Crankcase relief valves

Crankcase explosion valves are special valves which are mounted on the doors of the crankcase. These valves are spring loaded and operate when the pressure inside the crankcase increases due to an explosion.

Under normal conditions, they are mounted on a seat and are in the closed conditions. When they are pushed open from the inside, the release the high pressure gases in the crankcase.

They are usually provided with a flame trap which prevents flames, if any, from escaping outside. Once the pressure has been relieved, the valves will return to their closed position.