96040 Lifeboat Equipment Failure

19 Sep 1996 MARS

 Lifeboat Equipment Failure
Cherbourg

Report No. OR08


The idea of embarking everyone into the lifeboat whilstit is still in the davits is also not recommended, in fact, for standardlifeboats in gravity davits, it is positively discouraged by the UK MAIBas the following Official Report shows. Their investigations into accidentswhich have occurred in the last few years with crews being injured or killedby accidents during drills have led to the recommendation that these lifeboatsare fully embarked only when bowsed in and after the tricing pendants havebeen released. This is to avoid overloading the lifeboat davit structure.Full MAIB reports are available from The Stationery Office Books, PO Box276, London SW8 5DR, Tel.0171 873 0011, Fax 0171 873 8247.
SUMMARY

The ro-ro passenger ferry PRIDE OF HAMPSHIRE was berthed at Cherbourgon the morning of 25 September 1994 when No 2 lifeboat launching equipmentfailed whilst the crew were undergoing a lifeboat drill. The lifeboat fell,pitching 6 of the 32 occupants into the water. All were accounted for but16 persons were taken to hospital. The cause of the accident was due tobreakage of the lifeboat suspension link joining the aft lifeboat hook tothe suspension chain of the fall block.

The suspension link was made of alloy steel which had not been suitablyheat treated for use in the marine environment. As a result the link weakeneddue to stress corrosion cracking, finally breaking catastrophically. Examinationof the damaged davit structure found that the welded joints, crucial tothe integrity of the structure, were of inferior quality with incompletepenetration and lack of fusion. These welds rendered the davits unsafe,although they did not contribute to the accident. The investigation raisedthe issues of quality control procedures for lifeboat davit suspension componentsand davit structure welds. The problem of quality control is a matter thatmust be addressed by the shipping industry as a whole and not just by P& O Ferries.

FINDINGS

  • The collapse of No 2 lifeboat davit installation and subsequent injuries to crew members was due to the failure of the aft lifeboat hook suspension link.
  • Failure of the link was caused by pre-existing cracks at its intrados (inner curved surface) and the effects of stress corrosion in these cracks.
  • The cracking initiated in the area between the contact surface of the intrados of the lifeboat suspension link and the adjacent surfaces of the lifeboat hook and suspension chain "D" shackle.
  • The primary cause of the cracking was due to the high tensile strength of the suspension link material which, in this state, is susceptible to stress corrosion in the marine environment.
  • The high tensile strength of the material used for the lifeboat hook suspension link resulted because the link was not heat treated in accordance with the requirements of British Standards specifications.
  • Had the lifeboat hook suspension links been heat treated under suitable conditions to give a lower tensile strength, it is considered that stress corrosion cracking would not have occurred.
  • Neither the MSA, P & O Ferries nor the supplier have any record to show that a Certificate of Test had been issued for the suspension chain and the associated link which fractured catastrophically on PRIDE OF HAMPSHIRE. Similarly, there are no records of Test Certificates for the other suspension chain components on this vessel and other vessels in P & O Ferries.
  • The finding that davit suspension chain components are not correctly certificated is not confined to P & O Ferries alone but is a universal problem throughout the shipping industry.
  • Failure of the fillet welded joints connecting the lower end of the forward davit arm to the pivot pin bosses of No 2 lifeboat launching installation was brought about by rapid overload. However, this was a consequence of the failure of the suspension link, and not the cause of the accident.
  • The fillet welded joints connecting the lower end of the forward davit arm to the pivot pin bosses were of inferior quality because of incomplete penetration and lack of fusion.
  • The visual inspection and non-destructive testing (magnetic particle inspection) procedures for davit load bearing welds had not been effective in detecting the inferior quality fillet welded joints connecting the lower end of the forward davit arm to the pivot bosses on PRIDE OF HAMPSHIRE.
  • The quality assurance procedures carried out by manufacturers of the lifeboat davit structures on other vessels did not detect faults in welded joints that were critical in maintaining the integrity of the structure.
  • Lifeboat davit suspension links and chains, and davit installations of the same type installed in other vessels of the P & O Ferries fleet, were found to have similar structural defects to those on PRIDE OF HAMPSHIRE. All the defects rendered the installations unsafe, posing a serious threat to their structural integrity.
  • Despite the advice given by the Marine Safety Agency "Survey of Life-Saving Appliances Volume 1 Instructions for the Guidance of Surveyors" regarding the requirements for the survey and approval of lifeboat davit lifting chains, the components, which included suspension links on the PRIODE OF HAMPSHIRE and other vessels, were not correctly identified and certificated.
  • The effect of connecting both the tricing pendant and the bowsing tackle to the long link and of inverting the suspension link resulted in the suspension link being intermittently loaded in a manner contrary to that of its original design. However, this loading did not affect the cracks found in the suspension links of No 1 lifeboat launching installation, nor was this loading a causative factor of the accident.
  • The Interim recommendations that lifeboat suspension systems and davitsof a similar specification should be withdrawn until further tests werecarried out were fully accepted by MSA and P & O Ferries. The subsequentmetallurgical investigation fully supported MAIB's interim recommendations.

FURTHER RECOMMENDATIONS


TO THE MARINE SAFETY AGENCY AND P & O FERRIES

  • To prevent the possibility of further serious problems resulting from the omission of heat treatment, normally undertaken during manufacture of alloy steel lifeboat hook suspension links and sling assemblies, hardness tests should be carried out on new components to confirm that the material has been suitably heat treated. The results of these tests should be recorded, together with the particulars of the heat treatment, preferably in the form of a Certificate of Test. The Certificate should also include particulars of the material and the safe working load (SWL). The records should be available on board the vessel for inspection.
  • Those alloy steel lifeboat suspension links and chains already in use which do not have the required quality assurance records should be hardness tested. The equipment should be replaced if found unsuitable.
  • Officers and crew should be informed that there is a possibility of overloading the lifeboat davit structure if the lifeboat is embarked with tricing pennants attached. Embarkation should only take place when the lifeboat is bowsed in by the bowsing tackles and after the tricing pennants have been detached.

TO THE MARINE SAFETY AGENCY

  • Surveyors should ensure that the suspension chain components satisfy the relevant British Standard or equivalent. The MSA "Survey of Life Saving Appliances - Volume 1 - Instructions for the Guidance of Surveyors", should therefore be revised so that the standard requirements for alloy steel suspension chains are clearly stated.
  • With the objective of providing an effective inspection and non-destructive testing procedure to eliminate faults in critical weld joints in lifeboat davit installations, the present quality control procedures for detecting these faults should be reviewed.
  • Alloy links and chain should be examined regularly by a person with a defined competence. A Certificate of Examination should be signed by that person.
  • When the lifeboat launching system is installed on board, the system may be assembled using components supplied from several different sources. A dossier should be placed on the vessel containing drawings of components, sub-assemblies and completed installation, together with the approved details and supporting certification. This dossier should be updated when the complete installation is tested and also when the components and sub-assemblies are tested and replaced.
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