For typical conventional safety relief valves, there is very little flow before the relief pressure (set pressure + overpressure). You'll have the seat rise slightly, which will result in simmering/leakage. As pressure reaches the the relief pressure, it quickly opens. To my knowledge, you cannot take credit for or assume reduced flow for something less than the relief pressure.

Note some relief valves, such as pilot operated, have very low leakage even very close to the relief pressure.

MSPVIN

When asking a detailed technical question about matters that under normal circumstances are without importance, there is most often a special working situation or problem behind. If you detailed, you could perhaps get a beter answer.

As RVAmeche explains, pilot operaated SRV valves are very precise, while spring type SRV's can vary regarding accuracy, and more easily give premature leakages, uncompleted lifts and even 'simmering, banging' repeated small lifts in series, which in all cases would be difficult to give accurate teorethical flow descriptions.

Figueres can however be given if this, for instance, is a disc valve, (centric or excentric) weight, and/or hydraulic damped type, built for relief, damping and reducing flow.

Answers are best given by producers of original or replacement types.

Good luck!

It's 10000 GPM.

Perhaps this explanation might help http://www.valvemagazine.com/magazine/sections/bac...

Relief valves are designed to "pop" open and flow of the fluid helps to keep them at full opening. If a relief valve opens and the flow is maintained at the same pressure then the valve stays open.

The 10% is the maximum "accumulation" the protected vessel or pipe can see to take account of losses in the inlet piping, the valve and the outlet piping when flowing at maximum relief flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.