What is Flexible Metal Conduit?

A flexible metal conduit is a variety of piping used to hold electrical wires and similar cabling. This style of conduit is common in areas where the strength of metal is required, but the conduit still needs flexibility. These conduits bend to accommodate their environment, but do not permanently take on any specific shape. Depending on its overall design and purpose, the flexible metal conduit may be waterproof, or it may have gaps.

In nearly all cases, a flexible metal conduit contains cables. These cables are usual electric wires, but some conduits protect the coaxial cables or fiber optic systems used in closed-circuit security systems. These tubes are usually made of either steel or aluminum. The steel is harder and protects the interior cables better, but aluminum is much lighter.

There are three basic styles of flexible metal conduit. The common style, called flexible metallic conduit (FMC), is made of a single strip of steel or aluminum. This strip is coiled into a tight circle where is interlocks with itself. It is not watertight, but it does provide basic protection to any cables that may be inside. The strange design and shape of these conduits give them a distinctive, spring-like appearance.

A liquidtight flexible metallic conduit (LFMC) is essentially an FMC encased in plastic. This plastic coating makes the conduit waterproof. The coating on an LFMC can be anything from a hose-like sheath to a tight polyvinyl coating. The more bulky coatings reduce the flexibility of the conduit, but increase its weather protection, so these coverings are common for exterior lines.

The last type of flexible metal conduit is the flexible metallic tubing (FMT). These are essentially the heavy-duty version of the FMC. This variety of conduit is stronger and heavier than FMC and is always waterproof without a plastic coating. These tubes occasionally have end caps that act as connectors for electrical systems, allowing users to plug the tube directly into a device, and an output, which keeps the interior entirely self-contained.

The most common places to see any form of flexible metal conduit include public structures and manufacturing locations. Private homes and businesses are less likely to use metallic conduits, and when they do, it is typically inside a wall. Public areas, particularly those made primarily of steel and concrete, use flexible metal conduits to protect interior systems and prevent unintentional damage or vandalism. Manufacturing areas use these systems to accommodate machinery movement and maintenance.