Michell Bearings completes SBO on thrust and guide bearings

Michell Bearings Power

Michell Bearings has completed station blackout (SBO) tests on thrust and guide bearings used within the reactor coolant pump at a new-build nuclear power plant. The test demonstrated the bearing’s ability to survive a station blackout condition eliminating the use of an externally powered high-pressure oil injection system.

Failure of the on-site power generators concurrent with the loss of offsite power ultimately results in a station blackout condition as there is no on-site electricity available to power the high-pressure oil injection system.

To meet testing requirements the bearing must be able to run down to a stop, under full load, and restart without any subsequent intervention. As part of the contract to supply six thrusts and guide bearings, a custom-made test rig was constructed at the Michell Bearings site to satisfy the test conditions.

The test rig was designed to closely replicate real-world bearing operating conditions such as the possibility of a station blackout where the bearings are required to shut down safely without the aid of electrical power to drive the reactor coolant pumps. 

Paul Bruce, Engineering Director, Michell Bearings, said: “We were delighted to be able to provide a solution to satisfy such challenging conditions. This is a testament to the operation of our bearings, along with our high levels of research and development. Damage to the working surfaces of the tilting thrust pads is not permitted. The combination of full thrust load and very slow rotational speeds over a sustained period results in the bearing operating under very low oil film thicknesses. Consequently, special design considerations are required to survive such a condition.”

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