Use of electromagnets for suspension and position control of power-station air preheater seals

This paper is concerned with the use of electromagnetic linear actuators for the suspension and position control of the cast-iron seals employed in large regenerative air preheaters. The function and operation of power-station air preheaters are discussed and the problems arising from differential expansion and thermal distortion in the large steel structures are explained. A solution for seal-wear and air-to-gas leakage, using a composite magnet/spring suspension system, is presented and the design, construction, supply and control of suitable electromagnets are described. Particular attention is paid to the problems posed by the extreme severity of the working environment during both design and operation of the electrical equipment. The paper concludes with attempts to assess the effectiveness of the modified seal suspension system and to quantify the benefits which might be expected as a result of improved preheater performance.