Al-Sulaiman, Saleh (Kuwait Oil Company) | Kuthe, Sundip (Kuwait Oil Company) | Al-Shamari, Abdul Razzaq (Kuwait Oil Company) | Khuraibut, Yousef (Kuwait Oil Company) | Londhe, Sharad (Kuwait Oil Company)
A Gas/Gas shell and tube heat exchanger in gas dehydration unit in gathering center of Oil & Gas production company had failed repeatedly over the years. To investigate the cause of this repetitive failure, detailed visual inspection & Non-Destructive testing (NDT) of a piece of shell plate and pieces of tube from an old scrapped gas/gas heat exchanger was carried out. Additionally X-Ray Diffraction (XRD), Inductively Coupled Plasma (ICP) and chemical analyses of deposits from tube and shell side were performed.
The investigation showed that corrosion products, consisting of particles of several forms of iron oxides-hydroxides, sulfides and carbonates that form the basis for the black powder phenomenon, along with sulfur deposits had resulted in the blockage of the Gas/Gas shell & tube heat exchanger, as well as under deposit corrosion. The incidence of pitting / under deposit corrosion of the tubes resulted in perforations in the tubes and leakages. The online corrosion (coupon) monitoring data also showed severe corrosion and pitting in the downstream of Gas/Gas exchanger.
Several recommendations have been made to prevent deposit accumulation and failures in the Gas/Gas heat exchanger.
The Gas/Gas shell and tube heat exchanger in gas dehydration unit of Gathering Center (GC) in Kuwait Oil Company (KOC) operates such that the incoming feed wet gas is cooled against the dry gas exiting the dehydration unit. This heat exchanger was commissioned in 2001 and had failed repeatedly over the years. The exchanger is fixed tube-sheet type shell and tubes heat exchanger. The material for the shell plate is ASTM A 516 – Gr.60 and material for tube is ASTM A 179 (NACE). Figure 1 below shows the failed Gas/Gas heat exchanger in the gas compression and dehydration unit along with locations of online corrosion monitoring coupons.
January 2001: The Gas/Gas heat exchanger in gas dehydration unit was commissioned.
August 2005: Major inspection survey was undertaken with the following finding.