UMC introduces innovative external shaft sealing system

UMC International recently designed and applied an innovative underwater temporary shaft sealing system, which allowed the British Ministry of Defence (MoD) to successfully undertake afloat modifications to the design of the inboard shaft seal system fitted to the Royal Navy?s amphibious assault ship, HMS Ocean. UMC?s innovative solution allowed the inboard work to be undertaken afloat while the ship was berthed, at a jetty, for a programmed maintenance period in its base port. The successful application of the underwater shaft sealing system avoided the need for an un-programmed docking, which would have otherwise severely imposed on the ships demanding operational schedule.

The requirement emerged following a report of water ingress in the area of the ship?s internal shaft seal. A subsequent inspection revealed that the pipe work, which feeds cooling water to the shaft seals and the shaft bearings, required modification. To allow this work to be undertaken safely afloat, avoiding the risk of catastrophic flooding, there was a requirement to seal, underwater, the gap surrounding each shaft as it exits the hull.

To satisfy this requirement UMC, worked with the MoD?s Warship Support Agency MPS and MW Integrated Project Teams to design and manufacture a temporary underwater shaft seal and develop an associated procedure and risk assessment for the seal?s installation and removal. The aft face of the shaft?s stern tube was selected as the location for the temporary seal. However, direct access to this face, is barred by an outer bossing (installed to enhance hydrodynamic efficiency as the shaft exits the hull). To gain access to this face it was therefore necessary to first unbolt and removed a large portable GRP fairing plate that forms part of the outer bossing.

With the stern tube aft face exposed the temporary sealing system, which had been designed by UMC’s Design and Consultancy Division specifically for this task, was quickly installed.