Gold Mine Crusher with Erratic Pressure
A hydraulic power unit operating a rock-crushing machine had erratic pressure problems, causing the crusher to stall when the pressure seemed to relieve at a lower pressure than needed. The machine was over 30 years old and was somewhat quite simple in design.
The circuit attached shows the main relief valve remotely controlled so the operator could reverse the motor’s rotation with the directional valve and adjust the pressure higher than normal to clear jambs. Once the jamb was cleared, he would reset the pressure back to the normal setting and shift the directional valve back to rotate the crusher motor in the normal operational direction.
They determined that the remote control relief valve was worn badly and needed to be replaced. Their storeroom had the same brand of relief with the same spring range, but with just one letter difference in the model number. They installed it in the manifold, adjusted the valve from fully open to the number of turns closed used by the old, similar valve with the same spring rating, and then started the system up. It seemed to run fine until the crusher jammed and blew the side of the pump out. Luckily, no one got hurt.
What could have caused the problem?
See the Solution
The gold mine power unit where the side of the pump blew out had a relief valve installed that had the inlet and outlet reversed, taking the pilot relief out of the circuit. Without a drain, the main relief would not open, causing an unwanted pressure spike that blew the side out of the pump. Sun, Parker, and Eaton all over the years have produced relief valves where the pressure inlet comes into the side and out the bottoms, as well as units that have the inlet in the bottom and out the side.
It’s so important to verify which ports on the manifold or housing are inlet and outlet, and that the screw-in cartridge matches the same configuration.
By Robert Sheaf, CFPAI/AJPP, CFPE, CFPS, CFPECS, CFPMT, CFPMIP, CFPMMH, CFPMIH, CFPMM CFC Industrial Training