|About this Abstract
||Materials Science & Technology 2019
||Failure Analysis: Industry Specific Failures
||Failure Analysis on Cracked Outlet Nozzles (2 off) from a Regeneration Gas Heater Economizer
||Riza Khan, Kavir Ryan Ramdass
|On-Site Speaker (Planned)
The economizer represents a vertical finned hairpin tube design which utilizes combustion flue gases to heat up Regeneration Gas in two coils. Numerous cracks were observed on the welded regions of the pair of 5” Sch. 80 outlet nozzle welds and their reinforcement pad welds after only 3 years service. The addition of a repad was a modification from the original design based on recommendations made by consultants following similar previous failures on identical economizers. The findings indicated that the root cause of failure was attributed to a combination of poor engineering design, and incomplete joint penetration of the nozzle attachment welds, which facilitated an unusual acid dew-point corrosion mechanism (Nitrate SCC) to manifest itself in the relatively cool plenum chamber. This was the first time such a failure was reported and was considered unique. Piping stress, flexibility analyses and thermal distortion stresses were also considered.