Page 221 - Chemical engineering design
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                                                        CHEMICAL ENGINEERING












                                                               (c)
























                                            (d)                                    (e)
                                          Figure 5.5.  (c) Ball valve (d) Globe valve (e) Diaphragm valve

                             The main types of valves used are:
                                Gate        Figure 5.5a
                                Plug        Figure 5.5b
                                Ball        Figure 5.5c
                                Globe       Figure 5.5d
                                Diaphragm   Figure 5.5e
                                Butterfly    Figure 5.5f
                           A valve selected for shut-off purposes should give a positive seal in the closed position and
                           minimum resistance to flow when open. Gate, plug and ball valves are most frequently
                           used for this purpose. The selection of values is discussed by Merrick (1986) (1990),
                           Smith and Vivian (1995) and Smith and Zappe (2003).
                             If flow control is required, the valve should be capable of giving smooth control over the
                           full range of flow, from fully open to closed. Globe valves are normally used, though the
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