SUBMARINE PROPELLER SHAFT SEALS:Six composite materials examined Available to Purchase

Submarine propeller shaft seals operate under onerous conditions in an aggressive environment and their effective life is vitally dependent upon the durability of the seal face materials. The combination of physical and mechanical properties of certain carbon‐carbon composites makes them potentially suitable for this critical service, but a literature search revealed no prior reference to their deployment in any liquid sealing application nor, indeed, to their behaviour in an aqueous environment. In consequence, a programme of work has been carried out to determine the effect of prolonged exposure to high‐pressure sea water upon their properties, and to assess their performance when run in a seal test rig against a variety of counter surfaces. The assessments were made under a reproducible condition of boundary lubrication stabilised by control of interface torque. The effects of composite anisotrophy and of graphitisation have been examined using specimen rings with the direction of fibre lay‐up either in, or normal to, the rubbing plane, and in the graphitised or non‐graphitised condition. It has been shown that the carbon‐carbon composites are stable in water and perform well as a seal face material; however, current high procurement cost will probably restrict their use to the more exacting applications.