Answer EKM Question 21

Q21. In operation of a 2-stroke marine diesel engine, following conditions are observed at different occasions:

(a) A gradual rise in exhaust temperature at one cylinder.

(b) A rise in crankcase sump level.Explain the reasons and subsequent actions taken for each of the above.

Answer: (A) A gradual rise in exhaust temperature at one cylinder.
Reasons:
(a) False alarm: Read local temperature thermometer or redundant sensor valves, if found faulty rectify the sensor.
(b) Fuel injector faulty: This will cause improper atomization. The defects in the fuel injector are as follow:
(i) Defective fuel injection nozzle. This can be minimized by maintaining nozzles as recommended by manufacturer.
(ii) Pressure setting of nozzles is lower it is to be taken care by Frequently overhaul and setting of injectors.
(iii) Compression spring broken, this require regular overhaul and inspection
(iv) Improper fuel viscosity. Check fuel temperature and adjust according to fuel test report
(c) Exhaust valve leaking:
Exhaust valve leak causes un-burnt fuel to escape to the manifold which burns the manifold and causes high temperature. Also leak of combustion products can trigger high exhaust temperature.
(d) Engine overload: Check and reduce load, if weather is bad, activate 'rough weather' mode.
(e) After burning: Take indicator cards to ascertain, check timing, fuel injector issues and rectify.
(f) Scavenge fire: Check the temperature of under piston space for the affected unit, if scavenge fire is seen, take remedial measures accordingly.
(B) A rise in crankcase sump level.
(a) Faulty level transmitter: Check dip stick or sounding manually to ensure the level is corresponding to the remote level, If the level is not matching rectify the sensor.
(b)Water Ingress:
(i) Jacket cooling water leakage: A cracked liner, cracked cylinder head can leak water however this is suitable only for 4 stroke engines. For a 2 stroke engines, the leaks will be collected in the under piston space, however if the stuffing box is leaking the water can pass through to the crank case.
(ii) Leaky Lub oil purifier/Heater: Lube oil purifier heater could be leaking or the purifier operating water malfunctioning can also lead to water ingress. Sample Lube oil return from purifier to check for the water content.
(iii) Jacket cooling water (JCW) pump leak: Engine driven JCW pump attached to engine may develop leak on the seal which can accumulate in the sump.
(iv) Piston cooling water leak: Piston cooling water leak could accumulate water in the sump.
(v) LO cooler: LO cooler may develop leak and water ingress could occur.
Fuel Ingress:
(a) Fuel pump: Oil sealing in the fuel pump may develop leak and cause fuel leaking into the LO side.
Lube oil leak:
(a) Lube oil filling: Lube oil filling link may be left open or passing.
(b) Sludge / Dirty lube oil pump: Dirty lube oil pump circuit be leaking sludge / Bilge into the sump.