A rupture disc, also known as a pressure safety disc or bursting disc, is a non-reclosing pressure relief device that breaks when exposed to a pressure higher than dimensioned to. They are used in pressure systems as isolation of safety valves. Or they are used as an independent protection unit that breaks by an unintended increase in the pressure and in that way protect the other components of the application. Bursting discs are a non-reusable pressure release unit.
A rupture disc is a type of sacrificial part because it has a one-time-use membrane that fails at a predetermined differential pressure, either positive or vacuum. The membrane is usually made out of metal but nearly any material (or different materials in layers) can be used to suit a particular application.
How does a bursting disc work?
Rupture discs provide instant response (within milliseconds) to an increase or decrease in system pressure. Once the disc has ruptured it will not reseal. Major advantages of the application of rupture discs compared to using pressure relief valves include leak-tightness and costs.
If the pressure increases and the safety valve fails to operate (or cannot relieve enough pressure fast enough) the rupture disc will burst. Rupture discs are very often used in combination with safety relief valves, isolating the valves from the process. In that way you are saving on valve maintenance and creating a leak-tight pressure relief solution.
The dome is weakened by precision cut scores in the material during manufacturing, often using laser technology. So-called forward acting rupture discs have the overpressure on the concave side (inside) of the dome. Rupture of the membrane takes place when tensile forces exceed the ultimate tensile stress of the membrane material. Reverse acting rupture discs have the overpressure on the convex side (outside) of the dome. Stresses cause the dome to buckle after which it fails. Correct installation is essential. If installed upside down, the reliability of the overpressure safety device is compromised. Bursting discs can be fragile and has to be handled carefully during installation and transport. Often bursting discs will be mounted in a disc holder.