To ensure safety in a given situation, equipment is placed into protection level categories according to manufacture method andsuitability for different situations. Category 1 is the highest safety level and Category 3 the lowest. Although there are many types of protection, a few are detailed
|Flame proof||d||Equipment construction is such that it can withstand an internal explosion and provide relief of the external pressure via flamegap(s) such as the labyrinth created by threaded fittings or machined flanges. The escaping (hot) gases must sufficiently cool down along the escape path that by the time they reach the outside of the enclosure not to be a source of ignition of the outside, potentially ignitable surroundings.|
Equipment has flameproof gaps (max 0.006″ (150 um) propane/ethylene, 0.004″ (100 um) acetylene/hydrogen)
|IEC/EN 60079-1||Zone 1 if gas group & temp. class correct||Motors, lighting, junction boxes, electronics|
|Increased Safety||e||Equipment is very robust and components are made to a high quality||IEC/EN 60079-7||Zone 2 or Zone 1||Motors, lighting, junction boxes|
|Oil Filled||o||Equipment components are completely submerged in oil||IEC/EN 60079-6||Zone 2 or Zone 1||switchgear|
|Sand/Powder/Quartz Filled||q||Equipment components are completely covered with a layer of Sand, powder or quartz||IEC/EN 60079-5||Zone 2 or Zone 1||Electronics, telephones, chokes|
|Encapsulated||m||Equipment components of the equipment are usually encased in a resin type material||IEC/EN 60079-18||Zone 1 (Ex mb) or Zone 0 (Ex ma)||Electronics (no heat)|
|Pressurised/purged||p||Equipment is pressurised to a positive pressure relative to the surrounding atmosphere with air or an inert gas, thus the surrounding ignitable atmosphere can not come in contact with energized parts of the apparatus. The overpressure is monitored, maintained and controlled.||IEC/EN 60079-2||Zone 1 (px or py), or zone 2 (pz)||Analysers, motors, control boxes, computers|
|Intrinsically safe||i||Any arcs or sparks in this equipment has insufficient energy (heat) to ignite a vapour|
Equipment can be installed in ANY housing provided to IP54.
A ‘Zener Barrier’, opto-isolator or galvanic unit may be used to assist with certification.
A special standard for instrumentation is IEC/EN 60079-27, describing requirements for Fieldbus Intrinsically Safe Concept (FISCO) (zone 0, 1 or 2)
|‘ia’: Zone 0 &|
‘ib’: Zone 1
‘ic: zone 2
|Instrumentation, measurement, control|
|Non Incendive||n||Equipment is non-incendive or non-sparking.|
A special standard for instrumentation is IEC/EN 60079-27, describing requirements for Fieldbus Non-Incendive Concept (FNICO) (zone 2)
|Zone 2||Motors, lighting, junction boxes, electronic equipment|
|Special Protection||s||This method, being by definition special, has no specific rules. In effect it is any method which can be shown to have the required degree of safety in use. Much early equipment having Ex s protection was designed with encapsulation and this has now been incorporated into IEC 60079-18 [Ex m]. Ex s is a coding referenced in IEC 60079-0. The use of EPL and ATEX Category directly is an alternative for “s” marking. The IEC standard EN 60079-33 is made public and is expected to become effective soon, so that the normal Ex certification will also be possible for Ex-s||IEC/EN 60079-33||Zone depending upon Manufacturers Certification.||As its certification states|
The types of protection are subdivided into several sub classes, linked to EPL: ma and mb, px, py and pz, ia, ib and ic. The a subdivisions have the most stringent safety requirements, taking into account more the one independent component faults simultaneously.
Many items of EEx rated equipment will employ more than one method of protection in different components of the apparatus. These would be then labeled with each of the individual methods. For example, a socket outlet labeled EEx’de’ might have a case made to EEx ‘e’ and switches that are made to EEx ‘d’.