FIGURE IT OUT
Oil Rig Top Drive Knocking Noise in the Pump
GOLD MINE CRUSHER WITH ERRATIC PRESSURE PROBLEMS
A drill rig operator was complaining about a knocking noise coming from his topdrive HPU. It controlled a hydraulic motor that drove a winch attached to the drive. The noise reminded me of my first car that lost a rod bearing. I felt the noise was coming from the pump, so I had them remove and disassemble the pump. We found one piston’s brass shoe worn down approximately 1/16 of an inch compared to the other apparently good pistons. We noticed the small lubrication hole was plugged with brass, possibly from the shoe wearing down on this piston. All the other piston lubrication holes were clear, and their shoes looked fine except for quite a few scratches on their face. The scratches were probably caused by the one piston’s wear material. We checked the filters and found everything in good working order with the elements having been recently changed before the noise developed. There was a nick in the housing O-ring, Why would only but it didn’t leak when re-assembled. The HPU was a simple one piston fail tank, pressure-compensated piston pump, safety relief, proportional valve, brake valve, and motor. while the others
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
seem OK?
Solution to Previous Problem
The problem was printed in our January/ February 2016 issue. See it on our website, www.fluidpowerjournal.com.
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www.FluidPowerJournal.com • March/April 2016 • www.IFPS.org