Standards Development

Scope

This document specifies the general requirements for flap valves used for dust explosion isolation. An explosion isolation flap valve is a protective system, which prevents a dust explosion from propagating via connecting pipes or ducts into other parts of apparatus or plant areas.

NOTE 1 An explosion isolation flap valve is also used as a process equipment (back pressure flap valve), to prevent the exposure of workers to dust cloud at workplaces when the flow is stopped in normal operation or by a process shut down. This function which is not related to explosion isolation is not in the scope of this European Standard.

An explosion isolation flap valve can only stop the propagation of a dust explosion when it propagates against the direction of the normal process flow. It does not stop explosions running in the normal process flow direction. This European Standard specifies methods for evaluating the efficacy of explosion isolation flap valves.

This document is applicable only to explosion isolation flap valves which are intended to avoid explosion propagation from a vessel, into other parts of the installation via connecting pipes or ducts. The standard covers isolation of such vessels that are protected by explosion venting (including flameless venting), explosion suppression or explosion-resistant design.

NOTE 2 This document is only applicable to cases where the explosion starts in a vessel and not in pipes or ducting.

Explosion isolation flap valves are not designed to prevent the transmission of fire or burning powder transported by the normal process flow.

Very weak explosions can still lead to an isolation failure. This residual risk is not covered by this document.

NOTE 3 It is necessary to take this into account in risk assessments.

Explosion isolation flap valves that are kept open by a retention mechanism that prevents valve closure under gravity when there is no process air flow, require a certain explosion over-pressure to overcome the forces of the retention mechanism and to start closure. Such devices do not fall under the scope of this document, but fall under the scope of EN 15089.

This document is only applicable for dust explosions.

This document is not applicable for explosions of materials listed below, or for mixtures containing some of those materials:

a) gases, vapours and hybrid mixtures;

b) chemically unstable substances;

c) explosive substances;

d) pyrotechnic substances.