Moog Hyd Valves

Are you speaking of internal leakage, such as from one passage to another in a spool valve? (As distinct from external leakage through O-ring, chevron, or other seals.) From my understanding--correct me if I'm wrong--spool valves cannot be made absolutely immune to internal leakage, whether from tiny clearances or scoring from fine particles.

I don't know, but I imagine there are specialty control valves that can take care of this.

its leaking between the vavle body and the block.... its just a tiny bit, but a leak is a leak

Chech the o-rings and the block surface and how the bolts have been tightened. If you use the valves (I presume servo or proportional valves) at a higher pressure it is possible to have such surprises since the bolts extend more and the pressure between seal an surfaces is not any more sufficient. Check also if the O -rings do not have a too important permanent set. Where does the leak come from: from the A/B orifices or from the P orifice ? Do you have high pressure changes in the motors (cylinders or rotary motors) an oil "creep" a kind of "pumping" can occur. This has been proved by experiments.

well this forum appears to have been for nought. at our mill the operators do theyre maint. on the machines and when a big problem occurs we get called in. i have always felt that was huge mistake, cause im trained in feilds they are not. anyways back to leak I took valve down and found a double o-ring causin g the separation on the valve block therefore creating leak. everything you all have said has been helpful and i thank you!