Vessel heads under external pressure

The head for the circulating pump and the slurry pumps can be calculated from information in the Chemical Engineers Handbook (Perry 1973). The mechanical design should be in accordance with the information in the american Society of Mechanical Engineers Code for Unfired Pressure Vessels, Section VIII, for the current year. There is a section devoted to the design of vessels under external pressure. 

A module just described is a fixed module in which the membrane elements are stationary. A radical departure from the conventional mode of R.O. systems operations is the rotary system wherein externally wound membrane elements clustered around a central shaft are rotated in a stationary pressure vessel filled with pressurized feed stock. Here the separated permeate is replaced by an equivalent volume of fresh feed stock under a constant head. The basic rotary concept is depicted in Fig. 3. 

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