What Is a Steel Conduit?
A steel conduit is a steel pipe designed to protect electrical wires. Available in various types, diameters, and thicknesses, the most common length is 12 feet, aligning with the standard in Europe and the United States.
Its primary role is to safeguard wires physically, prevent fire spread, protect wires in case of a fire, reduce electrical leakage, and facilitate wire maintenance and replacement.
Steel conduits are tailored to various conditions, including indoor/outdoor, exposed/buried environments, corrosion resistance, workability, cost, and size considerations.
Uses of Steel Conduits
There are three main types of steel conduits:
- Thick Steel Conduits (G-pipe): With a wall thickness over 2.3 mm, these are often hot-dip galvanized and used outdoors for their weather resistance. Suitable for harsh conditions and high-voltage or explosion-proof cables.
- Thin Steel Conduits (C-pipe): About 1.6 mm thick, these are less durable than G-pipes and primarily used for indoor exposed piping.
- Screwless Conduit (E-pipe): With a wall thickness of around 1.2 mm, these are lightweight and easy to install but offer lower strength. They are used for indoor exposure and ceiling installations.
Features of Steel Conduits
Besides the main types, steel conduits also include metal flexible conduits and lined steel pipes. Metal flexible conduits, known for easy bending, are used in areas with vibrations or expansion joints. Lined steel conduits, coated with synthetic resin, are used for underground installations, like cable protection, gas, and water pipes.
Conduit design considers the occupancy ratio, the ratio of wire area to the conduit’s inner diameter, which should not exceed 32%. A high occupancy ratio can hinder wire insertion, increase wire damage risk, and complicate wire replacement. For long conduits or those with many turns, boxes are recommended at intervals.
When housing multiple wires in a conduit, the current reduction factor, based on the number of wires and their heat dissipation, adjusts the allowable current: 0.7 times for up to 3 wires, 0.6 times for 4 to 6 wires, and 0.5 times for 7 to 15 wires.