ASTM A524 pipe API standard 650 mechanically-anchored flat-bottom tanks

The API standard 650 mechanically-anchored flat-bottom tanks stiffener ring and backing strip (if used) are primary components, and they shall comply with the requirements of API 620 storage steel tank Q.2.1. The stiffener rings may be fabricated from plate using an intermittent weld on alternating sides between the web and the flange.
Except for aluminum or stainless steel tanks, all fillet welds shall consist of a minimum of two passes. The ends of the fillet welds shall be 2 in. from the rat hole (see Figure Q-1), and these welds shall be deposited by starting 2 in. from the rat hole and welding away from the rat hole. An acceptable alternative to the detail that includes stopping fillet welds 2 in. short of the rat hole would be to weld continuously through the rat hole from one side of the stiffener to the opposite side. All craters in fillet welds shall be repaired by back welding.

Floating roofs shall comply with API Standard 650, Appendix C (Attachment 01) or with the API standard 650 mechanically-anchored flat-bottom tanks requirements as layed (laid )down in the national Chinese specifications SH3046-92 and GBJ128-90.

Prefabrication requirements for API standard 650 mechanically-anchored flat-bottom tanks, large vertical storage tanks:
1. The machined surface of the edge of the steel plate should be smooth, and there should be no defects such as slag inclusion, delamination, cracks, etc., and the surface hardened layer produced by the flame cutting groove should be removed.
2. Dimension deviation after steel plate processing: the deviation of plate width is less than 1.5 mm, the deviation of plate length is less than 2 mm, and the difference between diagonals is less than 3 mm.