The Development of a PTFE Faced Thrust Bearing for Dinorwig Pumped Storage Power Station

Abstract

The use of PTFE as the working surface of pivoted pads used in the heavily loaded thrust bearings of hydrogenerators confers some advantages in terms of higher specific loadings and increased margins of safety. These advantages have been realised in recent, successful installations in the UK, Japan and Greece. Further development work involving the use of filled rather than unfilled PTFE as the pad surface material and the re-incorporation of high-pressure oil injection has been necessary prior to the introduction of a second set of PTFE faced pads for use at the Dinorwig Pumped Storage Power Station. The facility at Dinorwig is the largest of its type in Europe and one of the most important such schemes in the world. Following successful laboratory based experimental work, installation of the pads in one of the motor/generator units at Dinorwig is programmed for 2000.

Introduction

PTFE (Polytetrafluoroethylene) faced thrust bearings are a development of the tried and trusted pivoting pad bearing installed in hydrogenerator machines as the main thrust bearing. The pivoting pads are invariably faced with a layer of whitemetal or babbitt. However in the case of the PTFE bearing this surface is replaced by a relatively thick dual layer made from PTFE and compressed copper wire. The load bearing surface is PTFE and the copper wire provides strength and a means of adherence to the steel backing of the pad.

The use of PTFE confers many benefits upon the bearing; the most important of which is the ability to operate at significantly higher specific loads. This benefit can be used to produce smaller more energy efficient bearings, or in the case of marginal applications, to produce a bearing which has significantly greater tolerance to abuse and transient overload.

The development of PTFE faced thrust bearings originated in the former USSR from the 1960’s and more latterly in China. In both countries there are hundreds of machines fitted with PTFE faced bearings operating at specific loads of up to 1 0 MPa. Recent development work at Michell Bearings has led to successful applications at Ffestiniog Pumped Storage Power Plant, in Wales, UK; at Hidaka Power Station in Hokkaido, Japan; and at Thissavros Pumped Storage Power Station in Greece.

The purpose of this paper is to report on new developments and progress leading to the installation of PTFE bearings at Dinorwig Power Plant, one of Europe’s largest and most demanding pumped storage generating facilities. Both Dinorwig and Ffestiniog are facilities owned and operated by First Hydro, an Edison Mission Energy company.