A Review of Thrust Bearings Used in Rotary Regenerative Air Preheaters

Introduction

By Fabijonas BR, Kingsbury Inc, 10385 Drummond Rd, Philadelphia, PA, 19154, USA.

Rotary Regenerative Air Preheaters (RRAPs) are devices installed typically in steam turbine power plants which reuse the heat of the exhaust gasses to heat the incoming fresh air, thus improving the plants’ efficiency.

The fluid film thrust bearings used in these devices range from 0.580 m to 2.2 m in diameter and are subjected to continuous loads in excess of 4 MPa at incredibly slow speeds, less than 0.1 m/s at mean diameter.

Calculated minimum fluid film thicknesses using a high-viscosity oil (1000 SSU at operating Temperature) are on the order of 6 μm or smaller. Such conditions place the bearing in the mixed-lubrication region on a Stribeck curve. Nonetheless, Kingsbury has a long history of these bearings running successfully.

We review this history, discuss performance calculations, and speak about attempts to improve the bearings’ operations.