Injury on board the offshore supply vessel Pacific Commander

Summary

In the early hours of 29 October 1993, the offshore supply vessel Pacific Commander manoeuvred stern-to the semi-submersible drilling rig Atwood Falcon to back-load some sections of casing. The Master was advised the cargo operation would be of short duration and, as a result, he chose not to use an anchor, making fast with two lines aft and maintaining position, at right angles to the rig, with the bow thruster.

After the planned cargo operation was completed and some further equipment transferred, Atwood Falcon then decided to take the opportunity to top up with cement from Pacific Commander, thereby extending the cargo operation significantly. Weather conditions were good, and the Master continued to maintain position by use of the bow thruster. In the early afternoon, the Mate was unable to maintain the position and the Master decided to suspend operations and let go. During the operation of letting go, a nylon mooring line, jammed on the bitts, parted under strain, injuring the Mate.

Conclusions

It is considered that:

1. The information provided to the Master prior to Pacific Commander going alongside Atwood Falcon gave no indication that the operation would be other than relatively short.
2. Based on the initial information provided to him and his experience in the industry, the Master's decision not to use an anchor on that particular occasion was not unreasonable. However, an earlier exercising of his power of discretion to suspend operations, while he remoored using an anchor, would have been appropriate.
3. Full length nylon mooring ropes should not be used, because of the inherent dangers of their elasticity.
4. The configuration of the capstans and bitts on Pacific Commander, with capstans at a higher level than the bitts and close in fore and aft alignment, is such that the mooring lines are prone to becoming jammed when turned up on both and under tension.
5. As changes in plans can occur at short notice, and as the operations of anchoring and weighing anchor are routine, provided water depth permits, an anchor should be used during cargo operations as a standard procedure for vessels not equipped with directional/azimuth thrusters, unless the operation is limited to a single lift.
6. The planning of cargo transfer operations by rig staff was deficient and subject to ad hoc alterations without proper consultation with the Master of the support vessel.