Internal leakage of plate heat exchangers caused by cooperation of pitting, crevice corrosion, and fretting

• Published in: Engineering failure analysis Vol. 96; pp. 340 - 347
• Main Authors: Fan, Z.D., Du, J.S., Zhang, Z.B., Ma, Y.C., Cao, S.Y., Niu, K., Liu, C.X.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2019
• Subjects: Crevice corrosion; Failure analysis; Fretting; Pitting; Plate heat exchanger; Pitting; Fretting; Crevice corrosion; Failure analysis; Plate heat exchanger
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2018.10.007

Comprehensive failure analysis was carried out on internal leakage of 316L plates in a plate heat exchanger operated in a co-generation power plant. Causes of failure were bowl-like perforations that were regularly distributed on the crossing contact points (CCPs) between zigzag peaks of neighboring corrugated plates. Other potential failure mechanisms were ruled out through a process of elimination, although some of the observed features increased the difficulty in the failure analysis. The bowl-like perforations are induced by the cooperation of pitting, crevice corrosion, and fretting. The pressure of high-temperature hot water (HTHW) is much higher than that of low-temperature hot water (LTHW), and this results in a narrower crevice and compressive stress between CCPs at LTHW sides of corrugated plates. A narrower crevice assembles a lot of corrosive elements such as Cl−, and compressive stress induces fretting with a fluctuation in water pressure. Where the surface passive film is damaged by fretting, CCPs first suffer crevice corrosion and pitting. In the process of perforation growth, the combination of pitting, crevice corrosion, and fretting had the primary role in the circumferential direction, whereas both pitting and crevice corrosion had the main role in the depth direction. Thus, pits were corroded more severely in the circumferential direction, resulting in a bowl-shape perforation or pit. •Failures in plate heat exchanger in heating power plant.•Bowl-like perforations were regularly distributed on the crossing contact points of neighboring plates.•Perforations was induced by the cooperation of pitting, crevice corrosion and fretting.