Online Injection of Vapor Phase Corrosion Inhibitors to Extend Storage Tank Floor Life

摘要

The API 650 oil storage tanks in a refinery have experienced accelerated corrosion from the soil side at the rate of 1 to 2 mm/year, primarily due to inefficiency of the impressed current ca-thodic protection system and underde-posit corrosion caused by the presence of corrosive bacteria in the soil. This caused failure of several tank bottom plates within eight years of commissioning, resulting in loss of primary containment. With no other means of corrosion control from the soil side, the priority was to apply a short-term stratagy by which the corrosion rate is substantially slowed and enable the refinery to distribute these tank turnarounds across as many years as possible. If this is not achieved, a large number of tanks might be expected to perforate in any given year, overwhelming refinery maintenance and disrupting operations. The short-term strategy adopted with best likelihood of success and minimal disruption to maintenance and operations was to drill under the tanks and inject vapor phase corrosion inhibitors. The primary objective was to increase the reliability by extending the floor life and meeting the agreed tank out-of-service schedule.