Emerson Damcos, Service Manual

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Service Manual Damcos LPU: Troubleshooting Guide LPU
SM 8000-100-01 Ed 04 February 2017
62
Motor running for a short time and stops
High pressure on the port to which oil is led
Action: Mount pressure gauge on quick connection on return oil from actuator (LPU-D). At the same time
check that actuator is moving.
Then if: • High pressure on return oil. Actuator is not moving, or is hardly moving
DPCV does not open check valve for return oil. Check slide, sealings and check-valves for DPCV.
• Low pressure on return oil. Actuator is running, but not to end position
Operating pressure for actuator too high due to blocking in return, could be dirt in holes near the
port surface or in actuator.
• Low pressure on return oil. Actuator is not moving, or is hardly moving
Operating pressure for actuator too high due to blocking in return, could be dirt in holes near the
port surface or in actuator.
Fault in actuator, valve (requires a too high torque or more than 7 seconds before breaking away
from the seat), or choice of actuator for the valve in question.
Motor running for a short time and stops
Reason: Pressure switch does not break, or fault on control print.
Action: • Try dismounting a wire for the pressure switch in question. LPU shall then operate as long as ter-
minal is energized. If not so, there is a fault on the printed circuit board which is then replaced
(see “Replace Printed Circuit Board” on page 105).
• Control card receives a signal for stop of motor from pressure switch. For LPU-S and LPU-D-
Power, pressure switch connections and adjustment are to be checked. Pressure switch is possi-
bly replaced (see “Replace pressure switch” on page 109).