Aft COMPAC bearing with fixed key Kaministiqua

The COMPAC bearing system uses seawater as the lubrication medium in place of oil. Seawater is taken from the sea, pumped through non-metallic COMPAC propeller shaft bearings and returned to the sea. The COMPAC polymer alloy bearing is homogeneous (there are no layers of differing materials) with properties that are consistent throughout the wall thickness. To ensure that abrasives are removed from the seawater supply, a Thordon Water Quality Package is used.  Use of seawater lubricated bearings eliminates the aft seal, as well as the storage, sampling and disposal of oil.  

The Thordon COMPAC bearing is an elastomeric polymer alloy designed in a 2:1 L/D configuration in the AFT bearing.  To promote early formation of a hydrodynamic film between the shaft and bearing, the lower (loaded) portion of the bearing is smooth, while the upper half of the bearing incorporates grooves for flow of the water lubricant/coolant. The COMPAC system typically includes COMPAC bearings, shaft liners, a Water Quality Package, ThorShield shaft coating and a forward seal.

  • Reduced seal maintenance costs
  • Zero pollution risk (no oil required)
  • Smooth, quiet operation at all speeds
  • Proven long wear life
  • Easy to machine and install
  • 15-Year Wear Life Guarantee for COMPAC in bluewater  operation*

COMPAC Lifetime Bearing Wearlife Guarantee

The Thordon seawater lubricated COMPAC bearing is guaranteed to meet Classification Society propeller shaft bearing wear specifications for the lifetime of the vessel or Thordon Bearings will supply new bearings free of charge.*


Commercial newbuild ship owners of Classed ships with stern tube (single/twin screw) with shaft diameter of 300mm (12”) or greater. The program excludes vessels such as naval/coast guard/government vessels.  COMPAC conversions may also be considered on a case by case basis.


The ship owner must clearly specify the complete COMPAC system (see below) to the shipyard in order to qualify for the lifetime bearing wearlife guarantee. There will be a full technical signoff by Thordon Bearings prior to issuance of the lifetime wear life guarantee.   A copy of the specification is available from Thordon.

COMPAC Propeller Shaft Bearing System:

The COMPAC propeller shaft bearing system specification includes:

a) COMPAC propeller shaft bearings for shafts of 300mm (12”) or greater

b) Thordon Water Quality Package

c) Shaft liners

d) ThorShield shaft coating

e) Forward seal (SeaThigor or Blue Water or seal approved by Thordon Bearings)

Items a, b, c, and d must be supplied by Thordon. Item e must be approved by Thordon before issuance of the guarantee. If bearing carriers are a required part of the design, they would also be supplied by Thordon Bearings.

* What is the Guarantee?

The Thordon seawater lubricated COMPAC bearing system is guaranteed to meet Classification Society propeller shaft bearing wear specifications for 25 years or Thordon Bearings will supply new bearings free of charge. The guarantee is limited to the supply of replacement bearings delivered to the ship. It does not include replacement of any other Thordon supplied components nor any drydocking or installation costs.  Standard operating parameters as specified by Thordon Bearings (for example – system maintenance, minimum water flows, etc.) must have been provided and maintained by the ship owner.

The guarantee is limited to the owner of the ship. If the ship were sold, the balance of the time outstanding on the guarantee can be transferred to the new ship owner for a fee (25% of price of fully machined set of bearings). The guarantee would be issued by Thordon Bearings directly to the shipowner or his designate and would not be offered through the shipyard.

Thordon is offering this guarantee because of our confidence in Thordon COMPAC propeller shaft bearings and the proven experience and wear life of COMPAC bearings operating in commercial vessels in the last 35 years.

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