Frequently Asked Questions

How can I assemble a stack of sandwiches and keep it dry?

  • Make sure the surfaces are flat and that there are no burrs. Do not polish the surface; machining marks are good. The machining marks help stop the o-rings from acting as pumps.
  • Look for dings on the corners of seal plates that will create gaps.
  • Stud rods or cap screws must not bottom out in the sub-plate.
  • It is very important to assemble a stack of sandwich valves keeping the o-ring sealing surfaces “dry.” The hydrostatic properties of an oil film under the o-rings, and at the seal plate interface, can create a fluid path leading from the pressurized port interfaces to the outside edge of the stack. (Under this condition, as noted in bullet point above, an o-ring can actually act as a “pump.”) So, if you start with a wet seal interface in your stack, there’s a good chance it will always stay wet.