Abstract
Fuel storage tanks like other utilities in the oil industry are subjected to corrosion due to their content, operation conditions, and environment. Corrosion has a big impact on the integrity of the storage tanks leading to failure of the tank bottom plate and tank shell. The consequences of corrosion damage are fuel leak, tank damage and risk of fire, as well as environmental risks. The aim of this work is to investigate the actual condition of the tank internal shell, bottom plates, and to identify the cause of failure. It investigates the structural integrity of heavy fuel tanks through internal and external inspections for the tank. Visual inspection coincides with ultrasonic thickness measurements are carried out. Microstructure analyses are also conducted for the corroded areas. The results showed that the bottom plate was attacked by severe pitting corrosion in the center of the tank with a massive loss of the plate thickness. The pittings observed were of various depths and sizes that scattered on localized areas where some of them having thorough holes. Several corrosion mechanisms could occur concurrently or separately. The inspection interval should be rescheduled and may be lowered to two years as the study revealed due to high corrosion rates which were calculated based on a 25 years period.