Failure Analysis of TEG Purification Fire Tube in a Natural Gas Station

The research was conducted on failed S355 fire tube used for purification of triethylene glycol (TEG) solution, with the matrix materials destructively cracked and deformed after 3 years and 8 months of service. Through integrated experimental analyses (macroscopic/microscopic characterization, chemical composition, mechanical testing, and corrosion product analysis) coupled with finite element analysis (FEA), the failure was attributed to synergistic effects of stress concentration and localized overheating. Results revealed that the right-angle elbow geometry induced severe stress concentration (148.7 MPa via FEA), while reduced gas flow velocity at the elbow promoted localized heating. Thick inner-wall corrosion products (5.70 mm, primarily FeO/ Fe3O4) and external carbon deposits (graphitized carbon with I(D)/I(G) = 2.65) exacerbated thermal resistance, reducing heat transfer efficiency. Material degradation from prolonged hightemperature exposure and wall thinning (from 8.0 to 4.0 mm) further compromised structural integrity. Finally, preventive measures are being suggested to avoid occurrence of such failure of fire tube.