Exam Question
(a) Describe crank case Oil Mist Detector and the principle of its operation. (8)
(b) Draw crank case explosion relief door and name the parts. State pressure setting of the door. (8)
Class 4 (4th Engineer)
MEKM
📅 Feb 2024
Reference Answer
### (a) Crankcase Oil Mist Detector (OMD)
#### Concept and Purpose
An Oil Mist Detector (OMD) is a critical safety device fitted to marine diesel engines. Its primary function is to continuously monitor the atmosphere within the crankcase for the presence of oil mist. The objective is to detect an increase in oil mist concentration at a very early stage, well below the Lower Explosive Limit (LEL), which is approximately 50 mg/litre. By providing an early warning, it allows for timely intervention, such as slowing down the engine, to prevent the formation of an explosive mixture and a potential primary crankcase explosion.
According to SOLAS regulations (Chapter II-1, Reg 27), OMDs are mandatory for low-speed diesel engines with a cylinder bore of 300 mm or more, or a power output of 2250 kW or more.
#### Concept and Purpose
An Oil Mist Detector (OMD) is a critical safety device fitted to marine diesel engines. Its primary function is to continuously monitor the atmosphere within the crankcase for the presence of oil mist. The objective is to detect an increase in oil mist concentration at a very early stage, well below the Lower Explosive Limit (LEL), which is approximately 50 mg/litre. By providing an early warning, it allows for timely intervention, such as slowing down the engine, to prevent the formation of an explosive mixture and a potential primary crankcase explosion.
According to SOLAS regulations (Chapter II-1, Reg 27), OMDs are mandatory for low-speed diesel engines with a cylinder bore of 300 mm or more, or a power output of 2250 kW or more.
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