When transmitting data or conducting power in harsh environments, protecting your cables is crucial to safe and reliable operation. This is where armored cables come into play. They are used primarily in industrial applications, often in cable trays and raceways. They often not used in flexing applications. While they could operate there, the connector cable would create a weak link. To combat this, you should use either a high-flex cable on the inside or discreet wires.
Armored cables feature some type of metal sheath that is the first layer of armor. It is usually made of interlocking or continuous aluminum or stainless steel, or it can be covered in a smooth or corrugated metal tape. According to Mencom, which uses a stainless-steel design, the armor protects the cable inside from water damage by high-pressure washdown, cleaning agents and extreme temperatures.
Unlike cable shielding, which is often braided or a foil wrap design, the armor shield is wound around the cable, giving it a corded, corrugated appearance.
Jacketing materials—such as a silicone tube-covered, thermoplastic elastomer or PVC—further protect the cables from harsh chemicals, oils and sunlight, but also prevent physical failure by repetitive impacts, abrasion with loaded components, and weld slag. In addition, most armored cable jacketing materials are flame resistant.
Two gentleman named Edwin Greenfield and Gus Johnson first developed armored cable, or BX cable, in the early 20th century. It used a flexible steel cover, but now more commonly uses flexible aluminum conduits. Metal-clad cables are typically galvanized steel or aluminum interlocking cable. And some companies’ armored cables, such as Mencom, use a woven flexible stainless-steel design.
A big difference in the three designs is in how they are ground. BX are usually ground through the sheath; this is why BX cables most often need to be buried. Armored cables also ground through the sheath but can be exposed at certain areas without causing the system to ground. Metal-clad armored cables, like those used in industrial settings, feature a grounding wire—usually an annealed bare copper wire—inside the wire bundle. This allows them to be used in open areas, such as in running through factories and plants throughout raceways and cable trays and carriers.
Armored cables must be IP67-rated and certified to UL and NEC standards, among others.
Special thanks to Mencom Corp. (www.mencom.com) for assisting with this article.