Failure analysis of an air-cooled heat exchanger in natural gas dehydration unit. (September 2020)

• Record Type: Journal Article
• Authors: Javidi, Mehdi; Sadeghi, Mohammad Amin; Jafari, Raheleh; Hoodi, Amir Ardalan
• Is Part Of: Engineering failure analysis. Volume 115(2020)
• Publication Date: 2020-09
• Subjects: CO2 Corrosion -- Erosion Corrosion -- Flow-Induced Localized Corrosion -- Critical Velocity; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2020.104678
• Languages: English
• ISSNs: 1350-6307

Abstract

Highlights: Failure of outlet nozzle of air-cooled heat exchanger has been investigated. Flow regime was determined based on API 14E which was turbulence/ vortex flow. Flow velocity was found to be more than critical velocity for erosion. No visible corrosion product was found on the surface due to high flow velocity. Mode of failure was flow induced localized CO2 corrosion due to high flow velocity. Abstract: Corrosion and erosion can have a synergistic effect on failure related to heat exchangers in gas refineries. This work presents failure analysis of outlet piping of an air-cooled gas cooler in a natural gas refinery. Visual inspection as well as thickness measurements were employed to determine the severity of metal loss. Chemical composition analysis and hardness measurements were performed in order to make sure of authentication of base and weld metals. Metallographic investigation indicated that no metallurgical changes have been occurred. Assessment of service condition revealed that temperature drop of gas stream passing through the gas cooler resulted in water condensation followed by corrosion. On the other hand, calculations of critical velocity of fluid revealed that gas velocity exceeded the critical velocity which intensified the erosion and flow induced damages. Thus, it was concluded that although general CO2 corrosion plays a role on the metal loss, flow induced localized corrosion and erosion were the main causes of failure.