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Knowledge – General.

The answers provided herewith will hopefully assist you in studying for the exam. They are just

one possibility of an answer. Nor is this a definitive list of questions and answers. You are

therefore encouraged to keep an objectionable view.

I am fully aware, as are most of your peers, how antiquated some of the questions are, as they

pertain to equipment and procedures aboard modern ships. Bear in mind that these questions

remain in the “question bank” judging from feedback I get.

Martin Leduc

Martin’s Marine Engineering Page

www.dieselduck.net

[email protected]

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8.7 Sketch and describe a purifier showing the construction and operation. Explain the startup

procedure, the purpose of the gravity disc and what happens when the gravity disc is change?

An oil purifier is an essential part of any system of forced lubrication. Its purpose, as the name

suggest is to purify the oil by the removal of impurities and so maintain the oil conditions that it

can be used over and over again with perfect safety. Water, dust, sand, and metallic dust are the

most common impurities and of them water forms the larger proportion. Also water and oil

when together tend to emulsify, water finds its way into storage tanks through leakage from

sea, condensation. Dirt, sand and metallic dust are picked up from the engine parts and pipe

connections through which it circulates, and rust from the tanks in which it is stored. The

purifier, which is also a separator, depends for its action on centrifugal force.

The bowl in which the separation takes place carries a number of coned shaped metal discs, the

revolve, about 7000 rpm, the centrifugal force imparted to the oil causes it to ascend through

the holes in the disc. In the process any solid material is thrown outward to the periphery of the

bowl, where it is retained in sediment. Water being heavier than the oil passes outward and

upward along the outer edges of the disc and from there to the water discharge outlet. The oil

having a lesser specific gravity than the water, passes upward between the disc and then to the

oil discharge outlet. The construction of the purifier is such that that it will adjust itself

automatically to varying proportion of oil and water, so that when no water is in the oil there is

no discharge from the water outlet and vice versa. The same type of purifier can be used in the

purification of fuel oils, but it may be necessary to change the discharge discs used in the bowl

sealing ring in the rim of the cover. Solid from the oil are thrown outwards by centrifugal force

and collect against the bowl periphery. At intervals dictated by either time or choice the oil feed

is turned off and the bowl opened to discharge the solids. There are a number of discharge ports

around the bowl. At the end of the discharge the bowl is closed and after the liquid seal has

been established the oil feed is continued. During normal running the pressure exerted by the

water under the sliding bottom is sufficient to keep it closed against the pressure from the liquid

in the bowl. The operating water tank maintains a constant head of water to the passing

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through the operating valves. The paring discs, which acts like a pump opposing this head

provided that the radius of the liquid remains constant. If the evaporating or leakage causes a

slight water loss the reverse pumping effect of the paring disc is reduced and water from the

operating tank and the quantity of water in the passing chamber back to the correct radius. The

If a sample of oil in a test tube is heated any water drops in the sample will cause a crackling

noise, and can cause the formation of steam bubbles. A simple settling would be sufficient to

detect large quantities of water in the oil. Also a water detection paste can be used changing

color when there is no water present and changing color when there is water present. Some fuel

reject water easily, others retain it, and have a cloudy appearance for an extended period after

being mixed with water. Some fuels contain as little as .01 percent of water will appear cloudy.

When lube oil is contaminated by water it turns cloudy or a milky color. This cuts down

considerably on the efficiency of the lubricating oil. It also causes parts of the engine to rust and

moving parts to stick. Water is an undesirably contaminant because apart from the fact that it is

not a good lubricant it may combine with oil in tank to form of an emulsion which by adhering to

8.4 Sketch and describe the pneumatic guage. State its use and how it operates. Does the

specific gravity of a liquid in the tanks have any effect on this guage?

picture

The pneumercator guage is a simple and reliable apparatus used to measure the quantity of

liquid in a tank. It consist of these main parts, a balance chamber fixed to the bottom of the

tank, a hand operated air pump placed near the tank, and a graduated mercury guage column. A

steady the air can escape passing upward through the liquid to the atmosphere via the vent

pipe. The air pressure necessary to displace the liquid from the balance chamber is a measure of

the weight of depth of the liquid in the tank.

When the pump has displaced the liquid in its chamber the cock is switched over to admit the

air pressure to the mercury guage and the height of the mercury is read off the graduated scale.

The scale is graduated for sole average specific gravity and a correction has to be made for oils

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of different specific gravity and a chart is provided to ascertain the tanks depths.

8.5 What is meant by flashpoint of oil? What is meant by fire and ignition point? What is

Firing or ignition point: is generally about 40 degree to 50 degree above flashpoint. This is the

temp at which the vapours given off from the heated sample are ignited by flame application

and will burn continuously.

Viscosity: is a measured on a time basis. It is expressed as the number of seconds for the

outflow of a fluid quantity of a fluid through a specially calibrated instrument of a specified

temperature British praticier uses the Redwood viscometer. This redwood #1 is the flow time of

50ml of fluid up to 2000 seconds. Is an oils resistance to flow?

Picture

To determine the closed flashpoint of oil, an apparatus known as the Pensky Martin Test can be

used.

• A fresh sample must be used for every test and

can be taken from tank but caution must be taken that no trace of cleaning solvents is

present in the oil cup.

stirring being discontinued during flame depression.

• Oils with flashpoint below 22C are classified as

dangerous (highly flammable such as gasoline )

• Flash points in the range 22-66C would relate to

kerosene and vapouring oils

• above 66 safe and include diesel and fuel oils

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8.6 Describe, with the aid of a sketch, a carburetor for gas engine.

flows from the chamber to the orifice through a jet or restriction, which controls the rate of

flow. The air flow is controlled by a butterfly valve.

When the fuel moves into the intake manifold under partial vacuum the boiling point of the

gasoline is lower. This causes many of the atomized particles of fuel to flash into vapor. As the

partially vaporized fuel moves through the manifold it is warmed by the heat of the many......

This causes further vaporization. When the mixture enters the combustion chamber, both the

swirling motion and the sudden increase in temp due to the compression stroke causes ignition

of the fuel.

Picture

Tube coolers for engine jacket water and lubricating oil cooling are usually circulated with sea

provided it is not reactive with chemicals, because it is not in contact with sea water. The tubes

are made of stress relieved aluminum brass tubes expanded into Naval brass tube plates. The

coolers are made up to have a fixed plate at one end and a tube plate at the other end which is

free to move with expansion of the tubes. “Other materials found in service are gunmetal

aluminum bronze and sometimes special alloys.

The tube stack is fitted with disc and ring baffles. The fitted end, gaskets are fitted between

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either side of the tube plate and the shell and end cover. At the other end, the tube plate is free

to move with seals fitted either side of a safety expansion ring. Should either liquid leak past the

seal it will pass out of the cooler and be visible. If the joints leak at the other end the special "tell

tale" ring will allow the liquids to escape without mixing. The joint rings are of synthetic rubber.

Manufacturer recommends that coolers are arranged vertical. If horizontal installation is

necessary the sea water should enter at the bottom and leave at the top. This system will

ensure less corrosion, and air lock will reduce the cooling area and cause overheating. Therefore

vent cocks should be fitted, for purging air. Clearance is required at the cooler fixed end for

removal of the tube nest. Before cleaning coolers are isolated from the system by valves and

blanks or by removing pipe and blanking the cooler flanges. Flushing is necessary after the

cleaning agent has been drained from the cooler.

In the open hearth process a broad shallow furnace is used to support the charge of pig iron and

scrap steel. Pig iron content of the charge may constitute 25% to 75%of the total, which may

vary in size depending upon furnace capacity, between 10 to 50 tonnes. Scrap steel is added to

reduce melting time if starting from cold. Fuel employed in this process may be enriched blast

furnace gas (blast furnace gas may contain 30% CO after cleaning) which melts the charge by

burning across its surface. Reduction of carbon content is achieved by oxidation; this may be

assisted by adding pure iron oxide to the charge. Other impurities are reduced either by

oxidation or absorption in the slag. At frequent intervals samples of the charge are taken for

avoiding the reaction acid plus base =salt plus water. Both acid and basic process can be

operated in the open hearth, Bessemer, LD and electric are furnace.

1.6 Name materials used to make the following: cylinder line, connecting rods, and fuel lines.

State the properties of each.

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Cylinder liner:

Cylinder liners must not only withstand serve stresses due to differences in temp and pressure

but must resist the abrasive action of the piston rings. The composition on the material of

cylinder liners is so as follows, but it must be remembered that the foundly methods employed

• combine carbon 0.8 to 0.9 %

• free carbon 2.2 to 2.4%

• silicon 0.8 to 1.0%

• manganese 1.0 to 1.7%

Brinell hardness figure- over 200

Connecting rod:

For connecting rods the scemins- martin open hearth or ingot mild annealed steel is used.

Ultimate tensile strength: 28 to 32 tons/ sq. in.

Elongation 25 to 29%

Low medium carbon steel with 3 to 3.5%nickel content.

Fuel lines:

These lines must be of a strong solid drawn ....high pressure steel tubing. It must have a high

Case hardening is also sometimes referred to as “pack carbonizing". The steel component to be

case harden is packed in a box, which may be made of fire clay cast iron or a heat resisting

nickel, usually alloy carbon rich material such as charred leather, charcoal, crushed bone and

horn or other material containing carbon is the packing medium which upon encompass the

component. The box is then placed in a furnace and raised in temp to above 900 C. The surface

of the component will then absorb carbon forming an extremely hard case.

Depth of case hardening depends upon two main factors, the length of time and the carbon rich

material used. Actual case depth with this process may vary between 0.8 mm to 3mm requiring

certain places depending on the type of work the steel will be doing. Low carbon steels (0.08 to

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0.34 carbon do not harden to any extent even when combines with other alloying elements.

Therefore when a soft tough core and extremely hard outside surface are needed the steel

should be case hardened. Gudgeon pins and other bearing pins are examples of components

which may be case hardened. They would possess a hard outer case with good wearing

The propeller or tail end shaft is the aftermost length of shaft from good quality mild steel of 28

tons tensile strengths. It requires having toughness and being resistant to fatigue. In the past

propeller shaft were commonly made of wrought Iron. The tail end shaft is 10% greater in

strength than the tunnel shafting by reason of the varied stresses to which it is subjected, also to

the liable to corrosion by its contact with sea water.

The shaft is machined over with a taper at the end for taking the propeller. The propeller boss is

of the order of (0.75 inch per feet 1mm per 10mm length) length and has a length of approx. 3

times the shaft dia. The keyway is milled out and has semicircular ends to avoid stress

COMPRESSION: while going ahead

TENSION: while going astern

BENDING AND SHEERING: due to the weight of the propeller and its overhang.

1.2 describe as many as you can of the physical test supplied to metals in construction of

boilers.

The metal used for most of the main parts of a marine boiler, both multi-tubular and water tube

1. Radiographic examination for the detection of faults in the metal

2. Micro examination for picturing the structure of the .....

This test is carried out to ascertain the strength and ductility of a material. To carry out this test

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a specific testing machine is necessary. The specimen to be tested is held in self-aligning gripe

and is subjected to a gradually increasing tensile load. The beam must be maintained in a

floating condition by movement of the jockey weight as the oil pressure to the straining cylinder

is increased. An enteriameter fitted across the specimen gives extension readings as the load is

section, the gauge length being found by reducing the cross section of the certain portion of the

specimen. This reduction must be gradually, rapid change of section can affect the results. In the

tensile test the specimen is broken. After breakage the broken ends are fitted together and the

distance between reference marks and the smallest diameter is measured. Maximum load and

load at yield are also determined. The tensile stress can be calculated by.

ULTIMATE TENSILE STRESS= MAXIMUN LOAD .

ORIGINAL CROSS SECTIONAL AREA

BENDING TEST:

times the diameter of the shank. The ends are then inspected for defects. The shank of the rivet

is bent cold and then hammered until the end meet. The curved part is then inspected for

defect.

To test the welds on a pressure vessel the following tests are carried out.

CADIOGRAPHY:

This can be used for the examination of welds, forgings and casting, that is x-rays, which

penetrate up to 180mm of steel pass through the metal and impinge up a photographic plate or

With ultrasonic we do have the limitations of metal thickness to consider so we have radio sonic

testing. High frequency sound waves reflect from internal interfaces of good metal and defects.

These reflected sound waves are then displayed onto a screen of cathode-ray oscilloscope. Size

and position of a defect can be ascertained. It can also be used for checking material thickness

that is a probe could be passed down a heat exchanger tube. a portable battery operated, hand

held cylindrical detector with cable to a set of headphones can be used to detect leakage in

vacuum, air lines, superheated steam, air conditioning etc. a recent application of ultrasonic is

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in boiler work cast steel is seldom used unless for mounting included above.

To reline the bearing the following method is used.

1) First the upper and lower halves of the bearing are removed.

2) Next the old Babbitt is melted out of the shells by heating the bearing with a blowtorch or

acetylene torch to a temp about 20 F above the melting point of the bearing metal. Before this

is done however care must be taken that all recesses if the bearings are free of moisture in

order to avoid explosion.

number of shims between the joints, to serve as parting piece for separating the halves of the

bearing. The halves then clamped together.

5) The assembled bearing is placed on its end on a flat-finished clay surface. An oiler or mandrel

from 1/8" to 1/4" smaller in diameter than the crank is placed in the center of the box with an

evenly divided space all around the outside. The mandrel itself is lined with white lead and the

parting piece should bear against the mandrel. In this way there will be only a thin strip of

Babbitt lines to connect the halves of the lining, which facilitates the breaking apart of the lining

after it is cast. Mandrels may consist of machined pieces of pipe having an outside diameter

right the stick will char, but not burn. Keep the molten metal thoroughly mixed before pouring.

7) Be sure the mold is clean and dry. Then preheat the shell and mandrel to 250 For (120 C

approx.) before pouring the Babbitt, as this will reduce the difference between the amounts the

Babbitt and the box will contrast while cooling and will aid in the free flow of the molten steel.

Pour the molten metal slowly to allow air to escape from the mold, thus preventing air holes. If

the ladle does not pour from the bottom, skim drops from the surface before pouring t...

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8) Metal is poured around the mandrel, and as the metal shrinks upon cooling, the clamps are

removed and the two halves are separated.

re-melts of an unknown or inferior quality. Small amounts of tin in a lead base Babbitt represent

contamination while as little as 3 % of lead in a tin based Babbitt reduce its physical properties.

Lead softens an alloy while antimony hardens it. Copper is used in some of the better grades of

Babbitt. High antimony babbits are used in large bearing operating under high pressure. Babbitt

metals low in antimony are used in bearings of high speed engines. A very high grade of bearing

metal may be made by melting 7 percent of copper at as low a heat as possible and adding 25

parts of antimony and 200 parts of tin. The metal is cast in ingot molds and re-melted, then 8 lbs

of tin is added to each 5lbs of the batch. The final mixture can then be cast until needed.

As a general rule the clearance for a 12" shaft is from 8-9 thousandths of an inch. Therefore for a

SAFETY:

CO2 TOTAL FLOODING SYSTEM FORMACHINESPACES:

PICTURE

First ensure that the compartment is evacuated of personal and sealed off. This necessitates

closing all doors to the engine room, shutting down skylights, closing dampers on vents and

stopping ventilation fans. Pumps should also be stopped and collapsible bridge valves closed. In

a modern vessel the sealing off can be done by remote control from the fire control station

generally using compressed air or hydraulic system. The door of the steel control box situated at

the fire centre station would then be opened; this operates a switch which may have a dual

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purpose. One is to operate audile and visual alarms in the engine room spaces, the other may be

to shut off ventilation fans. The CO2 direction valve handle would then be pulled and that would

be followed by gas released. Ensure that all moving parts are kept clean free and will lubricated.

Wires must be checked for tightness, toggles and pulleys must grease. With the use of

the lines will cause alarm to be sounded vents to the atmosphere can then be operated.

The CO2 system is used if a fire is severe enough to force evacuation of the engine room. An

alarm is sounded by an alarm button as the co2 cabinet is opened and in some ships there is

also a stop for the engine room fans incorporated.

Before releasing the CO2 personal must be counted and the engine room must be in a shut

down condition with all openings and vent flaps closed. It is a requirement the 85% percent of

the required quantity of gas is released into the space within two minutes of operating the

actuating handle. In the system the actuating handle opens the operating bottle of CO2 and the

gas from this pushes down the piston to release the other bottles. To avoid sticking, all the

engine room and it is despised safety a relief on the manifold.

Rapid injection of CO2 is necessary to combat an engine room fire, which has attained such

magnitude that the space has to be evacuated. This is the reason for the rule that 85% of the gas

must be released within two minutes.

The quantity of gas carried

a) must be sufficient to give a free gas volume equal to 40 percent of the volume of the space

for fuel can be shut down remotely, as can valves on fuel pipes from fuel service and storage

tanks.

CO bottles made of solid drawn steel, hydraulically tested to 228. The contents are checked by

weighing or by means of radioactive level indicator. Recharging is necessary if there is a 10

percent weight loss. Pipe work is of solid drawn mild steel, galvanized for protection against

corrosion. The syphen tube in the bottle ensures that liquid if discharged from the bottle,

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without the syphen tube CO2 would evaporate.

CO2 FLOODING SYSTEM FOR HOLDS

wheelhouse.

When a fire burst out in a compartment smoke issues from the diverting valve into the

wheelhouse, warning bridge personal of the outbreak. Simultaneously, an electronic smoke

detector in the cabinet sets off audible alarms, hence if the bridge is unoccupied (e.g. in port)

the notice of outbreak fire is still obtained. Within the cabinet is a dark chamber where in the

sampling pipes goes into labeled chimneys. Diffused light illuminates strongly as smoke issuing

from chimney, hence the compartment which is affected by fire can easily be identified. Before

the dark chamber in the cabinet is well lighted compartment fitted with a glass window and

hinged for cover.

cabinet one fore each of the sampling pipes. To flood an affected compartment with CO2 gas,

the operator would first operate the appropriate change over valve and secondly release the

requiste number of CO2 cylinders for the compartment. CO2 gas would then pass through the

sampling pipe to the space in which the fire exists.

When a smoke detection system is to be used for the hold compartments of a refrigerated cargo

vessel the lines to the refrigerated holds will be blanked off in the detector cabinet. These

blanks can be removed once per watch as a test (for a few days after loading cargo) and

removed altogether when the hold is open and debusted. When an outbreak of fire in a

is about to be used. After the fire has been extinguished the compartment must be well

ventilated before entry for damage inspection, as CO2 gas is heavier than air and does not

support human life.

6.6 Describe a sprinkler system and explain how it operates. Describe the control valve and

explain how it is reset after use or testing of system.

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picture

accommodations or other spaces. The system is composed of a pressurized water tank with

water pipes leading to various compartments. In these compartments the water pipes have

sprinklers heads fitted which come into operation when there is an outbreak of fire. The

pressure tank is half fitted with fresh water, through the fresh water supply line. Compressed air

is delivered from the electrically driven air compressor raises the pressure in the tank to a

predetermined level, this should be such that the pressure at the highest sprinkler head in the

system is not less than 4.8 bars. Sprinkler heads are grouped into sections with not more than

150 heads per section and each section has an alarm system. Each sprinkler head is made up of

a steel cage fitted with a water deflector.

limit of temp can be increased this would be depending upon the position where the sprinkler

head or heads is the rated. Quartriod bulbs are manufactured in different color the colors

indicate the temp rating for the bulb.

rating

68C = red

80C = yellow

93C = green

automatically operated. Stop valves, A and B are locked open and if either of these valves are

inadvertently closed a switch will be operated that brings the alarms into operation. The alarm

system can be tested by opening valve C, which allows a delivery of water similar to that of one

sprinkler head to flow to drain.

An electrically operated pump with a direct suction to the sea comes into operation when the

fresh water charge in the pressure tank has been used up. This arranged to operate

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automatically through the pressure relay. A hose connection is also provided so that water can

be supplied to the system from shore when the vessel is in dry dock. This connection must be an

international shore hose connection. Any part of the system which might be subjected to

freezing must be protected.

made watertight by a joint and intermediate sprinkler is dry. When operation of a sprinkler a

sprinkler head releases the pressure in the dry pipe, the centre valve is pushed by the force of

water under the clapper. The clappers lifts and rotates on the yoke being swing to one side by

the effect on the water flow on the skirt. The water floods up through the dry pipe causing the

centre valve to lock open, and in filling the intermediate chamber pressurizes and operates the

alarm.

Pressure gauges for air and water are required. The section valve opens when air pressure drops

to 1/16th that of water pressure. The cover has to be removed to reset the valve. The clapper

valve alarm is tested by opening a testing valve on the dry side of the suction valve alarm

picture

DRY PIPE SECTION ALARM FOR SPRINKLER SYSTEM

6.3

A) Foam

unscrewed; hence these holes serve as a vent if the nozzle is blocked.

Contents:

The inner container is filled with aluminum sulphate and the annular space formed by the inner

and outer container is filled up to the level indicator with a solution of sodium bicarbonate and

foam stabilizer. 1:3 inner and outer containers respectively.

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Operation:

By inverting the extinguisher the lead seal will fall, clearing the ports in the inner container and

the two solutions will mix. As the solutions mix they react, generating foam under pressure

which is discharged through the nozzle.

Duration of discharge 1.5 min

6.3

B) soda-acid portable fire extinguisher

picture

The body of a soda-acid portable fire extinguisher is made of riveted mild steel, lead coated

internally and externally. A screwed brass neck ring is riveted to the top dome of the mild steel

indicator and the glass bottle in the carrying cage contains sulphuric acid.

Operation:

When the plunger is depressed the seal bottle is shattered and the acid is released. The acid will

then react with the surface of the sodium bicarbonate solution and the result of this chemical

reaction is CO2. The CO 2 builds up in pressure and the solution is then driven out of the

extinguisher through the dip tube and nozzle.

Performance:

from freezing. They should be recharged annually and immediately after each use. During

annual recharging all parts must be carefully inspected and washed with fresh water. the hose

and nozzle should be checked for deterioration and clogging. The proper chemicals must be

used for recharging. The sodium bicarbonate solution should be prepared outside the

extinguisher preferable with Luke warm water. The recharge data and the signature of the

person who serviced the extinguisher must be placed on the tag attached to the extinguisher.

Several times a year the extinguisher should be checked for damage and to ensure that it is fully

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charge and the nozzle is not clogged. this extinguisher is only used on class A fires.

C) DRY POWDER FIRE EXTINGUISHER

head assembly which is fitted with a spring loaded plunger, and has screwed into it a

replaceable CO 2 bottle. Connected to the outlet end of the discharge tube is a reinforced hose

which leads to a brass nozzle that is fitted with a lever operated control valve the body of the

extinguisher contains approx. 4.5 kg of dry powder. The powder charge is principally sodium

bicarbonate with some magnesium stearate added to prevent the powder from caking. The CO2

bottle contains about 60 mg of CO2.

To operate the extinguisher remove the safety cap and depress the plunger. When the plunger

is depressed it pierces the CO2 bottle seal. The CO2 then blows out the powder charge. the

charge is aimed towards the fire and the discharge is controlled by the valve ....... and hose. the

further assist in smothering the fire. Dry powder extinguishers have at least a B and C rating and

the multipurpose type is also availed.

Some extinguishers are stored pressure dry powder extinguisher which have the propellant gas

mixed in with the dry powder. This extinguisher is controlled with a squeeze-grip trigger on top

of the container. A pressure gauge indicates the condition of the charge. Dry powder and their

propellants are unaffected by extreme temp and may be stored anywhere about the ship. They

do not deteriorate or evaporate so periodic recharging is not necessary. However the cartridges

should be inspected and weighted every six months. Cartridges that are punctured should be

picture

The body of a CO2 portable fire extinguisher is made of solid drawn steel which is hydraulic

tested to 227bar (22.7 MN/2) and it is coated internally and externally with zinc, the external

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surface being finally painted. A solid brass pressing forms the head assembly and this is screwed

into the neck of the steel bottle. The head assembly incorporates a lever operated valve, copper

dip tube, bursting disc and a discharge horn, made of non-conducting ( electrically) material that

can be swiveled in one plane only into the desire position. The body is charged with 4.5 kg of

gas has the advantage that it can get into inaccessible places. CO2 extinguishers need not be

protected for freezing. However they should be stored at temps below 54C to keep their

internal pressure at a safe level. At 57C bursting disc erupts at 2700 psi to release excess

pressure. Several times a year, CO2 extinguisher should be examined for damage and to ensure

they are not empty. An extinguisher that has lost more than 10% OF ITS CO2 weight should be

recharged.

CO 2 AND WATER PORTABLE FIRE EXTINGUISHER

internal pressure when the head is being unscrewed in the event of the nozzle being blocked. A

brass double purpose nozzle is fitted to the delivery end of the reinforced rubber hose and the

nozzle can be operated to give water jet or spray.

The body of the extinguisher contains 9 liters of fresh water, usually a wetting agent is added to

the able the water to spread more readily. The inner container is welded steel, zinc coated, and

charged with 74 mg of CO2 at a pressure of approx 36 bar (3.6 MN/m2). When operating the fire

extinguisher the hose is first uncoiled from the body and the swivel guard is swing to uncover

the plunger. The plunger is then depressed; this releases the co2 which then drives the water

The extinguishes should be stored in place above freezing point.

Another type of fire extinguisher is the stored pressure fire extinguisher. With this type the

extinguisher is fitted with water or an anti-freezing solution to within 15 cm of the top. The

screw on cap holds a lever operated discharge valve, a pressure gauge and an automobile tire-

type valve. The extinguisher is pressurized through the air valve with normal charging pressure is

about 100 psi the gauge allows the pressure in the extinguisher to check at any time, with most

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gauges being color coded to indicate a normal or abnormal charge.

To operate, the pin is removed and the trigger depressed (discharge lever). The steam should be

directed at the seat of the fire, and moved back and forth to ensure complete coverage of the

Sand is also an extinguishing agent that can be used on ships to fight fires. Sand is required as an

extinguishing agent in the amount of 10 cubic feet for spaces containing oil fired boilers.

However sand is not very efficient when compared with modern extinguishing agents and thus

can be replaced by an extra class B fire extinguisher.

The function of the sand is to smoother the oil fire by covering its surface. But if the oil is more

than an inch or so in depth the sand will just sink below the surface. Then unless a sufficient

amount of sand is available to cover the oil, it is rendered ineffective. However, when properly

used, sand can be used to dam fire with a scoop or shovel. Its minimal effectiveness may be

explosions; it would be very unusually to find completely dry sand aboard ship. Sand may be

used to dam off running molten metal but an approved dry powder should be used to extinguish

the fire.

6.9 DESCRIBE SOME TYPE OF EMERGENCY BILGE PUMP AND HOW IT IS CONSTRUCTED

Picture

head. The motor is usually DC operated by a remote controlled electric circuit which is part of

the vessels emergency power.

The pump is designed to operate for long periods without attention and is also suitable for an

emergency fire pump. This design is particular suited for use in large passenger vessels giving

outputs of 60 kg/sec. In the ordinary centrifugal pump priming usually required to facilitate

good pumping. In the emergency bilge, pump this process is taken care of by properly designed

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an equation where (x) is the specific heat of copper.

BTU before mixing= BTU after mixing

2.10 With reference to heat give definition of the following:

Explain the terms Joules mechanical equivalent of heat. What is the numerical valve? Describe

the apparatus used by Doctor Joule to find this value. Where would there be found in

reference to a boiler.

a) RADIATION:

Radiation is the transfer of heat energy from one body to another through space by rays of

electro-magnetic waves. The rays of heat travel in straight lines in all directions at approx. the

same velocity as light.

B) CONDUCTION:

Conduction is the flow of heat energy through a body or from one body to another in contact

with each other, due to difference in temp. The natural flow of heat takes place from a region of

high temp to a region of lower temperature.

Example: in boilers heat is conducted through the heating surface to the water. Heat is also

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conducted through the shell end plates and steam drums. In diesel engines, conduction of heat

takes place through the metal of all parts in contact with the burning fuel, this heat being

carried away by the cooling medium used for the purpose.

This fig shows a vessel containing water with an inclined tube connected at the bottom. When

heat is applied to the tube, the heated particles of water become less dense and rise. Denser

particles move to take their place and thus convection current is set moving resulting in all the

vessels water becoming uniformly heated due to continuous circulation of the water.

Example: In the water tube boiler the tubes are arranged to assist the convection current and

the boiler designed to take full advantage of the law of heat transmission.

D) LATENT HEAT:

Latent heat is the heat which supplies the energy necessary to overcome some of the binding

changes in temp only, and no physical change of state.

Joule:

A joule is the basic unit of all energy including heat

MECHANICAL EQUIVALENT OF HEAT:

Is the relationship between mechanical energy and heat energy? This was determined by doctor

joule using an apparatus which generated heat by the expenditure of mechanical work. In

Imperial units the accepted figure was 778 ft of work = 1 BTU of heat. In the S.I. system, the

2.2 What is the average density of sea water? List the scale forming salts usually present in

a) fresh water

b) salt water

At approx. what temp does calcium carbonate and calcium sulphate deposit? Under what

circumstanced is thus deposit of sodium chloride (common salt )? How would you find the

density of boiler water?

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The average density of sea water is 1.025 tons/m3

The scale forming salts in fresh water are

• calcium carbonate 200 ppm(carbonate of lime)

• calcium sulphate 90 ppm (carbonate of lime)

• sodium chloride 50ppm

• sodium nitrate 35ppm

• sodium sulphate 30 ppm

• calcium sulphate 1200 ppm

• calcium bicarbonate 200 ppm

TOTAL 32000PPM APPROX

Calcium carbonate deposits at a temp of 212F at atmospheric pressure in a high pressure boiler

and evaporator calcium sulphate deposits at a temp of 280 F, 34.5 psi pressure in a high

pressure boiler and at a density of 5/32 NDS in an evaporator. Magnesium sulphate is too

soluble to deposit under normal boiler operating temp but if too high a density is carried it may

deposit.

Sodium chloride (salts) deposits at 7/32 nds in either a high pressure boiler or evaporator. The

saturated point is 7/32 with the exception of the salt, the solid matter in solutions in sea water

will deposit or break up with temp or --- which ever is encountered first.

To find the density of boiler water a sample is drawn through the test cock into the salinometer

pot. The salinometer is placed on the pot where it floats upright in the sample of water. The

salinometer sinks according with the density of the water and the density measured off the

scale on stem at the water level.

2.3 Sketch and describe a salinometer. How is it graduated? What results would you expect

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picture

water = 5/160=1/32nd density.

The density of the sample is read off the surface of the water and must be taken at the

temperature specified on the instrument. thus a reading of 1/32 density indicates for every 32

pounds of water. The water density of a multi-tubular boiler can be measured by a salinometer.

A sample of boiler water is drawn off to fill a salinometer pot. A salinometer is inserted and a

reading taken when the temperature is right. The range of scale is normally from 0 to 4/32 and

while the salinometer is floating in pure water at 93C which has a relative density at that

temperature of unity, the salinometer reading is zero. When the salinometer reading is 1/32

(approx. 32000ppm) when the relative density of solution is 1.025 or 1/32 on the scale, and sea

Describe how you would carry out any these of the following tests in a sample of boiler water.

1. hardness

2. alkalinity

3. chlorides

4. excess phosphate

5. excess sulphites

6. pH

A waters ability to form a lather with soap depends upon the hardness salts which are present,

ALKALINITY:

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ALKALINITY TO PHENOLPHTHALEN

carbonate it will turn pink in color. The acid used after this coloration will first the

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or a primed evaporator. The alkalinity to phenolphthalum sample taken has hydroxides and

carbonate dealt with and they will play further part in test no conducted for chloride the

sample is made definitely acidic by the addition. A further small quality of acid, this is to speed

up the chemical reaction which next takes place. Silver nitrate has an affinity for potassium

4. PHOSPHATE TEST

• calculation: phosphate reserve in ppm from the disc reading

5. EXCESS SULPHITES:

producing a blue coloration. It is therefore apparent that the amount of potassium iodide-iodate

solution used is a direct measure of the sulphite content on the boiler water sample. As far as is

possible, the atmosphere should be excluded in this test otherwise an incorrect result may

occur. If the test indicates that an adequate reserve of sodium sulphite is present in the boiler

water there in no need to conduct a test for dissolve oxygen

6. PH VALVE

A boiler water pH valve can be obtained by three basic methods:

1 litmus paper

2 colourimeterically

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valve of the boiler water.

COLOURIMETRIC METHOD

Take a sample of boiler water. Place one thymol blue tablet in a 50 ml cylinder. Add 50 ml of

An electric cell, using the boiler water as an electrolyte and two special electrodes, both made of

glass are used. The potential difference between the electrodes id directly dependent upon the

hydrogen control of the electrolyte (boiler water). The potential difference is measured by a

sensitive voltmeter connected into the external circuit of the cell and calibrated to read pH

valves.

7. DISSOLVED OXYGEN

Take 500ml of boiler water sample, add 0.3ml of manganese chloride, add 0.3 ml of potassium

hydroxide, add 1 ml of hydro-chloride acid, and add 2 ml ortho tolidine. In this test it is essential

the atmosphere be excluded from the sample being tested. To arrange for this a special

water tested for density, alkalinity and acidity? What is the maximum density you would

oplaite the following boiler at and why?

a) scotch marine boiler

b) water tube boiler

Feed water employed for boilers is usually, un-evaporator fresh water or evaporated salt water.

The first and third of these are normally employed as feed for low pressure boilers such as the

scotch boiler. Evaporated fresh water and evaporated salt water is employed with water tube

boilers. All of this water can contain salts which could be harmful to the boiler from the point of

Acidity and alkalinity- litmus paper can be used turning blue for alkalinity and red for acidity.

However methyl-orange or phenolphthalum are more reliable and sensitive as testing agents.

One or two drops of methyl-orange, will turn yellowish to indicate alkalinity and pink to indicate

acidity. In the phenolphthalum test the sample will turn purplish for alkalinity and cloudy white

for acidity.

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Scotch boilers

Maximum density would be 2.5/32 - 3/32 but if the feed consist entirely of sea water then a

convenient density would be 4/32.

involved in this process?

The oil use in connection with the turbine is a special grade of pure mineral oil. Even a small

quantity of another oil might ruin the whole charge of oil in the system. In all modern

installations an oil separated of the centrifugal type is provided and full advantage can be taken

of this unit to maintain the oil in a proper condition.

Despite all precautions a certain amount of moisture will find its way into the system. There is

usually a certain amount of solid material present in a very finely divided state, and there may

be a certain amount of sludge formation. The use of the separator will remove these impurities

Any time when the vessel is in port and the oil allowed settling, advantage should be taken of

this fact that most of the impurities in the oil such as water, sludge and particles of metal having

a higher specific gravity than the oil will settle to the bottom of the containing vessel. If these

impurities are drawn off from the bottom of the drain tank by means of a hand pump better

results will be obtained with the separator. The efficiency of the clarification will be increased if

the oil being passed through the separator.

In addition, about 2 % by volume of hot distilled water should be added the oil at the separator.

This helps to dissolve out the acids of a corrosive nature which are sometimes formed and also

Picture

2.9 Trace the path of fuel from the settling tank to the burners. List the temp and pressure at

intervals.

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Picture

1. Double bottom fuel oil tank

8. centrifugal oil purifier

9. main service tank

10. gauge glass

11. float control cock

12. engine service tank has overflow to DB tank, also low level alarm

13. quick shut off valve controlled from deck

14. change cock

15. filter in duplicate

16. M/E fuel pump

17. settling tank vent

The fuel oil transfer pump 3) draws oil from the double bottom tanks and delivers it to one of

the settling tanks. One tank is in use while the oil in the other is being heated by means of steam

coils in the tanks or by other means. The temp of the oil in these tanks should never exceed

150F. The heating of the oil allow some of the water which may be mixed with oil to settle to

the bottom. A drain connection, fitted very bottom of the tanks, allows the water to be drained

to the dirty oil tank. The oil may be transferred to the main service tanks (9) direct or may be

passed through a second heating system (7) and from there to any of the centrifugal separator

and then to the main service tanks. The transfer valves in the settling tanks are at higher level

than the drain valves. below the tanks (5)(9)(12) trays are fitted. The drains from the trays are

have self closing cocks or valves.

From the main service tanks (9) the purified oil is led to the engine or boiler service tanks. The

oil for the main engine or boiler enters the tank (12) through a float control cock. The oil leaving

this tank passes through a quick shut off valve (13) and then one of two filters (15). This are

duplex filters, one can be cleaned while one is use. The oil now goes to the fuel pumps on the

engine or boiler from while it delivers at high pressure also metered as to the quantity to the

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fuel valves. The outlet pipes from all of theses tanks can be shut remotely in case of fire.

The flexible rubber coupling are used between engine and gearbox to damper the torque

fluctuations, reduce the effect of shock loading on gears and engine. They also cater for

misalignment, minimize vibration and reduce noise levels. Since oil will attach natural to rubber

these coupling are usually made with reinforced synthetic rubber which is oil resistant.

Before these coupling are installed all parts must be cleaned and free from grease and oil. The

coupling disc is held in position by nut and bolts. A steel ring is fitted on the side opposite the

contact side, when in position will ensure even torque on the coupling disc. Marks on the

coupling will change form, if the coupling starts to wear and loose its strength. Another

The engine under test drives the shaft to which the rotor is directly coupled. The shaft bearings

are inside the casing containing the stator, which is free to serve... trunion supports. Each face

of the rotor has pockets or cells of semi-elliptical or oval cross section divided from one another

by oblique 45 vanes. The stator inlet channel, entering between 45 vanes and passes into a

rotating rotor. The water constantly circulated around the cells in as torque is transmitted from

rotor to stator via the water. This torque tends to turn the stator, this action being resisted by a

load measuring device so that the resisting torque will equal the applied torque and thus being a

measured.

Brake horse power = 2pie N X torque

60

10.4 Describe the method in which the following types of machinery are reversed.

a. steam reciprocating engines

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the thrust block, which being securely fitted to the hull of the ship. The shaft is comparatively

short with a coupling at each end a thrust collar in the middle of its length and a ? at each side

of the thrust collar.

a film of oil maintained between the faces and there is consequently no metallic contact.

Thrust pressures in the region of 24 bar can therefore be carried without danger of overheating

due to friction. Particular attention is giving to the strengthening of the structure of the double

bottom heavy loads be supported and vibration minimized, but the thrust from the thrust block

is to be transmitted to ship’s hull.

All structure below the boiler and engine rooms is increased in thickness, additional longitudinal

girders are incorporated so that they are pitched closer together, all girders have double angles

and all parts are bearing fit. A tank top plate of extra thickness ( 40mm or more ) runs

thrust force is taken up by the surface of collars. This reduces the length of the block and it will

be obvious that this is not a drawback as the engines only need to run astern for short period.

The thrust block is secured to the hull of the ship by means of a pedestal made up of plates and

angle iron, the hull being strengthened at this part so to transfer the thrust and distribute it over

the hull. The shoes are usually held in position by large adjusting screws each shoe having

separate jam nuts to permit the load to be distributed evenly over the various collars. The faces

of the shoes are usually filled with white metal which permits about 70lbs per sq in of effective

surface when the engine are running at full speed ahead.

Base and covers are made of cast iron, while the bearing at each end are made of gunmetal.

Lubrication carried out by means of an oil scraper, fitted in the collar which intercepts the oil

brought up by the rotating collar from the oil bath below, so forming a cascade of oil over the

thrust pads. The end bearings are self lubricated and oil deflecting rings are fitted at each end to

prevent oil escaping.

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4.1 Describe in detail, how you would fit a new propeller to a tail shaft already in place. State

size of shaft and size of key used. How would you ascertain that the propeller is in right place?

When fitting a new propeller to a tail shaft already in place, the tall shaft should be checked for

examined for corrosion. If the old propeller was moving the cone will not be true and a new

propeller will not fit as it should. The propeller is fitted by smearing the taper with mechanical

blue. The propeller is then slipped on over the taper and any high spots will be noted by the

taper being scraped clear and the mechanical blue showing up on the propeller boss. The high

spots are scraped down again and the propeller is placed on the shaft taper. The process is

continued until about 80% or more of the propeller has turned blue.

When the taper is fitted perfectly the nut and bossier marked, when the boss is hold up on the

taper. The nut is then slacked back and the propeller is dropped back against the nut. A ball of

soft lead wire is laid on the top of the shaft close to the lines and the propeller is then

is taken right back in order to insert the key in the keyway. The propeller is forced upon the

taper again until the marks coincide, the nut is removed again and feeler is inserted on the top

of the keyway its whole length. Top of the key must not touch the boss. When this is checked

the rubber ring is put in place, up against the lines.

The propeller is put on the taper again and the nut hammered up with a ring spanner until the

marks on the nut goes beyond the mark on the boss slightly. This is to ensure the propeller is

hard in its place. A stopper plate is next bolted to a recess in the propeller nut. A pintle on the

plate passes through the hole drilled into the propeller nut. This is a locking device to prevent

grease) over the nut and bolt and bolt it to the propeller boss. Therefore no part of the steel tail-

shaft will be in contact with the sea water if the various parts have been properly fitted. If no

cone is fitted over the propeller nut it should be cemented over.

4.2 Describe a modern method of aligning shafting on a ship. What method is used for boring

out to fit a stern tube?

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The first important step to the fitting of the length of shafting from the propeller to engine in

correct alignment is the installation of the stern tube to carry the propeller shaft, at its

designated height from the keel and in the, directional line, so that the remaining shafting can

the keel as required according to the plans of the ship and carefully athwarthip. At the height

and athward centre line of the engine shaft, a similar hole is drilled a plate in the engine room

forward bulkhead, and a strong tight is placed on the forward side of the hole.

Therefore by sighting from the after wall of the small hole drilled in the stern frame plate, the

tiny beam of light can be seen through the hole in the engine room forward bulkhead and any

other water tight bulkheads through which the shafting is to pass. Beginning at the after peak

bulkhead and later taking the others in turn, a sighting plate with a horizontal straight edge is

moved vertically upwards over the hole from below the centre until the beam of light is just cut

off from sight, and a horizontal reference line is drawn alone this straight edge on the bulkhead

movement of a plate with a straight vertical edge to obtain the exact vertical center line of the

shafting. A bridge plate is now fixed into the rough hole and the shafting center scrub on it by

intersecting the vertical and horizontal centerlines, and a small sighting hole drilled through this

centre.

When this is done to all intermediate water tight bulkheads, the beam of light should be seen

right through the entire centre sighting holes from stern frame to engine room. With the

sighting holes as centers, references circles of the correct diameter are scribe with dividers on

the stern frame and bulkheads. Then the bridge plates are removed, the boring gear set up and

Each shaft form aft to forward is line up by the use of feeler gauges between the coupling faces,

chocking the tunnel bearings on their pedestals as required. A final check for alignment is made

with all shafts in position by the optical telescope which is placed at one end and a target at the

other end. Both telescope and target are setup at the same height above the shaft journals, and

sighting takes place on a graduated seal mounted on each shaft journal in turn. Final

adjustments are made to the bearing chock bearing firmly bolted down on their pedestals and

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coupling bolts fitted.

4.5 Describe the construction of a tail shaft. What metals are used? What test would the tailed

shaft be subjected to and what would the results be?

water. The shaft is machined all over.

The taper at the end for taking the propeller or propeller boss in (of the order of .75inch per

foot) length of shafting and has a length of approx. three times the shaft diameter. The keyway

is milled out and has semicircular end to avoid stress concentration. To protect the shaft from

corrosion and from wear it has a sleeve or liner of gunmetal shrunk on. The liner may be in one

or more length and is machined to have the diameter of the forward length slightly greater than

after length. The difference in diameter is an aid in fitting shaft into the stern tube.

The following are working stresses induced in a propeller shaft.

BENDING AND SHEARING: Due to the weight of the propeller and its overhang from the end of

the ship.

TENSION AT TAPER: Due to the tightening of the tail end nut.

FATIGUE: This results from the variation and combination of all other stress.

It should be noted that when bending occurs the upper layers of metal are put into tension, and

the bottom layers in compression. It therefore follows that with overhang of the propeller these

charging lines.

Picture

The electric hydraulic steering gear uses an electric motor to drive a hydraulic pump for piping

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and discharging hydraulic oil from one cylinder to the other depending upon the direction

required. Movement of the rudder stock is achieved by the force of the hydraulic oil being

exerted. These rams are of steel construction while the cylinders usually gunmetal. The

hydraulic pipes in the system are heavy gauge copper, and the hydraulic fluid is a mineral oil.

crosshead and swivel block, the other ends of the rams working inside their own hydraulic

cylinder, pipes connect these cylinders to a hydraulic pump. The function of the pump is to draw

oil from one cylinder and pump it (at high pressure) into the other, thus causing one ram to

move out and push the tiller over while the other moves back into its cylinder.

The hydraulic pump is of the rotary displacement types driven by an electric motor. The pup is

of special construction and may be a Hele-shaw or Williams-Janney design. It runs continuously

in the same direction and the position of a moveable plate inside the pump controls the suction

and discharge of the oil. When the plate is moved in one direction from mid position no oil is

drawn in or discharged. When the plate is moved in one direction from the mid position oil is

bypassing a little of the oil into the other cylinder resulting displacement of the rudder, tiller and

ram crosshead moves the pump control rod through the hunting gear and the tiller is

automatically brought back to proper position. The following sketch shows simply to operation

of the hunting gear.

picture

The telemotor moves the end of the floating rod A to A1 and the pump control is moved,

The steering gear itself must be completely filler with oil and all air must be excluded. Thus the

air release valves are opened on hydraulic cylinders and pumps also stop valves pump can be

used to pump the oil around the system (while keeping the replenishing tank topped up) It can

be put on stroke by the hand wheel and turned by a bar. The rams may be filled through the

filling holes until all air has been displaced, before starting to pump the system through. When

all the air has been purged from the system and the level in the relishing tank ceases to fall, the

air released valves are closed. Finally the by-pass and stop valves are set for normal operation

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and the pump started. Using the hand control, the gear is then run from hard over to hard over

slowly and the air release valves are open again to check. To allow for wear down in the

crosshead arrangement a wear down rudder allowance of 19mm is provided so as not to induce

bending stresses on the ram.

picture

The steering engine or electric motor transmits its movement to the tiller, firmly keyed to the

rudder stock by means of a worm on the engine crankshaft which engages with a worm wheel.

The shaft of this worm wheel carries a pinion which meshes with a large quadrant, the centre of

which sets loosely over the head of the rudder stock above the tiller. Two heavy shock absorbing

helical buffer springs connect the two side of the fixed tiller to the loose quadrant. When the

extension secured to an arm on the tiller, the drive being from a hand wheel carries on a

pedestal above the steering gear, through a worm gearing, friction clutch and vertical shaft

down to the quadrant driving pinion. The shackle shown on the line of each wing of the loose

quadrant is for coupling block and tackle gear to operate the rudder (and also the emergency

hand wheel fitted). The block and tackle arrangement is worked through wire rope, guided by

puller and led to the after winch. A screw-operated brake is fitted to enable the rudder stock to

be locked while changing over from engine to emergency steering, or while repairs are being

carried out and the steering engine and driving pinion can be slid out of gear after the

emergency gear has been coupled up. If one of the helical springs breaks a key can be placed in

picture

The constant speed Hele-shaw pump has its output controlled by a simple push/pull rod

attached to guide rings in the pump. Without stopping or starting the pump, the output can be

varied from zero to full in either direction. The pump consists of a bronze cylinder body with

seven or nine radial cylinders which is rotated at constant speed in one direction. The radial

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cylinder block rotates on a fixed steel constructed piece having two ports opposite to one

another and in line with the bottom of the rotating cylinders. In each cylinder there is oil

hardened steel piston having a gudgeon pin with bronze slippers on the ends. The slippers

revolve with the cylinder block in grooves machined in a pair of floating rings. These are the

have no relative reciprocating motion in their cylinders. As an result no oil is pumped and the

pump although rotating is not delivering any oil

B) If however the ring is pulled to the right then a reciprocating motion of the piston in their

cylinder does occur. The lower piston moves inward, it discharges fluid out through the lower

port in the central v/v arrangement. As it continues to pass the horizontal position the piston

moves out drawing in the fluid from the upper port.

C) Once past the horizontal position on the other side it begins to discharge fluid. If the floating

ring was pushed to the left the suction and discharge ports would be reversed.

picture

This is a rotary pump which works on the principal of centrifugal force, that is, that outward

radial force set up by a mass rotated in a circular path due to its natural tendency to fly off at a

these ports, and due to the circular motion given to the water it is thrown by centrifugal force to

the open periphery of the impeller and the casing and directed to the outlet branch.

The centrifugal pump does not have a positive suction action and must be primed by flooding

before it will draw water from a lower level. Therefore it is employed mainly where the suction

is submerged of the lift is very small. Centrifugal pumps will only pump in one direction of

rotation. The drive for these pumps is most often directly from an electric motor but can be

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from an auxiliary turbine. In the latter case the prefix turbo is adopted for exam; " turbo feed

pump"

This water-oil ballast chest is a standard fitting on many cargo vessels, on the double piping

systems. Normally all chest are open to oil fired (bend) and blanked to water ballast. For ballast

or ballast prior cleaning, the bend and blanks are as shown in the sketch. This means that an

error in opening the wrong valve would not in itself allow crossing of circulation.

As an alternative to this fitting hollow one way discharge plug cocks or a system of interlocking

valves would be acceptable. Any system employed must prevent easy joins of oil and water

5.4 What type of valves are fitted to double bottom or water ballast tanks and why? How

would you proceed to pump out a double bottom tank? Why vents fitted? Why are sounding

pipes fitted and where?

Double bottom and water ballast tanks are fitted with screw lift valves. In these cases screw lift

valves are used in order to pump in and out thus the same valve. Once opened they stay opened

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until closed manually. To empty a tank, the appropriate valve for the tank on the distribution

chest in the engine room is opened, next the tank suction valve to pump distribution chest is

opened. The discharge overboard valve on the discharge chest and ships side is opened and the

pump started up. All other valves should be shut. To fill a tank, open appropriate tank valve in

starboard this end being the lower end under normal trim. Sounding pipes are fitted so the level

of the liquid in the tanks can be ensured. These pipes may also serve as vent pipes when filling

tanks, but it should be noted that it is still essential to also have vent pipes.

5.1 Describe with a simple line sketch a bilge system a ballast system for a 7000 ton cargo

ship. What is bilge injection valve? What is the main difference between bilge and ballast?

picture

prevent water flowing back and flooding the bilges. The operated hand wheels are labeled by

engraved brass plates as to which bilge the pipe runs into. A mud box is fitted on the bilge

suction of each pump and open end of every bilge pipe in the bilges is enclosed a strainer box.

1) a bilge pump has suctions from all bilge main and engine room bilge, with discharge to fire

main, oily water separator and overboard.

2) a ballast pump has suctions from sea, ballast main, engine room bilge direct and bilge main

with discharge to overboard, the ballast main, the oily water separator and possibly the main

The pumps should be of the self priming type unless efficient priming devices are provided. The

capacity of the pumps should give water speeding the main line of not less than 2m/s and the

capacity should be about 65% of the displacement of the ship. Vessels should have at least four

independent power pumps connected to the main line pump should have a direct suction to the

space in which it is situated, such suction to be at least the same bore as the bilge line. Not more

than two such suctions are required and in the machinery space such suctions should be

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arranged, one each side.

Emergency bilge pumps are also used on ships in the case of emergency such as a compartment

flooding due to, most likely, hull damage. It is a self-contained unit consisting of a centrifugal

The bilge injection valve is one of the most important fitting in the machinery space. It is

provided for use in the event of serious flooding in the machinery space. By closing in the main

injection valve and opening up the bilge injection valve the largest pump (or pump) in the

engine room are drawing directly from the lowest point in the space; this suction can remove

large quality of water. The diameter of the BILGE INJECTION VALVE IS AT LEAST 2/3 OF THE

DIAMETER OF THE MAIN SEA INLET. Valve spindle should be clear above the engine room deck

plating so that examination and greasing, with cleaning of strum or strainer.

Picture of injection valve

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4. make sure lifting gear like wire slings, chain blocks have proper certification before being

taken into service.

5. A check list should be made and verified before flooding the dock for undocking the vessel.

7. After flooding dock to sea chest level, open and check sea suction valves for any abnormality

like leaky joints or packing

8. Main engine crankshaft deflections are taken before and after docking to check out any

deviations from standard readings.

9.5 What is meant by thermo dynamic, volumetric efficiency, mechanical efficiency, and

thermal efficiency?

MECHINICAL EFFICIENCY

The mechanical efficiency id the ratio of the brake power to the indicated power

THERMAL EFFICIENCY

The thermal efficiency of an engine is the relationship between the quantity of heat energy

converted into work and the quantity of heat energy supplied.