I am looking at a design for a 50 foot diameter sewage digester cover (roof). It has 20ea 3x4 inch arched tubes 23-foot +/- long extending inward and upward from a 50-foot diameter tension ring and ending at a 2-foot diameter compression ring. The rings are either 3x3 tubes or 3-inch pipe. Welded to the underside of the radial beams (tubes) are 20ea pie shaped plates. This is a standard design and thousands have been made of mild steel/structural steel with a painted finish. As all of the shapes are available in 304SS, I am thinking of specifying SS for all members/plates. Could anyone hazard a guess as to the cost multiplier?
This project needs to be completed in a 90 day window (college campus) and is in an environmentally sensitive area. I am thinking that the additional cost could be justified by the elimination of blasting and painting on-site. Also, the steel plates need to be welded continuously at the bottom of the lap where SS plates need only to be welded at the top lap. I am thinking that elimination of the overhead weld would save some money. Thanks in advance !! Steve
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