Frequently Asked Questions

My load keeps drifting and every time I take your valves out, the nose seals have been blown out of their grooves.

There are 4 explanations that we know of:

  • Many cycles to high pressures. Back up rings serve a sacrificial purpose. Their job is to fill the clearance gap we need to fit our cartridge into the cavity and protect the primary seal, the O ring. If the gap is too large or the pressure is too high they extrude into the gap and wear away. When a breach in the back up ring occurs the O ring starts to nibble away and fails rather quickly. Under 3000 psi (210 bar) this should never happen. At 5000 psi (350 bar) the seals may need to be replaced after 1,000,000 cycles. Oversized cavities and rough surface finishes can greatly accelerate the wear.
  • Incorrectly machined cavities. One common problem is not taking the reamer deep enough to create a good O ring lead. Another is a side connection that violates the O ring lead. The symptom is a slice missing from the seal.
  • Undertorqued cartridges. If cartridges are not torqued to a high enough level they may start to back out. When they back out far enough they expose the seals causing abrupt seal failure. The symptom is that there is a section missing from the seal. See the related cartridge back out FAQ.
  • Oil filled cavity. The first time the cartridge is pulled is to check a load drift problem. When the cartridge is replaced the drift is worse. Every time the cartridge is checked the seals are displaced. This is an interesting phenomenon that is explainable and demonstrable. It starts with a cavity that is full of oil. Sun load holding cartridges block flow from the nose of the cartridge, port 1, to the side, port 2. When you insert a cartridge into an oil filled cavity, the oil is displaced either into port 2 or outside the manifold. As the nose seals start into their bore they try to seal. If oil cannot be displaced, pressure builds in port 1. As the pressure builds the seals are lifted out of their grooves and shoved up onto the port 2 area. The symptom is the seals are sometimes intact, other times they are severely pinched.

The solution is easy. Stick your finger in the cavity (before you screw in the cartridge). If you create a small air pocket ahead of the cartridge the seals can fully engage their bore before enough pressure builds to displace the seals.