Locating Column Relief Devices

On the other hand, tray uplift prevention can (and should) be effectively done by alternative means (see Sec. 9.7), and should not be achieved at the expense of the disadvantages of a low placing of the relief device. 

The vapor product system in Fig. 9.3 is one example of a system that favors location C (60, 369). If the relief valve is upstream of the condenser (location A), the air condenser will be inert-blanketed and become completely ineffective during a power failure. A relief valve on the reflux drum (location C) will meiximize condensation. Location C also offers easier access to maintenance and a shorter blowdown line. 

6 Protection against Reiief Vaive Base Plugging 

Fitting a bursting disk upstream of the relief valve is often advo- 

Other techniques sometimes used to prevent plugging at the relief valve base include (98a) using a liquid seal, steam tracing, and heating (from outside). The last two are particularly useful if the plugging can be caused by freezing. The reliability and effectiveness of any specific technique for a specific service must be carefully evaluated. 

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Location of relief valves, bursting disks, and m or vents should be carefully reviewed. Normally, these should be at the top of superatmospheric columns (or in their overhead systems). Conversely, the vacuum-breaking device should normally be at the bottom of the column. This is important for avoiding damage to trays and for achieving the required relief rates. Detailed discussion is in Sec. 9.5. 

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