Frequent leaks were observed in the seal flush coolers of pumps in crude distillation unit where
shell side is open recirculation cooling water. These coolers are in small size and low value
items. However, repeated coil leaks resulted in failure of pump seals (increased maintenance
cost) & reduced standby redundancy of the pumps. Moreover, cooling water is often
contaminated with hydrocarbon (seal oil media) causing increased wastage of treated water by
blowdowns (environmental concern), additional consumption of fresh water & treatment
chemicals. Further, there is an increased threat of microbiological induced corrosion (MIC) in
the open recirculation cooling water system.
The coil tube material of coolers is Type 304 stainless steel [UNS S30400] as per original
design. The typical mean time between failure (MTBF) of these coils is approximately 2 years.
The failures are attributed to chloride stress corrosion cracking (ClSCC) of susceptible 300
series stainless steels in aqueous chloride environment. This paper details the investigation of
cracking degradation mechanisms, microstructural study, assessment of cooling water quality,
and review of design conditions & suitability of selected material. Also presented are
suggested alternate techno-economical solutions for affected cooler materials.
Key Words: Pump seal flush coolers, open recirculation cooling water, redundancy,
microbiological induced corrosion (MIC), mean time between failure (MTBF), 300 Series
stainless steels, chloride stress corrosion cracking (ClSCC), techno-economical solution