Single pull macgregor type hatch cover.pdf - Cochin University of ...

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about its roller to land horizontally with its wheels resting on the coaming. It is then pulled further over the hatchway and the chain linking it to the next panel becomes taut with the result it too is set in motion. On reaching the end of the stowage space, the second panel tips lie horizontally on the coaming behind the first and together they pull across the hatchway. The process is repeated with the third and fourth panels, ending only when all are lying flat on the coamings and the hatch is completely covered. 1.1 HATCH COVERS AND THEIR FUNCTION The purpose and function of a hatch cover and its coamings is to prevent ingress of water into a cargo hold after a large opening has been cut in the deck for cargo access. Hatch covers are a moveable structure designed to a weather tight standard. 1.1.1 Hatch Cover Construction Typically hatch covers are lightweight steel grillages. Modern design methods using finite element technology enable more efficient material distribution which results in lighter (thinner) structures. Construction from high tensile steel results in even thinner plate being used. For this reason these lightweight structures must be ‘handled with care’. Prevention of corrosion is essential – safety margins are finite. 1.1.2 Hatch Cover Function Hatch covers provide a primary structural and weather tight barrier to prevent water ingress into cargo holds. Rigorous inspection, regular maintenance and prompt repair of damaged covers, securing’s and supports are essential to maintain fitness for purpose and, in particular:- � To maintain sufficient strength to resist green seas landing on hatches in extreme weather; � To maintain a barrier against ingress of water during normal seagoing weather conditions. Failure to maintain hatch covers correctly can lead to physical loss of a cover in extreme weather and hold flooding and possible foundering. Minor 2
leakage can cause cargo damage and, if over a prolonged period, damage to the ship’s internal structure. Long-term structural decline can lead to structural collapse and total loss. 1.2 EARLY HATCH COVERS The upper deck hatches of early steamships, in common with those of sailing ships, were small by present standards: four meters by two would not have been untypical hatchway dimensions, even for ocean going vessels in the mid-19 th century. Deck openings were bounded by vertical coamings and spanned by wooden boards usually laid athwart ships: water tightness was maintained by tarpaulins spread over the boards and secured by wedges and cleats at the coamings, an arrangement which had then been in use for centuries. Web beams were sometimes placed across the largest hatchways but it was not until 1879 that their use became mandatory for all vessels classed with Lloyd’s Register of Shipping having hatchways more than 12 feet long. Coamings were required to be of iron constructions. No minimum height was specified and it was not until forty years later that they appeared in Lloyd’s Rules. Hatch boards were made of solid woods 63 mm thick and of such an overall size that they could be handled manually. Since they were laid transversely across the hatchway it was necessary to use ‘fore and afters’ to reduce their unsupported span. These were the heavy baulks of timber placed longitudinally across the hatchway, on the top of the transverse iron beams and supported at each end by brackets attached to the coamings. The hatch boards, in turn, were placed across the fore and after which were so spaced that the unsupported span of the boards did not exceed the maximum allowed. After the turn of the 20 th century, the practice of arranging hatch boards longitudinally began to be adopted. There were sound reasons for this change. A typical cargo ship hatch,7.5m(25 ft) long and 5 m(16 ft) wide, with athwart ship hatch boards, would have been fitted with two transverse web beams and three fore afters which, because of their overall length would each have been made up in three pieces, one for every beam space as shown in figure 1.1. With longitudinal hatch boards the same hatch would have required no more than four transverse beams space 1.5 m apart each of lighter construction than the two webs 3
Page 1 and 2: SINGLE PULL MACGREGOR TYPE HATCH CO
Page 3 and 4: ACKNOWLEDGEMENT First of all we hel
Page 5 and 6: TABLE OF CONTENTS v Page no. CERTIF
Page 7 and 8: 5.1.4 Hatch Covers Design. 58 5.1.5
Page 9 and 10: LIST OF FIGURES Figure no: Title Pa
Page 11 and 12: Figure7.10 Bulwark 84 Figure7.11 Bu
Page 13: CHAPTER 1 - INTRODUCTION The classi
Page 17 and 18: All types of wooden hatch were made
Page 19 and 20: The first horizontal rolling built
Page 21 and 22: CHAPTER 2 - TYPES OF HATCH COVERS M
Page 23 and 24: 2.1 SINGLE PULL 2.1.1 Description F
Page 25 and 26: 2.3 FOLDING & MULTI-TYPE 2.3.1 Desc
Page 27 and 28: 2.5 PIGGY BACK 2.5.1 Description Fi
Page 29 and 30: 2.7 REEFERS HATCH COVERS Figure 2.7
Page 31 and 32: CHAPTER 3 - GENERAL REQUIREMENTS 3.
Page 33 and 34: secured by tarpaulins and battening
Page 35 and 36: force by the 1967 Merchant shipping
Page 37 and 38: 3.2.2 Cover Stowage Where a designe
Page 39 and 40: It is also necessary to provide dra
Page 41 and 42: Other steel hatch cover secured wea
Page 43 and 44: Table 3.4 Access equipment strength
Page 45 and 46: Longitudinal deformation of the top
Page 47 and 48: (vii) It should retain all the abov
Page 49 and 50: easier to handle without power assi
Page 51 and 52: � Keep wheels, cleats, hinge pins
Page 53 and 54: 4.2.2 Drive Chains; Check their Len
Page 55 and 56: Figure 4.2 Vessel in rough weather
Page 57 and 58: Figure 4.5 Never smoke in a hold. S
Page 59 and 60: Figure 4.9 Always wear protective h
Page 61 and 62: e taken when opening hatch covers e
Page 63 and 64: Remember to carry out a chalk test
Page 65 and 66:
4.6.13 Painting Corrosion occurs ma
Page 67 and 68:
11. Coaming. 12. Sheave. 13. Cross
Page 69 and 70:
Breadth: 44.5cm 5.1.3 Hatch Coaming
Page 71 and 72:
Slope: 1cm Total number of panels:
Page 73 and 74:
Height of jack while normal conditi
Page 75 and 76:
Pulley for rope Diameter: 2cm Width
Page 77 and 78:
Height from the deck: 7.2cm Height
Page 79 and 80:
CHAPTER 6 - FABRICATION The design
Page 81 and 82:
6.3 HATCH COAMING FABRICATION Broug
Page 83 and 84:
Using wood cutter length of 320 cm
Page 85 and 86:
Plastic wheels (16 pieces), metalli
Page 87 and 88:
At the top of the iron plate, rail
Page 89 and 90:
Figure 6.12: Crane space Source: Te
Page 91 and 92:
CHAPTER 7-ASSEMBLY OF FABRICATED PA
Page 93 and 94:
Source: Team 7.3 ASSEMBLY OF SIDE D
Page 95 and 96:
7.6 ASSEMBLY OF HATCH COVER All the
Page 97 and 98:
The whole bulwark is placed over th
Page 99 and 100:
Through the middle top eye bolt rop
Page 101 and 102:
The test involves placing (with hat
Page 103 and 104:
CHAPTER 9 - CONCLUSION Right from t
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