A678 grade A plates API 650 low-alloy steel tanks

The API 620 large storage tank nozzle neck is fabricated by welding from 1/2-in. plate. The materials in the tank wall, the nozzle neck, and the reinforcing pad conform to ASTM A442 Grade 55. The main joints in the tank wall are fully radiographed, double-welded butt joints. The longitudinal joint in the nozzle neck is of the same type API 650 low-alloy steel tanks but is not radiographed; however, the longitudinal joint and all other parts of the nozzle-and-wall-plate assembly have been shop stress relieved after fabrication, as required by 5.25. The adequacy of the reinforcement and attachment welds shown in Figure F-6 shall be determined.

Before pressure testing, thoroughly flush the API 650 tank floating roof primary drain hose system. Supply API 650 low-alloy steel tanks blind flanges, gaskets, and bolting (for other types of blanking covers as may be required) necessary for testing.

Inspection of weld and micro crack of API 650 low-alloy steel tanks: the inner and outer surface of API 650 low-alloy steel tanks, weld and heat affected zone shall be observed by naked eyes first. 100% ultrasonic testing or 100% penetrant testing are carried out for butt welds of API 650 low-alloy steel tanks. For the defects found by 100% magnetic particle inspection, dye detection, 100% ultrasonic inspection or 100% penetrant inspection, the radiographic inspection shall be used again to ensure the accuracy of the test results.