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UNIT 32.

THE THIRD ENGINEER

A Second Assistant Engineer or Third Engineer is a licensed member of the

engineering department on a merchant vessel.

The Second Engineer is usually in charge of boilers, fuel, auxiliary engines , condensate

and feed system ,and is the third most senior marine engineer on board. Depending on

usage, The Second or The Third is also typically in charge of fueling (bunkering),

granted the officer holds a valid Person In Charge (PIC) endorsement for fuel transfer

operations.

The exact duties of this position will often depend upon the type of the ship and

arrangement of the engine department .On ships with steam propulsion plants , the

Second/ Third is in charge of the boilers, combustion control, soot blowers, condensate

and feed equipment ,feed pumps, fuels, and condensers. On diesel and gas turbine

propulsion plants, the Second is in charge of auxiliary boilers, auxiliary engines,

incinerator, air compressors, fuel, and fuel oil purifiers.

THE FOURTH ENGINEER.

The Third Assistant Engineer, also known as the Fourth Engineer, is a licensed

member of the engineering department on the merchant vessel.

Generally the most junior marine engineer of the ship,this person is usually responsible

for electrical ,sewage treatment ,lube oil, bilge, and oily water separation systems.

Depending on usage ,he is called The Third or The Fourth and usually stands a watch

and sometimes assists the third mate in maintaining proper operation of the lifeboats.


2/17

UNIT 33.

PREPARATIONS FOR STANDBY.

1. Before a large diesel is started ,it must be warmed through by circulating hotwater through the jackets, etc .This will enable the various engine parts to expand

in relation to one another.2. The various supply tanks ,filters ,valves and drains are all to be checked.3. The lubricating oil pumps and circulating water pumps are started and all the

visible returns should be observed.4. All control equipment and alarms should be examined for correct operation.5. The indicator cocks are opened, the turning gear engaged and the engine turned

through several complete revolutions. In this way, any water which may have

collected in the cylinders will be forced out.

6.

The fuel oil system is checked and circulated with hot oil.7. Auxiliary scavenge blowers, if manually operated, should be started.8. The turning gear is removed and if possible, the engine should be turned over

on air before closing the indicator cocks.9. The engine is now available for standby.The length of time involved in these preparations will depend upon the size of the

engine.


3/17

UNIT 34.

COOLING.

Cooling of engines is achieved by circulating a cooling liquid around internal

passages within the engine. The cooling liquid is thus heated up and is in turn cooled

by sea water circulating cooler . Without adequate cooling ,certain parts of the

engine which are exposed to very high temperatures, as a result of burning fuel,

would soon fail. Cooling enables the engine metals to retain their mechanical

properties. The usual coolant used is fresh water ,sea water is not used directly as a

coolant because of its corrosive action. Lubricating oil is sometimes used for piston

cooling since leaks into the crankcase would not cause problems. As a result of its

lower specific heat however about twice the quantity of oil compared to water

would be required.

UNIT 35.

PISTON COOLING WATER SYSTEM.

While all trunk piston engines, as well as some crosshead engines, use oil to

cool the pistons, a number of crosshead engines use a cooling water system separate

from the jacket water system. The water reaches and leaves the pitons through

telescoping tubes enclosed within compartments inside the crankcase in order to

avoid contamination of the LO should a gland fail.

Because of the high temperature of water draining from the pistons and the

resulting potential for flashing at the pump suction, some manufacturersrecommend the deep well pumps immersed in the tank be used. Both pumps will

be motor driven. Automation and other features will be similar to those described

for the main engine jacket water system.


4/17

UNIT 36.BOILER MOUNTINGS.

Main steam stop valve: This valve is fitted in the main steam supply line and is

usually of the non- return type.

Auxiliary steam stop valve : This is a smaller valve fitted in the auxiliary steam

supply line ,and is usually of the non-return type.

Feed check or control valve: A pair of valves are fitted; one is the main valve ,the

other is the auxiliary or standby. They are non-return valves and must give an

indication of their open and closed position.

Water level gauge: Water level gauge or gauge glasses are fitted in pairs, at

opposite ends of the boiler. The construction of the level gauge depends upon the boiler

pressure.

Pressure gauge connection: Where necessary on the boiler drum, superheater,

etc.., pressure gauges are fitted to provide pressure readings.

Air release cock: These are fitted in the headers, boiler drum, etc.., to release air

when filling the boiler or initiary raising steam.

Sampling connection: A water outlet cock and cooling arrangement is provided

for the sampling and analysis of feed water . A provision may also be made for

injecting water treatment chemicals.

Blow down valve: This valve enables water to be blow down or emptied from the

boiler . It may be used when partially or completely emptying the boiler.

Scum valve : A shallow dish positioned at the normal water level is connected to the

scum valve. This enables the blowing down or removal of scum and impurities from the

water surface.

Whistle stop valve : This is a small bore non-return valve which supplies the

whistle with steam straight from the boiler drum.


5/17

UNIT 37.INJECTORS.

An injector consists of a body, a springloaded, fuel pressure-actuated needle valve ,and

a nozzle . Spring loading is factory set to permit opening at 3,500psi. Two studs secure

each injector to the head through a gasket at a shoulder in the cylinder head bore

close to the bottom of the head. The injector body is sealed to the bore in the head at

the top by O-rings to prevent contamination of rocker arm lubricating oil. Needles are

precision fitted to the nozzle center bores and are interchanged only in matched sets.

Small amounts of fuel leaking past the needles are collected via gravity drains.

The nozzle has ten orifices symmetrically oriented at a 70 degree angle to the

vertical centerline. Orifice diameters of 0.60 mm and 0.65 mm are in use, with the

smaller ones fitted where lower viscosity fuels will be burned.

Injectors are cooled by water passages in the body and nozzle that connect to

supply and return tubes above the top of the head. On heavy fuel engines , the injector

circuit is separated to the enable the injector to be maintained at the correct temperature

for injection, or to be heated in case the engine has been stopped without first changing

over to distillate fuel.


6/17

UNIT 38.

MAINTENANCE SCHEDULE OF MARINE DIESEL ENGINE.

At intervals of six months the upper pistons, if cooled , must be inspected for deposits

of carbon in cooling spaces and cooling pipes. When new piston rings are fitted ,care

must be taken to ensure there is sufficient clearance to allow for the expansion of the

rings. Exhaust belts and manifold must also be removed from cylinder ports. Cylinder

liners must be examined externally for deposits of scale. If these deposits can not be

removed be flushing with water , then the liner muse be removed for cleaning. The liner

should also be measured for wear and renewed, if the limit for wear has been reached.

The clearances of collecting-rod top and bottom ends should also be examined every six

months and adjusted if necessary. In addition ,lubricating-oil pumps and tanks should be

cleaned of sediment.

At intervals of one year the maneuvering gear must be examined for wear at the

joints of levers and rods. The alignment of the crankshaft should be checked and any

incorrect alignment corrected . The main bearings must be examined and reading taken

for wear. The clearances of all crankshaft bearings must be maintained at the figure

recommended by the makers. Finally, starting air piping and air bottles must be cleaned

and steamed out, and the lubricating oil system thoroughly examined and cleared of

deposits.

It must be emphasized that the abovementioned parts are only some of the items whichmust be regularly maintained to ensure the efficient working of the machinery.


7/17

UNIT 39.

COMPARISON OF TWO-STROKE AND FOUR-STROKE CYCLES.

The main difference between the two cycles is the power developed. The two-stroke

cycle engine ,with one working or power stroke every revolution, will theoretically, develop

twice the power of a four-stroke engine of the same swept volume. Inefficient scavenging

however and other losses, reduce the power advantage to about 1.8.For a particular

engine power ,the two-stroke engine will be considerably lighter- an important

consideration for ships. Nor does the two-stroke engine require the complicated valve

operating mechanism of the fourstroke. The four-stroke engine however can operate

efficiently at high speeds which offsets its power disadvantage ,it also consumes less

lubricating oil.

Each type of engine has its applications which on board ship have resulted in the slow

speed( i.e. 80-100 rev/min) main propulsion diesel operating on the two-stroke cycle. At

this lower speed , the engine requires no reduction gearbox between it and the propeller .

The four-stroke engine (usually rotating at medium speed ,between 250 and 750 rev/min)

is used for auxiliaries such as alternators and sometimes for main propulsion with a

gearbox to provide a propeller speed of between 80-100 rev/min.

UNIT 40.

TURNINE CONTROL.

The valve which admit steam to the ahead or astern are know as maneuvering valve.

There are basically three valves, the ahead ,the astern and the guarding or guardian valve.

The guardian valve is an astern steam isolating valve. These valves are hydraulically

operated by an independent system employing a main and standby set of pumps.

Provision is also made for hand operation in the event of remote control system failure.

Operation of the ahead maneuvering valve will admit steam to the main nozzle box.

Remotely operated valves are used to open up the remaining nozzle boxes for steam

admission as increased power is required. A speedsensitive control device atcs on the

ahead maneuvering valve to hold the turbine speed constant at the desired value.

Operation of the astern maneuvering valve will admit steam to the guardian valve which

is opened in conjunction with the astern valve. Steam is then admitted to the astern

turbines.


8/17

UNIT 41.TURBINE PROTECTION.

A turbine protection system is provided with all installation to prevent damage resulting

from an interval turbine fault or the malfunction of some associated equipment.

Arrangements are made in the system to shut the turbine down using an emergency stop

and solenoid valve . Operation of this device cuts off the hydraulic oil supply to the

maneuvering valve and thus shuts off steam to the turbine. This main trip relay is

operated by a number of main fault conditions which are:

1. Low lubricating oil pressure .2. Overspeed .3. Low condenser vacuum.4. Emergency stop.5. High condensate level in condenser.6. High or low boiler water level.

Other fault conditions which must be monitored and from part of a total protection

system are:

1. HP and LP rotor eccentricity or vibration.2. HP and LP turbine differential expansion.3. HP and LP thrust bearing weardown.4. Main thrust bearing weardown.5. Turning gear engaged (this would prevent starting of the turbine).

Such turbovisory system ,as they may be called, operate in two ways.

If a tendency towards a dangerous condition is detected a first stage alarm is given. This

will enable corrective action to be taken and the turbine is not shut down. If corrective

action is not rapid, is unsuccessful, or a main fault condition quickly arises, the second

stage alarm is given and the main trip relay is operated to stop the turbine.


9/17

UNIT 42.

AIR EJECTOR.

The air ejector draws out the air and vapours which are released from the condensing

steam in the condenser. If the air were not removed from the system, it could cause

corrosion problems in the boiler. Also ,air present in the condenser would affect thecondensing process and cause a back pressure in the condenser. The back pressure would

increase the exhaust steam pressure and reduce the thermal efficiency of the plant.

In two-stage twin-element air ejector, in the first stage , a steamoperated air ejector

acts as a pump to draw in the air and vapours from the condenser. The mixture then

passes into condensing unit which is circulated by feed water. Then feed water is heated

and the steam and gases are mostly condensed. The condensed vapours and steam are

returned to the main condenser via a drain and the remaining air and gases pass to the

second stage where the process is repeated. Any remaining air and gases are released to the

atmosphere via a vacuum-retaining valve. The feed water is circulated through V-tubes ineach of the two stages. A pair of ejectors are fitted to each stage, although only one of each

is required for satisfactory operation of the unit.


10/17

UNIT 43.

HEAT EXCHANGEERS.

The gland steam condenser, drains cooler and low-pressure feed heater are all heat

exchangers of the shell and tube type. Each is used in some particular way to recover heat

from exhaust steam by heating the feedwater which is circulated through the units.

The gland steam condenser collects steam, vapour and air from the turbine gland

steam system. These returns are cooled by the circulating feed water and the team is

condensed. The condensate is returned to the system via a loop seal or some form of steam

trap and any air present is discharged in to atmosphere. The feed water passes through V-

tubes within the shell of the unit.

The drains cooler receives the exhaust drains from various auxiliary services and

condenses them: the condensate is returned to the feed system. The circulating feed waterpasses through straight tubes arranged in tube plates in the drains cooler. Baffles or

diaphragm plates are fitted to support the tubes and also direct the flow or the exhaust

drains over the outside surface of the tubes.

The low-pressure feed heater is supplied with steam usually bled from the low-

pressure turbine casing. The circulating feed is heated to assist in the de-aeration process.

The bleeding-off of steam from the turbine improves plant thermal efficiency as well as

reducing turbine blade heights in the final rows because of the reduced mass of steam

flowing. Either straight or V-tube construction may used with single or multiple passes of

feed water.

Question:

1. What are heat exchangers of the shell and tube type?2. What are the heat exchangers used to?


11/17

3. How is the heat from the exhaust steam recovered?4. What does the gland steam do?5. What is condensed?6. What is the condensed returned to?7. What does the drains cooler do?8. Why are baffles or diaphragm fitted?9. Where is the steam supplied to the low pressure feed water bled?10.Why is circulating feed water heated?11.What does the bleeding off of steam from the turbine do?

UNIT 44.

INCINERATION OF OIL WASTE AND GARBAGE.

The disposal of solid and liquid wastes other than sewage has become the subject of

investigation following the publication of the 1973 IMCO proposal. Garbage can be

contained and compacted, but storage is necessary and not always available. Packaging

will inevitable include a large quantity of plastics which must be retained on board since

discharging overboard at sea will not be permitted regardless of distance offshore. Liquid

wastes, mainly oil sludges, must be retained on board and ,along with garbage, will

necessitate the provision of storage space. Incineration of these materials is without doubt

the most effective means of dealing with the storage problem because the resultant residues

are extremely small in volume and easily disposed of.

Before deciding on the type of incinerator to be adopted ,an assessment of storage

requirements are necessary. Equally important in this assessment is the categorization of

the waste to be consumed. These categories are: (a) galley waste including food scraps,

bones ,cans ,bottles, plastics ,etc.; (b) accommodation wastes such as paper, cardboard,

cans, plastics, textiles ; (c) oils/sludge including bilge, oil purifiers, lubricating oils, etc..;

and (d) sewage sludges.

Question:

1. What has become the subject investigation of the IMCO proposal?


12/17

2. Can garbage be discharging overboard at sea?3. What should be done to liquid wastes and garbage?4. What is necessary to do before deciding on the type of incinerator to be adopted?5. What types of waste can be consumed?

UNIT 45.

OIL TREATMENT.

Both fuel oils and lubricating oils require treatment before passing to the engine. This

will involve storage and heating to allow separation of water present, coarse and fine

filtering to remove solid particles and also centrifuging.

The centrifugal separator is used to separate two liquids, for example oil and water , or a

liquid and solids as in contaminated oil. Separation is sped up by the use of a centrifuge

and can be arranged as a continuous process. Where a centrifuge is arranged to separate

two liquids, it is known as a purifier. Where a centrifuge is arranged to separate

impurities and small amounts of water from oil it is known as a clarifier.

The separation of impurities and water from fuel oil is essential for good combustion.

The removal of contaminating impurities from lubricating oil will reduce engine wear and

possible breakdowns. The centrifuging of all but the most pure clean oils is therefore an

absolute necessity.

Question:

1. What should be done to F.O and L.O before passing to the engine?2. Why do F.O and L.O require treatment ?3. How is water separated from F.O and L.O?4. What is the centrifugal separator used to?5. How is separation sped up?6. What is known as purifier/ clarifier?7. What can reduce the engine wear and possible breakdowns?


13/17

UNIT 46.

HYDRAULIC SYSTEM.

The open-loop circuit takes oil from the tank and pumps it into the hydraulic motor. A

control valve is positioned is parallel with the motor. When it is open the motor is

stationary ; when it is throttled or closed the motor will operate. The exhaust oil returns to

the tank. This method can provide stepless control , e.i. smooth changes in motor speed.

The live-line circuit, on the contrary, maintains a high pressure from which the control

valve draws pressurized oil to the hydraulic motor (in series with it), as and when

required.

In the closed-loop circuit , the exhaust oil is returned direct to the pump suction. Since

the oil does not enter an open tank, the system is considered closed.

Low- pressure systems use the open-loop circuit and are simple in design as well as

reliable. The equipment is ,however, large, inefficient in operation and overheats after

prolonged use.

Medium-pressure systems are favoured for marine applications, using either the open or

closed circuit. Smaller installations are of the open-loop type. Where considerable amounts

of hydraulic machinery are fitted, the live-circuit supplied by a centralized hydraulic

power system would be most economical.

Question:

1. Where does the open loop circuit take oil?2. How is the control valve positioned?3. What happens to the motor when the control valve is open?4. When will the motor operate?5. What does the live line circuit do?

UNIT 47.

STEERING GEAR TESTING.


14/17

Prior to a ships departure from any port the steering gear should be tested to ensure

satisfactory operation. These tests should include:

1. Operation of the main steering gear.2. Operation of the auxiliary steering gear or use of the second pump which acts as

the auxiliary.3. Operation of the remote control (telemotor) system or systems from the main

bridge steering positions.

4. Operation of the steering gear using the emergency power supply.5. The rudder angle indicator reading with respect to the actual rudder angle should

be checked.

6. The alarms fitted to the remote control system and the steering gear power unitsshould be checked for correct operation.

During these tests, the rudder should be moved through its full travel in both

directions and the various equipment items, linkages, etc.., visually inspected for damageor wear. The communication system between the bridge and the steering gear

compartment should also be operated.

Question:

1. Why should the steering gear be tested prior to a ships departure?2. What should these tests include?3. Should: +the operation of the mains steering gear be tested?

+the operation of the remote control be tested?

+..

4. Why should the alarms be tested?5. What should be done during these tested?

UNIT 48.

TURBOCHARGER WATER WASHING SYSTEM.

In order to avoid the decline in performance that is caused by fouled turbines and

compressors, many engines, including most intended for operation on heavier fuels, are

fitted with water washing systems. Most commonly , these systems take the form of small

tanks piped to the compressor inlet and the turbine inlet, fitted with water-filling and


15/17

compressed air connections. In use, the engine load is reduced, and the charge of water,

limited by the size of the tank, is injected over a period of about one minute. Solvents are

usually not recommended: it is the impact of the water which does the cleaning.

Frequency of use will depend on the rate of fouling , determined from experience. Water

wash of the compressor will most likely be required infrequently. On the other hand, it isnot uncommon, in the case of engines run on the heaviest fuels, for the turbine to be

washed daily.

Question:

1. Why are many engines fitted with water washing systems?2. What form do these system take?3. What are these system fitted with?4. How is the engine load reduced and limited?5. How long is water injected?6. Are solvents recommended?7. What depends on the rates of fouling?

UNIT 49.

REFRIGERANTS.

A refrigerant is the working fluid which picks up the heat from the enclosed

refrigerated space and transfers it to the surroundings. It should be understood that there

is no such thing as an ideal refrigerant. Due to various applications and operating

conditions, different refrigerants are suitable for different situations. A considerable

number of fluids are available for use. However, only a few are employed as refrigerants in

marine systems. Some which were popular a number of years ago (e.g., carbon dioxide and

ammonia) are no longer used in marine practice because of the development of more

suitable fluids. High on the list of desirable fluids are those that are nonflammable,

nontoxic, and non-explosive. In addition , the fluid should not react unfavorably with

lubricating oil or any material commonly used in refrigeration systems, and should possess

desirable thermodynamic properties that make it economical to use.

Question:


16/17

1. How does a refrigerant work?2. Is there any ideal refrigerant? Why?3. Why are carbon dioxide and ammonia no longer used in marine practice?4. What are high on the list of desirable fluids?5. Why are nonflammable, nontoxic used?

UNIT 50.

VENTILATION OF MACHINES.

Open machinery. A machine having ventilating openings that permit passage ofexternal cooling air over and around the windings.

Self-ventilated machine. A machine having its ventilating air circulated by means

integral with the machine.

Separately ventilated machine. A machine that has its ventilating air supplied by an

independent fan or blower external to the machine.

Enclosed self-ventilated machine. A machine having openings for the admission and

discharge of the ventilating air, which is circulated by means integral with the machine, the

machine being otherwise totally enclosed. These openings are so arranged that inlet and

outlet ducts or pipes may be connected to them.

Enclosed separately ventilated machine. A machine having openings for the admission

and discharge of the ventilating air, which is circulated by means external to and not a

part of the machine, the machine being otherwise totally enclosed. These openings are so

arranged that inlet and outlet duct pipes may be connected to them.

Totally enclosed machine. A machine so enclosed as to prevent the free exchange of air

between the inside and outside of the case, but not sufficiently enclosed to be termed

airtight.

Totally enclosed fan-cooled machine. A totally enclosed machine equipped for exterior

cooling by means of a fan or fans integral with the machine but external to the enclosing

parts.


17/17

Question:

1. What is an open machine?2. What is a self ventilated machine?3. How is ventilating air supplied in separately ventilated machine?4. How does an enclosed self ventilated machine work?5. In an enclosed separately separated machine, what are the openings used for?6. What type of machine can prevent the free exchange of air between the inside and

the outside of the case?

7. How many machines are mentioned in this lesson? What are they?

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