions.<br />
Figure 6.8: Metallic Wheels on A Pantoon<br />
Source: Team<br />
Washers were provided on both side <strong>of</strong> the metallic wheels for the smooth operation.<br />
6.7 SLIDING TRACK FABRICATION<br />
Z-section was welded to the jack top as shown in the figure 6.9.<br />
The dimensions <strong>of</strong> Z-section were:<br />
73
7.5cm toward the hold<br />
10.5cm towards the deck<br />
4cm towards the hold again<br />
Width <strong>of</strong> the plate was 2.56cm and thickness 0.3cm.<br />
The other end <strong>of</strong> Z section was welded to the iron plate as shown in the figure 6.10.<br />
A wooden piece was screwed to the iron plate and having dimensions:<br />
Length: 80cm<br />
Width: 2.5cm<br />
Thickness: 2cm<br />
Figure 6.9 Sliding Track<br />
Source: Team<br />
Figure 6.10: Hydraulic Jack and Sliding Track<br />
Source: Team<br />
74
At the top <strong>of</strong> the iron plate, rail was fitted for the sliding wheels.<br />
6.8 FABRICATION OF RISING TRACK<br />
Material used: Mild steel<br />
Two pieces i.e. rectangular & triangular were made separately and then joined<br />
together to get the final shape as shown in the figure 6.11<br />
Prepared for both i.e. port and starboard side<br />
Dimensions <strong>of</strong> triangular piece:<br />
Base: 12cm<br />
Perpendicular: 6.5cm<br />
Hypotenuse: 13.65<br />
Thickness: 1.cm<br />
Dimension <strong>of</strong> rectangular piece<br />
Length: 47cm<br />
Height: 6.5cm<br />
Width: 1.5cm<br />
Figure 6.11: Rising Track<br />
Source: Team<br />
Two supports were provided for the rising track.<br />
75
The dimensions were:<br />
Height: 15.7cm<br />
Width: 3.2cm<br />
Thickness: 1.5cm<br />
Four L angles were fitted with the supports as shown in the figure 6.11.<br />
6.9 FABRICATION OF CRANE SPACE<br />
Dimensions were marked on the wooden piece as<br />
Length: 50 cm<br />
Height: 35.5<br />
Thickness: 1.5cm<br />
Two pieces <strong>of</strong> above dimensions were made<br />
Again marking was done as<br />
Height: 35.5<br />
Breadth: 12.3cm<br />
Thickness: 1.5cm<br />
Two pieces <strong>of</strong> above dimensions were made<br />
These all four pieces were joined together by using nails and gum to form a<br />
rectangular box.<br />
Top platform dimensions:<br />
Length: 53cm<br />
Breadth: 14cm<br />
Thickness: 1.5<br />
76
Figure 6.12: Crane space<br />
Source: Team<br />
Top platform made was fixed at the top <strong>of</strong> the rectangular box made above as<br />
shown in the figure. A <strong>pull</strong>ey was then fitted at the middle at a height <strong>of</strong> 32.5cm from<br />
the weather deck<br />
6.10 MOTOR REDUCTION GEAR PULLEY FABRICATION<br />
Motor shaft and the smaller gear shaft were coupled together and bearing is provided.<br />
Bigger gear is engaged to the smaller gear and bearing is provided at each end. Pulley<br />
was fitted to the bigger gear shaft. Motor and gears were <strong>cover</strong>ed with casing for<br />
safely purpose.<br />
6.11 FABRICATION OF BULWARK<br />
10m <strong>of</strong> iron rods <strong>of</strong> diameter 4mm were brought to the work table.<br />
Four pieces <strong>of</strong> 150 cm length each were cut by using hack saw.<br />
Two rods were taken and kept parallel to each other at a distance <strong>of</strong> 3.2cm.<br />
Nails were taken and welded as shown in the figure 6.13.<br />
77
Distance between the nail: 7cm<br />
Figure 6.13: Bulwark<br />
Source: Team<br />
Repeat the same process for the remaining two rods.<br />
Rails were provided around the top platform too as shown in the figure 6.13.<br />
6.12 FABRICATION OF LADDER<br />
Two iron rods <strong>of</strong> length 36cm and diameter 5mm each were brought to the work table.<br />
These rods were kept parallel 4.7cm apart. 11 steps were welded 3.6cm apart.<br />
Figure 6.14: Ladder<br />
Source: Team<br />
78
CHAPTER 7-ASSEMBLY OF FABRICATED PARTS<br />
After the fabrication work the team collected the fabricated parts together and<br />
assembled them as per the design stated in the chapter 5.<br />
Different parts which was fabricated separately:<br />
Cargo hold<br />
Hatch coaming<br />
Hatch stay<br />
Side & end dogs<br />
Hatch <strong>cover</strong><br />
Sliding track<br />
Rising track<br />
Crane space<br />
Motor assembly<br />
Hand rail<br />
Ladder<br />
Figure 7.1 Assembly <strong>of</strong> fabricated parts<br />
Source: Team<br />
7.1 ASSEMBLY BETWEEN CARGO HOLD AND HATCH COAMING<br />
79
These parts were fabricated separately and assembled together by using nails and for<br />
extra support iron L-angles are provided.<br />
Figure 7.2 Cargo hold and Hatch coaming<br />
Source: Team<br />
Hatch comaing at port and starboard were provided with four L- angles and at<br />
aft forward were provided with three L-angles each. These L-angles were screwed<br />
well into the <strong>hatch</strong> coming and cargo hold. finally it was assured that the assembled<br />
part is rigid.<br />
7.2 ASSEMBLY OF HATCH STAY ON COAMING<br />
After fitting the coaming <strong>hatch</strong> stays were provided for additional rigidity <strong>of</strong> coaming.<br />
14 <strong>hatch</strong> stays were fabricated separately and were assembled as:<br />
4 at port & starboard each<br />
3 at aft & forward each<br />
Hatch stays were fitted using nails and gum.<br />
Figure 7.3 Hatch stay on coaming<br />
80
Source: Team<br />
7.3 ASSEMBLY OF SIDE DOGS AND END DOGS ON COAMING<br />
For the beading arrangement as well as fitting <strong>of</strong> sliding track side and end dogs were<br />
provided. These were fitted perpendicular to the coaming.<br />
Figure 7.4 Side dogs and end dogs on coaming<br />
source: Team<br />
Again this assembly was done by using nails.<br />
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7.4 ASSEMBLY OF SLIDING TRACKS<br />
Sliding tracks were fabricated separately and was welded with hydraulic jacks.<br />
Hydraulic jacks well positioned and screwed into the weather deck such a way that<br />
lifting and dropping action <strong>of</strong> tracks takes place effectively without interruption.<br />
7.5 ASSEMBLY OF RISING TRACK<br />
Figure 7.5 Sliding track<br />
Source: Team<br />
Rising tracks were fabricated and they were fitted according to the position <strong>of</strong><br />
balancing wheels. Supports provided for the rising tracks were fitted to the weather<br />
deck with the help <strong>of</strong> screws.<br />
Figure 7.6 Rising track<br />
Source: Team<br />
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7.6 ASSEMBLY OF HATCH COVER<br />
All the four <strong>hatch</strong> <strong>cover</strong>s were fitted with plastic sliding wheels at the four bottom<br />
corners. Also metallic balancing wheels were provided at port & starboard ends.<br />
All the <strong>hatch</strong> <strong>cover</strong>s were made in line above the sliding track. Bottom wheels<br />
were checked for alignment with the tracks.<br />
Figure 7.7 Hatch <strong>cover</strong><br />
Source: Team<br />
Chain is attached to each <strong>hatch</strong> <strong>cover</strong>’s metallic balancing wheels at both port<br />
and starboard ends. These metallic wheels were checked for their correct alignment<br />
with the rising track.<br />
Figure 7.8 Hatch <strong>cover</strong><br />
Source: Team<br />
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7.7 ASSEMBLY OF CRANE SPACE INTO CARGO HOLD<br />
Separately fabricated crane space was fitted over the weather deck at the specific<br />
position as shown in the figure by using nut and bolt arrangement.<br />
Figure 7.9 Cargo space into cargo hold<br />
Source: Team<br />
7.8 ASSEMBLY OF MOTOR PULLEY GEAR ARRANGEMENT INTO<br />
CARGO HOLD<br />
Motor was bolted into the weather deck with the help <strong>of</strong> nut and bolt arrangement.<br />
The roller bearings supports were too bolted to the weather deck.<br />
7.9 Assembly <strong>of</strong> Bulwark<br />
Holes were drilled into the weather deck using drilling machine and positions were<br />
adjusted according to the nail position welded.<br />
Figure 7.10 Bulwark<br />
Source: Team<br />
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The whole bulwark is placed over the drilled holes and forces inside to make it<br />
tight and rigid. The whole bulwark is placed over the drilled holes and forces inside to<br />
make it tight and rigid. Same procedure was followed for the crane top platform and<br />
bulwark fitting.<br />
7.10 ASSEMBLY OF LADDER<br />
Figure 7.11 Bulwark<br />
Source: Team<br />
This is provided to connect weather deck and crane top platform. Top <strong>of</strong> ladder is<br />
attached to the platform and bottom to the weather deck. Both ends were fitted<br />
permanently.<br />
Figure 7.12 Ladder<br />
Source: Team<br />
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7.11 ASSEMBLY OF LOCKING ARRANGEMENT<br />
For this purpose grooves were provided at each corner <strong>of</strong> the coaming such a way that<br />
the <strong>hatch</strong>es can lock well during normal voyage. This arrangement will helpful for<br />
avoiding unnecessary sliding <strong>of</strong> <strong>hatch</strong> <strong>cover</strong>s.<br />
7.12 ASSEMBLY OF WIRE ROPE<br />
Figure 7.13 Locking arrangement<br />
Source: Team<br />
Wire is provided for <strong>pull</strong>ing <strong>hatch</strong> <strong>cover</strong>s fore and aft direction with its wheel rolling<br />
between guides on the top <strong>of</strong> the coaming. For this purpose two eye bolts were<br />
provided to the furthest panel as shown in the figure 7.14.<br />
Figure 7.14 Wire rope<br />
Source: Team<br />
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Through the middle top eye bolt rope goes to the wheel provided on the crane space<br />
and finally to the motor <strong>pull</strong>ey. Through the bottom eye bolt rope goes directly to<br />
motor <strong>pull</strong>ey.<br />
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CHAPTER 8-TESTS AND TRIALS<br />
Since the ship trades in all <strong>type</strong> <strong>of</strong> environmental conditions including heavy weather<br />
condition etc, there is chance <strong>of</strong> damage <strong>of</strong> cargo or goods because <strong>of</strong> water or<br />
moisture entering to the hold. This may even damage the whole ship so in order to<br />
avoid this, <strong>cover</strong>s are made water tight and same is tested before proceedings. The<br />
two most common leak detection tests are the water hose test and the ultrasonic test.<br />
Ultrasonic testing is the preferred method because areas <strong>of</strong> inadequate <strong>hatch</strong><br />
sealing are accurately located. Chalk testing (another <strong>hatch</strong> test) gives only an<br />
indication <strong>of</strong> poor compression and potential leaks. Chalk testing is not a leak<br />
detection test. Light testing is also effective but is potentially dangerous because<br />
personnel are in a closed, dark hold looking for light infiltration between panels. If<br />
<strong>hatch</strong>es are found to leak during a test, make the necessary repairs, then test again.<br />
8.1 WATER HOSE LEAK DETECTION TEST<br />
Water hose tests are used to determine weather-tightness <strong>of</strong> <strong>hatch</strong> <strong>cover</strong>s. If correctly<br />
performed, hose testing will show <strong>hatch</strong> joints that leak.<br />
The general procedure for hose testing is to apply a powerful jet <strong>of</strong> water from<br />
a 20-50 mm diameter hose fitted with a 12 mm diameter nozzle held at a distance <strong>of</strong><br />
1-1.5 metres from a <strong>hatch</strong> joint, moving along the joint at a speed <strong>of</strong> 1 metre every 2<br />
seconds.<br />
The drawbacks <strong>of</strong> hose testing are:<br />
� The hold needs to be empty;<br />
� It cannot be performed in sub-zero conditions;<br />
� It requires the deck scupper drains to be open (potentially causing pollution);<br />
� The test cannot pinpoint leaks on the cross-joint or side joint accurately;<br />
� Two people are needed to supervise the test.<br />
Care should be taken to avoid excessive nozzle back-pressure.<br />
8.2 ULTRASONIC LEAK DETECTION TEST<br />
Ultrasonic leak detection is a viable alternative to the hose test for testing <strong>hatch</strong><br />
<strong>cover</strong>s, access doors and access <strong>hatch</strong>es for weather tightness, as it accurately locates<br />
potential points <strong>of</strong> leakage. This test should only be carried out using class approved<br />
equipment and approved test procedures.<br />
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The test involves placing (with <strong>hatch</strong>es closed and secure) an electronic signal<br />
generator inside the cargo hold. A sensor is then passed around the outside <strong>of</strong> all<br />
compression joints. Readings taken by the sensor indicate points <strong>of</strong> low compression<br />
or potential points <strong>of</strong> leakage. Ultrasonic testing overcomes the majority <strong>of</strong> limitations<br />
associated with hose testing and can be carried out when holds are loaded. The<br />
drawbacks <strong>of</strong> these section tests are:<br />
� The equipment requires an experienced and specialist operator to interpret the<br />
readings.<br />
� The equipment requires regular calibration;<br />
� The equipment is not normally part <strong>of</strong> the ship’s equipment.<br />
8.3 PUTTY OR MOULDING CLAY TEST<br />
This is a maintenance test mainly used by the maker’s representative to precisely<br />
determine alignment and clearances. Putty or moulding clay is placed at regular<br />
intervals in the packing retaining channels that have no packing in them. The <strong>hatch</strong><br />
<strong>cover</strong>s are closed then re-opened leaving an indentation. This allows the exact steet-<br />
to-steel wear down condition to be calculated and any panel distortion or<br />
misalignment to be measured and remedial action taken.<br />
8.4 CHALK TESTING<br />
When performing a chalk test, the top edge <strong>of</strong> every compression bar is <strong>cover</strong>ed with<br />
chalk.<br />
Hatches are then fully closed and reopened. The rubber packing is examined<br />
for a chalk mark, which should run continuously along the packing centre. Gaps in the<br />
chalk mark indicate lack <strong>of</strong> compression. Chalk testing merely indicates if <strong>hatch</strong><br />
panels are aligned and compression achieved. It will not show whether compression is<br />
adequate and therefore it is not a test for weather tightness.<br />
8.5 TOLERANCE TEST FOR HATCH COVERS<br />
This test is conducted on a jig to check the flatness <strong>of</strong> adjoining panels, as well as the<br />
dimensions and the hinge pin clearances where multiple panels are measured. It also<br />
checks cross joint steel to steel contact wear down.<br />
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It is a test done following extensive steel repairs to <strong>hatch</strong> <strong>cover</strong> panels and is<br />
essential if the panels are <strong>of</strong> double skinned construction. Always contact the makers<br />
for such testing’s, as original construction information is needed.<br />
8.6 RESULT<br />
Since the model is made <strong>of</strong> ply wood it cannot withstand the pressure and other<br />
governing regulations, the team was not able to perform the above stated test and<br />
trials. The main idea <strong>of</strong> presenting the model is to show the working and to know the<br />
basics <strong>of</strong> the MacGregor <strong>type</strong> <strong>hatch</strong> <strong>cover</strong>.<br />
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CHAPTER 9 - CONCLUSION<br />
Right from the starting i.e., designing <strong>of</strong> MacGregor <strong>hatch</strong> <strong>cover</strong> to its successful<br />
completion the team has given its full potential for the same. First <strong>of</strong> all, the suitable<br />
design was made. After taking all precautions and factors into consideration the<br />
fabrication process was performed. As the material selected for the <strong>hatch</strong> <strong>cover</strong>s was<br />
plywood for the easy fabrication and due to economic limits, the various leak tests<br />
were not performed. The model was completed based on the design taken by the team.<br />
The opening and closing trial <strong>of</strong> the <strong>hatch</strong> <strong>cover</strong> was done many times and it<br />
performed successfully and satisfactorily.<br />
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REFERENCES<br />
1. A.Bilbrough & Co. Ltd., Holds And Hatch Covers<br />
2. Buxton, I. L., (1978) Cargo Access Equipment for Merchant Ships, London,<br />
ICHCA.<br />
3. Lloyd’s Register, (2002) The Standard 2002, A Master’s Guide To Hatch<br />
Cover Maintenance.<br />
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