Effect of back pressure on the operational characteristics of the valve is minimized by incorporating bellows. The bellows encircle an area equal to the inlet orifice area. This area is maintained free from the effect of back pressure from the discharge side of the relief valve. The space enclosed by bellows is freely vented to air. Thus the opposing pressure on the inlet fluid is generated by the spring alone without contribution from any sort of backpressure. For these relief valves allowable back pressure is 10 - 50% of the set pressure.