Analysis of service problems of caustic tanks installed in oil and gas plants

The paper deals with the one of the most general classifications of atmospheric tanks according to their roof type in oil and gas plants. An overview of recommended periods of inspection of storage tanks is given, together with their structural characteristics. Upon irregularities in the process of water purification, the caustic soda tank is prematurely open for inspection. Visual inspection of the major elements, ultrasonic thickness measurements, penetrant tests of welded joints, and checking the functionalities: cathodic protection system, level controller, electric heater, are performed on the tank. On that occasion, it is noticed that the electric heater is found distorted and inoperative. The damaged heater made of Incoloy 800 is carefully removed from its holder and a new heater is welded to the holder by GTAW procedure. The necessary NDE is performed and required electric parameters after repair welding are confirmed.