This procedure is intended for Fluke Calibration Employees, Approved Service Providers, or other authorized personnel trained on service repairs of 725x pressure controllers.
This shows how to disassemble the valves in a 725x pressure controller and check if there is wear or contamination on the sealing surfaces.
- Power off
- **Remove Supply Pressure - supply pressure is always supplied to one side of Apply valve.**
- Remove cover, use a razor knife to make a clean cut through tamper-proof seal(s) as they are difficult to remove.
- Remove black coil from valve. Make sure you're on the correct valve, and manifold if you have a 7252.
- Using open end wrench remove tube from sub base. Note that plunger, outer spring and maybe a shim (control valves only) are inside the tube.
- Inspect seat and mating surface in sub base. Clean as needed. Apply very small amount of Krytox lubricant or similar to o-rings after cleaning.
- Remove screws to remove the sub base from manifold. Note the orientation, air flow holes in solenoid valves must align with air flow holes in the manifold block.
- Inspect o-rings on bottom of sub base and mating surface on manifold block. Clean with alcohol wipe as needed. Apply very small amount of Krytox lubricant or similar to o-rings after cleaning.
Valve orientation - The small valves are universal fit and will have 3 holes in the base that line up with the holes in the manifold. High pressure valves (large ones) have 2 holes and a drilled key hole that lines up with the hole in the manifold. The Isolation valve on the 7250xi controller also uses the large valve and has an arrow engraved on the base that points to the front of the controller.
See this article for valves used in 7250 and 7252 pressure controllers,
7250, 7252 valve and other part numbers