Marine Engineering

Safety Valve Relief Valve Safety valves are used in gas or steam systems. Relief valves are used in fluid or compressed air systems . Opening will happen at the set pressure. Opening is proportional to increase in the vessel pressure. Opening of valve is sudden if the set pressure is reached. Opening of valve is gradual, if the pressure increases gradually.   Safety valve can be operated manually. Relief valve cannot be operated manually. Safety valve is set at 3% above the working pressure   Relief valve is set at 10% above working pressure.

1.Any IC engine of cylinder diameter of 200 mm or a crankcase volume of 0.6 m3 and above shall be provide with crankcase relief valve of a suitable type with sufficient relief area. 2.In large engine, cylinder diameter more than 300mm, require one relief valve to be placed on each crankcase door. 3.In small engine, cylinder diameter not more than 300mm, crankcase door of which are usually very strong. It may have relief valve or valves at its end. 4.Its free area should not be smaller than 45cm2 and there shall be minimum of 115cm2 /m3 of the gross crankcase volume. 5.Spring setting for opening pressure is 0.07 bar at an internal pressure and will close when the pressure has been relieved. 6.The valves should open smartly and close positively and rapidly. 7. The relief valves shall be arranged or provided with means to ensure that discharge from them is so directed as to minimize the possibility of injury to personnel.