Damcos LPU: Troubleshooting Guide LPU Service Manual
February 2017 SM 8000-100-01 Ed 04
59
Emergency operation by key giving oil spillage through
breather valve
Reason: When valve is emergency operated by key, oil is pumped from actuator to LPU tank and further on to
the actuator. If the oil flow from LPU tank to actuator gives more than 3 bar pressure drop, the oil can
be pressed through the breather valve instead of back to actuator.
Action: Carrying out emergency operation at the same opening and closing speed to which the valve is set at
remote operation can solve the problem.
Caution! Avoid replacement of breather valve with plug, as this might result in too high pressure
at motor shaft sealing.
Emergency operation by key not possible, hydraulically
locked
Reason: Bypass not active or bypass valve is blocked.
Action: Open bypass valve and keep it opened during emergency operation. If emergency operation is still
locked - bypass valve is to be dismounted and checked. If bore contains dirt, it has to be removed.
Emergency operation by hand pump giving oil spillage
through breather valve
Reason: Tank pressure in LPU is too high. The pressure drop over quick connections due to very fast operation
or defective or not properly connected quick connections. If LPU is bulkhead mounted the pressure
drop might be in piping as well if they are long or if the inside diameter is narrow.
If oil cannot return to the hand pump tank, an LPU-S may be opened without problems. When valve
closes again, the LPU tank overflows.
When LPU’s closed system is filled with oil, the exceeding oil is let out through the breather valve to
prevent overpressure in the LPU.
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