Explosive dust extraction systems

Astra produces suction systems for potentially explosive dust that, if not properly treated, could cause serious accidents. These are the main types:

• ATEX bag filters
• ATEX cartridge filters

For the system’s design, it is necessary to define the characteristics of the filtered dust by establishing the kst (bar m/s) and the Pmax (bar); it is then essential to understand whether the filter must be protected against any explosion or whether preventive measures such as earthing, antistatic sleeves, or a suitable fan for the ATEX classified area will be sufficient.

If preventive measures are insufficient, the filter must be designed with special precautions to handle any explosion without damaging people or property. The main components can be:

• Vent membranes whose dimensioning must comply with EN 14491 must also be certified as a protection system per EN 14797.
• The filter must have a calculated structural resistance such as to withstand a possible explosion by venting it outside through the membrane; the construction specifications must comply with EN 14460 and EN13237 standards;
• a decoupling system consisting of a non-return damper, commonly called FLAP, capable of protecting the suction duct and therefore preventing any explosion from affecting the production department; this damper will be positioned on the inlet pipe to the filter and will be certified as a protection system according to EN16447:2014;
• a filter discharge rotary cell that must be flame-proof to prevent the explosion from passing through it; this valve is certified, in addition to being a suitable component to be installed in an ATEX classified area, also as a protection system per EN15089

Evaluating the effects of the explosion, even in the presence of a vent membrane, is an often underestimated detail. The area in front of the membrane should be considered a potential danger for the flame and the pressure wave that can escape from it: the standard provides for a space of respect, proportional to the filter’s volume, of tens of metres. For this reason, we have designed filters with the membrane positioned on top.