HMSEndurance had been experiencing oil leaks to sea and oil ingress to its sterntube lubricating system.

Deep Sea Seals were called in by the Ministry of Defence to supply and install new outboard and inboard seals and all the necessary pipework to connect with the tanks for the inboard lubricating system. DSS fitted an AC/Mk2 Coastguard anti-pollution seal system which differed from the existing system and required substantially modified pipework.

Previously only a single barrier seal had been used which was fed by a gravity lubrication system. The new AC system needed to be pump fed.

The new pipe configuration necessitated through-hole access holes in the aft and forward prop shaft bearing bosses and new drilled and tapped holes for the outboard AC seal. This work was contracted to Metalock Engineering, which also took responsibility for the new pipework (seal pipes) and necessary tanks installations.

For the outboard seal Metalock drilled and tapped 24 new M20 tapped holes equally spaced on a 710mm PCD with a minimum of 40mm full thread depth on the sterntube endplate. The new seal pipe arrangement had to pass through the 5,940mm long sterntube itself and to provide pipe access, four 20mm diameter holes had to be drilled through the 1.030mm of the aft bearing boss and four more through the 400 mm of the forward bearing boss. The holes were positioned 300 either side of top and bottom dead centres on a 680mm PCD in the aft bearing boss and a 640mm PCD in the forward bearing boss. Additionally, a 32mm diameter through hole was drilled at bottom dead centre on similar PCDs in one boss inward end to accept a large diameter pipe to drain oil from the sterntube.

Connections from the sterntube pipe runs to the various lubrication oil tanks were achieved using a spigot-located MK2 adaptor ring secured by twelve M20 hex head screws. The system uses three tanks, one for the inboard seal, a main header tank and a void space header tank, all of which were fitted by Metalock Engineering UK.

HMS Endurance is now back on station in the South Atlantic with its new anti-pollution seal system.

MJInformation No: 20603