Figure It Out: Ram Drifts Down After Replacing the Main Directional Valve

By Robert Sheaf, CFPAI/AJPP, CFPE, CFPS, CFPECS, CFPMT, CFPMIP, CFPMMH, CFPMIH, CFPMM, CFC Industrial Training.

A company that makes carbon fiber leaf springs for the GM Corvette had to replace the main pilot operated directional valve that was scarred badly by a broken spring from the load check that failed. They replaced both the check valve and directional valve from their stores room and after cycling the press several times to remove the air, maintenance turned it over to production.

The production group reported back that all was working fine other than the press would slowly drift down when they would break for lunch or when they would do a die change. Maintenance replaced the pilot operated check and the directly operated relief. But the press would still drift down. They then blocked the rod side outlet of the cylinder and determined the cylinder piston was not leaking since the drift stopped.

Any idea what could be causing the ram to drift down?

See Solution