Pressure-vessel design, discussion

The use of standards in design is illustrated in the discussion of the pressure vessel design standards (codes) in Chapter 13. 

Gases are stored at high pressures where this is a process requirement and to reduce the storage volume. For some gases the volume can be further reduced by liquefying the gas by pressure or refrigeration. Cylindrical and spherical vessels (Horton spheres) are used. The design of pressure vessels is discussed in Chapter 13. 

When the internal design pressure of a container exceeds 15 psig (101.3 kPa), it is called a pressure vessel. The ASME Boiler and Pressure Vessel Code is one of the primary standards used throughout the world to ensure safe storage vessels. Various substances, such as ammonia (qv) and many hydrocarbons (qv), are frequently stored in spherically shaped vessels that are often referred to as tanks. Most often the design pressure is 15 psig (101.3 kPa) or above. These are really spherical pressure vessels and fall under the rules of the ASME Boiler and Pressure Vessel Code. Discussion of pressure vessels are available (5,6) these are not covered in detail herein. 

We will now consider the special problems in tall tower design which are not described in the ASME Code for Unfired Pressure Vessels. As discussed previously, circumferential stresses control the design of cylindrical vessels if external loads are of small magnitude. In tall vertical vessels, four major factors (wind load, seismic loads, dead weight and vibration) may contribute to axial stresses — in addition to axial stress produced by the operating pressure or vacuum of the vessel. 

Within the context of pressure vessel design codes, the comparison of the allowable strength of the material is always done with respect to the stress intensities. This puts the comparison in terms of the appropriate failure theory either the maximum shear stress theory (Tresca criterion) or the maximum distortion energy theory (von Mises criterion). These failure theories have been discussed in some detail in Chapter 3. 

Portable tanks for regulated commodities in marine transportation must be designed and Built under Coast Guard regulations (see discussion under Pressure Vessels ). 

This discussion of pressure vessels is intended as an overview of the codes most frequently used for the design and construction of pressure vessels. Cnemical engineers who design or specify pressure vessels should determine the federal and local laws relevant to the problem and then refer to the most recent issue of the pertinent code or standard before proceeding. Laws, codes, and standards are frequently changed. 

Pressure Vessel Code as it existed in the past (and will continue). Division 2 was brought out as a means of permitting higher design stresses while ensuring at least as great a degree of safety as in Division I. These two divisions plus Secs. HI and X will be discussed briefly here. They refer to Secs. II and IX. 

We shall now examine material selection for a pressure vessel able to contain a gas at pressure p, first minimising the weight, and then the cost. We shall seek a design that will not fail by plastic collapse (i.e. general yield). But we must be cautious structures can also fail by fast fracture, by fatigue, and by corrosion superimposed on these other modes of failure. We shall discuss these in Chapters 13, 15 and 23. Here we shall assume that plastic collapse is our only problem. 

It is recommended that all pressure vessels and atmospheric vessels be designed, fabricated, tested, and code stamped according to the most applicable code as ASME or API, regardless of service application (nuclear is excluded from any discussion in these chapters) ... 

For a new installation, establish pressure vessel normal maximum operating pressure, and temperature, and then the safe increment above this for vessel design conditions and determine the maximum allowable working pressure (MAWP) of the new vessel. (Have qualified fabricator or designer establish this. See pretious discussion of topic.)... 

In operation the tube sheets are subjected to the differential pressure between shell and tube sides. The design of tube sheets as pressure-vessel components is covered by BS 5500 and is discussed in Chapter 13. Design formulae for calculating tube sheet thicknesses are also given in the TEMA standards. 

This chapter covers those aspects of the mechanical design of chemical plant that are of particular interest to chemical engineers. The main topic considered is the design of pressure vessels. The design of storage tanks, centrifuges and heat-exchanger tube sheets are also discussed briefly. 

This discussion of pressure vessels is intended as an overview of the codes most frequently used for the design and construction of pressure... 

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