Aug 272011

Mooring link had flared open

MAC is pleased to pass on this editted  internal company investigation into the separation of a mooring wire from its rope tail during the mooring of a tanker due to the failure of a MANDAL shackle.  Periodic checks did not prevent the incident. The Safety Management System procedures were lacking and did not identify the need to carry out the necessary checks on mooring equipment lines and fittings prior to mooring the vessel.

The tanker was scheduled to berth at San Francisco, Martinez Shell Terminal. To position the vessel it was agreed to pass one forward spring and one after spring line as first lines. The vessel is equipped with mooring wires of 38mm diameter on drums and fitted with an 11 metre polyamide mooring tail.

The wire and tail are joined together using a MANDAL Mooring link.

At 0400 hours it was ascertained that the vessel was in position and both stations were asked to tighten the spring lines and secure. When the forward station was tightening its spring line to secure it reported that the mooring wire had separated from the rope tail.

When the rope tail was retrieved it was observed that the mooring link had flared open. The roller and securing pin was missing and presumed lost to sea.

The mooring link was replaced with a spare link on board and the vessel went ahead with securing itself alongside the terminal without further incident.

Investigation Results
The mooring link (MANDAL Shackle) had been installed in March 2000 at the time when the vessel was delivered from the yard. It has been subject to periodic inspection (3
monthly visual checks) as laid down in the vessels Planned Maintenance System (PMS). The wire rope and the polyamide tail were connected using the shackle correctly.

The mooring links were last inspected on 14/03/2011 as per records in the PMS. In April 2011 when the mooring wires were renewed every link was opened up and the new wire connected. Since this there have been 6 mooring operations conducted and all of them were incident free.

Post the incident the mooring link was inspected and it was found that the thread on the mooring link where the securing pin is fastened was intact without any damage.

On the day of the incident prior to mooring operations a risk assessment was carried out for the mooring operation and a tool-box meeting was held with all the crew on mooring stations. Forward and after springs were given out as first line to position the vessel. The mooring lines were not warped on, their slack was picked up as and when required, The vessel was brought into position using tugs and engines.

As the spring line was being made tight to fasten, the incident occurred.


1) The mooring link was damaged to a point beyond use and had to be replaced.
2) Vessel used additional time to safely moor alongside since the mooring link had to be replaced.
3) The incident had the potential to cause serious injury to the ship’s crew as well as shore line handlers. It was a safe working culture at both ends that prevented such an injury.

CONTROL FAILURES [controls may be designed safeguards, procedures, competence of personnel, incident management systems (detection or response)]

Inspection of Mooring Links / Shackles

The PMS does identify a maintenance routine of checking Nylon Tail and Mandal Shackle with a periodicity of 3 months, this routine was being followed diligently by the crew on board. Although not a causal factor this control did not prevent the incident.

Pre-Mooring operations checks

This control failed since it never existed. Whenever the vessel was to be moored the crew used to layout the lines in accordance to the mooring plan, there were no specific checks on the mooring wire, tails and links carried out other than that which was readily apparent. [causal factor 1]

SMS Procedures
The Safety Management System procedures were lacking and did not identify the need to carry out the necessary checks on mooring equipment lines and fittings prior to mooring the vessel. [causal factor 2]


1) Since not all parts of the damaged mooring link could be retrieved there is an assumption made that the securing arrangement of the mooring link was not entirely tight and it slipped allowing the link to be subject to a force that caused it to flare and damage.


1) Pre-Mooring checks on mooring equipment and fittings
a. There were no pre-mooring checks made on the mooring link. The integrity of the securing arrangement could have been verified at this stage and the securing screw could have been tightened as required

b. Although a cursory check on the mooring wire / tail and mooring link was carried out it was not detailed and specific at identifying faults/defects

2) Poor seamanship
a. When the mooring link was opened to renew the wires in April it is assumed that correct securing procedures were not followed by the crew then and a play could have resulted which loosened the securing pin on subsequent use


ROOT CAUSE1) No Procedures
a. The Safety Management System did not address maintenance and inspection guidelines formooring links/shackles
b. The Safety Management System also did not identify a need to perform checks on mooring lines and equipment prior to mooring operations to ensure that every equipment is available for use


1) Mooring a vessel is an important operation and involves many hazards that should be mitigated to ensure that the resultant risk has been reduced to ALARP. Inspection of the mooring system and ensuring its availability is the key to safe mooring operations.

2) Adequate supervision should be provided whenever mooring systems are worked upon as part of planned maintenance. This is to ensure that critical components are handled correctly and returned to good operating order.



All mooring links on board connected to mooring wires and tails to be inspected and checked for tightness of the locking arrangement

MSQV Department

Broadcast the incident report to all vessels in the fleet to raise awareness

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