I couldn't help myself.  After thinking about the discussion regarding thermal expansion of the hydraulic fluid, I went out to the hangar and opened up the Oildyne pump I use on the test stand.  I removed the high side thermal relief valve and added a check nut, much like is found on the pressure relief valves.  Full engagement of the thermal relief valve spring is very close to two full revolutions of the assembly.  I backed this off one half turn and tightened the check nut.

After everything was put back together, I powered up the system and started heating the fluid.  When system pressure reached about 1800 psi, the thermal relief valve (TRV) cracked.  Pressure bled down about 100 psi.  With continued heating, the cycle continued -pressure cycling between 1,700 and 1,800 psi. 

This looks like a simple way to bring the maximum obtainable system pressure down to a more reasonable level relative to our normal operating pressures.

Write-up and video to follow.

 

Chris Zavatson

N91CZ

360std

www.N91CZ.net