Abstract
Sections of mild steel above-ground water-foam conveyance pipes were found to be leaking due to severe corrosion. These pipes were part of a deluge (fire suppression system) for a large fuel tank farm operated by the U. S. Army in Okinawa, Japan. Analysis of cross sections of the pipes indicated that corrosion had initiated on the exterior of the pipes, most likely due to salt–laden rain water running down the sides and collecting on the underside. The corrosion was especially severe at the saddles where the pipes were supported, and the chloride-containing water could easily pond. The most severely corroded pipe sections of the pipes were replaced with SAE 304L (UNS S30403) stainless steel and the fasteners were replaced with SAE 316L (UNS S31603) stainless steel, which are expected to be more resistant to the severely corrosive atmospheric environment. Although the total installed cost of the new stainless steel replacement is 25% greater than the cost of the replacing with similar mild steel, preliminary cost/benefits analysis indicates an expected useful life that exceeds 100 years for the stainless steel pipe and fasteners, as compared with the observed 17 year life of mild-carbon steel pipe. Details of the analysis, materials selection and replacement will be discussed.
