Discuss the precautions which can be taken to minimize the possibility of a diesel engine crankcase explosion and the transmission of dangerous flame into the machinery space:

1. Crankcase relief valves: fitted on the crankcase doors, designed to open and relieve the pressure quickly in the event of an explosion, and to close to prevent the ingress of air (which would feed the fire). They are fitted with a flame arrester to prevent the flame from escaping into the machinery space.
2. Oil mist detectors: fitted to detect the oil mist in the crankcase (a sign of a hot spot/overheating bearing) and to give an alarm, allowing action before an explosion occurs.
3. Proper crankcase ventilation: the crankcase is ventilated (via the breather) to prevent the accumulation of flammable vapours, but the ventilation must not allow the ingress of air that could feed a fire.
4. Bearing temperature monitoring: monitoring the bearing temperatures to detect overheating (a hot spot) before it ignites the oil mist.
5. Correct design of the crankcase: the crankcase is designed to be strong enough to withstand the pressure, and the doors are secured to prevent them from being blown open.
6. Flame arresters on the relief valves and the breather: to prevent the flame from passing into the machinery space.
7. Oil quality and level control: maintaining the correct oil level and quality to prevent the formation of flammable vapours.

1. Regular monitoring: the watchkeeper monitors the engine for abnormal noise, temperature, and the oil mist detector; any hot spot is investigated immediately.
2. Correct lubrication: ensure the bearings are properly lubricated (correct oil pressure, level, and quality) to prevent overheating.
3. Avoid overloading: do not overload the engine, which can cause bearing overheating.
4. Correct running-in: run in new/reconditioned bearings correctly to prevent hot spots.
5. Do not open the crankcase doors while the engine is running (or immediately after stopping) when there is a risk of an explosion; wait for the engine to cool and the pressure to be relieved.
6. Investigate any alarm (oil mist, high bearing temperature) immediately and take action (reduce load, stop the engine) before an explosion occurs.
7. Keep the crankcase clean and free of oil leaks.
8. Follow the maker's instructions and the safety procedures for the crankcase.

These precautions minimize the risk of a crankcase explosion and the transmission of flame into the machinery space.