Ex n Reduced Risk | Explosive Atmospheres & Explosion Proof Protection Concepts

Ex n Reduced Risk

Ex n or Reduced Risk protection is a standard of explosion protection applied to electrical equipment used in hazardous areas such that, in normal operating circumstances and in certain specified abnormal conditions, for example a hazardous area light fitting with a failed lamp, it is not capable of igniting a surrounding explosive atmosphere. The requirements of the Ex n standard IEC 60079-15 are intended to ensure that a fault capable of causing ignition is not likely to occur.

The Ex n standard is subdivided into sections:

Explosion Protection Type nA

‘Non-sparking’ equipment – has now been replaced by the Ex ec explosion protection standard.

Explosion Protection Type nR

‘Restricted Breathing’ enclosures – Where a hazardous area enclosure has been designed to restrict, but not completely prevent, the entry of hazardous gases. This is usually in the case of Zone 1 and Zone 2 light fittings. The positioning of enclosures adhering to the restricted breathing standard would need to be carefully considered, especially in locations with full sunlight. The manufactures instructions should always be followed regarding the periodic testing of the restricted breathing properties, replacement of gasket seals when re-lamping and cable entry requirements, for example, incorporating an IP washer.

Explosion Protection Type nL

‘Energy Limited’ equipment. Where the circuit components restrict the maximum available energy in an external circuit to a level incapable of causing ignition of gas. Ex nL has now been replaced by Ex ic explosion protection standard.

Explosion Protection Type nZ

An enclosure with ‘Ex n‘ pressurisation – has been replaced by Ex pz explosion protection standard

Explosion Protection Type nC

Sparking where the contacts are suitably protected other than by type nR, nL or nZ.

Hermetically Sealed Device – Sparking contacts will be safely enclosed within a completely airtight enclosure. The enclosure may be sealed by brazing soldering, welding or with the fusion of glass to metal.
Enclosed Break Devices – A type ‘n’ enclosed break device incorporates electrical contacts. It is able to safely withstand an internal explosion of any flammable gas that may have entered the enclosure.
Encapsulated Device – An encapsulated device is similar to a hermetically sealed device. The external connections are usually by flying leads or terminals.

Explosion Protection Standards

The current standard is IEC 60079-15 (EN 60079-15) for Explosive atmosphere Equipment protection by type of protection ‘n’.

The following standards have been superseded:

EN 50021 Type of protection ‘n’
BS 4137 Guide to the selection of electrical equipment for use in division 2 areas
BS 6941 Electrical apparatus for explosive atmospheres with type of protection ‘N’

Ex n equipment can only be used in areas requiring EPL ‘Gc’ or Category 3. Prior to 2007 it was restricted to use in Zone 2 hazardous areas only.

Reduced Risk, Ex n, equipment was designed for use with either any Group II gas or with a particular group II gas subdivision. It would be marked either with II or with IIA, IIB or IIC. If the equipment was suitable for use in all subdivisions, the marking would not include the subdivision, only ‘II’ followed by any other required details. More recently, the International Electrotechnical Commission, or IEC, has now dropped the Group II marking and instead requires equipment to be marked with either IIA, IIB or IIC.

Explosive Atmospheres &

Explosion Protection Concepts

💡 Thorne & Derrick, Specialist Suppliers & Stockists of Electrical and Process Instrumentation Equipment for installation in hazardous area location can assist with your project requirements. Know your Ex Concepts:

➡ For further technical information see | Hazardous Area Zones | Explosive Atmospheres | T Class Ratings

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