Marine Safety Forum issued a Safety Alert, describing a case where an Anchor Handling Tug (AHT) experienced a major flooding under challenging sea conditions.
The case
During a voyage from Las Palmas to Guyana across the North Atlantic an Anchor Handling Tug (AHT) found itself in the grip of a hurricane in very challenging sea conditions.
The AHT was struggling due to an un-noticed volume of sea water which had penetrated the stern compartment, this lead quickly into a major flooding and subsequent foundering of the AHT.
Although some crew manged to deploy lift rafts and were rescued, sadly there were multiple fatalities.
Findings:
“Shark Jaws” are critical equipment on an AHT, there are built in a housing frame which is secured at the stern of the vessel, their purpose is to secure Chain or Wires during Anchor Handling Operations.
As explained, “Shark Jaws” normally sit flush with the deck in a housing frame and are controlled from the Bridge.
The manufacturers of the “Shark Jaws” recommend maintenance to be carried out once every week, which states that the inspection covers are to be removed and all silt, sand, mud and obstructions removed. Upon completion of the maintenance, the inspection covers are to be installed with silicone sealant/gasket.
There was no evidence of this being completed on the Shark Jaw housing or other types of inspection covers, which compromised watertightness of the lower compartments.
This with a combination of other unfavourable circumstances enabled the water quantity to increase to a level which lead to the AHT foundering and subsequently sinking.
Lessons learned:
The investigation team recommended that all Shark Jaw housing systems are strictly maintained to the manufacturers guidance as a minimum standard, in addition to existing maintenance instructions, the items to be address by this procedure should include:
- Preventive actions to mitigate the risk of water ingress through the inspection openings during maintenance tasks on the anchor handling systems (e.g. sea state limitations, installation of anchor handling system deck cover plates).
- Instructions for the appropriate sealing method when installing the inspection covers to ensure the
watertightness of the anchor handling system housing (e.g. application of silicone sealant, installation of gasket). - Instructions for testing the watertightness of the anchor handling system after completion of the works and
installation of the inspection covers (e.g. flooding of anchor handling system housing frame with closed drainage by use of fire hose). - Maintenance actions to prevent a degradation of the inspection covers and securing devices, which could
compromise the watertightness of the anchor handling system. - Appropriate documentation of the actions performed during the maintenance work.
