Crankcase relief valves

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REGULATIONS

The provision of crankcase explosion relief valves for marine diesel engines is an international safety requirement stemming from two sources, IMO SOLAS Chapter II-1 and IACS Unified Requirements M9 and M10. Summarising, the requirements that relate to explosion relief valves are:

i. Crankcases for engines having a cylinder bore greater than 200mm and above or having a crankcase gross volume exceeding 0.6m3 are to be provided with explosion relief valves.

ii. Crankcases for engines having a cylinder bore not exceeding 250mm are to be provided with at least one explosion relief valve at each end of the engine. If an engine has more than eight crank throws an additional valve is be fitted at the middle of the engine.

iii. Crankcases for engines having a cylinder bore greater than 250mm but not exceeding 300mm are required to have at least one crankcase explosion relief valve at each alternate crankthrow with a minimum of two valves.

iv. Crankcases for engines having a cylinder bore exceeding 300mm are required to have at least one crankcase explosion relief valve at each crankthrow.

v. An additional explosion relief valve is required on separate crankcase spaces such as gear or chain cases for camshaft drives where the gross volume exceeds 0.6m3

vi. The free area of each crankcase relief valve is to be not less than 45cm2.

vii. The combined free area of all crankcase relief valves is to be not less than 115cm2 per m3 of crankcase gross volume.

viii. Crankcase explosion relief valves are required to open quickly at an overpressure not exceeding 0.2bar in the crankcase and close quickly to avoid inrush of air into the crankcase following an explosion.

ix. Crankcase explosion relief valves are required to be of an approved type.

The discharges from crankcase explosion relief valves are to be shielded to reduce the possible danger from emission of flame during an explosion

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