14
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January - February 2018
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www
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machinerylubrication.com
When a hydraulic issue occurs, the pump
usually is one of the first components changed
out, but it actually should be the last. Why?
Because a pump is the most time-consuming
part to replace and the most expensive. It should
never be changed before several tests are conducted. e
easiest tests and checks should be made first.
Visual Tests
Is the electric motor running? is sounds like
a no-brainer, but it should not be overlooked. I was
teaching a class at a plant in Kentucky a few years ago
when a student came in one morning and said they had
an overheating problem on the press the previous night.
He said they changed the filtering and cooling pump to
only find out later that the motor had been turned off.
Is the pump shaft rotating? Many times this is
difficult to tell because of coupling guards and C-face
mounts. I know of one plant where the pressure at the
pump outlet port was fluctuating. ey changed the
pump and found that the worn key on the shaft had
damaged the keyway on the coupling.
Check the oil level. is also should be obvious, as
it often is the only thing checked before the pump is
changed. e oil level should be 3 inches above the pump
suction. Otherwise, a vortex can form in the reservoir,
allowing air into the pump.
Troubleshooting
Hydraulic Pumps
HYDRAULICS
Al Smiley
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GPM Hydraulic Consulting
Inlet line unrestricted - Full flow into pump suction port Inlet line restricted - Air is "pulled" out of hydraulic oil
High vacuum pressure occurs when a pump does not receive adequate oil volume at its suction port.