CSA G40.21 Gr 260WT plates API 650 open-top tanks

The API 650 open-top 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.

Pipeline transportation of API 650 oil tank is not less than the maximum consumption of 3 to 5 days. The daily operating time of API 650 open-top tanks office buildings and fuel oil equipment is 12-16 hours; for high-end residential hotel buildings, the daily operating time is 16-24 hours.

Corrosion of the API 650 open-top tanks body caused by external conditions such as high temperature, rain, humidity, or inadequate anti-corrosion measures of the oil storage tank itself, the water-bearing deposits in the oil storage tank caused corrosion and perforation of the inner surface of the oil storage tank bottom plate. Defects fatigue cracks caused by stress, with the accumulation of time, the compressive strength of the API 650 open-top tanks body decreases and corrosion cracks occur.