Corrective/preventative action
The crew had only recently taken delivery of a very modern anchor handling, towing and supply ship (AHTS). The hydraulic power pack unit on this vessel, comprising five electric motor-driven hydraulic pumps that powered the windlass and multiple winches, was equipped with a touch screen control panel located on the navigating bridge. A notice pasted on top of the panel stated ‘For windlass or tugger winches, use No 3 or No 4 pump’.
The deck officer was instructed by the Master to start the pumps for the windlass in preparation for anchoring. After reading the notice on the panel, the officer duly started only pump no. 3. In view of the charted and measured depth in excess of 40 metres below the keel, the Master decided to walk out the anchor under power to 6 shackles.
As the 4th shackle was passing through the hawse pipe, with the ship making slight sternway, the cable suddenly began to run freely, despite the dog clutch being fully engaged and the windlass control lever being held in the full hoist position.
Fortunately, the crew quickly tightened the brake and the cable, which had run out to 8 shackles, was checked and prevented from running out entirely. On investigation, it was established that for mooring with ropes and for light hauling work, one pump was sufficient. However, for weighing anchor in deeper water and for heavy tugger loads both pumps must be run in conjunction.
Clearly, the pressure developed by a single pump was inadequate to handle the load of the anchor and 4 shackles. Later observations of the pressure gauge located at the windlass control showed that while a single pump generated about 50 bar, two pumps in tandem raised this to 130 bar under load. The pressure gauge itself was graduated to a maximum of 150 bar.
Corrective/preventative action
A permanent notice was affixed on the control panel clearly stating that pumps no. 3 and 4 should be used when using the windlass for weighing anchor.
Source: Mars/Nautical Institute
