As a result, the wire ropes may be seriously corroded due to passage of moisture/air inside and yet go undetected.
Serious incidents have occurred during launching and retrieval of freefall lifeboats using the secondary means of launching and retrieval with purpose built lifting slings encased in plastic sheathing.
The slings have parted resulting in the freefall lifeboat plunging several meters into the sea with crew inside.
Investigations into the failure of the slings revealed that the slings parted under normal operational load due to significant weakening, as a result of internal corrosion. The internal corrosion within the sheathing went undetected, even though regular inspections were reportedly being carried out, as required by SOLAS Chapter III, Regulation 20.
Risk to safety
The presence of the plastic sheathing encasing the wire rope means that neither the crew nor the various surveyors tasked with inspecting the launching system can inspect and maintain the wire rope as required by the IMO SOLAS and Res. MSC.402(96).
Furthermore, while it is a requirement under SOLAS Chapter III, Regulation 20.4 that falls used for launching of lifeboats are renewed when necessary if found deteriorated, or at intervals of not more than 5 years – there is no requirement in SOLAS for renewal of the slings used in secondary means of launching of freefall lifeboats.
As such, many owners of vessels do not consider renewing the slings, as the true condition of the encased wire ropes cannot be correctly determined.
- Masters and senior officers should physically check if freefall lifeboat lifting slings are encased in plastic sheathing.
- Masters, senior officers and surveyors should physically inspect the sling for signs of corrosion beneath the sheathing.
- Companies should consider means to ensure the inspection of slings encased in plastic sheathing and the risks posed by them is appropriately captured by their safety management system.
- Consideration should be given to the use of slings without a plastic sheath, or an alternative method of encasing the sheath which allows for removal for inspection. Operators may wish to contact the lifeboat manufacturer for guidance in this regard.
- Companies should ensure that the slings are renewed on a regular basis, using the same principle of maintenance of lifeboat falls as stipulated in SOLAS Chapter III, Regulation 20.4.