Glossary // Type of Protection

Type of Protection

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

Ex CodeDescriptionStandardLocationUse
Flame proofdEquipment 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 60079-1Zone 1 if gas group & temp. class correctMotors, lighting, junction boxes, electronics
Increased SafetyeEquipment is very robust and components are made to a high qualityIEC/EN 60079-7Zone 2 or Zone 1Motors, lighting, junction boxes
Oil FilledoEquipment components are completely submerged in oilIEC/EN 60079-6Zone 2 or Zone 1switchgear
Sand/Powder/Quartz FilledqEquipment components are completely covered with a layer of Sand, powder or quartzIEC/EN 60079-5Zone 2 or Zone 1Electronics, telephones, chokes
EncapsulatedmEquipment components of the equipment are usually encased in a resin type materialIEC/EN 60079-18Zone 1 (Ex mb) or Zone 0 (Ex ma)Electronics (no heat)
Pressurised/purgedpEquipment 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 60079-2Zone 1 (px or py), or zone 2 (pz)Analysers, motors, control boxes, computers
Intrinsically safeiAny 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)
IEC/EN 60079-25
IEC/EN 60079-11
IEC/EN60079-27
‘ia’: Zone 0 &
‘ib’: Zone 1
‘ic: zone 2
Instrumentation, measurement, control
Non IncendivenEquipment 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)
IEC/EN 60079-15
IEC/EN 60079-27
Zone 2Motors, lighting, junction boxes, electronic equipment
Special ProtectionsThis 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-sIEC/EN 60079-33Zone 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.

Multiple protection

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’.