Vessel supports saddles

Figure 7 shows nozzle locations and support arrangements for a typical horizontal vessel (7). The saddles used for support are sustained by concrete pedestals or steel stmctures. Sufficient clearance between the bottom nozzles and the support saddles needs to be provided for access to the nozzle flange bolts. The manway can be located on the end head of the vessel, the topside of the vessel, or the side of the vessel. The preference is for an end manway wherever possible for accessibiHty, except when it is limited by the level gauges and controls that are commonly mounted off the heads. 

Fig. 7. Vessel support and arrangement where d = nozzle diameter, D = vessel diameter, and L = length. Saddles can be straight or tapered. Single supports can be used for small dmms. Combining dmms saves the number of necessary supports (7).

Figure 13.22. Horizontal cylindrical vessel on saddle supports...

A vessel supported on two saddles can be considered as a simply supported beam, with an essentially uniform load, and the distribution of longitudinal axial bending moment will be as shown in Figure 13.22. Maxima occur at the supports and at mid-span. The... 

Figure 18.14. Methods of supporting vessels, (a) Saddle supports for horizontal vessels, usually of concrete, (b) Bracket or lug supports resting on legs, for either vertical or horizontal vessels, (c) Bracket or lug supports resting on steel structures, for either vertical or horizontal vessels, (d) Straight skirt support for towers and other tall vessels the bearing plate is bolted to the foundation, (e) Flared skirt for towers and other tall vessels, used when the required number of bolts is such that the bolt spacing becomes less than the desirable 2 ft.

A vessel supported on two saddles can be considered as a simply supported beam, with an essentially uniform load, and the distribution of longitudinal axial bending moment will be as shown in Figure 13.22. Maxima occur at the supports and at mid-span. The theoretical optimum position of the supports to give the least maximum bending moment will be the position at which the maxima at the supports and at mid-span are equal in magnitude. For a uniformly loaded beam the position will be at 21 per cent of the span, in from each end. The saddle supports for a vessel will usually be located nearer the ends than this value, to make use of the stiffening effect of the ends. 

For horizontal vessels with saddle supports, from the disposition of deadweight load (see Section 13.9.1). 

In addition to the longitudinal bending stress, a vessel supported on saddles will be subjected to tangential shear stresses, which transfer the load from the unsupported sections of the vessel to the supports, and to circumferential bending stresses. All these stresses need to be considered in the design of large, thin-walled... 

A methodology for the determination of the stresses in the shell and heads of a horizontal vessel supported on saddles was first published in 1951 by L. P. Zick. This effort was a continuation of others work, started as early as the 1930s. This procedure has been used, with certain refinements since that time, and is often called Zick s analysis, or the stresses are referred to as Zick s stresses. 

Figure 3-42. Typical dimensions for a horizontal vessel supported on two saddles.

Horizontal cylindrical vessels, supported by two or more saddles connected to a foundation platform. In this category many pressurized storage tanks and shell-and-... 

A full length concrete pad may be used as support for tanks and vessels without saddles or anchorage. In this case the taiik should never be placed directly on the concrete pad. At least 6 in and preferably... 

DESIGN OF HORIZONTAL VESSELS WITH SADDLE SUPPORTS... 

Design of Horizontoi Vessels with Saddle Supports... 

Horizontal vessels supported by two saddles (Fig, 12. le) act as simply supported beams. For vessels with dished heads (Fig, 12,16o) the equivalent beam length is taken as L + AH 3 where L is the tangent-to-tangent length of the vessel and... 

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

Small vertical vessels may be supported by angle support legs, as shown in Figure 12-11. Larger vertical vessels are generally supported by a skirt support, as shown in Figure 12-12. At least two (2) vent holes, 180" apart, should be provided at the uppermost location in the. skirt to prevent the accumulation of gas, which may create explosive conditions. Horizontal vessels are generally supported by a pair of saddle type supports. 

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