6 esential elements of ship production

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6 ESSENTIAL ELEMENTS OF SHIP PRODUCTION

6.1 AIMS OF THE LECTURE

a)To introduce the basic elements in ship production.

b)To give a general view of every aspect of the essential elements in the ship production.

c)To expose the ship production system, shipyard layout, and facilities involved.

6.2 BASIC ELEMENTS

Shipbuilding is a large and complex structure; it involves a great number of human resources,

facilities, equipment and machineries, as well as technology, skills, and knowledge to

produce a ship.

The basic elements of ship production would include the followings:

a)Human resources

Human resources is one of the key elements in ship production, it is the mover of all activities

involves in the production process both technical and managerial. It should be well managed

in order to obtain optimum benefit of its existence, and to manage the human resources one

cannot separate it from the organisation, including human resources planning and industrialrelation.

Detail of human resources management will be discussed in section 8.

b)Supplies

Beside machineries and equipment to support all the activities being undertaken ship

production processes also rely very much on the availability of supplies, which would

include: fresh water supply, power supply, compressed air supply, and gas supply.

Fresh water supply

The usage of fresh water is mainly for cleaning purposes, and in certain machining task it

is also used for cooling.

Power supply

Electricity is needed almost in every activity of the shipyard. It might come from two

different sources i.e. self-generated, and supplied from main public power source, or both

dependent on economic and reliability consideration.


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Compressed air supply

Compressed air is used for various pneumatic and spraying devices such as painting and

certain flame cutting.

Gas supply

Oxygen, acetylene, and any other gas are mainly used for flame cutting.

c)Space and location

In determining the size of space needed for a shipyard various aspects should be well

considered these include:

The types and size of ships to be built by the shipyard

The predicted number of ships to be built in one time

The number of ships expected to be built annually

What kind and capacity of machineries, equipment, and facilities will be employed

How much space needed for each production shop, stock yard, building dock, open airassembly yard, storage buildings, and other supporting buildings and facilities?

How wide is the water front needed for manoeuvring ship after launching, and for on-

board outfitting

Anticipated future expansion of the shipyard.

When the need of space has been predicted, it is also important to consider the location of the

shipyard, and this would include:

Access for the incoming materials and bought in ship equipment Access for the ship to leave the yard

Availability of supplies needed

The condition of the water front

Availability of qualified human resources

The distance with the supporting industries and market

The price of land

Local government regulations

d)Workshop s

Workshop is a dedicated place usually covered building where the typical production

processes are undertaken. The number and the size of a workshop are depended on the size

and complexity level of the ships planned to be built by the shipyard.

Each workshop has its own typical machinery, equipment, and facilities requirements

dependent on its individual function. In general there are five to six functional workshops in a

shipyard these include:


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Treatment and preparation shop

Fabrication shop

Panel lines shop

Sub-assembly and assembly shop

Block painting shop

Open air block assembly shop

e)Machinery and equipment

As has been mentioned in the previous sub-section that the types and capacity of machineries

and equipment in each individual workshop are determined by the size and types of ships are

planned to be built by the shipyard. The machinery and equipment are unique in each

individual workshop according to its function.

In line with the fast development of computer and fabrication technology many modernshipyards are also adopting new technologies in their production machineries and equipment,

such as computer integrated manufacturing (CIM), robotic cutting and welding, automatic

panel lines machinery etc.

6. ELEMENTS OF SHIP PRODUCTION PROCESSES

The typical process flow in shipyards starts with handling and stock of materials, marking the

plates and sections, then cutting the plates and sections, and welding the hull and the internal

structure, and finally the ship-block construction.

Main elements of this process can be explained as follows:

a)Handling

Handling is always involved in every stage of ship production process, starting from stock

yard to the completion of the ship construction. It comes in the following categories:

Lifting,

Lifting comes in many different ways and involving different sorts of equipment.

For lifting plates in the stock yard, for stacking or transferring plates magnetic gantry

crane is usually being used. And for sections sling of wire ropes are usually used.


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In the shops for lifting materials and structure, mostly overhead travelling cranes are

used in various capacities dependent on the weight of the object to be lifted.

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In the open air area such as block assembly yard and building berth or dock gantry

crane, level luffing crane, and mobile crane are used, and usually with high lifting

capacity which can reach up to the range of 500 to 800 tonnes.

Transporting

The progress of shipbuilding process always involves the transport of interim products

from one shop to another. There is various transportation aids being used in the

shipyard dependent on the objects to be transported among other things are:

Roller conveyor; it is employed to transfer material and interim products from one

station to another without lifting or removing the objects from their track. The

conveyor is generated by electro motor. Conveyors can be found in treatment shop,

preparation shop, and panel line.

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Forklift truck; small parts are sometimes put in pallets; the pallets are then transported

to another destination by the aid of forklift truck.

Multi-wheel transporter. This is a special vehicle to transport heavy structure such as

units, modules, and blocks from the assembly shop to the block buffer area.

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Holding

During the fabrication of certain ship parts due to their size or weight special device

sometimes is needed to hold them, such as for holding plate when it is rolled or bent.

Overhead crane or wall mounted crane

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b)Storage

There are three categories of storage in the ship production process in accordance to their

functions:

Stock yard

Stockyard is generally an open-air storage for storing raw materials such as plate and

section in the form of stacks. (Example of stockyard can be seen on figure 6.1).

Ship equipment store

This store is specially designed for storing of bought in ship equipment and

machineries such as pumps, engines etc. To prevent from damage to the equipment

due to weather, the storage is usually in the form of under covered building.

Buffer area

Buffer area is a particular space in the shop dedicated for storing interim products

waiting to be further processed.

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c) Marking

The main purpose of marking is to produce guidance for cutting the plates and sections, and

to put parts identification on the plates and sections.

In the conventional method plate marking and nesting are done manually using full scale loft.The next step in the evolution of flame cutting led to the introduction of the 1/10 scale loft

and the production of 1/10 scale templates. With these templates it became possible to

produce nested 1/10 scale templates where the individual parts were grouped on a scaled

shape. Photographic negatives of the nests were then prepared at a further reduced scale.

These negatives were projected on plates fed through a dark projection tower. Operators

marked the projected outline of the shapes on the plate.

Introduction of the electronic tracer made it possible to eliminate the hand guided cutting

method and quite accurately cut parts from full scale templates with an automatically guided

template scanning device.

Through the use of pilot machines equipped with photoelectric tracing heads that followed

the l/10th scaled templates or scaled projections of the original photo negatives it became

possible to operate large coordinate driven flame cutting machines from 1/10 or smaller

scaled templates.

With the development of numerical control machine tools punched tapes were used for

marking and cutting, then with fast improvement in computer numerical control speedy

plasma cutting is widely employed in the shipyards, and the tasks for marking also reduced,

because the machine can now cut the plate directly guided from the computer, only part

identification that still need to be marked on the plates or sections.

c)Nesting

Nesting is a process of optimising the use of plate for producing ship parts. In conventional

method it was done manually using full scale lofts which had been prepared beforehand

based on the workers experience. This was very time consuming.

As had been mentioned in the marking sub-section through the evolution in technology most

of the nesting tasks are carried out using computer software in the design office, and the data

are then sent to the cutting machine to be executed on the prepared plate.

The nesting arrangement is simulated on the computer screen before transfering to the cutting

machine, so that revision can still be carried out if necessary prior to the execution.

Illustration of the nesting arrangement using computer program is as shown on figure 6.10


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d) Cutting

Several cutting methods are being used in the shipyard especially in preparation stage for

planing the plates, and for preparing ship components before being fabricated to sub-

assemblies, assemblies, and units. Various machines and equipment are used for cutting and

shaping plates and sections among other things are:

Contour or profile cutting machine

Flame planer

Mechanical planer

(Picture of these machines can be seen in preparation and fabrication section)

In many modern shipyards for increasing productivity mass production methods are

implemented especially in cutting and shaping processes, where computer programmes and

robots are employed. CNC oxy-fuel/plasma/laser cutting machines, flame planer machines,

and portable cutting machines are used in the cutting process.

CO2laser cutting machines are gaining a good reputation as well because they reduce labour,

reduce welding cost/time, and reduce secondary processes after cutting. Laser cutting

machine is used especially for bevel planing and profiling.

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d)Welding

Welding plays important role in shipbuilding. It is estimated that almost 60 to 70 percent of

shipbuilding process involves many kind of welding, ranging from manual welding to fullyautomatic computer aided machines and robot operated welding machine.

In manual electric arc welding it should be noted that the equipment being used should enable

the operator to use high amperages with large gauge electrodes, and still have good control of

the current for various welding positions. It should be robust in construction and safe in

operation.

Types of weld joint

There are two types of weld joint generally known i.e. butt joint, and fillet joint

dependant on the parts to be joined. Illustration of these joints and their positions are

as follows:

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Welding procedure

The term welding procedure is used to describe the complete process involves in making

a weld. It covers choice of electrode, edge preparation, preheat, welding parameters

(voltage, current and travel speed), welding position, number of weld runs to fill the

groove, and post-weld treatments, e.g. grinding or heat treatment. Welding procedures

may be devised to meet various needs, e.g. to minimise costs, control distortion, avoid

defects or achieve good impact properties. Some aspects of welding procedure that need

to be noted are:

-

Weld current- Welding position

- Welding environment

Weld distortion

During cooling, the hot metal in the weld zone contracts, causing the joint to shrink. The

contraction is restrained by the cold metal surrounding the joint; stresses are set up

which, being in excess of the yield stress, produce plastic deformation. This can lead to

the distortion or buckling. Distortion can be reduced by choice of edge preparation and

weld procedure

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SHIP PRODUCTION SYSTEM

a)Main stages in ship production

After being awarded with shipbuilding contract shipyard should immediately start it

production process in order to be able to deliver the ship on schedule. With assumption that

the materials have been ordered and production planning has been prepared, there are several

stages in ship production that should be passed through before the ship is completed. These

stages generally would include:

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Bulk units assembly

Treatment and preparation

Fabrication of panel and sub-assembly

Plates and sections stock

Blocks erection

Outfitting

Hull launching or floating out

Post launching construction and outfitting

Commissioning

Delivery

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b)Flow of materials

In every stage of the production process flow of materials should be kept smooth and no

bottle neck or unnecessary idle of work station, this could be done by levelling the work load

in every stage of the production, and the zigzag or reciprocating paths of the material flow

should be avoided.

To level the work load; the work content and processing time of every part and interim

product should be well estimated, so that the production processes can be well scheduled.

6.5 SHIPYARD LAYOUT

The main aim of shipyard layout arrangement is to obtain an easy and efficient flow of

materials, so that a uniform work load, a shorter ship build cycle, and economies in

construction practices could be achieved.

Very rarely new shipyard could find site for ideal layout, and has to make best of the site it

can obtain by modifying the ideal layout.

a)Ideal layout

An ideal layout for a modern shipyard is based on a production flow basis, with the yard

extending back from the river or shore at which the berths or building dock are located. The

furthest area from the berths is reserved for the material stockyard, and between the two is

arranged in sequence the consecutive work and shop processes.

There are two ideal layouts being known for a shipyard i.e. L shape and U shape asfollows:

&

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Workshop

The layout of the workshops should be so arranged that ensure the smooth flow of the

materials and interim products from one workshop to another without creating any bottle

neck.

The size, space, and equipment and machineries in side of each workshop should be well

planned and arranged to accommodate the works to be carried out in it, so that good flow

of materials, and safety and good working environment are well maintained.

Supporting facility

The supporting facilities are the spaces or buildings that contribute to the production

processes undertaken by the shipyard, which include: access for the incoming materials,

parking ground, scrap dumping ground, stock yard, dock buffer area, outfitting quay,

water front, etc.

c)Shipyard access

One of the considerations in choosing the location of shipyard is the availability of good

access to and from the shipyard either land access as well as water access. The purpose of this

access is for bringing in materials, and bought in ship equipment and for shipping out the

ships when the production processes are completed.

Other access that needs to be paid attention in the shipyard is the access of interim products

from one shop to another, and to the building dock or berth, and access for ship launching or

floating out.

d)Future expansion

The investment cost of a shipyard is very high, and the productive life time of the

machineries, equipment, and facilities is relatively long, beside the size of ships is also

increasing from time to time, therefore it should be anticipated from the beginning the

possibility of expanding the shipyard for catering for larger ship size.

The expansion of the shipyard may be in the form of increasing the production capacity,

adding more production facilities, expanding the space, adding new larger building dock, or

expanding the capacity of the existing building dock.

6.6 CONCLUDING REMARKS

a)Basic elements in ship production would include: human resources, supplies, space and

location, workshops, machineries and equipment.

b)The elements of ship production processes would include: handling, storage, marking,

nesting, cutting, bending, and welding.


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c)Main stages in ship production consist of: plates and section stock, treatment and

preparation, fabrication of panes and sub-assemblies, bulk units assembly, block erection,

outfitting, hull launching or floating out, post launching construction and outfitting,

commisioning, and delivery.

) There are two ideal shapes of shipyard layout namely L shape and U shape, but rarely

shipyard could get ideal location, and there for has to adjust its layout to the existing

location.

e)Some considerations in arranging the shipyard layout are: size and location of buildings

and workshops, shipyards access, and future expantions.

6 esential elements of ship production

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