Rupture disc Wiki
What you should know.
Rupture discs are, next to safety valves, the most commonly used pressure protection devices in industrial plants. They protect vessels and pipelines from deformation and other damage. The main objective is to optimally protect and, at the same time, minimise the downtime of the system.
The advantages of bursting discs
- Immediate response – nothing responds faster than a rupture disc. Unwanted overpressure and vacuum are relieved in milliseconds.
- Complete release of the relief area – maximum opening cross-section for quick and safe pressure relief.
- Leakproof – prevents process media from escaping during normal operation, reducing the costs and impact associated with such losses.
- Economical solution – significant cost savings compared to other pressure protections.
Plant element to be protected, process medium, operating pressure, vacuum, pulsation, bursting pressure, bursting temperature, required nominal width, mass flow to be discharged
Design of rupture discs
For example, plastic film is sandwiched between metal layers for triple section rupture discs, in order to reach even the lowest burst pressures. The materials used range from various stainless steels to higher quality materials such as Inconel, Hastelloy, or Tantalum, and all the way up to coatings or plastic liners such as PTFE or FEP.
Rupture discs are either installed directly between flanges, or inserted into a corresponding rupture disc holder, which is then mounted between flanges. In some cases the rupture disc is already soldered or welded into the holder by the manufacturer. These holders are then fitted with the necessary connections, e.g. thread (NPT, G or customer-specific thread, connection systems (e.g. VCR) or various flanges (ISO-K, KF, ISO-F, CF)).
A large number of rupture discs and other safety devices are installed in industrial plants. A broad range of signalling options are available, to immediately receive information about the triggering (opening) of a rupture disc. The easiest way to achieve this is with a tripping wire which is fixed on the rupture disc, and is connected to the process control system. With the opening of the bursting disc, the wire breaks, the circuit is interrupted and the triggering of the rupture disc is communicated to the process control system. If there are particularly high demands for leak-tightness, non-invasive signalling methods (e.g. magnetic proximity sensor NIMU) are used.
Key Technical figures of rupture discs
The diameter of the rupture discs is specified matching the diameter of pipes or flanges as the nominal pipe size DN (Diamètre nominal) in the European context, or as NPS (Nominal Pipe Size) in other regions.
Burst pressure (also referred to as set pressure)
This is the pressure at which the rupture disc opens. It is selected in such a manner, that the rupture disc opens before there is any system damage. The burst pressure is above the prevailing pressure during normal operation (also referred to as working pressure or process pressure) and below the pressure resistance (MAWP) of the respective system. Example: At an operating pressure (working pressure) of 1 bar and a 2 bar pressure resistance (MAWP) of the system, the burst pressure is at max. 2 bar or lower, depending on the type of rupture disc.
Defines the tolerance around the defined burst pressure, which opens the rupture disc. If a rupture disc type has a burst tolerance of +/-10%, and the defined burst pressure is 1 bar, the rupture disc will open between 900 mbar and 1.1 bar. Depending on the valid or applied rules and regulations the burst tolerance is at +/-10% (e.g. Pressure Equipment Directive 2014/68/EC), or +/-5% (e.g. ASME section VIII, Division 1), or +/-3% for very high burst pressures. Other burst tolerances are possible depending on the requirements of the respective process.
What should I be aware of when selecting a rupture disc?
These parameters include:
The plant components to be protected
Nominal size required
Mass flow to be discharged
Type classification of rupture discs
The dome of the rupture disc faces the process and enables very high operating pressures (see also: key technical information on rupture discs) and a very high operating pressure ratio.
Forward acting rupture discs
The dome of the rupture discs is faced away from the process.
Compact rupture discs
These are usually very small nominal pipe size of reverse-acting or forward acting rupture discs which are often adhesively bonded or soldered to the housing / holder.