Exam Question
(a) Describe what would be the indications of crank case explosion in main engine. (4)
(b) Describe actions to be taken, if there is crank case explosion in main engine. (8)
(c) Describe means of prevention of crank case explosion. (4)
Class 4 (4th Engineer)
MEP
📅 Jul 2025
Reference Answer
### (a) Indications of an Impending or Occurred Crankcase Explosion (4 Marks)
A crankcase explosion is a two-stage event: a primary explosion followed by a much more violent secondary explosion. The indications can signal either the conditions leading to an explosion or that a primary explosion has already occurred.
1. **Oil Mist Detector (OMD) Alarm**: This is the primary and most reliable early warning. The OMD continuously monitors the density of oil mist within the crankcase. An alarm will be triggered when the mist concentration approaches the Lower Explosive Limit (LEL), indicating a dangerous condition is developing from a hot spot.
2. **Unusual Engine Operation and Noise**:
A crankcase explosion is a two-stage event: a primary explosion followed by a much more violent secondary explosion. The indications can signal either the conditions leading to an explosion or that a primary explosion has already occurred.
1. **Oil Mist Detector (OMD) Alarm**: This is the primary and most reliable early warning. The OMD continuously monitors the density of oil mist within the crankcase. An alarm will be triggered when the mist concentration approaches the Lower Explosive Limit (LEL), indicating a dangerous condition is developing from a hot spot.
2. **Unusual Engine Operation and Noise**:
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