Windlass Pressure Loss During Anchor Recovery
During anchor recovery in 28 meters of water, the hydraulic windlass must lift a 2.4-ton anchor and 60 meters of chain at about 9 meters per minute. Normal performance is 150 bar at 52 liters per minute with oil at 45 degrees Celsius. After five minutes the pressure gauge reads 95 bar, flow is 38 liters per minute, and oil temperature has risen to 57 degrees Celsius. The electric motor draws 88 percent of rated current. The relief-valve drain line is cool. The reservoir is full, the suction strainer is clean, and there is no unusual pump noise. The brake holds the load, but the chain is not moving. Heavy weather is expected in six hours and the anchorage is not tenable. The chief engineer asks whether to continue hoisting, switch to the emergency windlass, or troubleshoot in place.
1. What is the most probable cause, and what evidence rules out the alternatives?
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Most probable cause: internal leakage in the hydraulic pump or motor, such as worn clearances, seals, or internal valves, so pressure and flow fall together. Evidence: pressure is 95 bar instead of 150, flow is 38 L/min instead of 52, and oil temperature rises 12 degrees C in five minutes, consistent with energy lost to leakage. Motor current at 88 percent shows the motor is still trying, not electrically dead.
A bypassing relief valve is unlikely because its drain line is cool; a leaking relief would warm that line and usually hold pressure near the set point. Cavitation or starvation is unlikely because the reservoir is full, the suction strainer is clean, and there is no unusual noise. A mechanical jam would stop flow and raise pressure, not lower both. The next check is pump outlet versus motor inlet pressure and case-drain flow.
2. What immediate actions and troubleshooting sequence do you recommend?
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Stop hoisting, set the brake, and secure the windlass; do not keep loading a slipping pump. Keep the load on the brake and fit a chain stopper if available. Start the emergency or backup windlass if it is independent and has been tested.
Troubleshoot in this order:
- Confirm gauge calibration and valve lineup.
- Measure pump outlet pressure and case-drain flow; high case drain with low outlet pressure points to pump wear.
- Check motor inlet pressure; low pressure there points to a failed motor or internal leakage downstream.
- Inspect the relief valve for a partially open seat even if the drain is cool.
- Check the coupling and motor speed.
Do not open hydraulic lines under pressure. Record pressures, flows, temperatures, and times for the chief engineer.
3. Heavy weather in six hours; the anchorage is untenable. What decision do you recommend?
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The anchor must be recovered or the cable slipped; waiting for a full pump overhaul is not acceptable. I would set a decision timeline.
If the backup windlass can recover the anchor within two hours, use it with reduced speed and monitor pressure, flow, and temperature continuously. If not, prepare to slip the anchor, buoy the chain, and get underway before the weather arrives.
Continuing to hoist with the failed pump risks burning the pump, losing the anchor, or injuring the crew when the brake cannot hold. The commanding officer should be informed now, not at the six-hour limit. The safety of the ship outweighs the cost of an anchor and chain, and the decision must be made while there is still time to execute it.