Heads, vessel design example

FFand correlation, liquid-liquid equilibria, 463,465 Heads, vessel design example, 628... 

Set Pressure - The set pressure (the pressure at whieh the PR valve is designed to open) is speeified in accordance with Code requirements. In most vessel apphcations, the set pressure of at least one PR valve is equal to the design pressure. However, this set pressure is adjusted (up or down) for any effect of static pressure and friction pressure drop that may apply when the valve is installed elsewhere than directly on the vessel. For example, if a PR valve is installed in a non-flowing line above a liquid-filled vessel, the PR valve set pressure would be reduced sufficiently to allow for the liquid static head between the vessel and the valve. 

Process flow diagrams (see Figure 4.1 for an example) are more complex and will show all main flow streams including valves to enhance the understanding of the process, as well as pressures and temperatures on all feed and product lines within aU major vessels and in and out of headers and heat exchangers, and points of pressure and temperature control. Also, information on construction materials, pump capacities, and pressure heads, compressor horsepower, and vessel design pressures and temperatures are shown when necessary for clarity. 

Closures between heads and cylinders, often taking the form of clamps, split rings, or bolts, are also an important consideration in the proper design of the pressure vessel, for it is these components that must hold the vessel head to the cylinder. It is important to recognize the force that is exerted on the closure. For example, in a 1000 psi vessel, a circular head with a diameter of 12 in. will have over 110,0001b of force pushing on it. This force must be evenly divided between bolts or spread out over the clamp or split ring closure. 

Other examples of internals sometimes difficult to clean are coils, dip pipes, instrument probes, agitators, access ports and vessel heads. Nonprocess connections, which are usually dead spaces, can also be troublesome. These connections include pressure and level taps, sample connections, sight glasses, and the like. To avoid cleaning problems, such internals should be evaluated for their influence on the cleaning process during the equipment design phase. 

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