API standard 650 anchored liquid-storage tanks isolation valves

Tank cracks are common API standard 650 anchored liquid-storage tanks defects, mainly including tank wall cracks, internal cracks, weld zone cracks. The reason for these defects may be that the defects not exceeding the standard existed in the early stage of API standard 650 anchored liquid-storage tanks construction, which become obvious after the later use. Or in the process of using the API standard 650 anchored liquid-storage tanks, the tank body material generated new defects due to corrosion, pressure, wear and other reasons, and tank cracks.

The thickness of the API standard 650 anchored liquid-storage tanks wall plate, t, required by 5.10.3 for the latitudinal unit forces, T2, acting at this level is 0.57 in. The nozzle neck is seamless steel pipe and conforms to ASTM A53, Grade A; the materials in the tank wall and reinforcing pad conform to ASTM A442 Grade 55. The main joints in the tank walls are fully radiographed, double-welded butt joints. The adequacy of the reinforcement and attachment welds shown in Figure F-7 shall be determined.
To determine the length of the nozzle neck within the limits of reinforcement, the smaller of the following calculated values shall be used:(2.5)(0.625) = 1.56 in.
(2.5)(0.375) + 0.75 = 1.69 in.

The welded API 650 tank in various sizes and capacities for internal pressures approximating atmospheric pressure (internal pressures not exceeding the weight of the roof plates), but a higher internal pressure API standard 650 anchored liquid-storage tanks is permitted when additional requirements are met.