design for ship repair and survey doc

Design for ship repair and survey

(shiptechnique journal vol: XXV ,2009)

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K. Sivaprasad Reader, Department of Ship Technology, Cochin University of Science &

Technology ,Kochi, Kerala ,India

Ujjawal Kumar Vidyarthi & Suby chandy Final Year Student ,B.Tech , Naval Architecture & Ship

Building , Department of Ship Technology Cochin University of Science and Technology , Kochi

Kerala , India

Email Contact: [email protected] ,

The recent shipbuilding boom has produced unexpected development in almost all

shipping and marine technology sector. These include ship operation, new shipbuilding, ship repair and

surveying etc …. In shipping industry acute shortage effective manpower is visible in all trade sectors.

The order book of almost all the medium and large building yards is full. The shipbuilding yards and ship

design offices all over the world are facing it difficult to manage their projects due to unavailability of

qualified Naval Architects and Shipbuilding Engineers. The situation in Ship Repair firms is also not very

different. The technical institutions which offer Naval Architecture and Shipbuilding courses are also

affected very badly as the faculty positions are lying vacant ever since the boom started.

In this context, it will be interesting to note the effect of the shipbuilding boom in one of the critical

fields in the entire marine technology sector, i.e. Ship Classification and Survey. Ship classification

societies are also affected adversely in the manpower crises. First time in the history of ship

classification and survey, the classification societies are struggling to keep the experienced hull

surveyors with them. Hull surveyors with more than 5 years of solid service are even moving out of

classification jobs and they are accepting positions elsewhere in ship design consultancy firms and

Shipbuilding yards. The present shipbuilding boom is only partly responsible for this situation. A close

look at the profile of ship surveyor’s responsibilities and activities will reveal more information regarding

the present exodus of qualified and experienced Naval Architects. The tough environments in which

surveyors there routine survey and inspection works, have an important role to play in this

extraordinary phenomenon.

In the recent past, there have been significant developments in the shipyard facilities and shipbuilding

policies, such as general yard infrastructure, shipbuilding techniques and methods, safety practices and

environment policies which have contributed considerably to the quality of working conditions of the

workforce. Though some of them were implemented as per the guidelines issued by ship classification



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societies, they themselves are yet to get benefit out the same. The surveyors are discharging one of the

most critical duties for ensuring smooth international shipping activities in a relatively rough and tough

working conditions .Major area of concerns regarding this include ,

1. Access to surveying.

2. Protection design and safety practices.

3. Frequency of surveys.

4. Maintenance policies

All these topics can be included in an engineering philosophy frame work; Design for

Ship Repair and Survey. The philosophy should be developed into an engineering practice in ship design

and naval architecture through which the quality of working condition of surveyor, repair engineers and

workers can be improved substantially. Following discussion topics elaborate the need of such a frame

work.

1. Access To Survey And Inspection

Certain areas of ships are located a way that it is difficult to get an access into that for survey

and inspection. Owing to this; some areas of the ship may remain under inspected. Even small

defects can propagate slowly affecting the operation and life of ship adversely. Following are

the different problem areas in this regard,

1.1 Depth of under deck transverse webs, longitudinal, deck side girder etc (especially in

tanker ships), difficult to raft and do a close up inspection of the under deck structural

arrangement.

This problem can be solved by shifting the under deck transverse webs on the main

deck. Doing this does not influence the ships strength adversely .It has been tested and

implemented in chemical tankers and found to very effective. A drawback of this solution is

that the structural arrangement is weather exposed. But from survey point of view it is an

effective solution.

1.2 When ships are in dry-dock for repairs, shipyard arrange scaffolding in tanks mainly for

carrying out repairs, it is also used by surveyors. But this process is time consuming and

accessibility is often limited.



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This problem can be taken care of by providing stiffeners or longitudinal which

contain ladders or hand rails by which surveyors can walk through and inspect the

adjoining areas.

1.3 Height of double bottom is critical factor for surveying. Low height inhibits human

entrance. Apart from the access problem inadequacy of light and oxygen are also to be

taken into account.

Man movement and survey is difficult in double bottom and the process of

survey is time taking. In order to tackle this dual effect, an alternative surveying practice

is to be designed and developed. An effective solution for this can be a high quality

camera fitted robotic machine which will move over all the places of inspection. For free

and smooth movement of robotic camera system in the region of inspection, we need to

design the double bottom accordingly. The design of double bottom for ship survey

becomes particularly important. In this regard we need to carve and create a path for

the robotic camera system through the stiffeners or in floors in such a way that all area

of inspection is within the reach of the robotic camera. To do this sometimes we may

need to cut an access hole through the floors which may affect the strength of floors.

The floors which have been modified should be additionally strengthened without

affecting the free movement of the robotic camera unit. This technique of inspection

can be extended to other areas of ships also.

2. Protection & Accident Prevention Practice



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2.1 In House Inspection

Moving parts in open deck which are quite heavy and operates in one off the major area of

concern ensuring watertight integrity in very critical during the ships, these parts need to

examine regularly.

2.1.1 Hatch Cover

There is always a threat to the safety of crew, ship and its cargo due to loss of weathertight integrity and

ingress of water into hold spaces. This problem assumes a great perspective if the ship is heading for a

long voyage and the hatch covers is damaged early in the voyage. Proper vigilance from the crew of ship

becomes necessities to ensure that there no damage through flooding & hatch openings. Badly

maintained or damaged closing arrangements are mainly responsible for the menace. The classification

societies lay stress on hatch cover weathertightness and proper maintenance. Broadly, two kinds of

situation may bring about lack of weathertightness , one arising out of normal use of the hatch cover

system such as hatch coaming deformation or the normal wear and tear of the cleating arrangement ,

And second, resulting from lack of proper maintenance, corrosion, inadequate lubrication, non

replacement of old gaskets, ill standards of cleats and gaskets, and inappropriate repairs.

The classification society rules for the construction and inspection of hatch covers should be

more focused towards ensuring safety to the ship and cargo from such threats. The ship operation

manuals prepared by the ship builder should specifically mention the in-house maintenance practice

regarding watertight integrity of hatch covers. Efforts by owners, masters and crew in effective

maintenance are also required. To check the integrity of hatch covers during voyage, the ship’s crew

must keep a vigil eye on their condition by means of visual inspection and techniques like light

infiltration test and ultrasonic tests on board. In order to ensure proper inspection , all such ships should

have especially trained personnel who can inspect the hatch covers properly in all respects. They should

also send feedback to the manufacturers and classification societies for improvement in original design

specifications. Hatch covers should be designed with a view refer to ship motions and acceleration

induced stress as of the equipment, ease of operation and convenience of maintenance.

• Steel protection with high quality coatings and corrosion resistant materials should be used. A

strict maintenance programme should be run by the crew to avoid corrosion, lubricate the

moving parts and hatch covers kept in proper conditions, keeping damage holes clear.



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Peripheral and cross joint gaskets should be strictly vigilated. In case of hydraulic cleating or

securing, it should be ensured that the covers remain closed and weathertight in case of failure

of hydraulic mechanism.

• During voyage in emergency, tarpaulins or adhesive tapes may be used for closing the openings.

This can especially be done in cases of large cracks, hatch cover openings, and badly joined

parts. Containers and cargoes should not be stowed on hatch covers unless they have been

designed for such carriage. The securing devices must be checked and tightened by the crew,

especially in rough sea conditions. Proper stowage and security of deck cargo and derricks must

be ensured, To avoid dislodging and subsequent damage to hatch covers. The manufacturers’

instructions regarding safe operation, inspection, maintenance and repair must be followed in

all respects.

• Onboard repair welding can be done to close the gaps, cracks and other structure failure.

Cracks in the hatch cover... Damage to fertilizer

2.2 Forward End Form Design



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The flooding of spaces below the main deck due to hatch cover or securing device

failure, or failure of other deck fittings, is linked to green water loads. Failures have

been attributed both to direct impact loads of an impinging wave, and to impact by

loose gear, deck equipment or fittings that have broken away from their foundations

and then been carried by green water.

One of solution to this operation problem is the bow height and Provide increased

reserve buoyancy above the main deck and added bow protection against green sea

loads, such as increased bulwark height and flared upper bow part, are currently being

analyzed to reduce the occurrence and effects of green water on deck. Based on the

formal investigation report on the loss of the ship Derbyshire, new model tests and

extreme value predictions for severe wave conditions have been carried out and are

being used to re-assess strength requirements for hatch covers and foredeck fittings.

2.3 Pipe penetration arrangement.

Sleeve and doublers arrangements are two important penetration arrangements through

bulkhead. Such arrangements have various advantages depending upon location purpose of use

and piping system for which it is used, but whereas repair is concerned sleeve arrangement has

many advantages over doublers arrangement which are listed below



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Doublers arrangement Sleeve arrangement

• Sleeve arrangement require less weld length, less heat input eventually less man-hour

in comparison of doublers arrangement installation.

• Doublers arrangements need frequent replacement because more prone toward

corrosion

• While repairing, cut in bulkhead is small for sleeve arrangement.

Standard shipyard practice is to mark with welding rod on spool pieces for classification. It is

done to retain its identity forever even after galvanizing. It is time taking and needs extra

consumables and man-hour. Unwanted heat input in affected area make it more prone to

corrosion too.

It can avoided by using an aluminum foil attached with spool pieces and other marking

equipments on Flange can also serve the purpose.



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Marking with welding rod Aluminum foil for spool classification

3. Frequency of Survey

A part of ship’s surface is in direct contact with sea water and the rest is in touch with

atmosphere, but all these surfaces are still surrounded by the sea. So, the paints used

for ships must resist salt water activity and be able to oppose atmospheric corrosion.

The paints in general use are alkyd resin based

paints, bitumen based and glysorite based. they have protection life about 5 to 6

months after that ship has to repainted , Naval Material Research Laboratory Mumbai

has developed a new means of protective coating for naval vessel and platform , some

of recently developed paint are self healing paint , smarter paint and fire retardant

paint. Some of areas of ships are surveyed after enough gap of time in which there may

be inevitable damage to the paint and the surface may be in danger. in such area , self

healing paint play an important role in protecting the surface .if some damage is done to

the paint layer like crack etc , this paint itself cure the crack . If these new painting

scheme can implemented, the frequency of surveying can be decreased or gap can be

increased.

4. Maintance Polices



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For easy running of ship need to timely monitor the hull condition. Apart from severe corrosion the

outer hull experience due to presence of salt water in surrounding, the presence abrasive cargo

in hold also cause severe corrosion of inner parts of hull. In order to monitor the condition of

structural components, condition assessments are conducted within the scope of class surveys,

statutory surveys and ship owner's surveys in regular time intervals. Information to be recorded consists

of thickness measurements and other findings affecting structural strength like cracks, condition of

coating and sacrificial anode condition. Today, hull condition monitoring is tedious and time taking

process (Thickness measurement &comparison is done by manually). The major disadvantages of the

current procedure can be summarized as

a) Process involved is data collection, reporting and analysis is done by manually. Hence its time

consuming

b) Difficult to access the problems area

c) Automatic transfer of thickness measurement result to direct class calculation system is not

available

The ships hull can be monitored by a special mechanism. it involve a robotic machine clinging to the hull

structure for thickness measurement. These measured values can be stored in a file through software

which can be easily imported to the 3-D model of the ships. There it is checked analytically and

graphically by a computer and the danger areas are clearly shown through the automatic alarms.

INPUT hull condition model hull condition condition assement

TM, damage report for this survey model history ship condition alarm

Picture report, coating

In this context pioneer work proposed by GL is worth referring to. The Germanischer Lloyds has

developed software, PEGASUS to support the thickness measurement process for achieving fast and

easy input and visualization of the thickness measurement data .The software first accept the data input

and reports it .then analyses the data prepares the final report.



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Thickness measurement Dark areas show the danger zone

Conclusion

This paper has tried to highlight the need of implementing new design feature, focusing the

requirements of survey and inspection of ship hull. Some of the proposed ideas in this paper

have to be looked further into for its practical application possibilities within the scope of

present know-how and technology available in ship design and ship building. A feedback

from the surveyor community is a must for detail research in this subject, With the help of

the feedback data on hull survey of ships more suggestion can be incorporated in the frame

work of Design for Ship Survey and Repair.

References

1. IACS URZ, Requirements concerning Survey and Classification, 2003

2. Efficient Data Management for Hull Condition Assessment David Jaramillo Germanischer

Lloyd, Germany, Christian Cabos* Germanischer Lloyd, Germany, Philippe Renard Bureau

Veritas, France

3. IACS Rec. 1997/ Rev 2 1997

4. IMO Resolution MEPC.94(46), 2001, Condition Assessment Scheme



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design for ship repair and survey doc

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