Offshore Technology

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Underwater Vehicles: 

Maritime robots for survey 

and security 3 

“Neumayer III”: 

Sauna at the South Pole 6 

Ship Design: 

Drilling in Ice 8 

Offshore Technology 

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Propulsion: The Schottel 

Combi Drive: suited to offshore 

application 10 

Ocean energy: Rexroth rises 

to the Power Take-Off 12 

Hydac: Condition monitoring 

of oil systems 13 

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OMAE 2008 

Arctic shipping: Arctic 

knowledge at DNV informs 

risk management 14 

Ice barriers: Ice Protection 

Structures 16 

Pipeline monitoring: Hydrocarbon 

sensor systems 19

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Maritime robots for 

survey and security 

UNDERWATER VEHICLES Maritime investigations, measurements and inspections with autonomous 

underwater vehicles (AUV) are a core element of ATLAS Elektronik to discover the 

underwater resources for economic use as well as for the protection of maritime facilities. The 

operation under extreme and diffi cult environmental conditions requires the use of robots of 

the newest technology with high degree of automation and extreme navigation accuracy. 

Willi Hornfeld 

Economic use of the seas and 

oceans as well as protection of 

the ports and their access has a 

top-ranking position – the maritime 

market has reached world-wide an 

enormous order of magnitude. In this 

market a German company in general 

has not only a strong position, but in 

some special maritime engineering 

fi elds even a top place. In this environment 

the substantial target areas of the 

German maritime technologies are: 

� The strongly growing and important 

market segments such as oil and 

gas production from the sea bottom, 

underwater mining, exploration and 

exploitation of gas hydrates, etc.. 

� Maritime Homeland Security, one 

of the highest priority missions around 

the world with the strategic objectives 

� Prevent terrorist attacks within and 

terrorist exploitation of the national 

domain 

� Reduce the countries vulnerability 

to terrorism within the maritime domain 

� Protect the population centres, critical 

infrastructure, maritime borders, 

ports, coastal approaches, and the 

boundaries and seams between them 

� Protect the marine transportation 

� Minimize the damage and recover 

from attacks that may occur in the maritime 

domain as either the lead federal 

agency or a supporting agency. 

One of the core elements for a Maritime 

Homeland Security is the protection of 

harbours, a razor edge of danger. 

Sea Ports and Sea Lanes are the primary 

gateways for global trade and 

commerce. Ports are the nerve centers 

of the international supply chain network. 

Operational drop-outs of any of 

such critical hubs and bottlenecks will 

hence generate consequential damages 

on a truly global scale. 

The European Sea Ports Organisation 

(ESPO) determines that “the Eu- � 

Fig. 1: ATLAS’ UUV family 

Schiff & Hafen | June 2008 | No. 6 3 Special

SPECIAL | OFFSHORE TECHNOLOGY 

Parameter SeaFox 

Length [m] 1.3 

Width [m] Ø 0.4 (max) 

Weight [kg] 

Speed [ktd] 

40 

•max 

6 

•min 

0.5 (backwards) 

Diving depth [m] 300/600 

Payload [kg] 5 

Obstacle avoidance yes 

Hover capability yes 

Tab.1: SeaFox parameter 

Parameter SeaWolf 


Width [m] Ø 0.5 (max) 

Weight [kg] 

Speed [kts] 

110 

max 

8 

min 

Minus 0.5 

Turn radius < 3 m 

Diving depth [m] 3 to 300 

Payload [kg] > 30 

Obstacle avoidance yes 

Hover capability yes 

Navigation INS + DVL + (D)GPS + 

pressure sensor + compass 

Tab. 2: SeaWolf parameter 

Parameter SeaOtter Mk2 


Width [m] .90 

Height [m] .48 

Weight [kg] 

Speed [kts] 

1000 

•max 

8 

•optimal 

4.0 

•min 

0.5 (backwards) hover 

Diving depth [m] 5 to 600 

Duration [h] 24 @ 4 kts 

Obstacle avoidance Yes 

Hoover capability Yes 

Navigation MARPOS II 

(INS+DVL+DGPS+CTD+ pressure 

sensor) & CML 

Tab.3 : SeaOtter parameter 

� TYPICAL USERS OF UUV´S 

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Defence Forces 

Coast Guard 

Maritime Administration 

Customs and 

Immigration 

Port Authorities 

Environmental Agencies 

Commercial Operators 

Maritime Scientifi c Institutes 

Special 4 Schiff & Hafen | June 2008 | No. 6 

Fig.2: The SeaFox family 

ropean Union without its seas port 

cannot act directly. The entire foreign 

trade of the community and nearly 

half of their domestic trade are almost 

conducted via the more than 1,000 sea 

ports in the coastal member states of 

the European Union.” 

Autonomous underwater vehicles 

Maritime investigations, measurements 

and inspections with autonomous underwater 

vehicles (AUV) are a core element 

of the above mentioned market 

and growth fi elds. The fundamental 

pre-condition is however the ability for 

precise acting in unknown waters as 

well as the technologies for the protection 

of maritime facilities (e.g. inspection 

of berthing areas, piers and ship 

hulls) under extreme and diffi cult environmental 

condition. This requires 

the use of robots of newest technology 

with high degree of automation and 

extreme navigation accuracy with high 

manoeuvrability. 

Such unmanned underwater vehicles are 

one of the main product areas of ATLAS 

Elektronik. The company has been developing 

and delivering such vehicles for 

military and commercial applications for 

about thirty years. Current products to be 

noted are the SeaFox, the SeaWolf and the 

SeaOtter Mk II. 

The development of these AUVs respectively 

HAUVs (Hybrid Autonomous Underwater 

Vehicles) happens under consistent 

attention of as far as possible synergies 

between the individual systems. Beyond 

that the underwater vehicles are based substantially 

on dual use, i.e. they are designed 

for military and commercial missions, with 

that due to better serial production fi gures 

for the basic systems, a more attractive 

price for the customer can be reached. This 

philosophy shows Fig.1, the ATLAS UUV 

(Unmanned Underwater Vehicles) family 

which includes not only the Autonomous 

Underwater Vehicles (AUV) but also Remotely 

Operated Vehicles (ROV). 

A further characteristic of the here 

discussed underwater vehicles is their 

modularity which, depending on the 

specifi c payload capacity, will be realized 

by the possibility of plug and 

play integration of quasi any payload. 

Finally all ATLAS UUVs can be mission-specifi 

cally equipped by the user 

with a fi ber-optic cable (FOC), so that 

a wide-band, real time transmission to 

the surface of all sensor and status information 

can take place. Such hybrid 

AUVs (HAUVs) will open wider and 

completely new application areas. 

The UUVs SeaFox, SeaWolf and SeaOtter 

are characterised by most different 

users and several areas of application. 

With other the following applications 

are standing in the centre: 

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Mine counter measure 

Damage assessment 

Intelligence 

Rapid environmental assessment 

Route survey 

Maritime border control 

Waterways and port surveillance 

Passenger terminal protection 

Maritime science. 

The following features are, depending 

upon payload capacity, realized or will be 

realized in the systems: 

� Autonomous or operator supported inspection 

and classifi cation of all kinds 

of underwater areas, structures and objects 

� Adaptive autonomy in relation of the 

mission 

� On line data link via fi bre optic cable 

on request (hybrid) 

� Operation 

areas 

in confi ned and tidal 

� Inspection sensors of latest techno logies 

in underwater vehicles 

� Navigation/positioning of highest accuracy

� 

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Standard interfaces for simple integration 

of customer specifi ed sensors and 

software (plug and play) 

High-performance multi sensor image 

processing on board or in the surface 

console 

100% inspection of selected object assured 

CAD base inspection on request 

CAD object data creation during the inspection 

Alarm function in relation to the identifi 

ed anomaly 

Prepared for team operation 

Object oriented mission planning and 

control. 

The UUV SeaFox is a small and lightweight 

(see Tab. 1) vehicle with an endurance 

of more than one hour. The 

vehicle is available in several confi gurations 

from the military systems (SeaFoxC 

for mine disposal and SeaFoxI and T 

for inspection and training) till the 

modular one IQ, predominately used 

for commercial survey missions. 

Thanks to this modularity, missionadapted 

sensor suits with e.g. 360° and 

side looking sonar as well as a tiltable TV 

system are installable as shown in Fig. 2. 

The HAUV SeaWolf is a multirole system 

for all kinds of underwater inspection 

and anomaly identifi cation. 

The propulsion philosophy is comparable 

with the Seafox (four main propellers 

and one vertical thruster). Due to a 

special adjustment of the main motors 

a high effi ciency was achieved. 

The vehicle is equipped with the latest 

sensor and software technologies and 

therefore able to inspect autonomously 

even very complex 3D objects. 

For real time data transfer, the SeaWolf can 

be connected with the control console by 

a fi bre optic cable. In this case the mission 

will be executed autonomously but with a 

real time data transfer. 

SeaWolf achieves versatility and fl exibility 

of mission and payload confi guration 

by using plug and play modules 

for software, electronic and sensor devices 

within a generic architecture. 

The vehicle’s basic payload is a side 

scan and obstacle detection sonar as 

well as a TV camera with LED illumination. 

For operation in water with low visibility 

a three dimensional high frequency 

multibeam sonar and/or a laser projection 

unit are additional available. The 

navigation is of a very high accuracy and 

based on an IMU with DVL and differential 

GPS. Therefore the use of an acoustic 

positioning system is not necessary. 

Due to its relatively low weight, the system 

is easy to operate and applicable from all 

kind of vessels or from the shore. 

Fig.3: SeaWolf confi gurations 

Fig.4 : SeaOtter Mk II 

The mission planning, control and 

evaluation is done from a portable console, 

the same as used for the SeaFox. 

Tab.2 shows the SeaWolf parameter 

and Fig. 3 the system confi guration. 

The HAUV SeaOtter Mk II is based on 

the proven MARIDAN 600 and the Sea- 

Otter Mk I, which have been in operations 

throughout the world. Due to the 

design and the fl exible payload concept, 

the system is easily adaptable to 

various military and commercial missions. 

The SeaOtter Mk II also offers the benefi t 

of a real time data transfer to the operator 

consol through the fi bre optic link option. 

The standard version of the vehicle 

is equipped with side scan sonar, a 

multi-beam echo sounder, a sub-bottom 

profi ler, obstacle avoidance sonar, 

a TV camera and a precise navigation 

system. 

Due to its serious payload compartment 

(approx. 150 kg) the vehicle can 

per plug and play be adapted to nearly 

all kinds of required missions from 

scientifi c till maritime security applications. 

Tab. 3 gives the SeaOtter Mk II fi gures 

and Fig. 4 an impression of the design. 

Willi Hornfeld 

ATLAS ELEKTRONIK GmbH, Bremen 

Willi.hornfeld@atlas-elektronik.com 

www.atlas-elektronik.com 



Sauna at the South Pole 

RESEARCH STATION “NEUMAYER III” Germanischer Lloyd’s Business Segment Oil and Gas 

offers its wide range of services all over the world. Just recently the experts also conquered 

the ‘sixth continent’: they certify the new research station “Neumayer III” 

Not a single ray of sunlight penetrates 

the darkness of the polar 

winter night. The thermometer 

drops below 50°C as storms whip across 

the icy landscape. In this environment, 

buildings must be designed to withstand 

extremely hostile climate conditions. 

Materials must be selected carefully and 

the functional fi tness of elements must 

be tested in realistic simulations. 

A house in Antarctica: In December 

2006, Germanischer Lloyd received an 

order from the Alfred Wegener Polar 

and Marine Research Institute (AWI) in 

Bremerhaven, Germany, to certify the institute’s 

new research station “Neumayer 

III” in Antarctica. Even for an experienced 

classifi cation society, this project 

Assembly of the “Neumayer III“ in 

Bremerhaven 


is rather challenging. The station, named 

after the German polar explorer Georg 

von Neumayer (1826 to 1909), will consist 

of a structure supported by sixteen 

hydraulically operated posts. By moving 

up and down on these support legs, the 

building will adjust continuously to the 

changing level of the snow surface. As a 

consequence, the research station will 

not gradually disappear under masses of 

snow, as its predecessor did. 

Submerged in ice 

After 15 years of operation, the current 

Neumayer station has sunk twelve metres 

deep into the ice and will have to 

be abandoned in the near future. Built 

in 1992, the tube-type structure was state 

AWI-employees at the underwater 

acoustic measuring station “Palaoa“ 

of the art at the time. But the two steel 

tubes that form its outer shell have been 

deformed over the years by the movement 

of the shelf ice and the constantly 

increasing load of snow. Today, the once 

elliptical shape of the station is no longer 

discernible. Time and again, bolts burst 

with a loud bang, unable to withstand 

the weight of tons of snow bearing down 

on the station. The engineering concept 

of the new station consists of a building 

to be erected on top of a platform above 

the snow surface. The building will accommodate 

rooms for research and operations 

as well as living quarters. 

To construct this unique facility, a pit eight 

metres deep will have to be excavated for 

the foundations of the hydraulic support 

pillars of the station. Later on, the pit will 

also be used as a parking area for tracked 

vehicles and snowmobiles. A workshop, 

the hydraulics centre, exercise rooms and 

food stores will be located directly below 

the cover of the pit. The station itself will 

be positioned on stilts six metres above 

snow level so even high winds and dense 

snowfall will not cause any major snowdrifts. 

The two-story building will be standing 

on a platform 68 by 24 metres large 

and provide space for common rooms, a 

kitchen, an infi rmary and operating theatre, 

15 bedrooms with 40 beds, as well as 

twelve laboratory and offi ce rooms. Nine 

so-called “overwinterers” – scientists, physicians 

and technicians – will have nearly 

twice as much space for their work as in the 

subterranean station “Neumayer II”. For 

leisure, there will be a lounge with a bar 

and a sauna. Once the basic structure has 

been completed, a protective shell 120 mm 

thick with a blue, white and red coating 

– the colours of the AWI – will be placed 

on top of it to reduce wind loading. The 

roof offers enough space to accommodate 

a chamber for helium sounding balloons, 

as well as antennas and other measuring 

equipment. 

Certified containers 

The entire building itself will be assembled 

from containers certifi ed by Germanischer 

Lloyd. GL has many years of experience 

in container certifi cation. Today, the society 

certifi es up to 360 000 containers each 

year. After the design review, GL subjected 

the thermally insulated containers to spe-

The model shows the hydraulic posts of the garage level 

cial tests to check their fi tness for transport. 

Those tests included stackability, as well as 

loading and unloading strength, which ensured 

that the containers were taken safely to 

Antarctica aboard a Danish freighter. Now, 

the GL experts main task is to review the 

documentation for safety-relevant equipment 

for the entire station – including evacuation 

and survival systems, fi re extinguishing 

and fi re alarm systems, automation and 

alert systems. “Due to the exposed location, 

the system as a whole has to meet the most 

stringent reliability requirements,” says An- 

�BACKGROUND: 

ANTARCTICA 

The Antarctic Zone comprises the land 

and sea areas of the South Pole region. 

It covers a surface of approximately 12.5 

million square kilometres. 98 percent of 

this area is permanently covered by ice. 

The continent of Antarctica is located in 

the centre of the region. The Antarctic 

was explored by various scientists and 

seafarers from 1920 onwards. 

The continent is characterized by an 

extreme climate: It is the coldest, driest 

and most wind-ridden part of the earth. 

There have been reports of temperature 

readings as low as – 89 °C and wind 

speeds exceeding 300 km/h. According 

to CONMAP (Council of Managers of 

National Antarctic Programs), there are 

currently more than sixty active research 

stations on the continent. 

dreas Mäscher, project manager of GL. “In 

this respect we can draw on our experience 

in offshore installations.” 

The AWI order also includes tests of the 

energy supply systems as well as the acceptance 

inspection of a combustion engine-based 

cogeneration plant at the manufacturer 

site. “Supplying the station with 

heat and energy is a particular challenge, 

considering the extreme climate conditions 

– low temperatures, large quantities of 

snow, high winds,” Andreas Mäscher emphasizes. 

Thanks to more effi cient generation 

of heat and electricity in the cogeneration 

plant, the future station will need only 

30 percent more polar diesel (diesel plus 

kerosene) than its predecessor although 

it is twice as large and will be exposed to 

greater wind loading. 

GL conducted the component acceptance 

tests for both, the diesel-operated 

generator and the hydraulically operated 

stilts. Last year, the lifting units were tested 

under low-temperature conditions to 

ensure fl awless operation in the extreme 

temperature environment (+4 to -50° C) 

of Antarctica. 

In November 2007, the components were 

loaded onto the Danish freight vessel “Naja 

Arctica”, which reached the Antarctic Atka 

Bay on schedule in mid-December. However, 

a sea ice barrier of several metres 

thickness prevented the vessel from moving 

ahead. The research icebreaker “Polarstern” 

was appointed to free a navigation channel 

to the ice edge and helped “Naja Arctica” 

to reach her planned unloading position at 

the edge of the ice shelf only in mid-January 

2008. Despite the one-month delay, the 

construction of Neumeyer Station III moved 

rapidly ahead in good weather conditions. 

In only eight weeks, the entire steelworks of 

the underground garage section with 16 hydraulically 

operated posts as well as the fi rst 

fl oor of the future station were erected. The 

unfi nished building is intended to be used 

as a store room for construction equipment 

and materials until the next Antarctic summer. 

The completion of the new station is 

scheduled for spring 2009. Then, a GL surveyor 

will join the construction site at 70° 

40.8‘ south and 8° 16.2‘ west, 6.5 km away 

from the old station, to inspect the construction 

of the Neumayer III station and 

conduct the acceptance tests. 

The new research station, which will 

cost about 36 million euros, is designed 

for a service life of at least 25 years. The 

Alfred Wegener Institute, the operator 

of “Neumayer III”, will continue its research 

activities in Antarctica, recording 

important meteorological data and taking 

measurements of the earth’s magnetic 

fi eld as well as atmospheric readings 

of climate-relevant gases. GL will 

continue to keep an eye on the station 

as well, says Andreas Mäscher: “There 

are plans for periodic inspections of the 

structure and its equipment.” 

Germanischer Lloyd, Hamburg 

www.gl-group.com 



Drilling in ice 

SHIP DESIGN The challenge for discovering Arctic oil and gas reserves will be to fi nd solutions to 

produce gas and oil with the highest safety and environmental standards. For ice going drill vessels 

the Hamburg Ship Model Basin (HSVA) has done various innovative frontier developments. 

Karl-Heinz Rupp, Walter L. Kuehnlein 

It is estimated that the Arctic 

contains more than one third 

of the world’s undiscovered 

oil and gas reserves. Although 

some developments have already 

occurred, the region remains 

one of the last energy frontiers. 

But the region is also one of the 

most diffi cult areas in the world 

to work at, due to its remoteness, 

the extreme cold, dangerous sea 

ice and its fragile environment. 

Big energy companies are preparing 

to go into the Arctic, they 

are taking measures in order to 

ensure that they will operate 

safely and responsibly. 

This is not the fi rst run to the 

Arctic. Petroleum companies 

entered into the Arctic already 

half a century ago. Experiences 

from past Arctic developments 

show the potential hazards of 

further exploration. A key challenge 

will be developing and 

deploying solutions, which are 

currently at the cutting edge of 

technology. The Arctic Ocean is 

the only major sub-basin of the 

world’s oceans that has only occasionally 

been sampled by deep 

sea drilling. Today the properties 

of the Arctic Ocean are being 

focussed upon by both researchers 

and commercial oil and 

gas drilling companies. Research 

core drilling is of great impor- 

tance for the researchers because 

it allows them to increase their 

knowledge about that large ice 

covered area. And of course the 

present high prices for energy 

make it profi table to explore for 

reserves and to produce energy 

even in the ice covered waters of 

the High North. 

Drilling operations in ice have 

been already carried out at the 

ice border with “open water drill 

ships“, mainly with the support 

of icebreakers (e.g. “Joides Resolution” 

with “Maersk Master”). 

Some drill ships are reinforced 

for operation in ice, but this reinforcement 

is limited to the 

strengthening of the ship structure 

and does not include the propulsion 

and operational outfi tting. 

An ice-breaking drill ship should 

be capable of keeping its position 

so that the drilling operation can 

be continued, also when it is surrounded 

by drifting ice. 

Existing concepts and 

d esigns 

Some of the challenges which 

a drill ship in ice will experience, 

have been already described 

in 1983 (Dynamic 

Response of a Moored Drill 

ship to an Advancing Ice 

Cover, T. Kotras, A. Baird, E. 

Corona, Poac 83, Volume 3, 

Fig.1.: The cross section shows the sloped side of 

the HSVA drill ship design with ice accumulated 


page 433, Helsinki, Finland, 

1983): 

� “The ability of a vessel to stay 

within a prescribed operational 

radius is greatly enhanced when 

impacting ice in a head-on condition. 

Beam-on collisions cause 

excursions from two to fi ve times 

larger as those occurring head-on. 

� The ability of a drill ship to 

quickly yaw into a heading inline 

with the advancing ice is 

directly related to the maximum 

excursion seen. 

� In the Bering Sea, an unassisted 

drill ship may not be capable 

of year round operation during 

the heavy ice periods, ...“. 

Almost 30 years ago, in 1980, a 

drill-platform from Gulf Canada 

(Conical Drilling Unit) was tested 

in ice by HSVA. It was found 

that the rig could operate in an 

environment up to about one 

meter level ice thickness. This 

platform, the “Kulluk“, was kept 

in position with a mooring system. 

The shape of the platform 

was circular in the plan view 

and the section was similar to 

an asymmetrical sandglass. The 

turret was placed in the centre of 

this fl oating island. This platform 

was not suitable for being moved 

over a long distance at sea. 

In the last decade improvements 

in manoeuvrability and 

Fig.2: Side view of “Aurora Borealis“ with two moonpools 

(as designed by HSVA) 

ice breaking performance have 

been achieved by applying 

azimuth propulsors. Nowadays 

several ice going and ice 

breaking vessels, e.g. icebreakers, 

supply vessels, tankers and 

multi-purpose container vessels 

are equipped with this type 

of propulsion system. 

New technical developments 

In 2000 contracted the Alfred- 

Wegener-Institut (AWI) in 

Bremerhaven Germany (www. 

awi-bremerhaven.de) the Hamburgische-SchiffbauVersuchsanstalt 

(HSVA) to carry out a 

draft design study for an Arctic 

Drilling Research Vessel with 

dynamic positioning capabilities 

in ice. The project was entitled 

“Aurora Borealis”. 

Drifting ice may change in both 

in speed and direction. Furthermore 

the ice conditions vary 

from easy to heavy (e.g. ice 

ridges), therefore the drill ship 

must be able to keep position 

within a very narrow margin. All 

of these requirements, as well as 

the technological developments 

described above have been taken 

into consideration for HSVA’s 

conceptual design for the “Aurora 

Borealis”. 

The technical features of the 

HSVA design are:

� Low ice resistance of the drill 

ship at both bow and stern. This 

was achieved with an optimized 

icebreaking hull shape, similar 

to that of an icebreaker. 

� High ability to turn the vessel 

in ice in order to follow changes 

in ice drift. This was achieved by 

implementing a strong slope at 

the side of the vessel (see cross 

sections). This hull shape allows 

the vessel to break ice over 

the entire ship length. In order 

to break the ice the azimuth 

propulsors deliver the required 

thrust for turning the drill ship. 

� The vessel is able to operate in 

ice without icebreaker assistance 

up to very severe ice conditions, 

far above of the capabilities of 

all existing ice going drill vessels. 

With icebreaker assistance the 

operational limits of the drilling 

vessel can be further extended. 

� Consequently, the HSVA 

design is the fi rst design world 

wide, which will allow drilling 

in ice with a dynamic positioning, 

i.e. no fi xed mooring system 

will be required. 

The HSVA design study for “Aurora 

Borealis” has been presented 

in several publications and presentations 

since 2001. The fi gures 

1 and 2 are from: European Polar 

Board (EPB), Aurora Borealis “A 

long term European Science Perspective 

for Deep Arctic Ocean 

Research 2006-2016”, June 2004. 

Logistics in ice management 

In addition to the technological 

improvements, the logistics in 

ice management are also of great 

importance. 

The use of modern satellite ice 

and weather data are a fi rst step 

for obtaining information about 

the ice conditions ,ice drift speed 

and drifting direction over a large 

area. Closer to the drill ship, ice 

drift speed and direction can 

be detected by sensors installed 

on board of the drill vessel. The 

ice thickness can be measured 

with electro magnetic ice thickness 

measurement devices and 

together with visual ice observations, 

severe ice conditions can 

be detected and traced, and the 

potential danger to the drill ship 

can be calculated and predicted. 

An example for excellent ice 

management was the core drilling 

research work of “Vidar Viking” 

in 2004 close to the North 

Pole. “Vidar Viking” was built 

as an ice breaking supply vessel 

and was equipped with a drilling 

rig. The vessel alone was not able 

to keep position during drilling 

in the Arctic ice, although 

it is equipped with a dynamic 

positioning system (DP) for ice 

free waters. Manual DP in ice 

was only possible in well managed 

ice. The Russian nuclear 

icebreaker “Sowjetski Sojus“ and 

the Swedish Icebreaker “Oden“ 

broke the drifting ice into small 

pieces (well managed ice). 

Tests with a moored drilling 

vessel in drifting ice 

HSVA has tested several drilling, 

production and storage vessels in 

managed and in well managed 

ice. In these tests the ice drift is 

supposed to hit the vessel under 

different angles. Such “oblique 

towing tests” generate large deviations 

to the vessel’s position 

and the corresponding loads in 

the mooring systems. During 

the last few years HSVA has designed 

and/or optimized several 

of these vessels and consequently 

HSVA has gained a tremendous 

amount of expertise for such 

highly complex systems in ice. 

As an example: From 2006 until 

2008, HSVA carried out several 

ice model testing campaigns for 

a moored drilling vessel for the 

Norwegian engineering company 

LMG Marin in Bergen and 

Statoil (now StatoilHydro). The 

tests demonstrated the excellent 

ice breaking capabilities of the 

unit in level ice of up to 1.60m 

thickness, in ice ridges and in ice 

rubble fi elds. The main target of 

the investigations was to develop 

a concept for enabling the vessel 

to follow the ice drift change in 

order to keep the vessel within 

the range of the lowest ice resistance 

and therefore within the 

defi ned operational working 

area. The pictures 3–6 give an 

overview of several ice scenarios 

which have been tested. 

Dr. Karl-Heinz Rupp, 

Dr. Walter L. Kuehnlein 

Hamburg Ship Model Basin 

(HSVA), Hamburg 

Rupp@hsva.de 

Kuehnlein@hsva.de 

www.HSVA.de 

Fig. 3: The vessel is rotated around the centre of the turret 

using the thrust of the azimuth propulsors 

Fig. 4: The propeller wash is a useful tool for breaking ice or to 

wash ice away from the vessel 

Fig. 5: Track behind the drill ship after an ice drift course 

change of 20° 

Fig. 6: Tests in broken irregular thick ice 



The Schottel Combi Drive: 

suited to offshore application 

PROPULSION Schottel which develops, designs, manufactures and sells propulsion and 

manoeuvring systems with power ratings of up to 30 MW for vessels of all 

types and sizes set new standards for the manoeuvrability in the 

early 1950s with their Schottel Rudderpropeller (SRP). 

The SCHOTTEL Combi Drive (SCD) combines the main technical 

and economic criteria of both mechanical Rudderpropellers 

and pod drives. 

Schottel builds combi drives both in 

a twin-propeller version and as a 

ducted single-propeller system, at 

present covering a power range from 2,100 

to 3,300 kW. In contrast to pod drives with 

an electric motor inside the underwater 

pod, the motor in the Combi Drive is integrated 

vertically into the support tube of 

the Rudderpropeller. Neither an above-water 

gearbox nor a cardan shaft is required, 

making the system extremely compact and 

easy for the shipyard to install in the vessel 

with very low space requirements. 

Since the market launch, 16 of these innovative 

propulsion systems have already 

successfully entered everyday service. Three 

double-ended ferries built for Fjord1 

Fylkesbaatane in Norway by the shipyard 

Aker Brattvaag AS are each equipped with 

four gas-electric powered Schottel Combi 

Drives of type SCD 2020 in twin-propeller 

confi guration (4 x 2,750 kW). The ferries 

operate between Bergen and Stavanger. 

An ecological and safety-oriented concept 

The SCD has a promising future in the offshore 

sector. The Norwegian Ulstein Verft, 

for example, has chosen it as the propulsion 

system for two platform supply vessels 

of type PX105. These 4700 dwt ships 

with the distinctive Ulstein X-Bow were 

built for the shipping company Bourbon 

Offshore Norway IS KS, a subsidiary of the 

French Group Bourbon, based in Marseille. 

With their new bow, they are “highly-developed, 

large and reliable multifunctional 

platform supply vessels, which distinguish 

themselves particularly in terms of fuel 

consumption, good sea-going characteristics, 

positioning, speed, stability and loading 

capacity”, as the shipyard emphasizes. 

Both vessels are equipped with two 

SCD 2020 twin-propeller systems (max. 

2,700 kW). The decision to combine a 

diesel-electric propulsion concept with 

an azimuth drive system means a signifi - 

cant improvement to the performance of 


the vessels. The concept allows fl exible 

power distribution and offers a higher 

degree of redundant safety. The lower fuel 

consumption also makes the PSVs more 

environmentally friendly. 

The shipping company had stipulated that 

the vessels were to be equipped in accordance 

with the requirements of the DNV 

Clean Design Class. This means that 

the equipment had to meet strict 

criteria with regard to its environmental 

impact. BP Norway, the 

operator, also stressed that the 

ecological and safety-related 

concept of the new vessels had 

played a decisive role in the 

awarding of the contract. 

The economic expectations 

of Bourbon Offshore Norway 

with regard to these two innovative 

vessels were quickly confi rmed 

with the result that the company has 

mean while placed a further order with 

Ulstein Design for the design and technical 

equipment of four more vessels of the 

same type, also with Schottel SCD 2020 

Combi Drives. The construction contract 

was awarded to Zhejiang Shipbuilding Co. 

Ltd. in Zhejiang, China. The shipyard will 

be delivering the vessels in late 2009 or 

early 2010. 

Both Neptune Offshore in Norway and EDT 

on Cyprus have ordered two further vessels 

of the same design in the mean time. 

US owners such as Otto Candies LLC in 

New Orleans, a major offshore shipping 

company in the Gulf of Mexico, are also 

focussing on this innovative propulsion 

concept. For two of its new offshore supply 

vessels, built by Dakota Creek Industries 

(DCI), the company has chosen the Combi 

Drive. The ships are each to be equipped 

with two SCD 2020 systems (2 x 2,250 kW 

and 2 x 2,500 kW). 

Following the successful market launch of 

the twin-propeller version, intensive market 

research culminated in the decision to 

introduce a ducted variant of the SCD. 

Ducted variant of the SCD 

While the twin-propeller SCD is mostly 

used in vessels with an operating profi le 

in the transit range at medium to high 

speeds, the ducted propeller operates at 

its best in the lower speed range and at 

static thrust. Especially for vessels with 

an operating profi le characterized by dynamic 

positioning (DP) and partial-load 

operation, the ducted variant represents 

a particularly effi cient solution. 

Anchor Handling Tug Supply vessels 

(AHTS), seismic research vessels, cable 

ships and other work vessels are ideally 

suited to this propulsion solution. This 

presupposes, of course, that the vessels 

are equipped with a diesel-electric propulsion 

system. This is usually the case 

with cable ships or seismic research vessels; 

AHTS vessels, however, are still an 

exception – and not always with good 

reason, as investigations have shown.

Side view of a new Offshore Supply Vessel for Otto Candies LLC in New Orleans Design: MMC Ship Design & Marine Consulting, Ltd, Poland 

A diesel-electric propulsion system is 

endowed with a power management system 

that ensures that only the currently 

required power is generated and distributed 

to the various units in the vessel. 

The connected generators always run at 

the optimum operating point. In combination 

with a ducted fi xed-pitch propeller, 

as in the Schottel Combi Drive, 

such a system offers very high effi ciency, 

especially in the low-load range. 

In a diesel-electric fi xed-pitch system, the 

required thrust is regulated via the electric 

motor speed (frequency control). 

The connected generators run at the optimized 

operating point – as does the 

fi xed-pitch propeller if designed accordingly. 

Furthermore, for low to medium 

vessel speeds, a well-designed fi xed-pitch 

propeller with frequency control is more 

effi cient at the rated speed than a controllable-pitch 

propeller. 

Increased economic efficiency 

The space saved by the diesel-electric concept, 

together with the fl exible design of 

the vessel’s interior (the SCD requires no 

space-intensive shaft lines), result in a substantial 

increase in the usable volume. This 

is of particular importance with such complex 

vessels as AHTS, and increases their 

economic effi ciency. 

These arguments convinced the shipowner 

Great Offshore Ltd., based in Mumbai, India, 

so that it ordered for the fi rst time a 

150 t anchor handling tug with diesel-electric 

propulsion and two ducted SCD 3030s 

(2 x 3,300 kW) from Bharati Shipyard Ltd. 

in Mumbai. The newbuilding is scheduled 

to go into service at Great Offshore at the 

end of 2008. 

The trend towards diesel-electric powered 

vessels has sharply increased over the last 

few years. This is due to the fact that particularly 

work vessels in offshore operations 

are becoming ever more complex. Moreover, 

the leading seafaring nations in this 

segment, such as Norway or the USA, are 

enforcing more restrictive environmental 

and climate protection measures. 

Above all in harbours, the amount of pollutants 

emitted by conventional diesel engines 

is considerable, due to operation in 

the unfavourable partial-load range. Under 

the working title of “Green Tug”, dieselelectric 

concepts for harbour tugs have for 

the fi rst time now been developed in the 

USA for the harbours in Los Angeles and 

Houston. For example, in Los Angeles it 

is planned to allow tugs to operate only 

under battery power in the city area of the 

harbour. In the outer area of the harbour, 

the batteries can then be recharged via the 

generators. If such plans are implemented 

– and there are many arguments in their 

favour – the Schottel Combi Drive undoubtedly 

represents the optimal propulsion 

solution for harbour tugs meeting these 

requirements. 

Schottel GmbH 

Spay/Rhein 

www.schottel.de 

The platform supply vessel “Bourbon Mistral“ has already fulfi lled the shipping 

company´s economic expectation in just a short space of time. Photo: Tony Hall 


SPECIAL | OMAE 2008 

Wave ernergy utilisation 

Rexroth rises to the Power Take-Off 

UTILIZING OCEAN ENERGY One of the main challenges at the concept of ocean power stations 

which extract power from ocean energy lies in devising a suitable “power-take off“ system for 

converting the kinetic energy of the water into electrical power 

Nik Scharmann 

Experts tell us that within a few decades, 

innovative systems for the 

sustainable use of ocean energy may 

generate as much electricity as 150–200 

nuclear power stations. 

On the one hand the important advantages 

of utilizing ocean energy here is that around 

two third of the world‘s inhabitants live in 

coastal regions. The close proximity of ocean 

power stations to consumers simplifi es the 

infrastructure and minimizes power losses. 

On the other hand ocean energy is always 

available: tides, currents, and – to a certain 

extent – sea swells are ever present, thus enabling 

more long-term planning. As a result, 

ocean power stations are a much better option 

for providing the base load of the electricity 

networks. 

A number of companies are currently working 

on different concepts for large-scale facilities 

that will extract power from this renewable 

energy source. The main challenge lies 

in devising a suitable “power-take off“ system 

for converting the kinetic energy of the 

water to electrical power while ensuring that 

generation costs remain competitive. The 

development of the plants and the necessary 

PTOs is only in its infancy, but Rexroth is 

already supporting numerous projects with 

tailored solutions, just as it did for wind 

energy a few decades ago. These solutions 


are based on Rexroth hydraulic components 

and cross-technology systems, which have 

already proven extremely robust and reliable 

in a range of maritime applications. 

The ocean energy industry currently consists 

of two main sectors: tidal energy and 

wave energy. 

Tidal energy 

Tidal power stations use the energy of currents 

to power rotors – be they tidal or natural 

sea currents. Water has a density one 

thousand times greater than air and can thus 

generate signifi cant power even from low 

fl ow velocities. This requires specifi cally tailored 

solutions. 

The diameter of underwater rotors does not 

have to be large for them to be able to con- 

Mechanic Power-Take-Off 

duct energy effectively. Even at low speeds, 

the forces acting on the entire system are 

signifi cant. Rexroth is currently pursuing a 

development concept that adopts the generator 

gearbox technology employed in the 

wind energy sector, an area in which the 

company has established itself as a worldleading 

supplier for renewable energies. 

Research is also being conducted into the 

use of hydraulic converters. This simple yet 

highly robust concept transforms rotary 

motion into hydraulic fl ow, which powers 

an adjustable hydraulic motor for the generator 

with great effi ciency. A slow-running 

radial piston motor with constant displacement 

is employed on the pump side. It 

generates a volumetric current based on the 

rotor speed. A fast-running axial piston dis-

placement motor is connected on the motor 

side, which can be fi tted directly to the 

generator shaft. The motor-generating set is 

then operated directly at mains frequency. 

There is no need for elaborate control electronics 

or frequency converters. It is also 

possible to implement a continuous transmission 

ratio. The system can thus be used 

to quench short-term peak demand while 

also enabling long-term adaptation to the 

changing current fl ow rates throughout the 

tide cycle. A pitch system is not required. 

Since the displacement motors employed 

can be operated in dual-quadrant mode, it 

is even possible to reverse the direction of 

the rotor when the tide changes. It is not 

necessary to rotate the system. Another advantage 

of this system is the positioning of 

the gearbox components: while the highly 

robust radial piston pump is installed under 

water, the motor-generating set remains 

above water. 

However, the high level of fl exibility of a 

hydrostatic power train over a mechanical 

gearbox results in lower effi ciency overall. It 

is not yet clear which power train technology 

will eventually prevail, but it will certainly 

depend on the activities of the plant suppliers. 

Increased effi ciency, particularly in the 

case of the fast-running displacement motors, 

could result in the hydraulic concept 

gaining the upper hand. 

Wave energy 

Fluid technology is particularly well suited 

to meeting the requirements of wave energy 

utilization. In a system with a nominal 

power of 150 kW, travel speeds will gener- 

ally range between 1 and 2 m/s at forces of 

500 kN to 1 MN. It should be noted that 

the maximum forces and speeds do not 

correlate: high travel speeds are usually the 

result of small waves over short periods, 

while high forces are produced by high 

waves over longer periods. 

The challenge for the PTO is posed by the 

specifi c attribute of waves: within a wave period, 

the input power of the machine fl uctuates 

twice between zero and the maximum 

value. A typical wave period lasts 10 s, i.e. 

0.1 Hz; the main frequency is between 50 

and 60 Hz. This effectively requires a transmission 

ratio of i = 500-600. Furthermore, 

the power of a wave increases approximately 

with the square of the signifi cant wave 

height. As a result, a power ratio of 1/100 can 

soon develop between the lower and upper 

operating window of the WEC (wave energy 

converter). 

Efficiency is not everything 

From a technical point of view, the effi - 

ciency of the PTO is the fi rst target variable 

Condition monitoring of oil systems 

HYDAC | One customer of Hydac AS competent 

clientele is Maskindynamikk AS in 

Spjelkavik, which develops complete solutions 

for periodic and continuous monitoring 

of rotating machinery with varying 

loads. Maskindynamikk has extensive experience 

with vibration analysis and have now 

implemented Hydac’s particle counter if oil 

cleanliness should be monitored as well. 

The hydraulic market shows great interest 

in monitoring oil cleanliness through online 

particle counting, relative humidity 

and pressure measurements. This makes 

it possible to use condition based maintenance 

instead of periodic solutions. The 

advantages are many, but of course to have 

maximum up-time on the machinery to a 

minimized price is the most important one. 

The fear of choosing an alarm point which 

could be wrong has been one of the most 

diffi cult obstacles in the way of condition 

based maintenance. If it is able to defi ne 

what is „normal“ it is also possible to defi ne 

Hydrostatic Power-Take-Off 

what is irregular. With continuous signals 

Maskindynamikk’s system is able to „learn“ 

and defi ne what is normal and one is able 

to use all logic ( „OR“, „AND“, „THEN“ etc.) 

commands to interconnect different signals 

which give the basis for the alarm. This 

to catch the eye: the more effi ciently a PTO 

converts the energy, the more electricity 

is produced. However, the target variable 

that will ultimately overshadow all activities 

is the cost of electricity generation in 

c/kWh. As well as the afore mentioned 

system effi ciencies, this index also incorporates 

the facility costs, including operating 

and maintenance costs, as well as the 

service life of the installed systems. Only 

a comprehensive optimization of all variables 

will lead to the minimization of electricity 

production costs. 

The development of a WEC and PTO that 

generates competitively priced electricity 

under the described conditions is a challenge 

which the entire industry is currently 

tackling with great vigor. 

Nik Scharmann 

Bosch Rexroth AG, Lohr a. Main 

nik.scharmann@boschrexroth.de 

www.boschrexroth.com 

Example: Thruster systems for ships are a very good example of a system which is 

interesting to monitor. Both the manufacturers and the ship owners are very interested 

in online monitoring of the condition of the thruster system. If the monitoring 

system is approved by a classifi cation society, it is possible to reduce the amount of 

visual inspections of these systems. 

means an alarm triggers only if it’s real and 

important to act upon. 

HYDAC International GmbH, 

Sulzbach/Saar 

offshore@hydac.com 

www.hydac.com 



Arctic knowledge at DNV 

informs risk management 

ARCTIC SHIPPING DNV has class notations covering the entire spectrum of cold climate operations 

ranging from control of icing in open waters to ice-breaking abilities in temperatures 

as low as -55˚C and in recognition of the rapidly changing physical and business environment in 

the Arctic. This offers now greater fl exibility in winterisation notations. 

Wendy Laursen 

As recently as two years ago, it was estimated 

that the north-eastern Arctic 

shipping route would be open for 

most of the year in ten to 15 years time, but 

the latest Norwegian research predicts that 

this may happen earlier than that. Icebergs 

forming in the region, some weighing over 

six million tonnes, are the largest moving 

objects on earth. 

Johan Tutturen, DNV business director for 

tankers, presented research results at the 

Mare Forum, Athens, in March 2008 that 

quantifi ed the value of the most important 

risk control options for Arctic shipping. 

Based on a shuttle tanker project intended 

for operation in Arctic waters, the research 

used known risk elements from worldwide 

operation but added additional risk elements 

for both cold climate and ice. 

The project revealed that redundant propulsion 

offers a 6 % reduction in the likelihood 

of accidents involving collision, 

grounding, fi re and explosion. Use of an 

automatic identifi cation system and electronic 

chart display as well as information 

systems offer a further 6 % reduction. Setting 

high standards in bridge resource management 

and the selection and trai ning of 

crew can reduce risk by 44 % and minimising 

noise and vibration levels when travelling 

through ice can reduce risk by a further 

12 %. 

Previous studies have shown that ships 

built with additional DNV class notations 

for nautical and bridge safety experience 

risk reductions of nearly 50 %. Most accidents 

at sea are caused by human error 

and harsh climatic conditions can result 

in poor quality rest, reduced alertness and 

concentration and poor speech intelligibility. 

The main objective of DNV’s NAUT notation 

is to reduce the risk of human failure 

in bridge operations by specifying requirements 

for workplace design, equipment 

standards and operational procedures. 

“There are many types of mitigating measures 

that can be introduced to reduce cold 

stress and they should be considered as 

safety investments,” says Tutturen. “It all 

boils down to risk management: identify- 

ing the hazards, measuring specifi c risk elements 

and the way they interact and then 

evaluating and implementing control options.” 

Oil and gas recovery in the Arctic is increasing 

and DNV undertakes feasibility studies 

and concept evaluations for these cold 

climate activities. They use integrated risk 

management tools that assess the total investment 

risk over the full project life cycle. 

Factors such as component reliability and 

production profi les are used to develop 

forecasting models and the use of probability 

distributions in simulation model 

input parameters allows uncertainty and 

variation to be used in the development 

of a quantifi ed risk picture for any revenue 

stream. 

“It is vitally important that ship owners 

contemplating Arctic operations are 

aware of the possible challenges connected 

with their intended trading patterns. 

Our research capability, extensive 

experience and state-of-the-art simulation 

techniques bring value to these of- 

“Arctic Discoverer“ will be trading out of Hammerfest close to the Barents Sea. The vessel is managed by K Line and classed to DNV. Photo: DNV 

Special 14 Schiff & Hafen | Juni 2008 | Nr. 6

ten multi-billion dollar decision making 

processes,” said Tutturen. 

Once a project is live, DNV can assist with 

quality control, maintenance and repair 

evaluations. Vessel category and availability 

can be an important consideration and 

limited accessibility for remedial action if 

incidents occur means extra planning effort 

is essential for safe Arctic operations. 

The protection of Arctic and sub-Arctic environments 

has been of increasing importance 

in recent years. Petroleum and shipping 

companies are facing rising demand 

for environmental safety. DNV participates 

in baseline studies and environmental 

monitoring. Their environmental risk 

analysis approach gives decision makers a 

transparent and effi cient tool for identifying 

and quantifying risk due to accidental 

oil spills. It includes probabilistic oil drift 

modelling and toxicity and impact assessments 

on sensitive environmental resources. 

Their contingency planning toolkit 

includes an electronic map interface for oil 

spill response operations that is distributed 

in real time to all involved parties. 

More tanker operators are looking to venture 

into the Arctic as a means of shortening voyage 

times from Europe to Japan and the US. 

“Allowing for changing climatic conditions 

is an important consideration on a day-today 

basis for ship operators but I believe that 

operating fl exibility will grow in importance 

in the future,” said Tutturen. “This is already 

the case with the newbuildings we are involved 

in. Hull fatigue damage accumulation 

is about twice as rapid in North Atlantic 

conditions compared to the comparatively 

more benign environment of traditional 

LNG routes, for example, and there is an increasing 

trend amongst owners to specify 40 

years of fatigue life in the North Atlantic to 

ensure trouble free operation in these more 

demanding cold climates.” 

Traditional open water accidents such as 

groundings and collisions are more likely 

to occur in cold climates. Fires are responsible 

for 10 % of all fatalities at sea and fi re 

fi ghting in severe weather is more complicated 

and therefore more likely to cause 

critical damage. In addition to this, new 

sources of accident are introduced in cold 

climates. Ice may damage a vessel or force 

it aground. Icebergs and ice fl oes can cause 

serious damage to a vessel in the zone between 

open sea and solid ice and sea spray 

can lead to severe icing and damage from 

the clogging of vents and the freezing of 

pipes. 

Extra notations 

DNV has been delivering standards for 

ice class shipping since 1881. Currently, 

over 1900 vessels carry DNV ice class 

notations, including the four highest 

specifi cation LNG carriers in operation. 

They incorporate Finnish and Swedish 

Maritime Authorities’ rules in their Baltic 

specifi cations and although unifi ed International 

Association of Classifi cation 

Society rules are under development, 

DNV’s extra notations offer a greater 

depth of operational security based on 

extensive experience and intimate local 

knowledge. Safe ship operations require 

more than just ice strengthening of the 

ship’s structure and propeller, says Tutturen, 

and DNV has developed technical 

standards for all ship’s equipment and 

structures where reliability is important. 

DNV’s latest Winterised notations have 

been expanded effective 1 January 2008. 

The notations recognise that some vessels 

spend shorter times in cold climates 

than others and the expanded rules defi ne 

three different levels of cold climate safety 

design. Each has separate designations for 

temperature in material selection and extreme 

temperature performance. Nevertheless, 

emergency features relating to escape 

exits, lifeboats, towing and evacuation play 

an important part in all notations. 

The highest level, Winterised Arctic, is 

for ships such as ice breakers that are 

operating in the harshest cold climate 

conditions and the notation calls for redundant 

propulsion. “A loss of power in 

extremely low temperatures can quickly 

lead to a critical situation and freezing of 

water and vital parts in the engine room 

may reduce the possibility of a re-start. 

Ideally, a blackout period longer than 

ten minutes should be avoided,” says 

Johan Tutturen. “Emergency generators 

should be located in a tempered location 

to avoid starting problems at low 

temperatures and additional heating arrangements 

ensure that temperatures in 

the engine room are maintained above 

freezing point during a blackout.” 

Winterised Basic and Winterised Cold cater 

for vessels operating in cold climates on a 

seasonal basis. Winterised Basic includes 

anti-icing precautions for communication 

and navigation equipment, sea chests, 

fi re fi ghting capacity and some vents and 

valves. Winterised Cold specifi es additional 

requirements including temperature 

protection for equipment and spaces, stability 

under ice loads and the use of low 

temperature steel for some of the structures 

above the waterline. 

Vessels travelling in the Arctic tend to try 

and follow the same ice channel as each 

other to navigate a path of least resistance 

and often the most favourable ice conditions 

will be close to shore. In practice, 

though, ships may sometimes operate under 

heavier ice conditions that those stipulated 

for their ice class. As well the safety 

risks associated, this can bring vessels into 

contact with the Russian authorities. 

“Arctic Discoverer“ will be crossing the 

Northern Atlantic where the weather 

condition will create challenges Photo: DNV 

DNV’s established relations with Russian 

institutions, means that they can offer valuable 

assistance in meeting local regulations. 

In Russian waters, it may be necessary for a 

vessel to have an ice passport. This is not 

a building standard but a description of 

safe operating modes for a particular vessel 

based on how the ship is actually built. It 

is based on the ship’s structure, hull lines, 

dimensions, displacement, propulsion 

power, propeller thrust, age and the state 

of the shell plating. 

DNV contributes actively to the development 

of technical and operational codes 

and directives for offshore petroleum activity 

in the Arctic and they proactively maintain 

their position at the forefront of research 

and risk management solutions for 

cold climate business. Over the next three 

to six years their strategic research initiatives 

are focusing on extreme ice shipping 

and human responses to the associated 

cold, noise and isolation. They will also research 

best practice emergency evacuation 

from ships and platforms in the Arctic and 

work on achieving a greater understanding 

of the ever-changing Arctic environment 

from a risk acceptance perspective. 

Wendy Laursen 

Det Norske Veritas 

wlaursen@bigpond.com 

www.dnv.com 



Ice protection structures 

ICE BARRIERS For over 25 years IMPaC Offshore Engineering has gained substantial 

knowledge and experience in numerous ice engineering projects. One area of special expertise 

is the design of ice protection structures. 

Joachim Berger 

The increasing demand for 

hydrocarbons requires 

offshore exploration and 

production drilling activities 

in ice infested areas. In shallow 

water areas like the North Caspian 

Sea, purpose-designed ice 

protection structures also called 

ice barriers can lead to solutions 

that provide technical and economical 

advantages compared 

to fi eld developments without 

ice protection measures. 

For the protection of offshore 

production facilities in shallow 

water areas permanent ice 

barriers made from rock or 

concrete structures are often 

the appropriate solution. For 

drilling exploration facilities, 

which usually have to change 

their location after they have 

sunk the well, ice barriers made 

from steel are mostly the better 

solution as they are easier to install 

and de-install. 

Ice barriers can also be used to 

protect offshore wind parks or 

harbour installations. 

Advantages 

Ice barriers allow designing 

of an exploration platform or 

other offshore facility for re- 

duced ice loads. The ice load reduction 

is a function of the type 

and number of ice barriers. 

Less expenditure for the protected 

platform requires additional 

costs for the design 

construction, installation and 

operation of the ice barriers. 

However ice barrier structures 

also considerably improve the 

conditions under which supply 

of the offshore unit is possible. 

In some cases platforms 

can only be operated during 

the winter season with ice barriers 

in place. Also during the 

non-ice season ice barriers can 

improve the platform supply 

conditions by reducing wave 

heights in the vicinity of the 

offshore installation. Thus, ice 

barriers can considerably extend 

the availability of the platform 

with large positive effect 

on the overall economics of the 

offshore fi eld operation. 

Ice barriers can also be required 

to facilitate evacuation of the 

crew from the platform under 

ice conditions. Production on 

offshore platforms has to be 

stopped under extreme environmental 

conditions where rubble 

ice piles prevent the emergency 

evacuation of personnel. Therefore, 

ice barriers whilst protecting 

the integrity of the offshore 

platform structure also increase 

the availability of the platform’s 

production, thus improving the 

economics of the project. 

Requirements 

An ice protection structure has 

to be a simple, yet robust structure 

as it is exposed to harsh environmental 

conditions and has 

to withstand large ice loads. The 

main requirement on ice barriers 

is a high technical reliability at a 

minimum material expenditure. 

For the protection of mobile 

units like offshore exploration 

drilling rigs the de-installation 

and re-use of an ice barrier are 

also of importance. 

Full compliance with environmental 

protection requirements 

is mandatory for all ice barriers. 

Determination of design 

loads 

The technical reliability of 

an ice protection structure is 

strongly dependent on the correct 

ice load. In some cases especially 

in dee per water areas 

the hydrodynamic forces due to 

waves and current can become 

the dominating load situation. 

Deterministic methods are 

mostly applied to predict the 

ice loads as the data basis for a 

probabilistic approach is often 

insuffi cient. 

When the ice protection structure 

is of simple geometry analytical 

methods can be applied 

to establish the ice loads. When 

the shape of the ice barrier is 

too complicated for analytical 

methods ice model tests have 

to be carried out. 

In practice, the prediction of 

ice loads is not the major challenge 

but the determination 

of realistic full-scale ice conditions 

from which the ice loads 

will be derived. The uncertainty 

in the ice load conditions and 

the lack of full-scale data often 

require a conservative design 

approach and do not allow full 

design optimisation of the ice 

barrier structure. 

Due to the lack of ice data 

satellite imaging has been utilised 

to determine ice conditions. 

The satellite images allow 

a fairly good estimate of 

the ice coverage and the thickness 

of sheet ice. But in many 

Fig. 1: Drilling unit with driven piles as ice protection structure Fig. 2: Ice protection piles, view from drilling unit 

Special 16 Schiff & Hafen | June 2008 | No. 6

Fig. 3: Drilling unit with barge type ice barriers to protect against excessive ice loads 

cases the dominating ice loads 

for an ice protection structure 

result from the interaction 

with pressure ridges, which 

cannot be identifi ed from the 

satellite pictures. In such cases 

fi eld observations and surveys 

are of particular importance. 

Driven piles as ice protection 

structure 

Driven piles have been used as 

ice protection means at the fi rst 

two exploration sites of a mobile 

drilling barge, which has 

been operating since 1998 in 

the shallow water areas of the 

North Caspian Sea. The piles 

also serve as berthing and mooring 

piles for the supply vessels. 

The optimum pile arrangement 

has been determined in 

ice model tests. The main parameters 

infl uencing the ice 

load reduction for a given ice 

thickness are pile diameter 

and pile spacing. With the optimised 

pile arrangement the 

ice loads could be reduced by 

60 percent compared to the solution 

without any piles. 

Simple pontoons as ice protection 

structures 

As a larger number of wells 

had to be drilled as originally 

Fig. 4: Design options for optimised barge type ice barriers 

structures 

anticipated the piles have been 

replaced at later sites by pontoons, 

which have the advantage 

of easy re-usage. 

After de-ballasting and refl 

oating the ice barrier barge 

can be towed to the next exploration 

site of the drilling 

unit. At the drilling site the 

ice barrier barge needs to be 

ballasted with sea water in 

order to create suffi cient sliding 

resistance. In some cases 

concrete can be used as fi xed 

ballast. However, due to draft 

limitations fi xed ballast cannot 

always be used. Due to 

the simple geometrical form 

of the barge type ice barriers 

the ice loads could be established 

by analytical methods. 

How ever, for establishing the 

minimum number of ice barrier 

barges and their optimal 

arrangement relative to the 

drilling unit ice model tests 

have been carried out. 

In future, ice model tests may 

only be required for verifi cations 

purposes as latest developments 

of computer models 

allow a relatively good analytical 

simulation of the interaction 

of drifting ice with ice 

barriers of different arrangement. 

� 

Fig. 5: Ice barrier structure providing shelter for a supply 

vessel 



Fig. 6: Sketch of a light-weight ice barrier © IMPaC 

Purpose-designed ice protection 

barges 

Various types of barges have 

been developed by IMPaC 

aimed to optimise performance 

as an ice barrier. 

The vertical wall design has 

been compared to sloped 

walls with different slope angles. 

For sheet ice the sloped 

surface has advantages but often 

the interaction with pressure 

ridges is the dominating 

load scenario for which the 

slope angle of the wall is of 

lesser importance. 

Ice protection barges with 

one vertical long wall have 

advantages during site installation 

and de-installation or 

when the barge needs to be 

moored in a harbour or yard 

for inspection purposes. During 

operation the vertical wall 

normally facing towards to the 

drilling unit has the advantage 

of providing a berthing and 

mooring place for marine 

boats and barges. 

Sloped walls also have the advantage 

of smaller local ice 

loads compared to vertical 

walls. The weight of the steel 

shell of a barge type ice barrier 

strongly depends on the size 

and distribution of the local 

ice loads. The smaller the ice 

load exposed area considered 

in the stress analysis the lar ger 

the local design ice load to be 

applied. The distribution of 

the local ice loads including 

so-called “ice background pressures” 

acting on the sloped or 

vertical shell usually leads to a 

vertical stiffening of the shell. 

For economical reasons plastic 

deformations of the outer 

steel plate and the stiffening 

bulb profi les are normally accepted 

while stresses in frames 

and bulkheads have to remain 

within the elastic range. 

In Figure 5, a barge type ice 

barrier with one sloped and 

one vertical wall is shown, 

providing shelter for an ice 

breaking supply vessel. 

While the local ice loads have a 

large impact on the design of the 

steel shell the global ice loads 

usually dictate the overall height 

and bottom width of barge type 

ice protection structure. 

Fig. 7: Light-weight ice barrier with accumulated rubble ice and 

indicated ice drift direction 


The ice barrier has to provide 

suffi cient sliding and overturning 

resistance. In very 

shallow water areas sliding 

failure is more of a risk than 

overturning. 

When the seabed is of the 

non-cohesive type (sand) 

the overall design of the ice 

barrier is weight driven. The 

larger the contact pressure 

from the bottom plate to the 

top layer of the seabed, the 

larger the sliding resistance of 

the ice protection barge. The 

sliding resistance can be further 

improved by using skirts. 

Spray ice could also be used 

to increase the weight of the 

barrier. The larger weight of 

the barrier structure leads to 

larger sliding resistance. 

When the seabed is of the cohesive 

type (clay) the footprint 

of the ice barrier becomes important 

while the weight has 

less impact on the sliding resistance. 

At sites with cohesive 

seabed material, underwater 

berms or backberms can lead 

to an improvement of the sliding 

resistance. 

Light-weight ice protection 

structure 

IMPaC has developed a light 

weight ice barrier structure, 

which is based on the idea 

that the broken ice pieces will 

be collected and the mass of 

the accumulated rubble ice 

contributes to the overall resistance 

of the barrier. 

The principle of the lightweight 

ice barrier can be seen 

in Figure 6. It shows the fi rst 

stage of the interaction with 

drifting ice in early winter 

when relative thin ice has 

failed at the sloped wall and 

the broken ice piece start to 

accumulate. 

Various ice model tests have 

been carried out to verify the 

function of the light-weight 

ice barrier. The ice model 

tests were also performed to 

measure the ice forces acting 

on the structure during 

the different phases of the 

interaction with drifting ice 

features. Also the mass of the 

accumulated ice was determined 

which allowed checking 

the sliding stability of the 

light-weight barrier structure. 

Figure 7 shows the situation 

after the light-weight ice barrier 

has been fi lled-up with 

rubble ice. 

The research project was supported 

by the German Federal 

Ministry of Education and Research. 

Outlook 

Future exploration and production 

activities in the North 

Caspian Sea and other ice infested 

shallow water areas will 

require a considerable amount 

of ice protection structures, 

which need to be designed, 

built and operated. 

IMPaC Offshore Engineering 

will continue to play a leading 

role in the realisation of these 

projects and also in the future 

development of new ice protection 

technologies. 

Joachim Berger 

IMPaC Offshore Engineering 

Hamburg 

berger@impac.de 

www.impac.de

Hydrocarbon sensor systems 

PIPELINE MONITORING To improve detection effi ciency and to eliminate the need to introduce 

additional potential pollutants to underwater pipeline systems CONTROS has developed a new leak 

detection method, a “Hydrocarbon Sniffer System”, called HydroC. 

Daniel Esser 

The global demand for energy 

challenges the offshore 

oil & gas industry to go for 

deeper regions and the arctic 

areas. However, environmental 

awareness and concern puts the 

focus on effective and reliable 

monitoring systems to avoid leaks 

and spills of harmful fl uids. 

Subsea production systems are 

getting more and more common 

for these applications. Globally 

subsea pipelines and production 

systems are becoming a major 

concern as authorities are less tolerant 

to leaks of polluting material 

into the marine environment. 

In this respect, the ability to detect 

and also to locate any leakage of 

oil or gas to the surrounding water 

and environment is of utmost 

importance to safeguard a green 

and healthy planet. 

At a depth of 3,000 meters operation 

of a subsea production 

installation is a great challenge 

and a high risk. Not only are the 

costs for deep sea installation 

high, but the risk for the environment 

is evident – is it possible to 

detect or repair a leak? 

Subsea fi eld development and 

long pipeline transport may be 

the only alternative to develop a 

deep sea installation; if suffi cient 

water depths, infrastructure on 

the seafl oor can be advantageous. 

However, in Arctic areas where 

the surface ice and iceberg conditions 

can be problematic. Subsea 

processing is regarded as an effi - 

cient way to safe energy; reduce 

the use of chemicals and to reduce 

discharge of produced water. 

In the past three main methods 

of subsea leak detection have 

been used for leaks where obvious 

visual signs of large leaks 

such as bubbles, large clouds, 

etc. are either not present or have 

failed to locate these problems. 

These three main methods used 

are fl uorometric measurement, 

pig-systems (not useable for all 

types of pipelines of today) and 

passive acoustics, which listen 

for ultrasound created by fl uid 

leaking under pressure. 

The systems mostly used these 

days for permanent monitoring 

or pipeline inspection by ROV 

(Remotely Operated Vehicle) or 

AUV (Autonomous Underwater 

Vehicle) seem all to have disadvantages 

in detecting very small 

and non visible oil or gas leaks. 

In an effort to fi nd new leak detection 

methods that improve 

detection effi ciency and also 

eliminate the need to introduce 

additional potential pollutants to 

pipeline systems, CONTROS has 

been working on a “Hydrocarbon 

Sniffer System” called HydroC 

for the last fi ve years. This unique 

system which is now available 

has a worldwide patented optical 

analysing system. Hydrocarbon 

molecules diffuse through a special 

membrane (which keeps the 

water out) and enters into the detector 

chamber. The adsorption 

of light in gas leads to change 

of intensity which is measured 

electronically. The HydroC can 

detect the higher order chain 

of hydrocarbons or just CH 4 if 

Methane is of primary interest; 

which is a huge advantage as CH 4 

is the smallest molecule in nearly 

every crude oil and natural gas. 

A system can consist of one HydroC 

or an array of sniffers, current 

meters and other instrumentation 

required covering a large 

subsea installation or an area of 

manifolds. This HydroC system 

is unaffected by turbidity or 

other interferences such as H 2 S 

or any other gaseous substances 

in the environment. This system 

was developed specifi cally to allow 

fast, real-time and in-situ detection 

of dissolved and gaseous 

hydrocarbons/methane in water, 

whatever the source. It has been 

successful used in hydrocarbon 

surveys and pipeline inspections 

to water depth up to 3,000 metres 

worldwide. 

The very high sensitivity (down 

to 30 nmol/l) of the HydroC 

Monitoring of critical paths and pipelines 

system also makes it ideal for 

the detection of methane seepage 

from the seabed. Here it is 

also widely used for the exploration 

and the production process 

of methane hydrates in different 

projects around the world. 

CONTROS is also partner of the 

German Gashydrate Organisation 

(www.german-gashydrate. 

org) where another CONTROS 

HydroC instrument for CO2 

detection is used for the CO2 

sequestration process, which 

has become an important topic 

for the international oil companies. 

The calibrated HydroC 

(Hydrocarbon or CO 2 ) plug & 

play system records data ei ther 

internally or externally in units 

of hydrocarbon or methane concentration. 

By careful logging 

around an area of leakage from 

a pipeline, the seabed or a manifold, 

an estimate of the amount 

of leaking gas or oil can be made 

directly. HydroC is in use by 

several pipeline inspection companies 

and CONTROS has close 

cooperation with the leading 

ROV manufacturers to equip 

their inspection ROV’s with the 

latest leak detection technology. 

In summary CONTROS provides 

offshore pipeline inspection 

and long term monitoring solutions. 

HydroC leak detection 

product line, fi eld experience 

and advanced data management 

systems meet demanding regulatory 

requirements and enhancing 

safety during production from 

subsea production systems. 

Daniel Esser 

CONTROS Systems & 

Solutions GmbH, Kiel 

d.esser@contros.eu 

www.contros.eu 


Oil and Gas: a new perspective 

Your business is oil and gas – and our business is your safety. From industrial plant to pipelines, from planning to maintenance, 

whether its advice, testing or certification you require: Germanischer Lloyd Oil and Gas (GLO) is your reliable serviceprovider 

when it comes to verification, certification and quality assurance for your systems – anywhere in the world. Our range of services 

revolves around the safety and health of people, the protection of the environment, and the securing of investments. 

Welcome to GLO, your partner for the utmost safety, on- and offshore. 

Germanischer Lloyd Industrial Services GmbH 

Oil and Gas 

Steinhöft 9 · 20459 Hamburg, Germany 

Phone +49 40 36149-750 · Fax +49 40 36149-1707 

glo@gl-group.com · www.gl-group.com/glo

Offshore Technology

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