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Marine propulsion

The integrity of the entire propulsion chain from the motive unit (motor or engine) through to the propeller relies on effective sealing systems.

Whether keeping oil in hard working line shaft bearings or preventing seawater ingress through the stern tube, correct seal profile and optimised material selection are vital to efficient equipment operation.

James Walker has developed sealing products specifically for these arduous duties and we are able to design and manufacture solutions tailored to the individual mechanical configurations and operating conditions of each application.

•    Propeller shaft seal
The recommended seal arrangement consists of four seals: two seals facing the seawater and a second pair to retain the bearing lubricant.
Walkersele® D7 and Walkersele® D8 profile seals are recommended for this position as there will usually be a certain amount of pressure from the head of seawater.
A leak detection port is recommended between the central seals to collect any leakage and give early warning of the need to replace the seals.


•    Bulkhead seal
The bulkhead seal normally consists of a cartridge arrangement bolted to the bulkhead and its purpose is to prevent water passing between the adjacent chambers should a flooded condition occur.
Should the seals be called upon to operate there is likely to be a positive pressure on one side therefore Walkersele® D7 and Walkersele® D8 profiles are recommended.
As no other lubrication is present it is important to ensure that the inter-seal space is well packed with grease on assembly.

•    Line shaft bearing seal
The line shaft bearings are vital in supporting the propulsion shaft and can be subject to a wide variety of uneven and shock loads. The seals therefore must be capable of dealing with these same conditions and therefore flexible Walkersele® D6 and Walkersele® D8 seals are recommended both to retain bearing lubricant and exclude contaminants in a back-to-back arrangement.
Whilst D6 seals are not intended for pressure conditions, our in-house tests have proved that they will operate successfully under a flooded condition at a pressure of 1.5bar and a surface speed of 5m/s for a period of 72 hours, thus enabling the vessel to reach port if it finds itself in difficulties.
When two seals are housed with spacer rings of different axial lengths, it is possible to adjust the position of the seal lips on the shaft to move them to run on an unworn area of shaft surface. This is particularly useful when operating with relatively soft shaft materials and can significantly extend service life.