European Committee for Electrotechnical Standardization

Safety devices required for the safe functioning of equipment with respect to explosion risks
 N EN 50495

Annotation

This European Standard specifies the requirements of electrical safety devices, which are used to avoid potential ignition sources of equipment in explosive atmospheres.

This also includes safety devices, which are operated outside areas with explosive atmospheres, to guarantee the safe function of equipment with respect to explosion hazards.

NOTE 1 This European Standard can also be used to design and assess safety devices for protective systems.

Electrical equipment, which is intended for use in explosive atmospheres, may rely on the correct operation of safety devices which for example maintain certain characteristics of the equipment within acceptable limits. Examples of such safety devices are motor protection devices (to limit temperature rise during stall conditions) and controlling devices for pressurisation protection.

By means of control or monitoring devices, sources of ignition can be avoided. Therefore these devices shall execute the appropriate measures in the appropriate reaction time, for example the initiation of an alarm or an automatic shut down.

NOTE 2 Some potential ignition sources might not be controllable by safety devices, e.g. electrostatic discharges, ignition sparks caused by mechanical impact. Also some protection measures might not be controllable by safety devices, e.g. flameproof enclosures.

Safety devices, whose safety function can not adequately be specified under the existing EN 60079 or EN 61241 series of standards, shall additionally be designed according to the requirements of this standard. Generally for complex safety devices appropriate design requirements are not provided in the existing types of protection (see 3.13 for the definition of a complex device).