ship hull and machinery design

8/8/2019 Ship Hull and Machinery Design

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Ship Hull and Machinery Design - Choosing Main Engine for Your Ship

We all know that the heart of the ship is its main engine.A ship cannot run without its main engine. But how can we say that a

particular engine is optimum for use in a ship? What are the factors that needs to be taken into consideration while selectin g a

main engine for a ship? Read on to find out.

Main Diesel Marine Engine Selection - A Gigantic Dilemma

In this article we will see the different aspects that need to be taken into consideration when choosing a main engine for a ship.

The criteria for selecting a main engine may change from ship to ship and also according to the requirements. The emphasis on

each criterion will also differ. But there are few general aspects that remain same for almost all types of ships and we willenumerate them one by one, briefly.

The criteria includes: required horse power, weight, space, capital cost, running costs, requirement for electrical power and heat,

reliability and maintainability, maneuvering ability, ease of installation , vibration , noise and availability. As you would notice

the title takes into account the hull design as well. This is necessary because of the forces of vibration and weight of the engine

would have to be borne by the hull, hence ship hull design is equally important to be taken into consideration.

Let¶s learn about each of them.

A Huge Main Engine

How Many Horses?

The requirement of horsepower depends of quite a number of factors. It depends on the number, size, and type of propellers used.

It also depends on the number of revolutions a propeller makes.The decision on the requirement of the horse power is also made

on the basis of the type of machinery that is available for the ship and the fuel weight capacity.Apart from all these factors, the

overall power required by the ship and the auxiliary machineries is the fundamental requirement.

Weight

This is not considered an important point while choosing the main engine for most of the ships. This criterion is taken int o account

only in smaller ships such as ferries where the requirement of speed and exposure to confined waters is more.It is also an

important factor in designing war ships where the requirement of speed is more. In making of such designs the power/weight ratio

is of utmost importance.

Space

Space and weight almost holds equal importance when considering the criteria for main engine. But if a choice has to be made in

between weight and space then weight of the machinery is taken into consideration even if i t occupies a larger space. But if the

ship is designed on volume basis then the ship should be fitted with non bulky machinery even if they have higher weight.

Cost

The cost of main engine is always of prime importance. While calculating the cost of engine, the installation costs of the engine

are also taken into consideration. It will also include additional costs of gearing and pumps that needs to be set up.

Running costs

The cost is an important factor in determining the main engine. The fuel cost is an integral part of these costs. The annual fuel billis the most important item of running costs. Now as the fuel prices are volatile in this market scenario the costs would vary

according to the market price of the fuel.

There are two ways to reduce these costs. One is by choosing machinery that is fuel efficient and uses less fuel oil or choos ing

machinery that uses cheap and lower grade of oil but doesn¶t compromise on the power and load output.

The running costs will also include the cost of lubricating oils, spares, maintenance and the cost of manning.

Reliability and maintainability

These aspects should be taken into consideration for all ships. Breakdowns and emergency situations are a part of ship operat ions

and efforts should be made to see that costs incurred due to them are as low as possible. On passenger ships these factors ar e of



high importance as the consequences of a breakdown will incur heavy expenditure and will also mar the overall reputation and

thus the future profitability.On war ships these factors are important to prevent loss due to mechanical breakdown or enemy¶s

action.The advantage of using a slow speed engine is that as it will have few cylinders the maintenance cost arising will be

comparatively low.

Maneuvering ability

The maneuvering ability of the ship is an important factor while choosing a main engine. The amount of power required and the

frequency of running in confined water will affect the type of machinery required. If the ship is running at slow speed for more

time then accordingly an engine needs to be chosen.

Ease of installation

The ease of installation depends upon the size of the ship. If the size of the ship is small and the machinery is bulky there arises a

difficulty to install it. Thus according to the size and power requirement the machinery should be choose which will also support

the ease with which it is installed also.

Vibrations

Any vibration force that arises from the main engine should be properly assessed. Its intensity should be measured and its

acceptability with the tolerance level of the ship should be checked. Main engine should also be chosen on the basis of the type of

the ship. For example if the ship is a passenger ship then the allowance of vibrations would be very less. Thus special care should

be taken that the vibrations thus generated should not affect the personnel and equipments on ship.

Noise

All the main engines produce high levels of noise. Bigger the engine, higher will be the noise level. Keeping this thing in m ind it

is necessary that the engine is enclosed in an acoustic enclosure. Thus it is imperative to choose and install the main engine in

such a way that the noise levels doesn¶t create unwanted vibrations and doesn¶t affect ship¶s passengers.

Availability

The choice of machinery should be made in such a way that in case any part of the machinery breaks down or needs to be

replaced, spares are available for the same, easily at all places. It would be a situation of grave concern if the ship is us ing a high

end model of machinery whose spares are not so easily available or a model which is not available any more in the market, needs

a replacement of a part.

Different types of Engine Room Layout

A marine engineer during his career at sea sails on a multitude of ships built by different ship yards around the world. Each ship

has different features and characteristics. The care taken and planning done in the design stage decides to a large extent theworking conditions in the engine room and the quality of life on board. A good layout with ergonomically designed working

spaces makes life comfortable for the workforce. It would thus lead to a happy and safer engine room. It is well understood t hat it

would lead to better maintenance and increased life of the machinery.

There are different types of ships sailing worldwide with different structural arrangements. Some ships have the accommodatio nforward and the engine room aft, some ships have both the accommodation and the engine room aft, and some ships have a mid-

ship accommodation and engine room. All these arrangements affect the layout of the engine room. The naval architects designing

the ship have got more concerns about allotting the maximum volume of the ship for the carriage of the cargo and the engine room

layout and that of the accommodation quarters is secondary.

Some of the ships built by Japanese shipyards are so standard that you can guess the general location of the valves even before

boarding the ship. But some other ships, built by ship yards of countries with fast growing economies, have such a jumbled up

pipe line arrangement that it drives the engineers crazy.

In this article the different layouts and features of the engine room have been discussed. It is a simple fact that any human beingwould work to his fullest potential if the working conditions are ergonomically designed. Smoky and dark engine rooms or

unapproachable corners make maintenance difficult. A man would work hard and without fear where a risk to life and limb is not

involved, otherwise he will hardly work.

Location of generators



The generators, which are also known as the auxiliary engines, are the heart of the ship as they provide all of the electricity for

illumination and other services. The generators are best located near the engine control room as they can be frequently watched

over. On some ships the generators are located in a separate forward engine room or at the bottom platform, which cause

them to be a bit neglected. Also the bottom platform location is very bad because slight flooding of the sea water would go i nto

the alternator¶s windings causing a black out. The generators should be conveniently located near the engine room work

shop as the cylinder heads and the other spares could be brought in for repairs.

Engine Room Workshop

The engine room workshop is the dedicated place for hot work and is generally located near the main engine cylinder head

platform. The workshop should be well connected to the generator platform, purifier flat and the main engine cylinder head platform via guide rails, so that a component requiring extensive maintenance can be easily brought to and from the engine room

workshop. Also the overhead crane should reach near the guide rails so that the machine can be easily transferred via chain

blocks. A careful planning would save a lot of man hours and busted backs.

Location of Skylight

The skylight was used in old ships for the illumination and the ventilation of the engine room along with providing an opening for

lowering and removing heavy items with the ship or the shore crane. However in modern ships the sky light is normally bolted

shut and only opened for lowering goods and spares into the engine room.

The location of the sky light should be such that it can lower the spares near the cylinder head platform from where it can be

transferred easily to the overhead crane. In case it is not possible it should have guide rails near the opening so that once the items

have been lowered into the engine room it can be easily shifted by chain blocks and physical labor is saved.

The opening should be free of pipelines and obstructions, so that the spares can be easily lowered and lifted without much

maneuvering. Sometimes the restricted opening causes the crane hook to catch on to some obstructions or pipelines and the spares

can fall endangering life and property.

Location of Critical Spares

The location of major spares like the piston, cylinder head, and the liner of the main engine which are very heavy and weigh about

1000 to 3000 Kilograms should be carefully planned. On some ships they are located in corners to give a beautiful engine room

layout, but the removal from place and stowage back after use is very time consuming. There are some ships where you have to

put two or three chain blocks along with using the overhead crane to stow the spare piston in place. It not only affects the

productivity but also lowers the morale of the crew. A precious few hours are wasted in bringing the spare to work and can be

very dangerous in emergency situations like main engine failure in rough sea.

Ideally the main engine heavy spares should be located in such a way that they can be directly accessed by the engine room

overhead crane. In any other location guide rails should be provided so that the spare can be lifted by chain blocks and shifted to

their wanted location easily.

Layout of the Spares Store

The spare store is another area of concern as some ships have a very small storage space and when the ship gets older and the

demand of the spares escalates, there is no space to store them. Then they are kept in the packing boxes they were shipped in and

if proper records are not maintained they are forgotten and rust into oblivion. Extra space should be provided for the spares

store keeping the futuristic needs in mind. Spares for the main engine, auxiliary engine, purifiers, compressors, pumps etc. should

all be segregated and separate locations should be provided for them. Locking arrangement should be provided for the expensive

spares and the store room should be kept locked in the ports where theft is common. It should be noted that the spares are

very expensive and amount to thousands of US dollars. Each needle guide of the fuel injectors for the main engine costs about 500

US dollars. The mechanical seals can cost from 150 to 1500 US dollars and more depending on the size and application. The

corrosion resistant materials used in manufacturing of the spares like brass, bronze, copper, silver and zinc etc. make them very

attractive to petty thieves who often enter the engine room on some pretext or the other.

Engine Control Room

Many owners and designers are of a thought that since the engine control room is for work only it need not be made comfortable.

However it must be remembered that a comfortable and good looking engine control room will not only increase the pride of the

engineers but also will provide a good relaxed atmosphere during the coffee breaks. This would help in team building and increase

productivity. Also when the engineers have to be present in the control room for long periods like during maneuvering in the Suez

and Panama canals, it is a good idea to provide comfortable chairs and sofas.



It is a good practice to provide a dedicated area for making tea and coffee with fire proof appliances. The control room is the

dedicated smoking area in the engine room, and safety ashtrays should be provided by the designers. An electric lighter would do

away with the butane lighters and would lower the fire risk on board.

It must be remembered that incorrectly disposed butane lighter finding its way to the incinerator would cause a big explosion and

would cause a fire.

Overhead Crane

The overhead cranes take the burden off the engineers back and makes life and work better in the engine room. The reach of the

overhead crane should be such that it can cater for machines other than the main engine. A long reach to enable the ballast pump motor to be brought from the bottom platform to the workshop is very convenient.

Conclusion

The problems faced by marine engineers due to bad layout of the engine room are rarely discussed as there is no platform for

discussing them. Also as their contract is finished they go on other ships which are fortunately better designed. However bad ly

designed engine rooms can make life difficult for those on board. A conscious effort by the owner and the d esigner to look after

the comfort of the engineers at work would pay them back in increased productivity.

It is hoped that this article would apprise the design engineers and the naval architects of the difficulties faced by the ma rine

engineers in day to day working in a badly designed engine room. A well designed engine room definitely helps in better

maintenance,cheerful crew and a safer ship.

he word ³room´ normally brings forth the image of a small or average sized room which is used for domestic purposes. If I

mention the word ³engine room´ the best you might imagine could be a compartment with a small engine placed at the corner.

But remember we are talking in the context of ships and everything related to them is huge in size. So when I talk about th e engine

³room´, I am not referring to any small room or compartment but a space which is several stories high and many times bigger t han

an average sized house. So let us begin this journey in Wonderland of the ship engine room and bring out the Alice in ourselves.

The Engine Room

As the name itself suggests, the engine room is space on the ship where all the machineries are located. Well almost all, if not all

for there are several machineries or equipment which are outside the engine room such as say the cranes, winches and so forth.

the engine room extends right from the bottom most level to the level of the funnel. The main propulsion plant of the main marine

diesel engine which drives the propeller is located at the bottom but is several stories high. The next picture shows a human being

standing near one of the cylinders of the marine engine and that will give you the idea about its size.

Location on Ship

There is no hard and fast rule regarding the location of each equipment or machinery but normally the engine room would consist

of several levels having machineries such as auxiliary engines or diesel generators, boiler, inert gas plant, fresh water generator ,

purifiers, pumps, storage tanks, engine control room, waste incinerator and several other paraphernalia such as electrical panels at

various levels. The engine control room is the command center of the engine room and is the only air conditioned place within

the engine room having computer and delicate controls, which is otherwise full of heat and noise. Of course it also depen ds on the

area where the ship is sailing since in very cold areas, the engine room is cold rather than hot. I must also add here that apart

from the location of the machinery, the location of the engine room itself isnt fixed for all types of ship s. most ships have engine

room at the aft, while there are other variations where it is located either midships or front side of the ship

Control Room ,Safety & Manning

You are always supposed to wear the safety gear when entering the engine room which is through a air tight door. When you enter

that door you come to a changing room where you remove your normal shoes and put on accessories such as boiler suit, safety

shoes, safety helmet, gloves, and ear-muffs. A positive pressure is maintained inside the engine room most of the times by running

engine room blowers.

ship hull and machinery design

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