Friday, August 20, 2010
Electric actuators are used in applications where potentially explosive atmospheres may occur. This includes among others refineries, pipelines, oil and gas exploration or even mining. In case potentially explosive gas-air-mixtures or gas-dust-mixtures occur, the actuator may not act as ignition source. Basically, hot surfaces on the actuator as well as ignition sparks created by the actuator have to be avoided. This can be achieved by a flameproof enclosure, for example; i.e. the housing is designed as to prevent ignition sparks from leaving the housing even in case of an explosion inside.
Actuators designed for these applications, being explosion-proof devices, have to be qualified by a test authority (notified body). There is no such thing as a worldwide uniform standard: depending on the country where the actuators are used, different directives and regulations have to be observed. Within the European Union, ATEX 94/9/EC applies, in US, the NEC (approval by FM) or the CEC in Canada (approval by the CSA). Explosion-proof actuators have to meet the design requirements of these directives and regulations.