Explosion-Proof (Ex d) Electrical Equipment for Oil and Gas Sites
Where flammable gas or vapour can be present, ordinary electrical equipment is a source of ignition. Here is how Ex d protection works and what to specify.
Refineries, drilling sites, fuel depots and chemical plants can contain flammable gas or vapour. A spark from a switch, a motor or a junction box is enough to ignite it. Explosion-proof equipment is designed so that this cannot happen, and so that an internal ignition does not spread outside.
What Ex d means
"Ex d" stands for flameproof protection. The equipment sits inside a strong enclosure with precisely machined joints. If an explosive mixture gets inside and ignites, the enclosure withstands the pressure and the joints cool the escaping gases enough that they cannot ignite the atmosphere outside. It is the protection concept used for many motors, switches, junction boxes and control stations.
Know your hazardous area
Before choosing equipment, the area must be classified. Zones describe how often an explosive atmosphere is present.
- Zone 0: present continuously or for long periods.
- Zone 1: likely to occur in normal operation.
- Zone 2: not likely in normal operation, and only for a short time if it does occur.
Ex d equipment is commonly used in Zone 1 and Zone 2. The area classification comes from a qualified engineer and the site's hazardous area drawings.
What to check when specifying
- Gas group: IIA, IIB or IIC. Equipment must be rated for the gas group on site, and IIC covers the most demanding gases such as hydrogen.
- Temperature class: T1 to T6. The surface temperature of the equipment must stay below the ignition temperature of the gas.
- Certification: look for ATEX or IECEx certificates for the exact model, and check the marking on the nameplate.
- Ingress protection: oil and gas sites are often hot, dusty or corrosive, so check IP rating and enclosure material.
- Cable entries: glands and stopper plugs must also be certified for the same protection type, or the whole installation is compromised.
Installation and maintenance
Certified equipment only stays safe if it is installed and kept correctly. Do not drill, modify or repaint flameproof enclosures. Keep joint surfaces clean and undamaged, replace missing bolts with the correct type, and follow the inspection schedule of the relevant standard.
Get the right equipment
We supply explosion-proof and oilfield electrical products from established brands, and our catalogue for the sector is available on request. Share the zone, gas group and temperature class for your site, and we will recommend suitable items.