Thordon Bearings has unveiled what is potentially the marine industry’s safest, most robust shaft seal as part of a program of enhancements underway.

Targeting high quality, low leakage, long life and minimum maintenance, Thordon’s new SeaThigor forward seal was unveiled at SMM this week.

After several years of development and testing, the SeaThigor safety seal design uses a pneumatically activated inflatable element to stop water ingress along the shaft, allowing for the repair of the main seal whilst at sea, or allows for the shaft to turn at a lower speed so the vessel can safely return to port for primary seal repair or replacement.

Providing a new level of redundancy to single screw or mission-critical vessels operating seawater-lubricated propeller shafts, SeaThigor can function as both a dynamic and static seal to provide water-tight integrity around a shaft, while allowing the propeller shaft to rotate in both directions across a range of shaft speeds.

With inside the engine room application and typically mounted on a rear bulkhead or stern tube flange, the modular design incorporates two wear-resistant silicon carbide seal faces that contact each other to provide primary static and dynamic sealing.

The seal is designed with an enclosed housing protecting the rotor components, so no moving parts are exposed, resulting in installation simplicity and requiring minimal maintenance. Its “all-metal” construction made of marine-grade bronze also guarantees corrosion resistance for life.

Suitable for 300mm (11.8”) to 650mm (25.6”) diameter water-lubricated propeller shafts, the seal features a series of precision compression springs that are unaffected by water temperatures, pressure or draught. These springs are used to linearly load the seal faces, ensuring that the pressure is equally distributed to the entire contact surface.

Unlike other water-lubricated stern tube seals which adopt an “inside pressurised” design, the SeaThigor is designed to operate with a hydraulically-balanced, outside pressure to better withstand higher water drafts and pressure variability in rough seas. This “outside pressurisation” design also counters the natural outflow direction through the rotating seal face, further reducing leakage.

Since both the static and safety sealing elements use Thordon’s proprietary elastomer technology, shelf life concerns are allayed with a much longer service life than traditional rubber seals.

This was affirmed during Lloyd’s Register Type Approval trials last year when two 443mm (17.44-in.) shaft diameter SeaThigor seals were tested simultaneously on the Thordon Marine Seal Test Rig, in Burlington, Canada. After extensive testing, the Safe-Return-To-Port emergency seal showed no sign of wear after 15 days of use. SeaThigor received LR and DNV-GL Type Approval this summer.

SeaThigor principal particulars:

· Shaft diameter size: 300mm to 650mm (11.8 to 25.6-in.)

· Primary sealing faces: Silicon Carbide

· Quiet operation (no vibration)

· No visible leakage

· High Water pressure: rated to 2 Bar / 30 psi (0.2MPa)

· High Shaft Surface speeds: up to 10 m/s (32.8 ft/s)

· Axial shaft movement: +/-10 mm (+/- 3/8-in.)

· Radial shaft movement: +/-5 mm (+/- 1/5)

· Fully tested in Thordon Laboratory

· LR and DNV-GL Type Approval

Thordon Bearings
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