Explosion Venting (with either Explosion Vents/Bursting Discs or Explosion Doors) is a cost effective method to mitigate the consequences gas or dust explosions. Explosion vents are designed for venting of deflagrations. This is the rapid burning of a mixture of dust or gas or hybrid within an oxygen-rich atmosphere (typically air) leading to a very rapid pressure rise at subsonic speeds inside the vessel or system. The developed flame and pressure front can be discharged through the explosion vent opening and if the vent area design is done correctly (ie according to EN1449:2012 or NFPA68:2013) will reduce the explosion peek overpressure inside the equipment from a dangerous Pmax level (if the equipment is not designed to resist Pmax) to Pred (below the strength of the equipment)
Unless this pressure and flame is relieved the vessel or system can be ruptured, causing the products of the rapid combustion to be released uncontrollably causing widespread damage to plant and personnel. Explosion venting must be to a safe area where the vented flame width and length are calculated and taken into account or alteratively, flameless venting using IndoorVents may be considered.
The calculated explosion vent area is dependent on the geometry of the equipment being protected , the product explosion characteristics of the product Kst and Pmax as well as the pressure shock resistant strength related to Pred. The required effective vent area for isolated enclosures can be calculated using the most recent editions of internationally recognised NFPA 68:2013 and EN 14491:2012 (Adopted formulas from VDI3673) standards, depending on your requirements. The “Australian Code of Practice for Handling Combustible Dusts” AS/NZS :4745 requires the use of certified explosion vents and allows you the choice of which of the above standards and methods to use.
Explosion vents are categorised for “single use” applications – such as Bursting Discs or “multiple use” applications such as automatically reclosing Explosion Doors . There are not many explosion doors on the market that can guarantee high effective vent areas as well as multiple use because the forces of the explosion need to be resisted and absorbed by the explosion door. CMC Technologies does however have this unique product available through its distribution agreement with Thorwesten Vent. These explosion doors can be combined with emergency inerting systems to prevent secondary explosions so that they are activated after an explosion and after the explosion door closes.
Where the risk assessment allows for single use explosion vents (bursting discs) then CMC Technologies through its distribution agreement with Brilex – provides very high quality, cost effective explosion vents. Brilex explosion vents can be used for applications with vent ducts or flameless vents for protecting vessels that are located indoors. Brilex explosion vents can be used in combination with active and passive explosion isolation measures that are essential to comply with current standards.