Armored Cable: Structure and When to Use It

Introduction

Armored cable is a specialized type of electrical cable featuring a protective metal layer that shields its internal components from physical damage. In the world of electrical installations, selecting the appropriate cable type is crucial for ensuring safety, reliability, and compliance with regulations. This article explores the structure of armored cable and provides guidance on when this robust option is the ideal choice for your electrical projects.

What Is Armored Cable?

Armored cable refers to electrical cabling that incorporates a layer of metal armor within its construction. The primary purpose of this armor is to provide substantial mechanical protection to the electrical conductors inside, ensuring safe and reliable electrical transmission even in harsh or high-risk environments. This protective feature makes armored cable significantly more durable than standard cable options.

Structure of Armored Cable

Armored cable consists of several distinct layers, each serving a specific purpose in the cable's overall functionality and protection:

Core Conductors

The innermost component of armored cable consists of one or more conductors typically made from highly conductive metals such as copper or aluminum. These conductors are responsible for carrying the electrical current through the cable. The size and number of conductors vary depending on the cable's intended application and capacity requirements.

Insulation Layer

Surrounding each conductor is an insulation layer made of materials like PVC (polyvinyl chloride), XLPE (cross-linked polyethylene), or other specialized insulating compounds. This layer serves as the primary electrical barrier, preventing current leakage and short circuits between conductors or to the outside environment.

Inner Sheath (optional)

Some armored cables feature an inner sheath that encases all the insulated conductors together. This layer provides additional separation and protection before the armoring is applied, and may consist of various polymers or rubber-like materials.

Armoring Layer

The defining feature of armored cable is its metal armoring layer, which comes in several varieties:

• Steel Wire Armor (SWA): Consists of helically applied steel wires around the cable. This is the most common armoring type, offering excellent protection against crushing forces and impact.

• Steel Tape Armor (STA): Uses one or more layers of steel tape wrapped around the cable. This provides good protection against compression but less against impact than SWA.

• Aluminum Wire Armor (AWA): Primarily used for single-core cables to avoid magnetic effects. Aluminum armor provides protection while being lighter than steel alternatives.

The armoring layer creates a robust barrier against mechanical damage, impact, rodent attacks, and other physical threats that might compromise the cable integrity.

Outer Sheath

The final layer is a weather-resistant outer sheath typically made from materials like PVC or polyethylene (PE). This outer jacket shields the internal components from environmental factors such as moisture, UV radiation, and chemical exposure. The outer sheath may also include flame-retardant properties for additional safety.

When to Use Armored Cable

Underground Installations

When cables need to be buried directly in the ground or in shallow trenches, armored cable is an excellent choice. The armor layer protects against damage from digging tools, rocks, and soil movement that could otherwise damage standard cables. This makes armored cable ideal for garden lighting, outdoor power supplies, and connecting outbuildings.

Outdoor Environments

Exposed outdoor locations subject cables to harsh weather conditions, including rain, snow, and extreme temperatures. Armored cable's robust construction and protective layers make it well-suited for outdoor installations like street lighting, parking lot power distribution, and external building fixtures.

Industrial Facilities

Manufacturing plants, warehouses, and other industrial settings present numerous hazards to electrical cables, including heavy machinery, moving vehicles, and falling objects. In these environments, armored cable provides crucial protection against physical impacts and abrasion that would quickly damage standard cables.

Power Distribution Systems

For main power distribution lines that cover long distances and must maintain reliability, armored cable offers the necessary durability and protection. These cables often carry higher voltages and must remain operational despite environmental challenges, making the additional armor layer a worthwhile investment.

Areas with Rodent Activity

Rodents like rats and mice can cause significant damage to electrical cabling by gnawing through outer jackets and insulation. The metal armor layer presents a formidable barrier that most rodents cannot penetrate, making armored cable the best choice for installations in areas with known rodent problems, such as agricultural buildings or older structures.

Hazardous or Explosive Zones

In locations where flammable gases, vapors, or combustible dust may be present, specially designed armored cables with appropriate certifications can help maintain safety standards. These specialized armored cables are constructed to prevent ignition sources from reaching potentially explosive atmospheres and comply with strict safety regulations for hazardous areas.

When Not to Use Armored Cable

While armored cable excels in challenging environments, it's not always the best choice. For lightweight indoor applications like office or residential wiring within walls and ceilings, the additional protection is often unnecessary. Armored cable is also less flexible and more difficult to install in tight spaces compared to standard options. Additionally, for cost-sensitive projects where mechanical protection isn't a priority, more economical cable types may be more appropriate.

Conclusion

Armored cable provides superior protection for electrical installations in demanding environments where physical damage, exposure to elements, or animal interference are concerns. By understanding the structured layers of armored cable—from the core conductors through to the protective outer sheath—and recognizing appropriate applications, electrical professionals can make informed decisions about when to specify this robust solution.

Always consult local electrical codes and regulations when selecting cable types for any installation, as requirements vary by region and application. When properly matched to the environment and safety needs of the project, armored cable delivers the reliability and protection that standard cables simply cannot provide.