API Std 650 insulated tanks lap-welded bottom joints

Ultrasonic Examination of Butt-welds in Plates
Butt-welds in all tank wall courses subjected to a maximum actual operating membrane tensile stress, perpendicular to the welded joint, greater than 0.1 times the specified minimum tensile strength of the API Std 650 insulated tanks plate material shall be completely examined.
Butt-welds in API 620 oil tank wall courses subjected to maximum actual operating membrane tensile stress, perpendicular to the welded joint, less than or equal to 0.1 times the specified minimum tensile strength of plate material shall be spot examined in accordance with Figure Q-2.

When API 650 storage tank is designed, when the design pressure is small F2 kPa, the impact of air pressure on the API Std 650 insulated tanks tank wall thickness is not considered in the tank wall design.

The process parameters should be strictly controlled in sand blasting of API Std 650 insulated tanks. The working pressure of abrasive chamber is between 0.5 and 0.6a, and the outlet pressure of air compressor shall not be lower than 0.6 WPa. According to the test results, the distance between nozzle and workpiece shall be controlled at 80 - 200 mm and spraying angle of 30 ~ 75°is appropriate.