Ex nR Principles and Testing

What is Ex nR?

The Ex n protection method is applied to electrical equipment such that, in normal operation and in certain specified regular expected occurrences, it is not capable of igniting a surrounding explosive gas atmosphere.

Ex n, in line with the current Ex n standard IEC 60079-15, has been divided into 2 types of protection. One of these is Ex nR.

A restricted breathing enclosure, often referred to as an ‘Ex nR’ enclosure, is designed to restrict the entry of flammable or explosive gases.

Restricted breathing enclosures are certified for use within Zone 2 environments. This is an area in which an explosive gas atmosphere is unlikely to occur in normal operation and, if it occurs, will only exist for a short time.

How Does The Concept of Ex nR Work?

Contrary to, for example, an Ex d enclosure which permits all three elements of the fire triangle, (source of ignition, fuel and oxygen), an enclosure built to an Ex nR standard will reduce the rate at which the fuel source enters by restricting the rate at which a potentially explosive atmosphere can enter.

This is generally achieved by incorporating sealing gaskets and suitably rated cable glands to provide an effective pressure seal.

Features of an Ex nR enclosure:

Prevention of an explosive concentration

Includes a specified test port, in most cases

Enclosure built using lightweight metallic (e.g aluminium), stainless steel or GRP material

Enclosure built with high levels of sealing

Typically contains equipment with a high surface temperature or sparking potential

The Testing Method of Ex nR

Under EN 60079-17:2014 restrictive breathing enclosures with provision for routine checking shall be subject to periodic pressure test measurement.

Ex nR equipment shall be installed in a way that allows easy access to any test port.

Certain Ex nR equipment is manufactured to include a test port to enable the checking of breathing properties for the equipment

The periodic testing time and maintenance routines will be specified in the manufacturer’s instructions.

How is Testing Completed?

Typically, the test would involve applying a pressure to the enclosure which is to be tested, sealing the test port connection.

The equipment would pass the test when the change in pressure after a certain period of time is within acceptable limits.

The acceptable limits and specific testing criteria will be outlined in the manufacturer’s instructions.

Availability of Ex nR Test Equipment from JCE

JCE design and manufacture high-quality Restricted Breathing Test Kits (part number: 5365-EXMK) for the purpose of carrying out routine maintenance and inspection on all Ex nR equipment.

This simple-to-use & cost effective testing apparatus is available for direct sale, rental or as part our Ex nR testing service, which is conducted by highly qualified JCE engineers and technicians worldwide.

For any enquiries please email info@jcegroup.com or give us a call on 01224 798600.

View our Ex nR Testing Service & Kit flyer now for further information!