pressure relief valve setting

[jscotty29]

I have a hydraulic cylinder with an accumulator that is pressurized with nitrogen. Does anyone know what the appropriate setting for a relief valve that is going in the accumulator. i know the accepted setting for hydraulic relief valves are around 10% over MAWP. Do pneumatic relief valves follow the same principle? 3000 psi system. any info will help. thanks.

 

[Newmanite]

pre charge in an accumulator.It really depends on its application.Accumulators provide a way to store fluid under pressure.It should never be less than 25% of working pressure and preferably 30-35% of max working pressure.
A pnuematic relief valve is in principle the same as a hydraulic relief valve.This being they both have a bias spring which acts directly with the supply and when pressure rises above this spring "tension" venting occurs either to atmosphere or return to tank.

 

[hydromech]

Hydraulic accumulators don't have pressure relief valves for the nitrogen, making valves and pipework assemblies air tight upto 3000 PSI is very tricky.

I am not saying they don't exist, it's just that they are not usually required because the gas pressure will only follow the system pressure, except when there the acculator is exposed to heat.

The system pressure is regulated by a hydraulic relief valves and the nitrogen pressure is limited by a thermal fuse.

A combination of rising heat and pressure cause the fuse to open an vent the nitrogen to remove the risk of explosion.

'hope this helps

Adrian

 

[jscotty29]

Thanks. very helpful, not in the way i was expecting but helpful none the less.