API Std 650 storage tank requirement

The insert plate weld shall not cross any shell seams and shall be at least the greater of 10 times the shell thickness or 12 in. from any other weld in the API Std 650 storage tank shell including shell seams, shell-to-bottom weld or attachment welds. The butt weld around the periphery of the plate shall be examined over 100% of its length by both liquid penetrant method and radiographic method. The liquid penetrant examination is required on the root pass, on the back-gouged surface, and on the inside and outside finished weld surfaces. Additionally, the weld shall be vacuum box leak tested.

API 650 petroleum storage tank body design is mainly the design of tank bottom, API Std 650 storage tank tank top and tank wall, and the design of tank wall is particularly important. As the main pressure bearing part of API 650 petroleum storage tank, the tank wall bears loads including liquid pressure, wind pressure, seismic load, opening stress, etc. The calculation of such loads is explained in detail in various API Std 650 storage tank storage tank design standards. But in addition, the API 650 petroleum storage tank wall also bears the push-pull force and torque of the connected pipeline.

Treatment of API Std 650 storage tank welding defects:
1. Lack of fusion: once found, it should be shoveled and grinded off before re welding.
2. Incomplete penetration: over standard defects shall be removed and re welded. When welding on both sides, the shallow side of the groove can be grinded and shoveled to expose the welding root on one side, and then the welding is repaired.
3. Slag inclusion: over standard defects shall be removed and re welded.
4. Crater: weld to full after grinding.
5. Air hole: if the internal air hole exceeds the standard, it shall be welded again after being removed by grinding shovel, and the surface air hole shall be removed by grinding wheel and then repaired.