Metal Rupture Disks are made from very thin materials that have been carefully selected by actual trial and not by calculation. As a result, the strength is exactly what is required and there is no ‘corrosion allowance’ or other safety factors. The service life of the disk depends on many factors which could cause the disk to burst prematurely, some of these being:

Operating Pressure

All rupture disks have what is called an Operating Ratio (specified OR percentage is used to calculate the maximum operating pressure; see disk data sheets for more information). This varies for different disk designs and can be from 50% – 95%. To illustrate this, if the rupture disk has a 90% operating ratio and is rated at 145 psig (10 barg) with a +/- 10 % burst tolerance, to achieve a good service life the rupture disk should not be subjected to a system operating pressure in excess of 90% of the rupture disk’s minimum rated burst pressure. So in this case, it would be 145 psig (10 barg) less 10% burst tolerance multiplied by 90% = 117.5 psig (8.1 barg). If the rupture disk encounters pressures above this, it could stress the rupture disk membrane causing fatigue of the metal or graphite and could result in premature failure.

A rupture disk can become fatigued in pulsating type conditions. Some rupture disk designs are better suited than others for this type of duty – for example Reverse Acting (Reverse Buckling) type rupture disks.

Temperature

The temperature can affect the burst pressure of the rupture disk. For example, if the rupture disk is ordered at a particular pressure and temperature any temperature variance in the process conditions will affect the burst pressure of the rupture disk. It will be progressively weaker as the temperature rises and progressively stronger as the temperature decreases. The effect will vary depending on the rupture disk design and material of construction.

Pressure Cycling

Pressure cycling refers to the repeated rise and fall of pressure within a system, which can have a significant impact on the service life of a rupture disk. This cycling includes both gradual changes in pressure as well as more rapid fluctuations, commonly referred to as pulsating. While pulsating is a form of pressure cycling characterized by high-frequency, low-amplitude variations, pressure cycling as a whole encompasses a broader range of pressure changes. Both forms of pressure cycling can lead to material fatigue in the rupture disk, potentially reducing its burst pressure over time and increasing the risk of premature activation or failure. Some rupture disk designs are better suited than others for this type of duty – for example Reverse Acting (Reverse Buckling) type rupture disks. Understanding and managing the specific type of pressure cycling, including pulsating, is crucial for maintaining the rupture disk’s performance and extending its service life.

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