Maximum allowable accumulated pressure

Maximum Allowable Accumulated Pressure for Multiple-valve Installation (Other Than Fire Exposure)... 

MAXIMUM ALLOWABLE ACCUMULATED PRESSURE <FIRE EXPOSURE ONLY)... 

MAXIMUM ALLOWABLE ACCUMULATED PRESSURE — FOR single-valve installation... 

Maximum allowable accumulated pressure (fire exposure only)... 

Maximum allowable accumulated pressure for Installation of a multiple rupture disk device (other than fire exposure)... 

For this condition, the API-RP-521 Code [13] (Figure 7-7A) shows an allowable 16% maximum accumulation relieving pressure above the set pressure. For external fire conditions on a vessel, the maximum allowable accumulation pressure is 21% above the set pressure [13] for both single or multiple relieving devices (Figure 7-7A). 

Maximum allowable accumulated pressure The sum of the MAWP and the allowable accumulation. 

The pressure drop allowed through the inlet and discharge lines is unlimited as long as the capacity of the line is adequate for the relief requirements. That is, at the required flow rate the vessel pressure must not exceed the maximum allowable accumulated pressure. In sizing a safety disc, it is usually assumed that the entrance loss at the nozzle is the governing restriction insofar as capacity is concerned. Thus the effective orifice area is considerably larger than the effective orifice area of a safety valve of the same pipe size. Consequently,... 

This is the sum of MAWP and maximum accumulation. The following guidelines are used to set the maximum allowable accumulated pressure ... 

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