Emerson Damcos, Service Manual

Page: 47 / 144

Damcos LPU: Troubleshooting Guide LPU Service Manual
February 2017 SM 8000-100-01 Ed 04
47
LPU-S frequently restarting in open position
Action: Place pressure gauge on quick connection B.
Read maximum pressure and observe if pressure drops when motor stops.
Then if: 1. Pressure is raised to approx. 150 bar, but drops to 95 - 105 bar before motor is restarted.
Goto “Leakage in the hydraulic system between check valve and actuator or in actuator” on
page 47.
2. Pressure is raised to approx. 150 bar and motor stops, but is restarted before pressure drops
below 115 bar.
Goto “Fault on pressure switch or wires, possibly on printed circuit board” on page 47.
3. Pressure is raised to below 120 bar and drops to 90 - 110 bar before motor is restarted.
Goto “Large leakage in the hydraulic system, or misadjusted safety valve” on page 48.
1. Leakage in the hydraulic system between check valve and actuator or in
actuator
Action: Mount hand pump, pressure gauge is already mounted (see above), and open actuator fully by hand
pump.
Then if: • Pressure remains constant
Leakage in solenoid valve or leakage at check valve in valve block:
– Check for leakage in solenoid valve.
– Check valve in valve block for external leakage, e.g. at pressure switch or closing speed adjust-
ment. Check for external leakage and if no leakage is found replace solenoid valve or check
valve.
• Pressure drops
Leakage in bypass valve at actuator, release valve, shuttle valve, emergency valve or actuator.
– Check o-rings on emergency slide and shuttle valve, possibly replace release valve or shuttle
valve if shuttle valve is version with internal slide.
– Check that bypass valve in actuator is closed.
– Possibly dismount LPU from actuator and check if actuator has leakage, internal or external.
2. Fault on pressure switch or wires, possibly on printed circuit board
Action: Wires to pressure switch are dismounted from pressure switch and connected to each others, simu-
lating high pressure.
Caution!
For LPU power these wires are supplied by 230 V. When the LPU is energized, the motor
must run for 7 - 12 seconds, then stop, and not start until the wires are disconnected
from each other.
Pressure Switch is electrically measured fully pressurized for short breaks (loose connections). Pres-
sure gauge is mounted on quick connection for B and pressure is read when pressure switch breaks.
Then if: • Pressure switch breaks above 105 bar