Welding saddle supports

Zick, L. P., Stresses in Large Horizontal Cylindrical Pressure Vessels on Two Saddle Supports, Welding Journal Research Supplement, 1951. 

Zick, L. P. (1951) Welding J. Research Supplement 30, 435. Stresses in large horizontal cylindrical pressure vessels on two saddle supports. 

Storage tanks and pipelines should never be placed directly on concrete supporting to minimize corrosion, as the narrow gap between the pipe and concrete support would lead to severe corrosion of the bottom side of the tank. To prolong the service life of the tank, a metal pad made from the same metal as the tank must be welded around the tank and placed on metallic saddle supported on a concrete structure. The tank after welding with the metal pad maybe placed directly on the concrete support, depending on the period of service. 

Stiffeners should never be located over circumferential weld seams. If properly spaced they may also double as insulation support rings. Vacuum stiffeners, if combined with other stiffening rings, such as cone reinforctunent rings or saddle stiffeners on horizontal vessels, must be designed for the combined condition, not each independently. If at all... 

Zick s analysis is based on the assumption that the supports are rigid and are not connected to the vessel shell. In reality, most vessels have flexible supports which are attached to the vessel, usually by welding. Whatever the reason, and there are a myriad of them, Zick s assumptions may yield an analysis that is not 100% accurate. These results should, however, be viewed more in terms of the performance they have demonstrated in the past 45 years, than in the exact analytical numbers they produce. As a strate, the procedure is succ-essful when utilized properly. There are other issues that also would have an effect on the outcome of the numerical answers such as the relative rigidity of the saddle—from infinitely rigid to flexible. The answers should be viewed in light of the assumptions as well as the necessity for. 5-digit accuraty. 

Horizontal tanks are supported by steel saddles mounted on concrete piers. Top plates of the saddles are welded to the shell of the tank and span at least 120° of the circumference of the tank. 

There are a variety of ways to support the inner vessel within the vacuum jacket. Rods and cables are most widely used however, saddle bands, plastic compression blocks, stacked disks, compression tubes, and welded straps have also been employed. Often springs or washers are installed at the connecting ends of these supports to reduce the thermal conduction. 

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