202220 STS transfer incident: spring line breaks

Two tankers met at a specified ship-to-ship transfer (STS) area, and were secured together as shown in the diagram. Seas were smooth with a one metre swell and wind was very light (5 knots). Moderate rolling and pitching was noted. Loading commenced but at one point during loading the deck watch reported that a spring line had broken. The crew took immediate action and the failed line was replaced. Transfers continued without further incident.

The company investigation found that the vessel was equipped with two mooring systems - mooring wires fitted with tails, and mooring ropes. In this case, the vessel used mooring ropes. All were reported to be in excellent condition with a rating 10 on a scale of 1 to 10 where 10 is new, 9 excellent and 1 is for scrap.

The investigation found that excessive movement of the vessels in combination with a less than adequate arrangement of protective sleeves caused chafing damage on the mooring lines.

 

Lessons learned

• If wire ropes are available for such mooring arrangements they would be preferable to fibre ropes.
• A thorough mooring analysis and compatibility check should be performed before every STS operation.