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Section 6 • Troubleshooting
Table 6-1. Troubleshooting Guide - General Problems & Solutions (1 of 3)
Problem
Low Oil Pressure at Start
Low Run Oil Pressure
Oil flow or oil pressure
problems
Faulty pressure or temperature
readings
HPLD Single Screw Compressor • Installation, Operation and Service Manual • Emerson • 35391HP
• After failing to start compressor with "Prelube Oil Pump Inhibit", first allow
Discharge pressure, Oil Filter In pressure and Out pressure to equalize. Then
restart compressor. If compressor fails to start due to low oil pressure, contin-
ue troubleshooting with items below.
• Reset Prelube Oil Pressure Setpoint in Alarms and Trip Setpoints screen to
lowest recommended setpoints.
• Check calibration of oil manifold transducer, discharge pressure transducer,
and suction transducer.
• Check for correct oil pump motor rotation and operation.
• Ensure transducer isolation valves are open.
• Verify that the correct transducer ranges are selected.
• Check to see all oil line valves are open except the oil dump valve used to fill
the lines and oil cooler.
• Check oil strainer for dirt.
• Check oil filter pressure drop.
• Check "Prelube Oil Pump Time Limit" setpoint is sufficient in Compressor
Timer Setpoints screen.
• Prelube pressure is manifold pressure minus discharge pressure.
• Check solutions in "Low Oil Pressure at Start".
• Check that there is proper discharge pressure ratio to create differential pres-
sure, otherwise oil pressure can't be maintained. Oil pressure is manifold oil
pressure minus the suction pressure. It is a net pressure.
• If the oil pump is selected to be a part time oil pump in the "Setup" menu,
then ensure that it only shuts off at an appropriate pressure ration that takes
into account pressure drops through the oil cooler. This is a set point in the
"Compressor Control Setpoints" menu called "Oil Pump Restart." It is a pres-
sure ratio. (discharge pressure in psia/suction pressure in psia) Default ratio
is a pressure ratio of 3.00:1 that stops the pump and 2.80:1 that restarts the
pump. This ratio can be increased. Do not decrease without consulting Vilter.
• Clean oil strainer screen.
• Change oil filter, maybe plugged or collapsed.
• Oil pump gears worn internally, excessive end-clearance.
• Oil priming valve used on air-cooled cooler units is open.
• Relief in-line check valve stuck open.
• Pressure ratio too low, oil pump should be on.
• Check that the correct pressure or temperature range is selected in the
Instrument Calibration menu.
• Check cable connections at device, terminal strips, and PLC input card for
correct wiring and shielding (RF noise).
• Check calibration of RTDs and transducers.
Solution
6 – 1
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