Marine Production Technology

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Production -how ships are built

The objective is to provide a broad overview of the production process for ship construction.

Before production there are a number of essential pre-production activities

• Market analysis, product mix selection

• Design development, specification, strategic planing

• Estimating, tendering, contract negotiation

• Detailed design, product work breakdown

• Tactical planning, purchasing

• Detailed planning, scheduling, production information

• packaging of materials and information to work stations


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Shipyard Facilities (1)

The facilities which are found in a shipyard depend on the manufacturing strategy which is adopted. It may in some cases be more cost-effective to sub-contract certain activities. A comprehensive list is:

For Hull Production

• Steel Stockyard

• Steel Treatment (levelling, shotblasting, painting)

• Plate and profile cutting

• Plate and profile forming

• Workshops for sub-assembly, assembly and unit assembly

• Block assembly, outfitting and painting workshops

• Block storage area


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Outfitting facilities are also required. It is more common to sub-contract outfitting than hull work, but some shipyards retain a full range of facilities.

Outfitting

• Pipe storage, cutting and welding

• Machine Shop

• Accommodation work (woodwork, metal furniture, linings)

• Electrical and electronic workshop

• Sheet metal workshop (ventilation trunks, metal fittings)

• Riggers workshop

• Outfit unit assembly

• Material and equipment storage

Post-launch facilities for outfitting and trials are also required


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Ship Construction is the major facility in most cases. There are a number of methods for transfer of the completed ship to the water

• Inclined Slipway (for dynamic launch - traditional)

• Side launch slipway

• Graving Dock

• Shiplift

• Load-out (to floating dock)

There are other methods used occasionally

All the alternatives can be enclosed in a building for environmental protection.

All require large capacity cranes for lifting and manipulating blocks.


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Shipyard facilities (4)

A number of supporting facilities are also required. These can form a substantial part of the cost of a new facility.

• Electrical sub-stations

• Bulk gas storage facilities

• Compressed air plant

• Water storage tanks

• Associated services distribution systems

• Offices

• Amenities (changing rooms, canteens, et.)

• Training facilities

• Car and bus parking


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Which facilities are required for a shipyard?

For a new or re-developed site, the selection is on the basis of

• cost - can the requirement be met more cost-effectively by sub-contract?

• importance - is it essential to have control of the requirement?

Other factors could include

• space available

• funds available

• future changes in product mix


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Steel Storage

The first stage in the process is the stockyard for steel.

The need for this is dictated by the ability to match supply of steel to the facilities with the demand. If the steel mill is close, and can provide steel with a very short lead time, then storage is not a problem.

Most shipyards have a steel stock for one to three months.

Plates are generally stored horizontally and handled individually by magnet beam crane.

Profiles are usually handled in batches using slings.


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Steel Treatment

Assuming the shipyard does not but steel ready primed.

The treatment process includes

• pre-heating, usually water wash or gas

• levelling

• shot-blasting

• paint application

• drying

The processes are linked by a roller conveyor, and the operation is largely automated


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Steel Cutting

Plates are generally cut using Numerical Control (NC) machines.

Older shipyards use optically controlled machines.

The cutting process can be

• oxy-gas (smaller shipyards and where welding preparation is required)

• plasma (large production volumes but cutting is underwater)

• laser (rare to date and only for thinner plate)

• mechanical plane (straight edges only, but very accurate)

• edge milling (also only straight edges)

• guillotine (for small, straight-sided parts)

Profiles are cut using oxy-gas or mechanically

• robots are used for high volumes of throughput

• mechanised conveyors may be used to move the profiles

• hand or portable equipment is still used in small shipyards


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Plate Forming

Plates are formed using a number of machine types.

For small volumes of production, machines can be used for other purposes.

Heat-line bending is an alternative, but slower and labour-intensive.

Machines are

• Plate Rolls (for shell plates, best for single curvature)

• Gap Press (for most forming, including double curvature, but slow)

• Portal Press (for most forming)

• Press Brake (for flanging and corrugated stiffening)

Accurate bending is difficult because of “spring-back”.

Heat line bending can be used for final adjustment of formed plates

Templates can be produced used CAD-generated information.


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Profile Forming

Profile forming is primarily for transverse frames and uses a cold bender.

Templates are defined by CAD

The final shape of the frame is checked using

• templates

• wire sets

• inverse-curve bending

Other processes can be used for flanges and small stiffeners

• Press brakes

• Mast rolls


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Assembly

Shipbuilding is primarily an assembly industry, using the parts created in previous processes. Steelwork Assembly is usually in several stages and many definitions exist for these. The simplest are

• Assembly - all stages where interim products are joined together

• minor assembly - joining two or more individual pieces

• sub-assembly - joining parts and minor assemblies

• unit assembly - joining interim products to create a unit which could be taken to the final construction site

• block assembly - joining units to create larger products before they are taken to the construction site

Outfit Assemblies are also created, in similar stages between

• minor assemblies - e.g. pipes and supports

• engine room modules - complete sections with all equipment


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Specialist Steelwork Assembly Equipment and Processes

Curved Panel Assembly

• provides an accurately shaped jig for panel assembly– telescopic pins of adjustable height– magnetic or other faring equipment– single-sided welding

Flat Panel Assembly

• is frequently a flow line with work stations linked by conveyor

• provides specialised equipment for each stage of assembly– plate alignment and fairing using magnets– plate welding (single side or with a turnover crane included)– stiffener marking, location and fairing– stiffener welding– secondary stiffener location and welding

• generally automated welding systems


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Outfitting (1)

In many shipyards, outfitting organisation is less advanced than steelwork.

There may be automated or semi-automated processes at early stages.

Assembly is limited and manual.

Pipe Shop

• automated storage and retrieval where production volume is high

• automatic pipe cutting to length

• automatic flange welding can be used

• NC pipe benders are in use

• other specialised equipment is used for branches

• assembly is a manual operation


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Outfitting (2)

Other outfitting workshops generally provide basic facilities.

Sheet metal

• small mechanical cutting and forming equipment

• lock forming and other specialist equipment

• manual assembly

Machine Shop

• general purpose machine tools

• specialist equipment (e.g. shaft lathe)

Woodwork Shop

• frequently use bought-in items rather than manufacture at the shipyard

• general purpose equipment is used


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Further Block stages

Advanced shipyards are able to combine steel and outfitting at an early stage of production. It is more usual to install equipment and other outfitting at the block stage.

Typical activities carried out on completed hull blocks are

• shotblasting

• painting

• outfit installation

Specialised facilities may be provided for these activities.

• paint cells - (temperature and humidity control, access equipment)

• outfitting halls - (access equipment and cranes)


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Ship Construction

The choice of facility is wide.

• inclined slipway for end launch

• flat construction area – for load-out– for side launch

• graving dock

• flat area combined with a lift

Any of the above may be arranged to allow two vessels to be produced simultaneously

Any of which may be open, partly or completely to provide for weather protection

The final erection area is typically the area of highest capital cost


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Lifting and Handling

The method used to move final assemblies to the erection area is a major cost element

Alternatives include:

• level luffing jib cranes

• goliath cranes

• overhead cranes in buildings

• self-elevating transporters, in association with cranes

• ground level systems– wheeled systems– sliding or “walking” systems


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Post launch

Launching is traditionally a major milestone in ship production.

It is often of less significance, where the outfitting of the ship is substantially complete before launch. In some cases, standard cargo ships may be delivered within four weeks of launch.

A quay is required to moor the ship for the final outfitting period.

This period may still be extended in the case of a military vessel, a large cruise ship or other vessel with complex internal or deck outfitting.

The quay requires cranes and services to match the volume of work to be done. Separate stores and workshops may be needed.

Support for testing and trails is also provided at the quay.


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Post delivery

The production process is completed with delivery of the ship.

However, to complete the cycle from marketing, feedback from the customer should be sought.

As a minimum there will be a guarantee docking after twelve months.

Some advanced shipyards place a guarantee engineer on board the ship to monitor all aspects of operation and feedback to the design and production process.

The level of post delivery support will vary both wit the attitude of the shipyard and the technical and operational requirements.


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References

Ship Production, Storch, Hammon, Bunch, Moore

Creating a production facility for standard ships, Kimber, Hargroves

Shipbuilding Technology International Annual publication

Shipyard Technology Occasional publication

“Naval Architect” regular features on shipyards and technology

Marine Log, Maritime Reporter, Fairplay regular articles

Education

Marine Production Technology