Class 2 (2nd Engineer) MEKM 📅 Jan 2021

Exam Question

(a) Describe the events leading to a crankcase explosion.

(b) State how overheating might be indicated other than by a mist detector.

(d) State how severity of a crankcase explosion is limited.

Reference Answer

(a) Sequence of events leading to crankcase explosion:
If a hotspot exists in the crankcase, some lube oil will come in contact with it and will be vaporised.
The vapour will circulate to cooler parts of the crankcase and condense to form a white oil mist
The oil droplets in this white mist are very small. If this oil mist circulates back to the hotspot in such concentration (with typical particle sizes of around 0.5 to 5 microns in diameter, density between 30 to 50 mg/L (milligrams per litre)), it will be ignited, and a primary explosion will occur.

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