Skirt supports design

Figure 13.23. Typical skirt-support designs (a) Straight skirt (b) Conical skirt...

Design a skirt support for the column specified in Example 13.3. 

The main load carried by the brackets will be the weight of the vessel and contents in addition the bracket must be designed to resist the load due to any bending moment due to wind, or other loads. If the bending moment is likely to be significant skirt supports should be considered in preference to bracket supports. 

The method used to support a vessel will depend on the size, shape, and weight of the vessel the design temperature and pressure the vessel location and arrangement and the internal and external fittings and attachments. Horizontal vessels are usually mounted on two saddle supports see Figure 13.20. Skirt supports are used for tall, vertical columns see Figure 13.21. Brackets, or lugs, are used for all types of vessels ... 

Design and analysis of welded pressure vessel skirt supports. 

The critical line in the skirt support is the weld attaching the vessel to the skirt. This weld, in addition to transmitting the overall weight and overturning moments, must also resist the thermal and bending stresses due to the temperature drop in the skirt. The thinner the sldrt, the better it is able to adjust to temperature variations. A hot box design is... 

The pressurizer is supported by a cylindrical skirt welded to the pressurizer and bolted to the support structure. The skirt is designed to withstand deadweight and normal operating loads as well as the loads due to earthquakes, safety valve actuation, and Branch Line Pipe Breaks. Four keys welded to the upper shell provide additional restraint for earthquake, safety valve actuation, and Branch Line Pipe Break conditions. 

Bp = Allowable bearing pressure, PSI Do = OD of vessel shell, in Dsk = OD of skirt at base plate, in E = Modulus of elastidly, PSI Fc = Allowable compressive stress, PSI f = Load at support points. Lbs fp = Bearing pressure, PSI Ft = Allowable sttess, tension, PSI Fy = Minimum specified yield strength of skirt at design temperature, PSI... 

In order to design a skirt support for mechanical loads alone, consider the vessel deadweight, W, and the bending moment, M, produced by seismic, wind and other mechanical loads. The stress in the skirt is then a combination of axial and bending stresses and is given by... 

Design a skirt support for a pressure vessel with a total vertical load of 720 kN, and an overturning moment of 2050 kNm. The bolt circle diameter of the support may be assumed to be 4.5 m. Assume a thickness of 10 mm for the support skirt and the mean diameter of the support as 4.25 m. 

Integral pipe attachments are welded directly to the pipe and are usually of special design. They are used in high temperature services, with moderate or severe loads, and in conjunction with supports, braces, and restraints where rigidity with the pipe shell is desired. Integral attachments may be grouped into five types ears, lugs, shoes, cylindrical tmnnions, and skirts (see Fig. 8). 

Containment boom — A floating mechanical structure that extends above and below the water surface and is designed to stop or divert the spread or movement of an oil slick on the water. Booms consist of floats, a freeboard member to prevent oil from flowing over the top of the boom, a skirt below the water surface to prevent oil from being swept under the boom, and one or more tension members to support the entire boom. Booms are an integral part of virtually all cleanup programs after oil spills on water. (See also Boom failure, Critical velocity, Freeboard.)... 

One of the most common methods of supporting vertical pressure vessels is by means of a rolled cylindrical or conical shell called a skirt. The skirt can be either lap-, fillet-, or butt-welded directly to the vessel. This method of support is attractive from the designer s standpoint because it minimizes the local stresses at the point of attachment, and the direct load is uniformly distributed over the entire circumference. The use of conical skirts is more expensive from a fabrication standpoint, and unnecessary for most design situations. 

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