Motor Genral Oral Notes (2)

8/3/2019 Motor Genral Oral Notes (2)

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flash blowdown of a boiler

1.BOILER BLOWDOWN

Even with the best pretreatment programs, boiler feedwater often contains

some degree of impurities,such as suspended and dissolved solids. The

impurities can remain and accumulate inside the boiler as the boiler

operation continues. The increasing concentration of dissolved solids maylead to carryover

of boiler water into the steam, causing damage to piping, steam traps and

even process equipment. The increasing concentration of suspended solids

can form sludge, which impairs boiler efficiency and heat

transfer capability. To avoid boiler problems, water must be periodically

discharged or blown down from the boiler to

control the concentrations of suspended and total dissolved solids in the

boiler. Surface water blowdown is often done continuously to reduce the level

of dissolved solids, and bottom blowdown is performed periodically to remove

sludge from the bottom of the boiler. The importance of boiler blowdown is

often overlooked. Improper blowdown can cause increased fuel

consumption, additional chemical treatment requirements, and heat loss. In

addition, the blowdown water has the same temperature and pressure as the

boiler water. This blowdown heat can be recovered and reused in the boiler

operations.

Boiler Blowdown Benefits

Less water, fuel and treatment chemicals needed;

Less maintenance and repair cost (minimized carryover and deposits);

Saves manual supervision for other tasks (with automatic control);

Cleaner and more efficient steam;

Reduced operating cost (reduction in consumption, disposal, treatment andheating of water);

Minimized energy loss from boiler blowdown can save about 2 percent of a

facilitys total energy use with an average simple payback of less than one

year.

Flash Tank System The flash tank system shown in the figure below can be

used when expense and complexity must be reduced to a minimum. In this

system, the blowdowns from the boilers are sent through a flash tank, where

they are converted into low-pressure steam. This low-pressure steam is most

typically used in deaerators or makeup water heaters.

see diagrams on post dated 3-02-2011 by me(felix pinto)Flash Tank Heat Exchanger System

The system shown below consists of a flash tank and a heat exchanger. The

temperature of the blowdown leaving the flash tank is usually still above

220F. The heat of this flash blowdown can be used to heat makeup water by

sending it

through the heat exchanger, while cooling the blowdown at the same time.

Heating boiler makeup water saves on fuel costs. An additional advantage of


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cooling blowdown is in helping to comply with local codes regulating the

discharge of high temperature liquids into the sewer system.

2.Catalytic Fines

Catalytic Fines

Origin:

By-product from the catalytic cracking process in the refinery

Catalyst consists of complex crystalline particles containing aluminium

silicate

Catalyst fines result from catalyst particles breaking into smaller particles

Catalyst is expensive, i.e. refiners minimise loss but not 100%

Effects

* Severe wear of Liners

* Severe wear of Rings

* Wear out of Cyl-grooves

* Scuffing of liner

* Abrasive Wear of Spindle-Guide & cut-off shaft & nozzles

* Scuffing of Fuel Pump spindle guide

Specification

Variable in size ranging from sub microic to about 30 microns even seenlarger

Frequently considered spherical but this is not necessarily the case

Hard particles

Hardness not directly related to relative hardness of Al or Si

Can cause abrasive wear

ISO 8217 specifies the catalyst fines by Al and Si

ISO 8217 limit is 80 mg/kg Al+Si for marine residual fuels

(Note: ISO 8217 limit is for bunker not at engine inlet)

Reduction

Gravitational settling

Centrifuge

(Note: Homogenisers will not reduce the amount of catalyst fines but might

instead

break them into even smaller particles)

Overhaul and maintenance intervals must be kept according to


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manufacturers

recommendation

Temperature control very important

The higher the temperature the better the separation efficiency. Both density

and viscosity of the oil decrease when the temperature rises, therebyincreasing the settling velocity (Stokes law)

(If the separation temperature is lowered from 98C to90C the separator

throughput has to be reduced by25-30% to maintain the same separation

efficiency!!)

3.CRANK CASE INSPECTION (20 points)

1. Firstly check the oil condition for any smell,discolouration or degradation.

2. Turn the Engine to BDC & start checking from under stuffing box area for

any signs of black oil, if so indication of stuffing box leaking.3. Check piston rod surface for scoring marks & roughness.

4. Check Piston palm bolts & locking device for slackness & fretting.

5. Check guide & guide shoe bearing general condition & area around frame

where guide is attached for any visible cracks.

6. Check guide shoe end cover bolts in place & not slack.

7. Check cross head general bearing condition.

8. Top & Bottom end of the con rod bolt, nut & locking devices for

slackness,sign of fretting etc.

9. Check sliding of bottom end bearing (floating of con rod).

10. Check for slip of web & journal by checking the reference mark.

11. Check the web in the area of stress concenteration & check tie bolts

(bottomside).

12. Check cross girder , area around main bearing & bearing keep for signs of

cracks & check the main bearing.

13. All bearings to be checked for silvery colour, (indicates bearing wiping)

14. Check all the surrounding oil pan area of all units for any sludge deposits,

bearing metal pieces etc.

15. Check crankcase releif door (wire mesh should be wet, spring tension

sealing condition etc.)

16. Check the teeth of transmission gears for signs of wear.

17. Check chain drive for tightness.18. Oil mist detector sampling pipe to be checked for clear passage.

19. Clear all foreign materials from the C.C. & tools accounted for.

20. Start L.O.p/p & X-Hd p/p & check oil flow & distribution.

21Check C.C.door sealing condition & close the door.


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4.BABBITTING is a process by which relatively soft metals are bonded

chemically or mechanically to a stronger shell or stiffener, which supports the

weight and torsion of a rotating, oscillating, or sliding shaft. The babbitt,

being softer than the shaft and having excellent antifrictional qualities,prevents galling and/or scoring of the shaft over long periods of use.

Compositions and selected properties of babbitts are summarized in Tables

and and Fig.. Babbitting is named for Isaac Babbitt, who patented the process

in the United States in 1863. Babbitt metals, which are more widely known as

white metals, are comprised principally of tin alloys (hardened with copper

and antimony) or lead alloys (hardened with tin and antimony and, in some

cases, arsenic). In the babbitting process, the relatively soft bearing material

(babbitt) is bonded to a stronger supporting base metal, typically mild steel,

cast iron, or bronze. The base metal may be in the form of mild steel strip

unwound from a coil, a half-round mild steel pressing or bushing, or a bronze

or iron casting. The bonded bimetal material is shaped and machined to

make plain, fluid film lubricated bearings for a wide variety of automotive,

industrial, and marine applications. Babbitt is used in small bearings for high-

volume applications, such as electric motors and internal combustion

engines, and for large rotating and reciprocating machinery with low to

modest volume requirements, such as high-speed turbines and low-speed

marine diesel engines. In addition, babbitt has been used for jewelry, shot,

filler metals, and various other applications. Lead-base alloys enjoy a cost

advantage, while tin alloys offer modest technical advantages, particularly in

high-speed centrifugal equipment. It should be noted that government

regulations now discourage the use of lead-base alloys for health andhazardous waste disposal reasons. Babbitting of bearing shells can be

accomplished by three methods: Static babbitting (hand casting) Centrifugal

casting Metal spray babbitting Centrifugal casting and static (gravity) casting

are the two babbitting methods used in the manufacture and repair of large,

low-volume journal (radial) and thrust bearings. Centrifugal casting of journal

bearings offers both technical and economic advantages if special spinning

equipment is available. Flat shapes (thrust bearings) are usually statically

cast. Repairing of industrial and marine babbitted bearings is routinely

accomplished by melting off the old metal and rebabbitting the shells with

new metal, following the same basic casting methods described below for

producing new products. Emergency repair methods using proprietary tinning

compounds, babbitt spray, or welding techniques can be employed. Suppliers

of such repair equipment should be consulted for operating instructions. Thin-

wall babbitted half bearings, rolled bushings, and flat thrust washers are

mass produced from bimetal strip stock. The strip stock is produced by

continuously feeding coils of low-carbon steel in ribbon form first through

appropriate cleaning and tinning baths and then through a stream of molten


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babbitt, which is gravity cast on the moving strip. The strip is immediately

water-chilled from below. After excess babbitt is removed, the stock is

recoiled and is ready for press blanking, forming, and finish machining

operations. Details of mass production methods for making babbitted

bearings are proprietary to the manufacturers involved, and beyond the

scope of this article.

5.Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the

following components of the conventional MC engine:

Chain drive for camshaft

Camshaft with fuel cams, exhaust cams and indicator cams

Fuel pump actuating gear, including roller guides and reversing mechanism

Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides

Engine driven starting air distributor

Electronic governor with actuator

Regulating shaft

Engine side control console

Mechanical cylinder lubricators.

The Engine Control System of the ME engine comprises:

Control units

Hydraulic power supply unit

Hydraulic cylinder units, including:

Electronically controlled fuel injection, and

Electronically controlled exhaust valve activation

Electronically controlled starting air valves

Electronically controlled auxiliary blowers

Integrated electronic governor functions

Tacho system

Electronically controlled Alpha lubricators

6.Actions taken during boiler uptake fire? (Boiler uptake fire is because of wet

soot deposited during low steaming and also during uptake fire do not carry

out soot blow reduce the load and stop the engine , cover the m/e t/c with the

canvas so that no air is supplied)


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7.Needle vv lift. (1.4mm for 250 bar lifting pressure)

8. Boiler corrosion how it happens and how to prevent. (Acidic corrosion-CO2,

O2, OIL, CHLORIDES, BICARBONATES and pitting corrosion: scales such as

calcium and magnesium salts.)

9. Accumulation pressure test in boiler ( accumulation pr should not more

than 10 percent of working pr. when boiler is firing on full load for boiler).

10. How to reduce maintenance in exhaust vv (good quality fuel usage , vit

adjustment, avoid running engine on low load, check fuel injection system,

good scavenging, maintaining cooling water temp, check rotation of exhaust

v/v)

11. Refrigeration gases how its classified according to environment hazard

(ozone depletion potential- max R11, for R22 is 0.05 and global warming

potential- max is R11.and R22 is 0.365)

12. AE inlet vv big or exhaust vv big and y?

A/e inlet valves are bigger, no back pressure in t/c free flow, better

scavenging exhaust gas expelled easily, and exhaust v/v is smaller due to

less power required to open

13.SCR system, ammonia slip, catalyst? (selective catalyst reaction- exhaust

is mixed with ammonia and passed through a catalytic reactor, hence

reduction in NOx. And soot in exhaust. Temp.-290-450 C. FINAL PRODUCTS

WATER AND NITROGEN PG 78-80 POUNDERS)

14.ASTM means American society for testing of materials, it develops

standard for materials, product, systems used in construction, manufacturing

and transportation.

15. SAE is society of automotive engineers; it gives the viscosity of oil based

on a classification involving 2 temperatures

16. composition of lpg, lng and cng (lpg-propane, butane, lng-metane, cng-

methane)


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17. Maintenance on QCV?

Try out once every 3 months, drain air bottle, check hand operation, spring

condition, check piston

18.Manhole door elliptical...why?

Manhole door elliptical: longitudinal pressure = pd/4t or circumferential

pressure=pd/2t where p=pressure, d=diameter, t=thickness...so

circumferential pressure is more

19. Why 3 injectors are used in modern 2 stroke engines (There will be better

turbulence since three fuel injectors at an angle and the scavenge air enters

at an angle so there will be better turbulence, there will be more proper heatdissipation in piston and cylinder head)

20.Why steam is grey in color and not transparent? (water content in soot

release)

21. How does MGPS works? (2purpose: Cu kills sea growth and Al stops

corrosion, the system is based on electrolytic reaction and dc supplied to

anode)

22.What is Muntz metal, monel metal, white metal compositions and which is

more electrochemically active of them?

Monel- copper-38 n nickel-60,al and manganese-2, white metal- tin-88,

antimony-7.5, copper-4,lead-0.35, muntz metal-copper-60, zinc-40

23.A compressor was overhauled and bumping clearance was found to be

normal inspite of that piston strikes the head. Give reasons? (in unloaded

condition: Bottom end bearing wear down of lower half will cause this--

maybe

24.What is dealuminification where is it observed and why?

Form of corrosion in which amount of aluminium decreases in an alloy

pumps, valves coz Al is comparatively more reactive


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25. Function of motor on governor

Remote operation of speed setting knob-by adjusting spring pressure

26.How to prevent Dezincification? (put soft iron anodes)

27. How will you make camshaft float while adjusting its position?

hydraulic pressure

28.Limitations of ODME

Difficulty in analyzing- bad weather, muddy water, discharge capacity

increases in bad weather as speed is measured when the ship is not moving

as much

29.DESUPERHEATED STEAM. WHY AFTER SUPERHEATING WE ARE USING

DESUPERHEATER

Desuperheating, sometimes called attemperation or steam conditioning, is

the reduction of gas temperature. Its most common application is the

reduction of temperature in a steam line through the direct contact and

evaporation of water. Most Desuperheaters incorporate the venturi design

which uses the velocity of the steam to atomize the cooling water. In

addition, Ejector Atomizing Desuperheaters, Attemperator Desuperheaters,

Surface Absorption Desuperheaters and Mechanical Atomizing Desuperheater

designs are available. In most types, water pressure requirements are the

same as the steam line pressure

30.COP OF REFERIGERATION. (A refrigerator is a device for removing heat at

a cold temp so heat absorbed in the evaporator fi(in),the cop is also called

advantage and is defined as C.O.P. In a refrigeration cycle, the ratio of the

heat energy extracted by the heat engine at the low temperature to the work

supplied to operate the cycle; when used as a heating device, it is the ratio of

the heat delivered in the high-temperature coils to the work supplied)

31. Refrigerant properties?

pg-335 mc. G: the heat of vaporization of the refrigerant should be high, the

specific heat of the refrigerant should be low. the specific volume of the

refrigerant should be low to minimize the work required per kg of refrigerant

circulated, since evaporation and condenser temperatures are? xed by the

temperatures of the surroundings - selection is based on operating pressures


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in the evaporator and the condenser selection is based on the suitability of

the pressure-temperature relationship of the refrigerant other factors include

chemical stability toxicity cost environmental friendliness does not result in

very low pressures in the evaporator (air leakage) does not result in very high

pressures in the condenser (refrigerant leakage) OR condensing pressure

should be moderate. b) But the pressure should be preferably above theatmospheric pressure so as to prevent air from entering the system in the

event of leak. c.) Low freezing point d.)Volume of refrigerant gas need to be

pumped per ton of refrigerating effect should be low. d.) it should have high

Thermodynamic efficiency - Thermodynamic efficiency is the ratio between

heat abstracted by the refrigerating machinery and the heat equivalent of the

power supplied the compressors e.) it should not be flammable or explosive.

f.) it should not be toxic. g.) the tendency of a refrigerant to leak should be

low, and the detection of leak should be easy. h.) for good heat transfer

viscosity should be low, thermal conductivity high. i.) it is preferred that there

should not be a chemical reaction between the refrigerant and the lub oil. j.)

cheaper in cost. k.) non corrosive, non flammable, chemically stable, non

explosive, miscibility with oil, ozne depletion potential, high critical

temperature.

32.What is lean mixture in dual fuel combustion engine?

Lean burn means the mixture of air and gas in the cylinder has more air than

needed for complete combustion, reducing peak temp- less NOx, eff inc bcoz

of higher compression ratio and optimsed injection timing.

33.Whats the time period to discard a chain and renew with new one in B&W

tell the percentage elongation max allowed in 1 inch chain link?

Max allowable limit of elongation is 1.2% , chains should be removed once in

8 yrs or 50,000 hours)

Exhaust gas of all units high cause? (bad quality fuel, faulty fuel system,

poor scavenging)

34.LONG STROKE AND SUPER LONG STROKE ENGINES CONSTRUCTION DIFF.

AND ADVANTAGES OF SUPERLONG OVER LONG STROKE. (super long adv is

more time for scavenging and more air so more eff, less speed)

35.SPCV IN SULZER


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Spcv is stagnation pressure control valve used to suppress the after injection

on RTA engines. If the SPCV is removed, the fuel pump is directly connected

to the high pressure pipe allowing stagnation pressure to drop to a level

where cavitations can occur.

36. Why AE NOX is less

Time is very less for producing NOx as reaction time is less

37 .The m/e t/c lub is supplied by m/e lo p/p, during sudden lub p/p failure

how t/c is protected.

POST LUBRICATION TANK and lubrication system. During normal engine

operation the post lubrication system is continuously filled by lube oil via a

small bypass line from the m/e l.o. system that also supplies the t/c.

Excessive ...l.o. is unpressurised supplied back to the m/e l.o. circuit by

means of a free o'flow.In case of a shutdown or blackout of the m/e where the

l.o. supply from the m/e to the t/c is interrupted, the l.o. flows down from the

from the post lubrication tk by gravity, ensuring the lubrication and cooling of

the two plain bearings during running out of the rotor for up to 20 mins. The

m/e should be stopped within this time!! This system features 2 separate oil

inlet pipes and 2 running down pipes with different levels from the post

lubrication tk to the brgs. This ensures that in case of standstill of m/e and

shut off l.o. supply that the turbine side brg is longer lubricated and cooled

than the blower side brg. This tk is @ atmospheric pressure.)

38. what is d difference between pipe thread and bolt thread

pipe thread is bsp, less deep, lesser pitch and bolt thread is metric

39.what are the safeties on air bottle (relief valve, bursting disc, pressure

cut-out

switch, low pr. Alarm)

40.Cylinder lubrication, TBN how much it should be (HFO-70, LSFO-30-40)

41.What all checks to be made on liner before giving it for survey


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Ovality, wear, surface condition, polishing, glazing, cracks

42.What causes ovality of liner

Crosshead guide shoe and guide clearance

43.what are liner ribs and why they are in segments and use

Provided at upper parts of liner to withstand combustion pressure and

strengthening, in segments for freedom of coolant to flow

44.what is the special construction of pedestal bearing on free end of rotor in

auxiliary engine (margin for expansion)

45.What is fitted bolt? How is it fitted? Where is it used?

Fitted bolts are used to connect rudder stock with rudder. This is a closelyfitted bolt. The holes are initially drilled to undersize and are reamed in the

assembling place before the bolts are tightened in place. Accuracy is required

in the machining. These bolts could be of two types one having ...a slight

taper of about 1:100 on diameter and the other having a large taper of about

1:15 on diameter. However, the holes in either case are reamed in final place.

Sometimes an oversized bolt is stretched hydraulically reducing the bolt

diameter. When tightened down and the hydraulic pressure is released the

final exact fit in the bolt hole is achieved, like a pilgrim nut on coupling

shafts. These bolts find place in engine / boiler mountings, coupling shafts

etc. and form a rigid fixture. On main engine mounting these are situated aft

of the engine in the way of thrust block.

46. Interference bolt and fitted bolt are they same?

Fitted bolt dia and hole dia are the same. They are fitted by hammering.

Interference bolt dia is slightly bigger than the hole dia and these bolts are

fitted by hydraulic stretching and later bolted and the hydraulic pressure

released.

47. Waste gas system

A waste gate arrangement is a valve in turbocharger that regulate amount of

exhaust gases in the turbine side of tc diverting some of the exhaust gases

directly in exhaust piping this will regulate the speed of tc and thus the

compression ratio on the compressor side of tc. this is sometimes required in

winter season as the air is cold thereby dense and less compression is

needed as tc are designed on normal temp so this arrangement is sometimes


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there for winter season.

48.What is VIT and super VIT.

Before the Super VIT was introduced variable injection timing was obtained

by means of a special profile on the fuel pump plunger. Hence there was afixed relationship between the injection timing and the fuel index. Thus it was

not possible to adjust the fuel index of the individual pumps without also

altering the injection timing. For this reason the Super VIT was introduced,

where it is possible to adjust the fuel index and the injection timing

independently In VIT beginning of injection could be controlled, but end of

injection was fixed, due to profile of plunger n thus amount of fuel injected

could not be changed with varying angle of injection at beginning. Thus MAN

came up with super VIT where beginning n end both could be controlled by

raising or lowering barrel in relation to plunger. Sulzer system when

introduced vit way back in 80's it could control both beginning n end. Thus

super VIT is for MAN B&W engines only

49. Wat is nitriding?

Nitriding is a heat treating process that alloys nitrogen onto the surface of a

metal to create a case hardened surface. Three methods are there for

nitriding 1. gas nitriding 2. salt bath nitriding. 3. plasma nitriding.) Nitriding is

a surface-hardening heat treatment that introduces nitrogen into the surface

of steel at a temperature range (500 to 550C or 930 to 1020F), while it is in

the ferrite condition. Thus, nitriding is similar to carburizing in that surface

composition is altered, but different in that nitrogen is added into ferrite

instead of austenite.Because nitriding does not involve heating into the austenite phase field and

a subsequent quench to form martensite, nitriding can be accomplished with

a minimum of distortion and with excellent dimensional control.

50. What is the similarity and difference between a m/e governor and

flywheel (gov maintains speed of engine, flywheel controls cyclic fluctuation

of engine rpm, flywheel works on virtue of inertia alone, govnr uses inertia to

actuate fuel linkage to counter change in rpm)

51. What is a thermal boiler?

Water and steam are typically used as heat carriers in process heating

systems. But at high temperatures, water and steam requires a

corresponding high operating pressure.

In industrial heating systems this high temperature level is often a great

advantage in order to get a high output of the process. Thus establishing this


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with water and steam, you must deal with systems and components of high

pressure. This means large dimensions, weights, more safety issues and thus

extra costs.

In thermal oil boilers (thermal oil heaters), a special oil-based thermal fluid is

used as the heat carrier, instead of water or steam. This oil operates at

atmospheric pressure up to 300C. Comparing to water and steam, it wouldrequire a corresponding pressure of 85 bar to obtain this temperature. This

system is used in ships which carry cargo like bitumin n coaltar

52.What are persistent oils? What are its effects on marine environment?

(persistent oils generally contain a large proportion of heavy fractions or

boiling materials. Dont dissipate rapidly)

53,TYPES OF TEMPERING :

Tempering from outside:

The cold workpiece is slowly

Heated by means of appropriate heat sources and after having

reached the tempering temperature (between 200C and 500C) it is

cooled down.

Tempering from inside:

The workpiece is shortly quenched after having been hardened so that

only outer

layer is cold. The residual heat penetrates from inside, after having

reached the tempering temperature it is cooled down. The same effect

can be reached when the workpiece is cooled down only on one side

and the heat contained in the

other part runs after again.

54. Compression ratio:- The ratio is calculated by the following formula:

, where

= cylinderbore (diameter)

= pistonstroke length

= clearance volume. It is the volume of the combustion chamber

(including head gasket). This is the minimum volume of the space at
http://en.wikipedia.org/wiki/Cylinder_(engine)http://en.wikipedia.org/wiki/Bore_(engine)http://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Stroke_(engine)http://en.wikipedia.org/w/index.php?title=Clearance_volume&action=edit&redlink=1http://en.wikipedia.org/wiki/Head_gaskethttp://en.wikipedia.org/wiki/Bore_(engine)http://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Stroke_(engine)http://en.wikipedia.org/w/index.php?title=Clearance_volume&action=edit&redlink=1http://en.wikipedia.org/wiki/Head_gaskethttp://en.wikipedia.org/wiki/Cylinder_(engine)


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the end of the compression stroke, i.e. when the piston reaches top

dead center (TDC). Because of the complex shape of this space, it is

usually measured directly rather than calculated

55. Shrouding :- shrouding occurs if mitered valve seats are repeatedlyground and the consequent ridges are not removed. If the material of the

valve is harder than the valve seats the shroud builds up in the seat. If the

seat is harder than the valve then shrouding occurs in the valve. When a

valve and seat are ground together with grinding paste some material is

removed and eventually the seating faces become lower than the shrouding

material and a step is formed circumferentially. Although the actual distance

that the valves opens remains constant the effective opening area across the

valve and seats face is reduced by the amount of the shroud. Even small

amount of shrouding can seriously affect the air or gas flow across a valve.

56 .Why during rudder test we are doing 35 degree and 30 degree y not both

35 degree

The feedback system on the steering gear gradually reduces the speed of the

gear with in the last 5 degrees of the gears full rotation. if we put to 35 then

the hunting gear will start to reduce the pump stroke and achieving this in a

time frmame of 28sec will nt be possible .so the test is done frm 35 to 30....

57. Procedure for CWT test

1. Fill the sample cup to the 25 mL mark with sample (fig 1).

2. Slide the open end of the valve assembly over the tapered tip of the Titret1

so that it fits snugly to the reference line (fig 2).

3. Snap the tip of the Titret at the score mark (fig 3).

4. Lift the control bar and insert the Titret assembly into the body of the

Titrettor2 (fig 4).

5. With the tip of the valve assembly immersed in the sample, press the

control bar firmly, but briefly, to pull in a small amount of sample (fig 5). Thecontents will turn a green color.

CAUTION: Do not press the control bar unless the tip of the valve assembly is

immersed below the surface of the liquid.

6.Press the control bar again briefly to allow another small amount of sample

to be drawn into the ampoule (fig 5).

7. After each addition, rock the entire assembly to mix the contents of the


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ampoule. Watch for a color change FROM GREEN TO BRIGHT ORANGE.

NOTE: Immediately before the contents turn bright orange, they will briefly

turn blue. Make further additions with care.

8. Repeat steps 6 and 7 until a permanent color change occurs.

9. When the color of the liquid in the ampoule changes to BRIGHT ORANGE,

remove the ampoule from the Titrettor. Hold the ampoule in a verticalposition and carefully read the test result on the scale opposite the liquid

level (fig 6). See the following chart to obtain results in ppm product.

Satisfactory Ranges Scale

Figure e

Product Scale ppm product

LIQUIDEWT 1.2-1.8 3 10,0000 -15000

^ MAXIGARD1 1.6-3.0 19,000-36,000

' DEWT NC .5-5.0 3,000-4,300

58. What are the most dimension of engine.

Stroke, bore, distance between 2 cylinders,crank shaft dia.

59.what is the advantage of sleeve bearing in turbocharger in man b&w

engine?how many hours after u will do major overhaul as per manual.

sleeve type brg is in man b&w engines are provided are lengthier and have a

stabilizin influence on shaft alignment and long vibrnthey have a face

machined to take the thrust similar to thrust pad type..these are supplied by

extrnl oil feed and emergncy lo sup tk

60. why jack bolts are provided in sulzer engine?main purpose?

To hold the bedplate,frames and entablature firmly together in compression

and to transmit the firing forces back to the bedplate long tie bolts are fitted

in through this 3 components and then tighten hydraulically. To prevent this

excessive bending moment in transverse girder the tie bolts are positioned

as centre of the crankshaft as possible. Because of the tie bolts so close to

the crankshaft sulzer employs jack bolts to hold the crankshaft main bearingcap in position instead of conventional studs and bolts.

61. How you will purge air from refrigerant compressor?

Close condenser liquid outlet valve


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Keep cooling water to condenser on till s.w.outlet temp = inlet temp

Check condenser sw outlet temp

Check correct condenser pr for the corresponding temp

Release air ( using purge v/v on top of the condenser) till the pressure

in the condenser comes correct.

Law used is Dalton law of partial pressure.

62. Induction hardening

Induction hardening is a form ofheat treatment in which a metal part is

heated by induction heating and then quenched. The quenched metal

undergoes a martensitic transformation, increasing the hardness andbrittleness of the part. Induction hardening is used to selectively harden

areas of a part or assembly without affecting the properties of the part as a

whole.

Induction heating is a non contact heating process which utilises the principle

ofelectromagnetic induction to produce heat inside the surface layer of a

work-piece. By placing a conductive material into a strong

alternating magnetic field electrical current can be made to flow in the steel

thereby creating heat due to the I2R losses in the material. In magnetic

materials, further heat is generated below the curie point due

to hysteresis losses. The current generated flows predominantly in thesurface layer, the depth of this layer being dictated by the frequency of the

alternating field, the surface power density, the permeability of the material,

the heat time and the diameter of the bar or material thickness.

By quenching this heated layer in water, oil or a polymer based quench the

surface layer is altered to form a martensitic structure which is harder than

the base metal.[2]

63. Volumetric efficiency.

This is the ratio of the volume of air drawn into the cylinder(at normal temp

and pressure) to swept volume . In naturally aspirated four stroke engines the

volumetric efficiency will be from 0.85 to 0.95.

64. How to order greese?
http://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Induction_heatinghttp://en.wikipedia.org/wiki/Quenchedhttp://en.wikipedia.org/wiki/Martensitic_transformationhttp://en.wikipedia.org/wiki/Hardness_(materials_science)http://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Conductivehttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Curie_pointhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Permeability_(electromagnetism)http://en.wikipedia.org/wiki/Quenchinghttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Martensitichttp://en.wikipedia.org/wiki/Induction_hardening#cite_note-rudnev58-1http://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Induction_heatinghttp://en.wikipedia.org/wiki/Quenchedhttp://en.wikipedia.org/wiki/Martensitic_transformationhttp://en.wikipedia.org/wiki/Hardness_(materials_science)http://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Conductivehttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Curie_pointhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Permeability_(electromagnetism)http://en.wikipedia.org/wiki/Quenchinghttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Martensitichttp://en.wikipedia.org/wiki/Induction_hardening#cite_note-rudnev58-1


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NLGI Grades 000 to 1 are used in application requirings low viscous friction.

Examples include enclosed gear drives operating at low speeds and open

gearing. Grades 0, 1 and 2 are used in highly loaded gearing. Grades 1

through 4 are often used in rolling contact bearings where grade 2 is the

most common.

65. Compression ratio,Stoichiometric ratio values of your last ship

compression ratio min req for combustion of diesel is arnd 16 but is

maintained arnd 22 in most of the engines stoichiometric ratio is 14~15.

Stoichiometric ratio is around 14 to 15 :1 that is 14 parts of air per part of

fuel. It does not depend upon whether the engine is 2 stroke or 4 stroke. It is

just the value of right quantity of air required for complete combustion of fuel

so it a function of fuel quality and depend upon the chemical composition of

fuel.

Why piston rings are positioned in a down place in a marine engines as

compared

piston rings are down in IC engines as the temperature above will be higher

and may cause LO particles to break down and hence loss of lubrication while

in case of AC compressors temp is not so high as no combustion of fuel is

there and hence less temp are experienced so the only criterion is to increase

the volumteric efficeincy of the engine.

66.How to measure T/C rpm.

Turbocharger rpm s measured on the same principle of induction motor. A

magnet is there at the end of the turbocharger shaft and it is rotating in a coil

now the emf generated in the coil will be a function of rpm of the turbochager

shaft and hence the emf can be calibrated as a function of rpm of

turbocharger

66.Bore cooling,why in angular direction

bore cooling is in angular direction as it increases the effective heat transfer

area and also does not compromise on the strenghth too much\

67.Bumping clearance =so so; but still piston hitting,what are the reasons.
http://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/w/index.php?title=Gear_drive&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Open_gearing&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Open_gearing&action=edit&redlink=1http://en.wikipedia.org/wiki/Rolling-element_bearinghttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/w/index.php?title=Gear_drive&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Open_gearing&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Open_gearing&action=edit&redlink=1http://en.wikipedia.org/wiki/Rolling-element_bearing


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if the bumping clearance is ok and piston is still hitting the crown this means

ur bottom end bearing has worn out and clearance has increased and when

the

piston is moving up its hitting the cyl head due to inertia.

68. Change fuel oil from HFO to DO at same fuel rack,whether speed increase

or decrease,Why.

The calorific value of diesel oil is higher than that of heavy oil so the speed in

diesel should increase but the calaorific value is measured per unit mass and

not volume and all ur fuel pumps that is the metering devices of fuel controls

the

volume of fuel oil injected. now the effective mass of heavy oil is much more

than the diesel oil for same volumes of both oils. taking both into account

the effective result is that the speed is DECREASED when u changeover from

heavy to diesel oil.

69. Hydrodynamic lubrication and boundary lubrication.

Diesel engine bearings are lubricated by fluid films. The journal is always

smaller than its surrounding bearing. When the shaft is static it will make

contact with the bearing and this contact will be a line. On each side of this

line the normal distance betweens the shaft and the bearing will increasegradually and will in effect be a curved wedge. When the shaft revolves in the

presence of an adequate liquid supply (lub oil) the oil is pulled into the

wedge and pressure is set up. The pressure of liquid in the wedge shaped

space sets the shaft over to one side and lifts the shaft away from the

bearing so it is supported by an oil film. The position where the oil film

thickness is least will be a small distance away from the static contact line in

the direction of shaft rotation. For pressures to build up to a value high

enough to separate shaft from the bearing, the oil must have sufficient

viscosity and the speed of the shaft muct be above a certain value. This form

of lubrication is known as fluid film or hydrodynamic.

Boundary lubrication occurs when the rotational shaft speed falls and oil

wedge is lost. Metal to metal contact then occurs. To prevent metallic contact

under boundary conditions grease may be used or additives may be added to

the oils. The bearing of the diesel engine do not work under boundary


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conditions. Very highly loaded crosshead bearing in 2 stroke engine may

approach boundary conditions.

In diesel engine bearings are supplied with large quantity of oil to maintain

the oil film and remove the heat generated.

70.Advantages and disadvantages of single and double volute casing.

Yes, single volutes have more radial load on the shaft but the advantage is

that the load is very predictable. We may not like radial loads but hey,

bearing technology is very well developed.

A dual volute is basically two pumps in one casing. At one point or another

depending on the design and on the machining quality and precision one of

these pumps will shut off the other and radial loads will becomeunpredictable.

However, if your operation point is well known you will be able to stay out of

troublesome operation area's regardless of the type of design.

*A double volute scroll pump has almost no radial thrust at any point on the

curve, from zero flow all the way out to well beyond the BEP. In other words,

the double volute pump has little or no radial thrust reaction to operation

above or below BEP.

But a single volute pump has a very pronounced radial thrust reaction when

operated off BEP. If the bearings and shaft are insufficient to withstand the

thrust, bearing and shaft life are shortened.

*The single volute pump impeller will deflect either 60 or 240 from the cut

water depending upon which side of the pump's best efficiency point (BEP)

you are operating.

*The double volute design is actually two single volute designs combined

together.

Although this drawing does not show it clearly, the total throat area of the

two volutes is the same as the single volute design.

Double volute pumps were created to eliminate most of the radial thrust

caused by operating off the pump's best efficiency point (BEP).

*Testing has shown that the double volute does not entirely eliminate theradial forces, but they are reduced greatly. Although the volute is

symmetrical around its centerline, the two passages directing the liquid to

the discharge nozzle are not. This means that the radial forces do not exactly

cancel and a slight radial force does exist.

Testing has further shown that a double volute pump will be 1% to 2% less

efficient at its best efficiency point (BEP), but 2% or more efficient on either


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side of the best efficiency point (BEP). This means that the double volute will

have an overall higher efficiency than its single volute cousin. Unfortunately

many pumps are purchased with the efficiency given at the best efficiency

point not the actual operating point used to make the purchasing decision.

Double volute pumps should never be specified for low flow (less than 400

gpm or 90 m3/hr.) operations especially if there are solids in the product. Thenarrow passages behind the dividing rib can easily clog with solids. They

should, however, always be specified for larger volume applications.

The rib can cause some production problems with the castings especially in

small sizes.

Testing has shown the minimal radial thrust was experienced when the

dividing rib did not extend all the way to the volute discharge flange.

On large pumps there has been some problems with the rib cracking at the

center when the pump is subjected to high hydro test pressures. The reason

for this is not really understood. Some manufacturers ignore this because in

operation they know that the pressure will be the same on both sides of the

rib. Other manufacturers leave a gap of 2-3 millimeters in the center to

prevent the cracking.

Triple volute casings have been tried, but haven't proved to be effective

enough to justify their high manufacturing cost.

If you have an occasion to repair the double volute cutwaters (and you can

with some of the newer metal repair compounds), be sure the cutwaters are

located physically 180 degrees apart.

Many large double ended pumps have atrocious L3/D4 shaft numbers and are

therefore supplied with a double volute as a standard.

71.Advantages of plate type cooler

Plate cooler are smaller and lighter than tube type cooler giving the

same performance.

No extra space is required for dismantling

Higher efficiency is shown by the smaller size

Plates can be added in pairs to increase the capacity and similarly

damaged plates can be easily removed if necessary without

replacement.

Cleaning and maintenance is simple


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Turbulent flow helps to reduce the deposits which would interfere with

heat flow.

Flow velocity is not limited as is in the case of al br tube.

Mixing of fluids not possible unless plate cracks.

Disadvantages of plate type cooler

Plates cant be tested for leakage easily hence crack plates are difficult

to locate.

Deteriorated joint are difficult to remove and hence remove on the

site.

Expensive due to large number of plates and cost of titanium and joint

required.

Plates are easily damaged due to over tightening.

Operating temp limit (200 deg c)

Operating pressure limit (20 bar).

72. High lift and improved high lift safety valve.

High lift :- winged valve , waste steam piston and no floating ring.

Improved high lift safety valve:- wingless valve , waste steam piston, floating

ring.

Formula for calculating :-

C X A X P = 9.81 X H X E

Where c discharge coefficient which depends upon the type of valve.

c- for high lift 7.6

c- improved h.l. 9.2

A aggregate area through seating of v/v in mm2

P- working pressure of safety v/v in Mn/mm2

H- total heating surface in m2

E- evaporative rate in kg of steam /m2 of heating surface per hr.


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Deriving we get D2C=constant D is diameter of seating of one valve.

For super heated steam

As A(1+Ts/555)

As- aggregated area thorugh the seating of the valves in mm2 for

superheated steam.

aggregate area through seating of v/v in mm2

Ts- degree of superheat in degree celcius.

73.Laminar and turbulent flow Reynolds number.

Reynolds number = velocity of fluid x pipe diameter/ kinematic viscosity.

If the number is less than 2000 the flow is stram line

If the number is more then 2500 then flow is turbulent.

The laminar stream line flow of a fluid whose velocity variation is

approximately parabolic . being a max in center and zero where the fluid is in

contact with the pipe or plate surface.

74. Centrifugal pump cannot handle air but turbocharger can?

Both cent pp nd t/c does one thing in common ... it addes kinetic energy to

the medium by inducing centrifugal force to medium ... due to this cent

force , the medium moves out from impellar eye nd this creates a vaccum

behind it which causes low press and so the new medium is pushed in to theeye...... so the amount of cent force determines the medium being moved out

from eye to the periphery.... but this cent force = mv^2/r=mw^2r as

(v=wr) ....... so the cent force depends on mass and velocity ...... in cent pp ,

the medium being liquid mass is more so the velocity can be less to push the

liq out ... but in T/c , the medium being air , the mass is less so since the

velocity is high , it can pump out the air..


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75. How feed is adjusted in boiler corresponding to demand in auto

A drum level is only measured parameter, this type of control scheme is

usually referred to as single element feedwater control.

An electronic D/P cell monitors the drum level over a span of 2-3m, and

provides a measurement signal to the level controller(LIC)

The usual feedwater Cv is an to open (A/O) style which will fall closed upon

loss of instrument air,An increase in pneumatic signal applied to this actuator

will increase with feedwater flow.

76.Two element feed water control.

If the true steam flow was measured then a predictive control decision could

be made regarding the drum level. Elbow taps could be installed on the

steam line to provide a differential measuremtn input to an electronic D/P

cell. This differential signal is routed to a square root extractor to provide a

linear flow signal. A two element feed water control scheme can be

designed .


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77.why thrust pad is in pieces, y not single piece.

by being in pieces each pad can generate its own hydrodyn film.....so as

compared to a normal journal bearing more area can be utilized for the film

and taking load.

78. liner bending stress? where and how?

liner bending moment is maximum at the liner flange....its bcz the line of

action of forces by the cylinder head and reaction force from the entabulature

don't pass thru the same line and hence a bending moment is setup in the

liner flange..

79. Engine vibrations

Axial vibration when the crank throw is loaded by the gas pressure thru the

con rod mechanism the arms of the crank throw deflect in the axial direction

of the c/s exciting axial vibrations. These vibration may be transferred to the

ships hull thru the thrust bearing.

Remedy Axial vibration damper.

Torsional vibration the varying gas pressure in the cylinders during the

working and the c/s conrod mechanism create a varying torque in the c/s. it is

these vibration of the shaft system. Tortional excitation also comes from the

propeller thru its interaction with the non uniform wake field.

Remedy modify c/s natural frequency by adjusting its dia.

Use a torsion damper.

80. Under critical running

The natural frequency of the one node vibration is so adjusted that the

resonance with the main critical order occurs about 35 to 45 % above the

engine speed at specified MCR . the characteristic of an under critical system.

Relatively short shafting system

Probably no turning wheel

Turning wheel with relatively low inertia


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Large dia shafting

Without barred speed range

81. Over critical running

The natural frequency of the one node vibration is so adjusted that resonance

with the main critcal order occurs abt 30-40 % below the engine speed at

specified MCR. The characteristics

Turning wheel may be necessary on c/c fore end

Turning wheel with relatively high inertia

Shaft with relatively small dia (shaft mat with relatively high uts)

With barred speed range of about +/- 10% with respect to the critical enginespeed.

82. Choke The engine is supported on a series of chocks fitted around the

underside of the periphery of the base of the bedplate. The chocks sit on the

foundation plate which forms part of the inner bottom platting of the hull

structure. The holding down bolts pass through holes in the bed plate. Chocks

and foundation plate. When all the holding down bolts are tightened the bed

plate is held fast to the hull structure. The choks are fitted in place after the

engine has been aligned to the intermediate shafting. The spacing betweenthe choks is approx 250-400mm and they are closely spaced in the ;location

of cross girder so that good support is given to the area of the bed plate

which is supporting the main bearing and engine A frame. This prevents any

localized distortion or sag in the bed plate and so makes the support from

the chocks a continuous effect.

83. Light spring diagram :- it is also known as scavenge efficiency diagram.

This dig is taken with a light spring. The variation of pressure in the cylinder

during exhausting and scavenging is magnified in a separate dig. Thepressure during this part of the cycle is low so a light spring is utilized. For

most of the time cylinder pressure is outside the range of the spring. The

drop in pressure is a measure of clearances of exhaust passages . this dig

also shows the pressure of scavenge at cylinder intake.


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84. Why governor spring is conical.

It seen that variation of spring force is having non linear relation with the

variation of speed. The desired linear relation is achieved by designing the

spring conical or combination of springs of varying diameter and stiffness.

85. How signal is carried to ecr from rpm indiactor.

Magnetic pick up sends signal to transducers, o/p coming from the transducer

is filtered signal conditioned and chopped. Finally it is converted into square

waves. The square wave is passed through phase lock loop multipliers. The

o/p is gated by a precise time base generated through piezo crystal and then

counted. This counts are displayed in bright LED. Its nothing but RPM with

accuracy of +/- 1 .

86. What are the safeties provided on the A/C or fridge compressor.

L.P. cut out

H.P. cut out.

Relief valve

Check valve at the discharge of comp to prevent reverse rotation when

stopped.

High temp sensor at discharge

Oil diff pressure trip

Master solenoid valve at condenser discharge to prevent flooding of

evaporator in case of comp stop or abnormal stop.

87. Steering gear safeties

Hydraulic tank low level

Overload

Power failure

Relief valve


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Bypass valve

Auto change over

35 deg- telemotor change over switch

36 deg- telmotor limit switch

36.2 deg- ruddr angle limit switch

37deg rudder stopper

39 deg mechanical stopper

88. Windlass safety- electrical electromagnetic brake, motor overload, short

ckt protection, restart delay timer, remote stop.

Mechanical manual mechanical brake, cable stopper, slipping clutch, relief

valve.

89. Zero setting what is the significance of its name?

At zero position of the governor the load indicator and cut out servomotor

should coincide for zero fuel injection.

At zero setting shield position the suction and spill valves must never beclosed at the same time i.e. one is open other is closed.

90.Creep:- creep is the tendency of a solid material to slowly move or deform

permanently under the influence of stresses. It occurs as a result of long term

exposure to high level stresses that one below the yield strength of the

material . creep is more severe in materials that are subjected to heat for

long periods.

91. In life boat engine if all the flywheel marking have been erased/removed

how to check TDC or BDC position of piston.

Take out the injector now u can see access or see the piston put the dial

gauge with the pin touching the piston take the piston to almost TDC set the

gauge to any value say 0.2mm and make a mark on the flywheel rotate the

flywheel. Piston will move up will reach TDC and then will move down just as


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it comes to 0.2mm make another make on flywheel the midpoint of the 2

marks will be TDC.

92. Offset of propotional controller and how to counteract it.

In propotional control the output is proportional to the deviation hence for out

put to occur deviation has to be there i.e. a offset has to be there in

proportional control.

While in integral control rate of change of output of controller is proportional

to the deviation .so it is able to minimize the offset.

93. Cetane number it is an index if the ignition quality of the diesel fuel

which defines the way combustion proceeds in the engine. It is determinedby comparing the ignition quality of standard solution (which is mix of 2

hydrocarbon cetane and alpha methyl naphthalene) with the ignition quality

of fuel tested.

It is percentage of cetane contaianed in the standard solution which has

ignition delay equating the ignition delay of fuel tested. Cetane which has

good ignition quality

Is assigned the number 100. alpha methyl naphthalene is assigned the

number 0 due to its poor ignition quality. Higher the cetane number better is

the fuel shorter is the ignition delay.

94. Calculated carbon aromatic index(CCAI):- its is a rating of the fuel which

indicates ignition quality because ignition directly depends on the aromatic

content in the fuel. Aromatic is the compact benzene structures present in

the fuel which effects the ease of which a hydrocarbon fuel molecules can

burn. A low ccai means better ignition quality better fuel quality and low

ignition delay.

95. There r how many stern tube bearing n how they r connected with stern

stern tube bearings generally consists of two ( fwd & aft ) bearings which r

pressed in and secured to the stern tube the bearing sleeves r made of high

strength ductile iron and centrifugallylined with high tin base babbitt. the

bearing bore is normally finish machined to fit the propeller shaft and outside

diameter is semi finished for final machining in shipyard Two procedures are


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commonly used for fitting stern tubes 1.the stern frame is finish

machined.the stren tube is pressed in and secured by bolting or welding .the

stern tube is bored and bearings are then pressed into stern tube 2.In the

second procedure, the stern tube is bored in the shop and fitted with its

bearings then the entire assembly is pressed into the stern frame at shipyard.

Boring of stern tube to provide an interference fit

96. ECU- engine control unit engine control system has several integrated

units , engine control unit cylinder control unit engine interface control unit

and auxiliary unit.

ECU- the engine speed reference to the set reference

Governor control and functions

Engine protection system and faults

Optimum condition requirement running for that running condition

Control of the function for start stop and reversing

Control of the function of auxiliary blower and turbo charger.

CCU- the control of the fuel injection pump the injector , exhaust valve , start

air valve and cylinder lubrication for each cylinder.

97. What is RVK in piston ring what it means?

It is for surface roughness of the piston rings , RVK means depth of the

valleys and RPK means peak height. Rz is the mean highest peak to valley

measurement taken from 5 samples. RK is the average core roughness

depth.

98. Injection delay :- injerk type p/p spill port or spill valve and suction portboth get closed that time injection should start practically but due to inertia

of the moving parts and fluid injection doesnt start immediately all though oil

is considered in comprissible it get compressed slightly and at same time the

high pressure pipe gets an expansion all way and after that injection starts.

The potential energy gets released during termination of injection.


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99. Ignition delay :- the time span between commencement of injection and

start of ignition referred to as ignition delay. During ignition delay large part

of charge air is prepared for combustion.

100. After burning :- after burning is said to occur when the third phase of

combustion extends over a long period. It may be caused by incorrect fuel

grade bad atomization , poor or excess penetration , incorrect fuel temp,

incorrect injection timing insufficient air supply or any combination of these.

Slow burning high viscosity high density high carbon content may also cause

after burning of serious nature leading to engine damage.

101. Bearing faults and defects

Abrasive wear due to fine scoring by hard particles and impurities in

the lub oil.

Corrosive wear due to acidic lub oil

Erosive wear due to erosion

Adhesive wear due to galling scoring or scuffing

Fatigue failure cracks at areas of stress concentration

Overheating due to poor lubrication supply or contaminated oil ,misalignment, increase clearance ,uneven load distribution poor

surface finish and overloading

Misalignment of the bearing due to distorted bed plate adjacent

bearing failure or imbalanced cylinder pressure.

Incorrect clearance or incorrect tensioning of bolts.

Housing dimension not suitable for bearing shell especially during

replacement.

102. Puncture valve

It is device to positively stop engine irrespective of its rack position.

It reduces the high pressure of the fuel by connecting high pressure

side to the pump body thereby stopping the injection of the fuel.


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Engine stops and shutdown is carried out by the use of puncture valve.

It allows the fuel oil recirculation even when the engine is stopped as

the oil pressure is not totally bypassed

It is operated by pneumatic air pressure

Its used in MAN B&W

103. Under which condition spring of the stuffing box is changed

When oil from the tel tel hole of individual unit of stuffing box lot of oil

coming and lub oil loss is there and u dont have sealing ring or

lamellae so for time being spring can be changed

While completely ohauling the stuffing box

When spring elongation is exceeded as per manual. Usually checked

by hanging one kg wt at end and new length original original length

gives the elongation . check with manual for limit and replace it with

new one.

104. Whats the time period to discard the chain and renew with new one in

B&W engines . tell % elongation max .

Max allowable limit of elongation is 1-2% and chain should be renewed once

in 8 yrs or 50000 hrs

105. Distance of the lubricating quills from top of liner in terms of the length .

At 20% stroke from TDC . in this case lubrication is most effective especially

for single level of quills. Continuous groove row of quills at 30% stroke from

TDC.

Usually quills are 250mm apart from each other around the liner bore.

Grooves are angled downward. The combustion gas pressure differential

across the rings assist in pushing the oil downwards in the groove. The

disadvantage of grooves is that they increase the area of oil flow. Hence

velocity and pressure of the oil decreases there by reducing spreadibility.

106. What is the similarity and difference between governor and flywheel?


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Governor controls speed of the engine and flywheel controls cyclic fluctuation

of engine RPM.

Flywheel works on the virtue of inertia and governor uses inertia to actuate

fuel linkage to counter change RPM.

107. R.O. plant treatment?

Sea water feed for reverse osmosis plant is pretreated before being passed

through. the chemical sodium heat meta phosphate is added to assist wash

through the salt deposits on the filter elements and sea water is sterilized to

remove bacteria which could otherwise become resident in the filter. Chlorine

is reduced by the compressed carbon filter while solids are removed by the

other filter.

Post treatment of produced water is same as low temp evaporators.

108. Lantern ring

A latern ring is perforated hollow ring located near the center of packing box

that receives relatively cool clean liquid either from the discharge of the

pump or from the external source and distributes the liquid uniformly around

the shaft to provide lubrication and cooling. The fluid entering the lantern

ring can seal the joint between the shaft and packing against leakage of air

into the pump in the event pump suction pressure is less than that ofatmosphere.

109. Parts of electric governor

Load sensing unit

Speed sensing unit

Setting control unit

Setting for droop or isochronous mode

Speed setting signal

Ramp generator


35/51

The comparator/ampifiler control unit which compares the i/p signal with the

reference setting and sends o/p signal to the actuator to change the rack

position of the engine fuel pump.

110.Wear ring

Wear ring can be defined as a device used to seal the pressure leakage of

the liquid between i/l of the impeller and pump casing. Wear rings are

typically found on pumps with closed impeller. A similar device that serves

the same purpose called a wear plate can be found on some pump with semi

open impeller. The typical reason for using a wear ring is to decrease the

amount of leakage loss around the impeller. Due to more work available to

push the pumped liquid out of the discharge there is slight improvement in

the pump efficiency.

111. Motor used in governer

Synchronous / sleeping motor

Main characteristic of this motor are

Suitable for continuous operation

Precise variable speed

Motor electrically locked in position

Instant starting stopping

Permanent stalling

Easy to interface with any type of electronic interface.

112. What is the name of the instrument that measures vibration? How thusit work and part that measure it?

Accelerometer, and working on piezo crystals i.e. piezo electric effect

113. what is the crank pin oil hole position?


36/51

when the piston is at TDC the crank pin oil hole position is horizontal, this

done to reduce the stresses which could have generated if otherwise, this

position is the only position allowed.

114.why shims fitted on the bottom end bolts have to be of exact thickness?

This will lead to uneven tightening of palm nuts and they will bend.

115. What 4 criteria s r to be fulfilled for satisfactory working of a journal

bearing?

Viscosity of oil, clearance, load on the engine, rpm.

116. Sweating of refer compressor crankcase

When there is liquid flood back to the compressor the effect can be

detrimental. After creating a host of other problem the liquid eventually boils

off in that hot crankcase. Boling is possible by taking latent heat of

evaporation from the surrounding oil in the crankcase.

This leads to a cold crankcase if the temp of the crankcase reaches temp

below that of dew point the air outside. moisture on the oil precipitates in

the crankcase. This is commonly referred to as sweating of crankcase.

117. What is first order moment.

These moments acts in both vertical and horizontal direction.

For engines with 5 cyl and more the 1st order moment is rarely

any importance to the ship but it can be of disturbing magnitude ti

the ship with 4 cyl.

Resonance with 1st order moment may occur for hull vibrations

with 2-3 nodes.

Ist order compensator can be introduced in chain tightener wheel .

it comprises of 2 counter rotating masses rotating at the same

speed as the crank shaft.


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118. What is 2nd order moment

The 2nd order moments acts only in the vertical direction and

precaution need only to considered for 4,5 and 6 cyl units.

Resonance with the 2nd order moment can occur at hull vibration more

then 3 nodes.

A second order moment compensator comprises of 2 counter rotating

masses running at twice the engine speed.

Remedies

Compensator mounted on the aft end of the engine. Driven by the

main chain drive .

Compensator mounted on the fore end of the engine. Driven by the

crank shaft with a separate chain drive.

Compensator on both aft and fore completely eliminating 2nd order

moment.

119. Electric compensator

It is electrically driven compensator normally located at the steering gear

compartment,

Where deflection are largest and the effect of compensator with be therefore

greatest. Such a compensator is synchronized to the correct phase relative to

the external force or moment and can be neutralize the excitation. The

compensator required an extra seating be fitted.

120. Guide force moment

Guide force moment are caused by the transverse reaction forces acting on

the crosshead due to con rod/ crankshaft mechanism.

These moment may excite engine vibration moving the engine top athwart

ship and causing a rocking or twisting moment of the engine.

Guide force moment are harmless except when resonance vibration occur in

the engine. As a precaution top bracing is installed between the engines

upper platform brackets and the casing side for all its 2s models.


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121. Oros piston

With the view omitting the safety valve on the exhaust valve actuator the

oros P version of the oros design was chosen for the updated K engines. The

reason was the oros piston leaves less room for fitting the exh valve spindle

than with the traditional piston design . to prevent contact between piston

and spindle therefore a mechanical stop is built into the exh valve air spring

thus limiting the max spindle lift.

Using oros p version with a slightly lower piston dome creates enough space

to allow longer exh valve spindle lift. This makes it possible to exploit the well

proven relief bore design of the exh valve oil cylinder and safety valve on the

actuator is no longer necessary.

121. Fare line curve , procedure of drawing and what is base line? Where it

comes from?

Here it is based on the assumption that initially the bearings are in a straight

line and then load on each brg are found out and these are called influence

number. Using computer application data bank of influence numbers are

generated using different lifting condition. Of each bearing and their effect on

others and finally taking in to consideration of other external factors a

compromise of fair curve for the bearing is found out and shaft alignment is

done.

122. Wick boiling:-

Its a boiling process where boiler water enters the deposit though fine pores

drawn

through the capillary action. Evaporation takes place at this surface the

steam escapes through the larger pores. The evaporation causes

concentration of boiler salts and may reach a level of many thousands times

the concentration in the bulk fluid as there is no flow at the metal surface to

flush the salts away. The concentrated boiler solution rapidly attacks the

boiler steel. The deposits has an insulating effect and temp rise accelerates

the rate of attack. The tube thins down over the considerable length and

eventually fails.

123. Hoop stress


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The internal gas pressure within the cylinder liner causes a tensile stress,

referred as hoop tensile stress. the cooling water pressure on the outside of

the liner causes a hoop compressive stress, which is negligible....but the hoop

tensile stress due to internal gas pressure is prominent

124. Cascade system

Cascade system is useful when there are more then one variable that

influence the single parameter which is to be controlled.

The system consists of a pump drawing lubricating oil from the main engine

sump and pumping it through the cooler where the oil is cooled by circulating

sea water thorugh the cooler tubes . the outlet oil from the cooler is led to the

main engine bearing oil and piston cooling oil system.

For proper functioning of the system, it is desired to maintain a constant oiltemp of 45 deg celcius at the engine inlet. The control is by means of a 3 way

valve that allows a certain amount of oil to by pass the cooler . if the engine

inlet temp is too high more oil will be passed through the cooler and if too low

more oil will bypass the cooler.

There are 2main variables in this case that influence the oil inlet temp then

engine load and the sea water inlet temp forming 2 loops

An outer loop that measures the engine oil inlet temperature and

passes the information for the further processing to a controller which

is called the master or primary controller.

An inner loop that measures the sea water inlet temp and passes the

information to a secondary controller . the second controller is called

the slave or secondary controller. The secondary controller process

the signals from the primary controller and the second sensor and

sends an appropriate signal to the 3 way valve to control the oil temp

at inlet to the engine.

The main advantage of the cascade system is that it provided a quicker

response and better management of the controlled parameter. When the sea

water temp changes an immediate signal will be sent to the slave controllerfor adjustment of the 3 way valve even before the actual oil inlet temp begins

to change. The response is therefore faster.


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125. Draw back pressure v/v of ref. wat all considerations are taken wen

converting an meat room into veg

When 2-3 evaporator are used from same compressor temp of rooms are

different. Veg room is kept at positive and meat room and fish room are kept

at negative. So pressure of gas after evaporation also differs. As veg roomtemp is maintained at positive saturation temp will also be high. There is a

chance of reverse flow of gas from veg room to the other rooms evaporator.

So back pressure valve is provided at outlet of veg room evaporator. It is a

spring loaded non return valve . It throttles the ref from high pr to low

pressure.

Back pressure valve regulates pressure in the low pressure section and thes

evaporating temp of refrigerant is adjusted. Thats how different temp in

different room.

126. Material of fusible plug?

fusible plug 50% bismuth, 30%lead and 20% tin

127. Sn(tin) has a major disadvantage in white metal, what is that?

tin forms tin oxide,sno2

128. Function of inducer in centrifugal pump?

An Inducer is an axial flow impeller with blades that wrap in a helix around a

central hub. An Inducer serves as a small booster pump for the main impeller.

Usually inducers have between 2 and 4 vanes, although there may be more.

The inducer imparts sufficient head to the liquid so that the NPSH

requirement of the adjacent main impeller is satisfied. Although the inducer

usually has a lower NPSH requirement than the main impeller, it can, and

often does, cavitate during normal operation. The key is that there is so little

horsepower involved with an inducer that there is virtually no noise,

vibration, or resulting mechanical problems. Meanwhile, the higher

horsepower main impeller sees sufficient head to operate without cavitation.

129. Why droop is given in governor?


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Speed droop is a governor function which reduces the governor reference

speed as fuel position (load) increases.

Consider two diesel generators connected in parallel. fig 226 shows the

condition just after synchronization has been done to run the generators in

parallel. At x, its seen that generator 1 has full load and generator 2 has 0

load.

Fig 227 generator2 speed (frequency) control increase so as to take up partof the load.

Fig228 once generator 2 has taken some load generator 1 will decrease its

speed(frequency) as it takes up the less load . the frequency of generator 1

will now be bought back to 60hz.

By comparing 228 and 229 we can conclude that for stable operation droop is

necessary for load sharing between generators. In order to achieve sharing of

load the generator1 and 2 lines should intersect as in the case of fig 228. this

is only possible in case of droop i.e. change in speed of the generator during

transient conditions of load change.

130. Umbrella type fuel oil pump :- its sealing arrangement which eliminates

the risk of fuel oil penetrating the camshaft lube oil system(a separate

camshaft lube oil system is therefore no longer necessary) The uni- lub oil

system introduced as standards allows reductions in installation costs,


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maintenance and space over the separate systems previously used : tanks,

filters, pumps and piping for the camshaft system are eliminated.

131. what are the Advantages of using Wasted studs for securing main

bearing top keep in MAN B&W.Why not jacking bolts?

The main bearing keeps were held down by Jacking bolts (eg. Sulzer RND ).

The reason behind that was the the kind of construction of the bed plate

itself. When a cylinder fires, the pressure not only forces the main journals

down but there is also a component of force which pushes the cylinder head

up. Now the Cylinder Head, entablature and the bed plate is tied and

precompressed by the TIE RODS. Now when the firing forces come, then

there is a couple formed- a) One component of force tries to push the journal

down and b) the other component tries to Push the Tie Rods up. Now at the

bottom, the tie rods are bolted to the bed plate so a couple thus formed will

try to rock the bed plate and thus the engine. To counter attack this problem,

the tie rods were kept as close to the centerline of the engine as possible and

due to space restrictions, the jack bolts were used to keep the bearing top

covers tight(reaction force through the entablature). Note that there was only

one cover for the main bearing having two jack bolts. Now recent

development has waisted studs on the main bearing cap but the are OFFSET

FROM the transverse centerline of the engine. Waisted studs give more

comression as they have more elasticity and resilience. As a matter of fact,

from the foundation bolts to the con rod bolts, the x-head bolts etc are all

waisted studs. So care has to be taken while working as the necked region

should not be marked, scored or cracked as due to reversal os stresses,fatigue will cause a crack initiation and finally fracture.

The use of studs as opposed to bolts provides a more accurate and uniform

clamping load pattern..Waisted studs give more comression as they have

more elasticity and resilience...Studs also offer component installation

advantages over bolts. Studs act as guide pins during alignment.Studs are

available with "bullet" noses, where a slightly diminished-diameter bare tip is

featured. This greatly eases nut installation, allowing the nut to be dropped

into position before thread engagement begins

since wasted studs doesnt require any material to be removed from the bed

plate ... thus the position of the tie rod is made flexible

132. Difference between mc and mc-c engine?


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Shorter cylinder distance

Shorter chain drive

Shorter connecting rod

Longer stroke

Reinforced structure

Improved bearing material

Narrow shells = shorter engine

Increased journal diameter

Improved axial stiffness

Reduced edge pressure on main bearing

Easy mounting of second order moment for 4,5,and 6 cylinders

engines

Straight forward and more rigid housing design

Shorter stay bolts

Higher natural frequency no bracing required

Low postion of mating surface cylinder cover/ cylinder liner

Slim cylinder liner

Straight forward cooling jacket

Cylinder frames smaller and lighter

Uncooled and straight forward design

Combustion chamber

high top land

lower mating surface

lower heat load of upper piston ring

better cooling of piston rings


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cylinder frame

straight forward casting

no cooling water chamber

no cut tube for cooling water for telescopic cooling pipe

improved drain from scavenge space

telescopic mounting on wide guide shoes no need of dismantling pipe for

ohauling piston.

Crosshead straight forward design and reduced mass

Camshaft arrangement

Bearing located between roller guide

Camshaft on shrunk on cams

Reversing of fuel pumps only

Hydraulic activated exhaust valve

With indicator valve

133. Why is 2 stroke connecting rod of circular cross section and 4 stroke

conn. rod of I section?

In service, swing movement of the connecting rod sets up an inertial load on

the connecting rod in a transverse direction, and the inertial load depends on

mass and velocity.

1. In 2-stroke engines: The transverse inertia loading is not so much and the

round section connecting rod of normal length is strong enough to sustain the

connected gas loading in slow speed engines.

2. In 4-stroke engines: The transverse inertia loading is of such magnitude

that the weight of the connecting rod must be considered together with its

strength to resist these loads. Rectangular and I-section connecting rods

fulfill this requirement in the best manner, and this is the reason for using I-

section connecting rods in spite of the higher manufacturing cost.


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134. When changing a liner, u use an oversize o-ring at the lower end , what

will the consequence be ?

It will be very difficult to pull the cylinder liner home due to the rubber

completely filling the ring groove. If excess pull is placed on the liner drawing

gear the load exerted on the rubber may fracture the jacket. In someinstances when oversize rings have been fitted, fracture has occurred after

the engine has been started and come up to working temperature.

135. Where does the liner experience the maximum bending moment?

The liner is supported by the lower face of the flange over a small width at

the outermost radius. The joint face between the cylinder cover and the top

surface of the liner is usually at or near the bore of the liner.

When the cylinder cover is hardened down a downward force is exerted onthe joint face and an upward reaction is given on the outer landing face of

the flange. As the forece and reaction are not given on the same line , a

bending moment is created on the liner upper flange and the cylindrical part

of the liner adjacent to the flange.

136. How do u take bottom end bearing clearance in a 4 stroke engine?

Take the unit to tdc push the conrod up by a crowbar......take the clearance

at top half of the bottom end brg.

137. What is critical speed?

The critical speed is the theoretical angular velocity which excites the natural

frequency of a rotating object, such as a shaft, propeller. As the speed of

rotation approaches the object's natural frequency, the object begins

to resonate which dramatically increases systemic vibration .

When the rotational speed is equal to the numerical value of the natural

vibration then that speed is called critical speed.
http://en.wikipedia.org/wiki/Angular_velocityhttp://en.wikipedia.org/wiki/Natural_frequencyhttp://en.wikipedia.org/wiki/Natural_frequencyhttp://en.wikipedia.org/wiki/Resonatehttp://en.wikipedia.org/wiki/Angular_velocityhttp://en.wikipedia.org/wiki/Natural_frequencyhttp://en.wikipedia.org/wiki/Natural_frequencyhttp://en.wikipedia.org/wiki/Resonate


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138. How will u find the exact TDC of Main Engine, Auxilary Engine and Air

Compressor......He wanted 'EXACT' TDC???

In case of aux engine, access the piston top either by removing head or fuel

valve.....then take the unit to some angle before the approx tdc and measure

the depth by putting a depth gauge on top of p

Motor Genral Oral Notes (2)

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