Wire Bushings for Hazardous Locations

To design safe electrical systems for hazardous locations, you’ll have to pay close attention to each and every electrical component that you use—including any wire bushings.

It may be easy to overlook these bushings or conduit sealing hubs since they’re typically just one, seemingly minor part of a more complex electrical system. But these components actually play an outsized safety role in hazardous areas. Applications ranging from liquid natural gas (LNG) handling to factories with combustible dust all have a compelling need to prevent leaks around wires that pass through pressure walls, ensuring safety and compliance with agency requirements.

In the past, it was difficult to find feedthroughs and wire or line bushings that you could customize to your needs while meeting UL and other compliance standards for hazardous locations. Now, however, there’s an approach to feedthrough and wire bushing design that makes it far easier to meet all the relevant regulations without sacrificing design freedom. The key to this approach involves the use of epoxies to create hermetic seals around the wires.

Other Design Benefits

Our UL 1203 bushings have two less obvious design features that can reduce your engineering effort when you need to pass wires or cables into or out of a hazardous location:

Full chemical compatibility. One issue with many previous explosion-proof designs is that they used cement-based sealants that can be prone to cracking and fatigue due to mechanical and environmental stresses. Epoxy, by contrast, is well known for its excellent fatigue properties and resistance to environmental stress cracking. So not only does epoxy create a true hermetic seal around the wires, it also creates sealing that lasts out in the field.

Combined explosion and process seal. Most UL 1203 wire bushings seal against the direct causes
of explosions such as sparks, flames or even dust. However, many applications in hazardous locations also need reliable process sealing—for example, in a pressurized environment like a hazardous location pump. In these applications, two seals are often needed, one for primary process sealing and a second for explosion proofing. We took a different, simpler approach. Our UL 1203 bushings handle the explosion proofing and provide a true hermetic process seal with leakage rates down to less than 1x10^–8 cc-He/sec, operating pressures up to 10,000psi and burst pressures greater than 15,000psi.

Meeting Hazardous Location Standards with Epoxy

Long before we had taken the step to pursue a stand alone UL-listing of our NPT wire bushings, our
customers often used our epoxy-based feedthroughs, connectors, bushings and conduit fittings in a variety of equipment that complies with the stringent hazardous location requirements, including:

• IEC/EN 60079–0 General Requirements, IEC/EN 60079–1 Flameproof, IEC/EN 60079–2 Pressurized System.
• EN 60079–6 Liquid Immersion, IEC/EN 60079–7 Increased Safety and IEC/EN 60079-11 Intrinsic Safety.
• ATEX Ex d Flameproof Enclosure, ATEX Ex e Increased Safety, ATEX Ex de Flameproof with Increased Safety, and ATEX Ex pD Pressurized Equipment.
• CSA 22.2, CSA E60079 Increase Safety.
• UL 1203 Explosion Proof, UL 886 Hazardous Conduit Fittings, UL 674 Hazardous Locations
  for Motors and Generators, and UL 913 Intrinsically Safe Apparatus.
• FM 3611 Equipment in Hazardous Locations, FM 3615 Explosion Proof, FM 3620 Electrical
  Equipment in Explosive Atmospheres and FM 3610 Intrinsic Safety.
• And others.