If this sequence would leave any significant residual stress on the 1st circ sean, it would show itself by this seam exhibiting "positive Banding". IMHO, it is excessivly limiting when used on 'regular' tanks. My personal opinion is that the writers of API-650 intended the erection welding sequence to be "One size fits All". For thick - 1/2-inch, 12mm - tanks, I would follow the API sequence exactly. Meaning the shell is no more than 5/16" thick. It has for me on tanks ranging from 15-ft to 125-ft in diameter, of NORMAL thickness. This last recommendation of mine is in direct contravention to API-650, but is 'usual & customary' for field tank erection in USA. At this point, most of the shrinkage, and thus the potential stress, is done. With a modicum of skill, the 1st-side weld will be 1-pass and achieve approximately Full-Penn of that half of the double-welded full-joint. Reason is that 'Tankies' typically use a large E-6010 electrode to weld shell seams with. If big tacks are needed for stability, like erecting in the wind, they must be removed prior to starting the 'production welding' of the S-1 to S-2 root.ģ) Assuming a 'normal' thickness of 5/16-inch or less for S-2, one side of the S-2 verts must be welded prior to 'production' welding of the S-1 to S-2 circumferential seam. Nor should any tacks over about 1-inche long be allowed on this circ joint. Thus nobody much works to the inordinately strict recommendations, nor do they demand a revision to allow industry standard practices to be used.ġ) Completing the outer ring of floor plates, or annular ring, must be done prior to welding the 1st Shell Course "tub ring" to the floor.Ģ) The 1st course "tub ring" vert's must be fully complete prior to welding the 1st circ weld - Shell-1 to Shell-2. API-650 tanks are *very* flexible, and 650 is a "Standard", not a "Code".
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