All About Cable Armor
Cable armor is a metal layer wrapped around the exterior of a cable to provide mechanical protection. It is primarily used in hazardous environments that require an extra layer of cable defense or in situations where Type MC (metal clad) cable is required by the National Electric Code.
The metal armor can protect the cable against falling objects, crushing and other physical damage. It also adds extra fire resistance, is safer for electrical maintenance workers and can be used in both riser and plenum applications. Even in markets with strict building regulations, armoring makes almost any electronic cable installation possible.
Common Cable Armor Materials
The most common armor materials are interlocked galvanized steel, interlocked aluminum and corrugated and welded aluminum. All are similarly priced and, in most applications, steel and aluminum armor are equally sufficient. There are a few characteristics, however, that set them apart and could make one more appropriate for a specific application.
- Steel: This material is crush-resistant and impact-resistant. It is stronger than aluminum but is also 10 to 40 percent heavier. In high-current applications, steel is more effective than aluminum in blocking electromagnetic interference.
- Aluminum: Aluminum is about five times more conductive than steel armor and weighs much less. It is impact-resistant, but in order to achieve the same crush resistance as steel, aluminum armor must be five mils thicker. In low-current applications, aluminum better shields cable from electromagnetic interference.
Armor vs. Shielding
Many times the idea of armor and shielding go hand in hand. Although both are metal layers used in cable to provide protection, each provides a very different kind of protection. Armor, located on the outside of the cable, is a sturdy layer of metal designed to protect mechanical integrity. It defends the cable against physical hazards and prevents it from being crushed or damaged by outside forces. Shielding is incorporated in the inner layers of the cable, around the conductor. It works to minimize electromagnetic interference and prevents the cable from intercepting outside currents or signals that could damage its productivity. Whether armor and shielding are both used in a cable depends on the application for which it is being designed.