How does a bursting disc work?
We divide up our range of bursting discs into three basic types: Rupture discs, composite bursting discs and reverse buckling bursting discs.
The rupture disc is the simplest type of bursting discs. In this case, a foil, which can be smooth or provided with a predetermined breaking point (scored), is loaded with tensile stress by means of pressure. On reaching the tensile strength the foil ruptures. This type of bursting disc is well suited for the large-scale production and is frequently used for smallest bursting discs and higher pressures. Rupture discs can be easily installed, e.g. by welding. They are ideal for use at high temperatures. In order to reduce the burst pressure and to achieve a non-fragmenting, defined opening behaviour, rupture discs can be scored.
Composite bursting discs are named as such because of the various layers of different materials they are made of, for instance laser-slotted metal foils, which determine the pressure and the opening behaviour, and an internal sealing foil, usually made of PTFE. The burst pressure can be reduced a great deal by means of the net flow area, for example in the case of DN 150 right down to 25 mbar. However, the temperature range in which composite bursting discs can be used is limited to a maximum of 200°C (PTFE-diaphragm) or 260°C (PFA-foil) by the internal sealing foil. The use of composite bursting discs is very common in the chemical industry and the tank construction and plant engineering.
Reverse buckling bursting discs use a different principle than rupture discs and composite bursting discs do. For they are domed against the direction of pressure, compressive stress builds up inside, similar to a vault. On reaching the burst pressure the structure breaks down and the disc buckles. The energy released during this process is used to let the bursting disc open at a predetermined breaking point. The advantages of reverse buckling bursting discs are their excellent resistance to alternating loads and their independence from temperature. Then again it makes high demands on the installation environment and needs an expanding medium (in most cases a gaseous medium) in order to work properly.