The flexible electrical conduit is made of continuously interlocking metallic or non-metallic strips, which allows it to easily bend or take any shape. Designed to bend and respond to movements or vibrations, the conduits are suitable for applications where it is difficult or impractical to install the rigid types.
These are also suitable for applications where the wiring does not follow straight line sections, or keep on changing shapes such as in the lifts and escalators. Besides protecting the cables, the flexible electrical conduit prevents the passing of vibrations from machines and motors to the walls ot mountings.
The flexible type is the easiest to work with, requiring little effort and cutting since it can bend and go round the obstacles. Since there is minimal cutting and joining, the flexible electrical conduit requires less installation time and no special tools. However, it does not provide a strong protection like the rigid types. Special waterproof conduits are used in wet and damp environments such as water treatment systems, HVAC equipment systems, and others.
Construction of flexible electrical conduit
A flexible electrical conduit is either metallic or nonmetallic. The conduits can further be differentiated by the type of construction material, flexibility and ease of installation and fitting. Other properties include the corrosion resistance, waterproofing ability and level of mechanical protection.
Common construction materials include aluminum, steel, galvanized steel, PVC, organic compounds, etc. The type of material determines the level of mechanical protection, flexibility, resistance to flames and corrosion, as well as the temperature the conduit can withstand.
Other properties that depend on construction material include the resistance to chemicals, oils, as well as waterproof capabilities. UV resistance is also important if the conduit will provide outdoor protection to cables.
Generally, the conduits are made up of self-interlocked strips of steel, aluminum, PVC or other non-metallic material, coiled to form a hollow tube where wires can pass through. Although the exterior appears ribbed, the interior is usually smooth to enable easy pulling of the cables. The exterior is also smooth to an extent, to allow for easier conduit pulling.
Below are the common types of flexible electrical conduits that provide protection in a variety of applications.
Flexible Metallic Conduits (FMC)
The flexible metallic conduits (FMC) provide a strong protection in addition to being flexible. However, these have a lower protection than the rigid alternatives. Further, most of the standard flexible conduits are not waterproof, hence, not suitable for wet or moist environments.
Liquid Tight Flexible Metal Conduit (LFMC)
This is a waterproof flexible electrical conduit that provides protection to the wires in both dry and wet conditions. The flexible metallic conduit has a special waterproof coating that covers the metal, preventing the ingress of water or other liquids. The waterproof conduits are costly than the standard type.
Extreme temperature liquid tight flexible metal conduit
This type of metallic flexible electrical conduit has the ability to withstand high and low temperatures while providing the mechanical protection to the enclosed cables. It is suitable for continuous use at 70 °C in oily or wet conditions, and 150°C in dry environments. In addition, the conduit has a low brittle point temperature of about -60°C and able to safely provide protection in cold environments.
Typical flexible conduit uses a durable, halogen-free thermoplastic rubber jacket material. This has a low flammability and high resistance to breakdown by heat, oils, chemicals and mild acids.
The conduit is suitable for industrial setups where there is the need to protect cables from mechanical, chemical, corrosive and high-temperature conditions. In addition, most of these are UV stabilized and suitable for outdoor applications.
Flexible nonmetallic conduits
The flexible nonmetallic conduit, which is usually made from PVC, organic or other non-metallic materials, is almost similar in operation to the metallic type. However, it is lighter and less costly. Also, it offers a better corrosion and chemical resistance than the metal conduits.
The conduit is suitable for both indoor and outdoor applications. Because of its excellent electrical insulating properties, it is a good choice for use inside the machines or equipment where metal can lead to short circuits.
Liquid Tight Flexible Non-Metallic conduits
The liquid tight flexible nonmetallic conduit has a special coating that prevents water from entering into the tube. These are suitable for wet, damp or submerged applications. They are usually more costly than those that are not waterproof.
Some liquid tight flexible non-metallic conduits for demanding applications are built with multiple layers to withstand the harsh conditions as well as oily and wet conditions.
Applications of flexible electrical conduit
The flexible electrical conduits are suitable of protecting cables in residential, commercial and industrial indoor and outdoor applications. These includes protecting cables in systems such as motors, lighting, refrigeration, oil and gas refineries, rails systems, lifts, and more.
The choice of the specific flexible electrical conduit depends on the application, environment and level of protection required. Most of the standard types are not be waterproof and have limited bend angle. But others have special coatings that make them waterproof, while others such as extra flexible can make tighter U-bends.
The flexible electrical conduits are made of interlinked coils that result into a flexible hollow tube which can hold wires. This allows them to easily take multiple bends and fit in tight areas.
There are both metallic and non-metallic flexible conduits, and these can further be classified according the ability to provide protection in moist, wet, submerged conditions, or dry, dusty, high-temperature, corrosive, and other environments. Some, such as the galvanized steel provide superior mechanical and weathering resistance. While others such as the PVC can withstand oils, water, fluids, and coolants without degrading.
The flexible electrical conduits are suited in applications where there is a need to protect wires without confining the conduit into straight lines while still allowing for movements and vibrations. Finally, the design allows them to isolate the vibrations from the machines and prevent them from reaching the other structures.