COMPAC bearings are at the heart of the award-winning open seawater lubricated propeller shaft bearing system.The COMPAC polymer alloy bearing is homogeneous (there are no layers of differing materials) with properties that are consistent throughout the wall thickness. The Thordon COMPAC bearing is 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. And although start-up friction is initially higher than an oil system, at rated shaft speeds, viscous friction acting on the rotating shaft is lower with seawater than with oil. This has been shown to lead to fuel savings and thus reduced emissions. A key benefit of the seawater system is that it negates the need for a damage-prone aft seal.

A Thordon COMPAC open seawater lubricated propeller shaft system offers considerable advantages to ship owners, not only in bearing wear life predictability and reliability, but they are also cheaper to maintain, easier to install and are future compliant.

The COMPAC system typically includes COMPAC bearings, shaft liners, a Water Quality Package, ThorShield shaft coating and a forward seal.

  • Zero pollution risk
    (no oil required)
  • Lifetime Wear Life Guarantee for COMPAC in bluewater operation*
  • Turnkey engineering and installation support
  • Easy fitting
  • Reduced seal maintenance costs
  • Inspections without shaft withdrawal
  • Resistance to shock and edge loading
  • Survivability
    (our non-catastrophic failure mode allows ship to get to port)
  • Global availability

“We chose Thordon COMPAC for this vessel because these bearings are environmentally friendly, water lubricated and come with no risk of pollution.”

– Captain Simon Merritt, Technical Manager of Carisbrooke Shipping Ltd. (U.K.) 

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.


Find My Thordon Contact