Pressure Relief Valve-MAN B&W Engine

Pressure relief valve is designed to relieve the excess gas pressure developed inside the cylinder for its safety. It also releases the excess fluid created during the "water hammering" caused in the event of cooling water or oil leaking in the cylinder. This leaking fluid can cause excess pressure when engine is started, on the cylinder cover and on its mountings. This pressure may also burst open the cylinder cover if it is not released.

Fig: Pressure Relief Safety Valve 

The valve is of stainless steel with seat and it is loaded by compressing a helical spring. The lower end of the spindle is raised to allow the valve to align with its seat, valve lift is limited by a shoulder at the top of the spindle.

The spring keep or capnut is locked in position to regulate the correct spring compression and the valve is set to lift at not more than 20% above the designed engine pressure.

Maintenance consists of cleaning and inspecting at the same intervals as cylinder overhaul. The valve seat should be examined and re-grounded if necessary; the spring checked for its free length with no working.