Explosionsskydd

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.

This document specifies methods for the identification and assessment of hazardous situations leading to explosion and the design and construction measures appropriate for the required safety. This is achieved by: — risk assessment; — risk reduction. The safety of equipment, protective systems and components can be achieved by eliminating hazards and/or limiting the risk, i.e. by steps (figure below from ISO EN 12100): a) appropriate design (without using safeguarding) – Step 1; b) safeguarding – Step 2; c) information for use – Step 3; d) any other preventive measures. In this standard the measures in accordance with a) (prevention) and b) (protection) against explosions are dealt with in Clause 6. The measures according to c) against explosions are dealt with in Clause 7. Measures in accordance with d) are not specified in this standard. Refer to EN ISO 12100:2010 for complementary preventive and protective measures Inherently safe design measures are the first and most important step in the risk reduction process. This is because protective measures inherent to the characteristics of the product or system are likely to remain effective, whereas experience has shown that even well-designed guards and protective devices can fail or be violated, and information for use might not be followed. Guards and protective devices shall be used whenever an inherently safe design measure does not reasonably make it possible either to remove hazards or to sufficiently reduce risks. Complementary protective measures involving additional equipment (e.g. emergency stop equipment) might have to be implemented. The end user has a role to play in the risk reduction procedure by complying with the information provided by the designer/supplier. However, information for use shall not be a substitute for the correct application of inherently safe design measures, guards or complementary protective measures. The preventive and protective measures described in this document will not provide the required level of safety unless the equipment, protective systems and components are operated within their intended use and are installed and maintained according to the relevant codes of practice or requirements. This document specifies general design and construction methods to help designers and manufacturers in achieving explosion safety in the design of equipment, protective systems and components. This document is applicable to any equipment, protective systems and components intended to be used in potentially explosive atmospheres, under atmospheric conditions. These atmospheres can arise from flammable/combustible substances processed, used or released by the equipment, protective systems and components or from materials in the vicinity of the equipment, protective systems and components and/or from the materials of construction of the equipment, protective systems and components. This document is applicable to equipment, protective systems and components at all stages of its use. This document is only applicable to equipment group II which is intended for use in other places than underground parts of mines and those parts of surface installations of such mines endangered by firedamp and/or combustible dust.