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What actions must be taken when crankcase mist detector 
alarm activated?

21 Apr '18, 07:42

April 21, 2018, 7:42 a.m.
KnowledgeBase's gravatar image



Answer:

If the oil mist alarm is activated immediate action must be taken to reduce the risk of an explosion. Different methods may be used depending on the engine
 design. On a diesel-electric vessel with a multi-engine configuration, the engine
 with activated OMD may automatically shut down. However, it is different for a single main engine case because the risks caused 
by loss of propulsion may be greater than the possible risks of a crankcase explosion.
It is important to remember: in all cases, the immediate concern is to take off as 
much engine's load as possible and then stop it as soon as it is safe to do so.

  • In case of the unmanned engine room and using a shaft alternator the automation should be set to give the OOW 10 seconds to override the automatic slow
down procedure during which transfer of electrical load if will take place followed by immediate slow
down by passing any load reduction program.
  • If the engine is on bridge control with the engine room manned, then the engine should be switched to engine control room control.
 If a shaft alternator is in use: the auxiliary engines are run up and load transferred. The main engine is then reduced to 50% load 
bypassing any load reduction program. This will reduce the load on any bearings which may be overheating.
  • Engage and run turning gear if it can be done without being in the vicinity of the explosion doors.
  • Oil and cooling pumps must be
 left running.
  • All personnel must be cleared from the engine room.
  • At least 20 minutes must be allowed for the engine to cool before 
opening crankcase doors and investigation. During this time it advised running fire hoses out for boundary cooling as a 
precaution.
  • After giving the engine time to cool down (at least 20 minutes): it should be safe to re-enter the engine room and re-check the mist
 detector.
  • Check bearing temperature monitors if fitted. If the crankcase is not overheated, then the crankcase can be opened up after stopping the oil 
pumps: an inspection carried out on the unit which had alarmed, and adjacent units.

The cause of the alarm must be investigated. It could be:

  • Wiped bearing, which may have scored the crankshaft
  • Piston seizure
  • The fault of the camshaft chain
drive.
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24 Apr '18, 04:12

April 24, 2018, 4:12 a.m.
cheng's gravatar image


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