Q) Write short notes on: Protection / Precautions against Crank Case Explosion.
Ans:- Protection against Crankcase explosions:
- Crankcase doors of sufficient strength are provided so that they do not get displaced by crankcase explosion. They must be fastened sufficiently.
- One or more crankcase explosion relief doors are fitted, depending on engine size. Crankcase explosion relief valves are fitted with flame arrestors.
- Crankcase oil mist detectors (OMD) and monitoring equipment are provided. They give an alarm and also indicate the unit where the mist level is high. Low level of mist is generally an alarm only. But high level of mist gives an alarm / initiates slowdown of the main engine. The OMD must be checked to see it is functional.
- High bearing temperature alarms are provided.
- Warning notices are provided on crankcase doors indicating doors not to be opened immediately if overheating is suspected.
The figure alongside shows a Crankcase explosion relief door & valve. It consists of:-
- A woven wire gauze assembly that does not allow flame to travel out of the crankcase.
- A relief valve usually made of aluminum.
- A spring against a retaining plate and
- A discharge hood so designed that products of explosion are discharged in such a way that it does not cause harm to the engine room personnel.