Messenger Line in Propeller

A multi-purpose vessel was required to assist a tanker to connect to the transfer hose of an integrated pipeline and manifold system on the seabed, commonly called a Single Anchor Loading (SAL) operation.

The job entailed the multi-purpose vessel using the dynamic positioning joystick to maintain position, whilst the deck crew pick up the floating marker buoy which is connected to the messenger line. The messenger line in turn is connected to the transfer hose which is located on the seabed. Once retrieved the vessel can then pull up the transfer hose and pass it to the tanker.

The SAL operation is a complex system with multiple parties involved from various departments on board. In this incident, simultaneous errors occurred, both on the bridge and on deck. On the bridge, the Dynamic Position Operator (DPO) mistakenly shifted the vessel in the wrong direction, between 10 – 15 meters aft. At the same time, the deck crew were struggling to disconnect the messenger line from the buoy as the marker buoy had become entangled in it. These issues were not communicated to the DPO which resulted in the messenger line becoming slack in the water with the deck crew unable to pull the line in.

To view this Marine Safety Forum safety alert in full, click the 'Download Alert' button above.