MEO CLASS4 ORAL 25/03/2021

 

MEO CLASS4  25/03/2021

QUESTIONS AND ANSWERS

1. Crank case explosion
2. Main engine one unit exhaust temperature is increased ,what PARAMETERS will you Check,what will be ur action, what can be the reason?
3. BOILER MOUNTINGS
4. AIR IN THE REFER COMPRESSOR,HOW WILL YOU FIND AND WHAT WILL BE THE ACTION.
5. MAIN BEARING AND BOTTOM END BEARING CLEARANCE

CRANK CASE EXPLOSION

HOW IT WILL HAPPEN?

• TO MUCH CLEARANCE BETWEEN BEARINGS,
• OIL FLIMS MAY BREAKDOWN 
• DIAPHRAGM IS NOT SEALING PROPELY
• PISTON CROWN IS BROKEN, EXHAUST GAS MAY LEAK TO CRANK CASE,
• CIRCULATING LUBRICATION OIL NOT PROPER.
• ENGINE CHAIN DRIVE IS TOO TIGHT. WHICH MAY LEADS TO HOT SPOT.
• GEARS DONT HAVE PROPER LUBRICATION.

PRIMARY EXPLOSION?

• DUE TO ANY ABOVE REASON HOT SPOT WILL CREATE. WHEN LUBRICATION OIL CONTACT WITH HOTSPOT  OIL BECOMES VAPOUR, AGAIN VAPOUR WILL COME AND  CONTACT WITH THE HOTSPOT, PRIMARY EXPLOSION WILL HAPPENED.

SECONDARY EXPLOSION?

• AFTER THE PRIMARY EXPLOSION, PRESSURE WILL INCREASED INSIDE THE CRANKCASE.
• NOW CRANKCASE RELIEF VALVE WILL ACTIVATED RELEASE ALL PRESSURE .
• AFTER THIS CRANK CASE BECOME VACCUM AGAIN. NOW IF FRESH AIR WILL COME INSIDE THE CRANKCASE SECONDARY EXPLOSION WILL TAKE PLACE.

TO AVOID THE SECONDARY EXPLOSION

• ALL MAIN BEARINGS AND TRUST BEARINGS HAVE TEMPERATURE SENSORS. IT WILL GIVE ALARM ONCE TEMPERATURE INCREASED. 
• IN NEW TYPE OF ENGINES WE HAVE A SENSOR OF WEAR DOWN OF MAIN BEARINGS. (IF UNEQUAL WEAR DOWN MEANS OIL FLIMS WILL BREAKDOWN.)
• AND WE HAVE NON RETURN VALVE TYPE RELIEF VALVE WHICH WILL RELEASE ALL PRESSURE WHEN PRIMARY EXPLOSION TAKE PLACE INSIDE THE CRANK CASE.

MAIN ENGINE ONE UNIT  EXHAUST TEMPERATURE IS INCREASED- WHAT PARAMETERS YOU WILL CHECK,WHAT WILL BE YOUR ACTION AND WHAT CAN BE THE REASON?

REASON FOR ONE UNIT EXHAUST TEMPERATURE INCREASED?

• THERMOMETER FAULT
• BLOW PAST 
• SCAVENGE FIRE
• EXHAUST VALVE LEAKING
• FUEL PUMP MALFUNCTION
• FUEL INJECTOR FAULT
• LESS AIR IN FUEL 
• TAPPET CLEARANCE IS MORE.

WHAT ARE THE PARAMETERS SHOULD CHECK IF ONE UNIT EXHAUST TEMPERATURE IS INCREASED?

• THERMOMETER SHOULD CHECK IF IT'S WORKING PROPELY OR NOT.
• SCAVENGING MANIFOLD TEMPERATURE SHOULD CHECK 
• SHOULD CHECK TAPPET CLEARANCE 

ACTION WHEN INCREASED EXHAUST TEMPERATURE IN SINGLE UNIT.

• REDUCE ENGINE RPM 
• INCREASE CYLINDER LUBRICATION
• TAPPET CLEARANCE CHANGE 
• OVERHAULING FUEL PUMP 
• OVERHAULING FUEL INJECTOR
• ADJUST FUEL INJECTOR TIMING
• SENSORS CHECK OR CHANGEOVER

BOILER MOUNTINGS

 

• OGEE RINGS
• DEMISTER
• RING AND DISTRIBUTER
• FUSIBLE PLUG
• PRESSURE GAUGE
• STEAM STOP VALVE 
• AUXILIARY STEAM STOP VALVE 
• BOTTOM BLOW DOWN VALVE 
• SCUM BLOW DOWN VALVE 
• SAFETY VALVE 
• SALINOMETER VALVE 
• FEED CHECKER VALVE 
• GAUGE GLASS
• VENT

 

REFER AIR IN THE SYSTEM, HOW WILL YOU FIND AND WHAT WILL BE THE ACTION.

AIR IN THE REFER SYSTEM HOW WILL YOU FIND?

• ABNORMAL HIGH DISCHARGE PRESSURE
• JERKING OF COMPOUND PRESSURE GAUGE
• VERY SMALL BUBBLES IN SIGHT GLASS
• CONDENSER TEMPERATURE HIGH.

ACTION IF AIR IN THE REFER SYSTEM?

• CHANGE THE COMPRESSOR TO MANUAL MODE 
• BYPASS THE LOW PRESSURE CUT OUT 
• CLOSE THE LIQUID STOP VALVE AFTER THE CONDENSER.
• PUMPING ENTIRE  REFRIGERATION INTO CONDENSER.
• UNTIL SUCTION PRESSURE IS BECOME ZERO.
• STOP THE COMPRESSOR AND CLOSE THE CONDENSER SUCTION VALVE 
• THEN GIVE SOME TIME TO COOL DOWN
• THEN OPEN THE PURGE VALVE ON THE CONDENSER.
• AIR WILL GO OUT. WAIT FOR REFRIGERANT COME OUT.
• THEN CLOSE THE PURGE VALVE .
• OPEN THE LIQUID STOP VALVE AND COMPRESSOR SUCTION VALVE START THE COMPRESSOR. 
• CHECK THE SIGHT GLASS.

MAIN BEARING AND BOTTOM END BEARING CLEARANCE?

MAIN BEARING (JOURNAL BEARING) CLEARANCE?

• CLEARANCE MEASURES JOURNAL BEARING TO UPPER SHELL USING TELESCOPIC FEELER GAUGE

BOTTOM END BEARING (CRANK PIN)

PISTON - BDC 

• CLEARANCE BETWEEN BOTTOM END BEARING TO BOTTOM SHELL USING FEELER GAUGE.

Atomisation

Atomisation:

Break up of the liquid fuel into a minute vapour mist.

Factors affecting Atomisation:  

• small orifices of the injector.
• pressure difference between fuel line and cylinder.
• Temperature, mass flow rate and viscosity of the fuel.

Effect of too high atomisation - After burning

Very small fuel particles will not have enough kinetic energy to go through the whole combustion space. Fuel droplets gather near the fuel injector due to resistance from the dense compressed air. 

Hence, they will be starved during combustion and after burning will take place.

Effect of too low atomisation - Poor combustion 

Larger fuel droplets will possess more kinetic energy and get deposited on the liner wall. This causes after burning and poor combustion. Carbon deposits will be seen on the liner walls, side of the piston crown and piston rings.

Boiler Water Test

Boiler water tests:

1. Alkalinity test. [a.Phenopthelin (P) alkalinity test  b.Total (T) alkalinity test ]
2. Chloride test
3. Excess phosphate test
4. pH test 
5. Amerzine test (Hydrazine test)
6. Conductivity test (total dissolve solids test) 
7. Hardness test

Purpose of Boiler water Test:

1. To ensure that proper chemical treatment are maintained at all time.
2. To detect the presence of contaminants in the water that may damage the boiler and feed system.

How to collect water sample for test?

• Test sample must be cooled to 25°C with the help of sample cooler.
• Allow sufficient water to flow through sample line before taking the sample, this will clear it from sedimentation.
• Let the water overflow from sample bottle to prevent air being trapped.
• Keep the bottle air tight for testing.
• If sample is colored or turbid, filter paper should be used for testing.
• Try to take sample  from same point.
• Try to avoid the sample to contact with air,  this will change the dissolved Oxygen content.

Alkalinity test: 

This is to ensure that the boiler water prevent corrosion by neutralization of acidic gases.

Phenopthelin test [P-Alkalinity test]

This test is for finding amount of hydroxides in boiler water.

Procedure:

1. Take 100 ml of boiler water sample.
2. Add 10 drops of Phenopthelin.
3. Colour will change to Pink.
4. Now add N/50 Sulphuric acid, till colour will varnish.
5. The quantity of Sulphuric acid will indicate Phenopthelin alkalinity of boiler water.

Result:

P-Alkalinity in PPM=Drops of Sulphuric acid ×10

Total Alkalinity test: 

This test is to determine the amount of Hydroxide,Carbonate,Bi-Carbonate in boiler water.

Procedure:

1. With the above sample add 10 drops of Methyl Orange.
2. Colour will change to Orange.
3. Now add Sulphuric acid, till colour change to Pink.

Result: 

T-Alkalinity in PPM=Drops of Sulphuric acid × 10 

Hydroxides and Carbonates can co-exist together in a solution but Hydroxides and Bi-Carbonates cannot.

Chloride test:

This test is to know the amount of salt in boiler water. 

To minimize the chloride level and to adjust the blow down.

Procedure:

1. Sample after P-Alkalinity to be used.
2. Add 10 drops of Potasium Chromate.
3. Colour changes to Yellow.
4. Add N/35.5 Silver Nitrate (Ag NO3), till colour changes to Brick Red.

Result:

Chloride content =No. of drops of AgNO3 ×10 

Chloride content < 300 PPM

Phospate test: 

To control the scale formation due to hardness.(presence of Phospate sample means no hardness salts)

A reserve of Phospate should be maintained in the boiler water ready to neutralize any hardness salts which may enter.

Procedure:

1. Take 25 ml of filtered boiler water sample.
2. Add 25 ml of reagent Molybdate.
3. Then add one small spoon of stannous Chloride.
4. Colour will change to Blue.

Result: 

Use comparator to check the phospate.

40 - 60 PPM should be maintained. 

pH test: 

To control condensate pH value within limit.

To minimize corrosion in steam and condensate system.

Procedure: 

1. It is checked by using pH paper.
2. Dip the pH paper.
3. Use the colour comparator to check the pH.

Result: 

Should be 10-11

Hardness test: 

To check for salt causing "hardness "

Hardness test of boiler is not necessary when the Phospate is above the lower limit of control range.

Procedure: 

1. This test can be carried out by conductivity meter or by a standard soap solution.
2. Take boiler water in beaker.
3. Add soap solution and stir it for sometime.

Result: 

more foam formed, less is the hardness in boiler water. 

conductivity test: 

To measure the total amount of dissolved solids (T.D.S) including treatment chemicals.

(Excessive density leads to priming and deposits)

To remove dissolved and suspended solid by blowing .

1.Higher conductivity,  higher the hardness.

2.with the hardness test, have the general idea about conductivity. 

3000 micro siemens/cm for high pr. boiler 

400 micro Siemens/ cm for low pr. boiler 

Amerzine test (Hydrazine test) 

• To test for dissolved Oxygen content. 
• To know reserve Hydrazine (N2H4) ppm to prevent corrosion and aeration.
• To minimize Oxygen pitting and corrosion in boiler, steam and condensate system.

what do you do for preventing of Oxygen?

Oxygen scavenging chemical used for deaeration the water. 

Usually Sodium sulphate (Na2O3) or Hydrazine (N2H4) 

2Na2SO3 + O2 = 2Na2SO4

2N2H4 + O2 = 2H2O + 2NH3 

Excess dosage of Hydrazine lead to steam and condensate line corrosion due to Ammonia being produced as the  excess Hydrazine decomposed.

Fe3O4 --> Magnetite 

{some Hydrazine carried away to steam  line.  It forms layer on pipe line & it will give corrosion protection} 

Generator not coming on load

 Reasons: 

1. Generator lost its residual magnetism.
2. Faulty synchroscope.
3. Faulty Air Circuit Breaker.
4. Loss connection of Automatic Voltage Regulator. (exciter circuit may be open)
5. Faulty power cable.
6. Frequency and Voltage not matching with busbar.

Alternator Specification

 Brushless alternator 

Number of phases : 3

output: 937.5 KVA 

volts:  450V 

frequency: 60Hz 

RPM: 720rpm

Insulation : Armature 'F' class 

Rating: CONT

Power factor:  0.8 

Number of pole: 10 

Amps: 1203A 

Field: F'class 

Excitation phase: 3

Excitation output: 21.7KVA 

Excitation p.f: 0.95

Exciatation frequency: 84Hz

Excitation No. of poles: 4 

Excitation volts: 112V 

Excitation Amp: 112V 

Prime mover: Diesel engine 

(this is jz one of the example of  alternator specification. surveyor may ask this specification rarely and he will ask cross  questions about insualtion and its class,power generation, power factor ) 

Arrival port checklist

 Upon 1 hr. notice:

1. Stop FWG and shut valves.
2. Change over to high sea suction.
3. Soot blow Auxiliary boiler, check firing amd put on auto mode.
4. Check all air compressors oil level and put on auto mode.
5. Charge both air bottles and drain any water from bottles and air dryer. 
6. Shut and lock bilge overboard valve and hand over key to cheif engineer. Ensure that all bilge suction valves are shut, however not locked. [Thr security seals may be used to avoid inadvertent opening of any bilge suction valve]
7. Start additional generator for power to mooring machinery, thrusters, deck  water, etc.,
8. Shut steam to D.B F.O.T's.
9. Put on sewage plant and changeover valves. 

At standby

1. start additional generator as required.
2. At standby record M/E counter, flowmeter readings, L.O sump and cyl. oil tank levels.
3. Ensure adequate manpower available for arrival port.

At FWE (finish with engine)

1. Take over control from bridge to ECR and stop auxiliary blower.
2. Open indiactor cocks and engage turning gear.
3. Turn M/E by turning gear with cylinder lubricator rotated 20-30 turns each for about 15 mins.
4. Cover M/E T/C suction filters.
5. Put M/E on preheat and maintain temperature.
6. Stop unnecessary machinery and put off breakers. 
7. shift generator load and stop as required.