Calculation of Relieving Areas Rupture Disks for Non-Explosive Service

Calculation of Relieving Areas Rupture Disks for Non-Explosive Service 

The vessel nozzle diameter (inside) or net free area for relief of vapors through a rupture disk for the usual process applications is calculated in the same manner as for a safety relief valve, except that the nozzle coefficient is 0.62 for vapors and liquids. Most applications in this category are derived from predictable situations where the flow rates, pressures and temperatures can be established with a reasonable degree of certainty. 

For rupture disk sizing the downstream pressure is assumed to reach the critical flow pressure although the dow n stream pressure initially may be much lower. Under these conditions the flow through the orifice that the disk produces on rupture is considered to be at critical flow. The assumptions of critical pressure do not apply 

Applied Process Design for Chemical and Petrochemical Plants 

The coefficient of discharge, KD, is the actual flow divided by the theoretical flow and must be determined by tests for each type or style and size of rupture disk as well as pressure-relieving valve. For rupture disks, the minimum net flow area is the calculated net area after a complete burst of the disk, making allowance for any structural members that could reduce the net flow area of the disk. For sizing, the net flow area must not exceed the nominal pipe size area of the rupture disk assembly [1], 

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