Vessel heads 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. 

The MAWP for any vessel part is the maximum internal or external pressure, including any static head, together with the effect of any combination of loadings listed in UG-22 which are likely to occur, exclusive of corrosion allowance at the designated coincident operating temperature. The MAWP for the vessel will be governed by the MAWP of the weakest part. 

Maximum Allowable Working Pressure (MAWP) The maximum gage pressure permissible at the top of a completed vessel in its normal operating position in the hot and corroded condition. The pressure is the least of the values for the internal or external pressure to be determined by the Code mles for any of the pressure boundary parts, considering static head, using nominal thicknesses. 

The Pressurizer is a pressure vessel of slim cylindrical shape with hemispherical heads. The pressure control function is carried out in the upper part, which is externally insulated to limit heat losses from the steam and hot water plena. 

Vessel is final scrubber in a flare, relief, or vent system, i.s designed to withstand maximum built-up back-pressure, and is equipped with a rupture disk or safety head (PSE) to bypass any internal or external obstructions, such as mist extractors back-pressure valves, or flame arrestors. 

The IPL must be capable of detecting and preventing or mitigating the consequences of specified, potentially hazardous event(s), such as a runaway reaction, loss of containment, or an explosion. A single IPL may address the multiple causes for that hazardous event and, therefore, multiple event scenarios may initiate action of one IPL. For example, high pressure in a vessel could be caused by either a pump dead-heading into it or by external fire. For both cases the vessel s pressure safety relief valve counts as a valid IPL. 

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