FAILURE INVESTIGATION OF A PRIMARY SUPERHEATER TUBE

M.M. Rahman* and M.H.A. Zuhairi

  • Md Mujibur Rahman

Abstract

FAILURE INVESTIGATION OF A PRIMARY SUPERHEATER TUBE

 

M.M. Rahman* and M.H.A. Zuhairi

 

1Centre for Power Plant Technology and Performance Optimization, College of Engineering, Universiti Tenaga Nasional, Putrajaya Campus, 43000 Kajang, Selangor, MALAYSIA.

 

ABSTRACT

This paper presents the root cause failure investigation of P3T3 boiler tube of Unit 5 Stesen Janaelektrik Sultan Salahuddin Abdul Aziz (SJSSAA) Kapar. As Unit 5 requires running at  all the time, any disruption of operation because of failure would cause the lose in revenue and potential disruption to the customers. The investigation consists of visual inspection on the failed tube and surrounding primary superheater region. The tube samples were tested to determine Vicker’s hardness before put under observation using optical microscope to inspect microstructure. Information on operation history was collected and using available data, Larson-Miller analysis was conducted to determine the temperature the tube was subjected to. Visual inspection shows open burst failure and potential overheating left by burnt mark on surrounding tubes. It also revealed presence of clinker that covered almost the entire primary superheater region. Hardness results showed a decrease of hardness from 163 HV to 157.08 HV. Microstructures of the tube samples revealed spheroidization at specimens number 1, 2 and 4. Operation investigation found that three coals, i.e., Duiker, Ensham and Twisdraai with low ash fusion temperature were used prior to failure. Finally, Larson-Miller analysis proved that the tube was subjected to temperature estimated from 577.28oC - 601oC, which was  higher than the tube design temperature, i.e., 483oC. Thus the root cause failure was the use of coals with low ash fusion temperature that lead to the formation of clinker at primary superheater region.

 

Keywords: Primary superheater tube; Coal-fired boiler; Low ash fusion temperature; Clinker formation.

Published
2013-12-31
Section
Original Research Articles