Part Two: UL698A - Understanding Underwriters Laboratory (UL) Certifications Relating to Hazardous Locations

At Palmer DCS, we’re proud to carry our UL certifications. The UL label helps establish trust between us and our customers. We’re committed to making high quality industrial control panels (ICP) that our customers can count on. That little label helps communicate that commitment.

Familiar as the UL mark is to all sorts of consumers, there are a wide range of different certifications available from UL which many people don’t know much about. We want to help change that. We want you to get to know our certifications, understand the requirements for attaining them, and see what that level of quality means for our customers.

Meet UL698A NRBX**

As part of our ongoing series on our UL certifications, let’s look more closely at UL698A, category NRBX. This is actually a subcategory of the certification we discussed previously, UL508A—the standard for ICP.

There’s a lot of confusion when it comes to UL standards for ICP in “hazardous” locations. The UL698A NRBX certification governs panels “relating to hazardous locations.” This is different from the more stringent NNNY category—which we’ll explore in more depth next time. Put simply, UL698A NRBX deals with ICP intended to be placed in safe environments but whose circuits will feed out into hazardous environments. These panels do not require an explosion-proof, dust-proof, or pressurized enclosure, but do require intrinsically safe control circuits.

Provisions of an intrinsically safe control circuit enable installation of devices (such as switch contacts) in hazardous locations without providing an explosion-proof, dust-ignition-proof or pressurized enclosure for the device.

What constitutes a hazardous environment?*

Hazardous locations are defined by the National Electric Code (NEC), NFPA 70. Under our UL file for UL698A NRBX, Palmer DCS is certified for ICP relating to the following hazardous locations: Class I (Groups A, B, C, and D), Class II (Groups E, F, and G), and Class III.

Let’s summarize what each of those means.

Classes:

• Class I: Denotes areas where flammable gas, vapor, or liquid is present.

• Class II: Denotes areas where combustible dust is present.

• Class III: Denotes areas where ignitable fibers are present. The difference between flammable, combustible, and ignitable all has to do with the different temperatures at which a substance will ignite.

Groups:

• Group A (Class I): Acetylene

• Group B (Class I): Hydrogen

• Group C (Class I): Cyclopropane, ethel ether

• Group D (Class I): Acetone, butane, propane, hexane, natural gas fuel oil.

• Group E (Class II): Combustible metals (e.g. lithium, magnesium, titanium)

• Group F (Class II): Carbonaceous materials (such as coal dust)

• Group G CLASS II): Flour, starch, plastic

The NEC further categorizes areas into three different divisions:

• Division 1: Areas where flammable or combustible concentrations exist under normal circumstances OR are highly likely to exist under other circumstances.

• Division 2: Areas where flammable or combustible concentrations exist under abnormal circumstances OR are not likely to exist under other circumstances.

• Nonclassified/Unclassified: Areas where the presence of hazardous material is so infrequent, Electrical Area Classification is deemed unnecessary.

This can be a confusing area for many people. We hope that by laying out the different categories this way, we’ve helped to clarify hazardous environments for you.

As with the UL508A certification, our facilities are subject to routine inspection to make sure we uphold the standards UL requires to carry the 698A NRBX certification.

If you have any questions about our certifications or Palmer DCS in general, feel free to contact us.

We’re proud to carry our UL certifications here at Palmer. Because we carry this mark, our customers don’t have to deal with the stress and expense of having their panels rejected. It’s one of many reasons our customers trust us to do the job right.