This paper outlines the basic understanding of the operability of rupture disks, the concept of Manufacturing Design Range, ASME-dictated tolerance, and how the owner of rupture disks may inadvertently and surreptitiously slip into code violation due to misinterpretation of technicalities and testing lot-creeps.
In a subsequent paper, the plethora of mechanical designs of rupture disks and information necessary to complete the specification sheet will be presented.
A rupture disk is a non-reclosing, self-sacrificial device that protects equipment from overpressure by bursting at the specified burst pressure marked on the disk within code-allowed tolerance. It can be used as the primary protective device or in a combination with a pressure relief valve (PRV) when it is placed before the pressure relief valve to protect the PRV from exposure to harsh process environment and minimize fugitive emission, or as a supplementary device on a parallel nozzle of the protected equipment. It can be installed after a PRV to protect the PRV from exposure to a harsh process environment. In such applications, its burst pressure is lower than what impedes the operation of the associated PRV but higher than the superimposed backpressure in the downstream equipment. Rupture disks, like PRVs, are generally the last line of defense. It should neither be misused as a control device, nor as the only line of defense.
The Rupture Disk is made of two main components:
Figure 1: Components of a rupture disk device (Source: The National Board of Boiler and Pressure Vessel Inspectors website)
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