When sizing a safety valve, most focus only on set pressure, ignoring accumulation pressure – the pressure rise above set pressure during discharge. If no margin is left, relief capacity may be insufficient, and pressure may keep climbing.The main safety valve product names of China Safety Valve Network include:Spring Fall Lift Safety Valve,Spring Fall Lift Safety Valve, With RadiatorSpring Low Lift Air Compressor Safety Valve,(With Connecting Pipe)Safety Reflux ValveSingle Lever Safety Valve,Spring Fall Lift, Low Lift Thread Safety Valve,Sleeve Insulation Safety Valve,Safety Check ValveStatic Weight Type Safety Valve

Allowable accumulation

Per ASME, for a single valve, accumulation shall not exceed 10% of set pressure (21% for fire case). For a 1.0 MPa set pressure, the maximum inlet pressure during relief is 1.1 MPa. This 10% “extra space” determines whether the valve truly has enough capacity.

Why the margin matters

A safety valve needs travel from pop to full lift. Accumulation provides the force to push the disc higher, achieving rated orifice area. If set pressure is set exactly at MAWP (maximum allowable working pressure) with no accumulation room, the pressure may exceed the vessel limit during relief.

Common mistake

Many engineers set set pressure = MAWP, then calculate required capacity, without checking if accumulation exceeds MAWP. Correct practice: set pressure should be slightly below MAWP, leaving 10% for accumulation.

Bottom line: Do not size a safety valve by set pressure alone. Always verify accumulation margin. Set pressure ≤ MAWP × 0.9 (0.8 for fire case) ensures vessel limits are not exceeded during relief.

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