Collision with rig

There was an incident which led to the loss of position keeping ability of a Platform Supply Vessel (PSV) and the subsequent collision with the leg of a Drilling Rig.

The vessel was undertaking Deck Cargo Transfer Operations at the time.

The Drilling Rig was a self-elevating, 3 legged ‘Jack-up’ with its Drilling Station located at the stern of the rig in a ‘hang over’ position, and also a Helideck protruding out and up from the Starboard forward side of the Main Deck.

The Platform Supply Vessel (PSV) was a standard UT 755L and classed as a DP2 type vessel. The weather recorded at the time of the incident; winds from a South Westerly direction of 25 knots, wave height estimated at 3.5 metres and tide direction of 314° T at a rate of 0.7 knots.

Water spray was being experienced on deck, but latterly waves were witnessed breaking on the vessel deck. The vessel was operating in a close quarter’s position.

The vessel had been hit by a large wave, causing the vessel to be pushed out of position.

As the DP System responded to this position and heading change, the vessel came back toward the rig, overshot her position and collided with the aft Starboard leg of the rig.

The impact from a vessel perspective was approximately mid-ships, as the vessel was already listed to Starboard.

It was concluded that the Officer of the Watch had missed several early warning signals that should have 
driven his decision process to move away from the rig to either settle the DP sensors, or wait until the 
weather conditions had decreased.

The later signals from the rig that he was too close, and the communications with the deck crew that there 
was lots of spray/water on deck, and that he had to physically change the ships ballast to hold station was 
likely to have been too late to avoid this collision with the Rig.

Stop job policy and DP operational procedures where deviated from.