Thermal Shock: Early Stage Damage Detection and Monitoring or .....Failure Analysis

Cold Reheat Piping in power plants has received little attention for many years. Carbon Steel piping that handles steam at 500 F to 700 F has only had problems when not properly supported or water hammered on start up. Most recorded failures have been mechanical fatigue at a girth weld. Excessive attemperation in both coal fired plants and combined cycle ones, has become a routine practice. Consequently the number of failures (catastrophic or non-catastrophic) in Cold Reheat Piping have occurred in recent years. Most of these recent failures can be traced back to water hammer or a thermal shock due to changes in the operation of attemperator sprays. This paper shows how a Cold Reheat Piping system, that was included in a nondestructive test program, failed in a short period of time due to thermal fatigue, from a change in spray operation.