“N” type is an explosion-proof type of electrical equipment. This type of electrical equipment cannot ignite the surrounding explosive environment during normal operation and under certain conditions specified by corresponding standards.
Non-sparking type originally only refers to electrical equipment that does not produce sparks or arcs during normal operation, such as AC asynchronous motors.
On this basis, some safety measures are taken, such as fan blades using non-sparking materials, shell protection grade IP44 or IP54, electrical clearance and the creepage distance should be appropriately increased, etc. Later, this kind of explosion protection was expanded to electrical products that generate sparks during normal operation.
Measures such as air sealing, simple ventilation, or energy limitation should be taken according to the situation to achieve a certain level of safety. Due to the expansion of this type of explosion protection, the term “spark-free” has become less clear and is now often referred to as type “n”.
The “n” type explosion-proof method can be divided into five different types (i.e., five different explosion-proof markings)
Ex nA – The equipment does not produce sparks or arcs during normal operation (i.e., formerly known as non-sparking type).
Ex nC – The equipment produces sparks or arcs during normal operation, but employs appropriate design measures to make it a “closed switch device,” “non-ignition component,” “hermetic device,” “sealed device,” or “encapsulated device,” etc.
Ex nL – Uses energy limiting techniques, ensuring that under specified operating conditions, the energy stored in circuits or operational arcs and sparks is insufficient to cause ignition.
Ex nR – Restrictive breathing enclosure, meaning an enclosure designed to limit the ingress of gases, vapors, or mists.
Ex nZ – Pressurized enclosure type “n,” which involves the use of protective gas to fill the enclosure and maintain a pressure higher than the surrounding environment to prevent the formation of an explosive atmosphere inside the enclosure. In practice, this corresponds to the pz type pressurization explosion-proof technology specified in the national standard GB3836.5.
“n” type electrical equipment is specifically designed for use in Zone 2 explosive gas environments and was previously referred to as non-sparking electrical equipment. This type of electrical equipment, under normal operation and certain specified abnormal conditions, cannot ignite the surrounding explosive gas environment.
The “n” type equipment is basically similar to the enhanced safety “e” type equipment, but the structural requirements are more relaxed, as it can only be used where the required Equipment Protection Level (EPL) is Gc. Generally, this means it can only be used in Zone 2, unless a risk assessment indicates otherwise.
Standards
Current constructional standards
- IEC 60079-15: 2010 BS EN 60079-15: 2010
Explosive atmospheres – Parts 15: Equipment protection by type of protection ‘n’
Original standard
- BS 6941: 1988
Electrical equipment for explosive atmospheres with type of protection N
Codes of Practice
IEC 60079-14: 2013 BS EN 60079-14: 2014
Electrical Equipment for explosive gas atmospheres: Part 14 Electrical installations in hazardous areas (other than mines)IEC 60079-17: 2013 BS EN 60079-17: 2014
Electrical Equipment for explosive gas atmospheres: Part 17 Inspection and Maintenance of electrical installations in hazardous areas (other than mines)