UL 6 Electrical Hard Metal Conduit - Steel

The “UL 6 Electrical rigid metal conduit - Steel” standard developed by Underwriter Laboratories (UL) covers rigid electrical metal conduit (steel elbows, couplings and nipples) for use as metal conduit for the installation of electrical wires and cables.

For the purposes of this standard,

• Bare threaded pipe refers to standard length threaded pipe that is intended to be coated with an alternative corrosion-resistant coating and has a separate coupling.
• Alternative corrosion resistant coatings refer to primary coatings other than primary coatings, which consist solely of zinc and which, as a result of evaluation, demonstrate the ability to provide the required level of corrosion resistance on the outside of the pipe. Coatings may contain zinc.
• Organic coatings refer to an internal coating consisting only of zinc, which, as a result of evaluation, shows the ability to provide the required level of corrosion resistance in cases where the coating is not subject to physical damage.
• Zinc coatings refer to a primary coating consisting solely of zinc that, upon evaluation, has demonstrated its ability to provide the required level of corrosion resistance on the outside or inside of the pipe, as appropriate.
• Elbow refers to the manufactured curved section of the steel electrical hard metal cable duct, threaded at both ends.
• Electrical steel rigid metal cable conduit refers to a screwable steel conduit of circular cross section designed for the physical protection and routing of cable conductors and for use as an equipment grounding conductor when installed using appropriate fittings.
• The finished pipe is a straight pipe with a coupling attached.
• The nipple is a straight section of steel electrical carbide conduit, usually not longer than 0,6 m and threaded at both ends.
• Primary coating is a coating on the outside of the pipe to protect against corrosion.
• The sleeve coupling is a PVC coated steel threaded coupling that extends beyond the ends of the coupling to provide corrosion protection to the connection points.
• Straight conduit is a straight length of steel electrical hard metal conduit with protective coating applied but without connections.
• Supplementary coating is a coating on the outside of the pipe in addition to the main coating to protect against severe corrosive conditions.
• Threaded coupling is an internally threaded cylinder that connects two sections of steel electrical hard metal cable.

Each tube must be of steel and have a circular cross-section, the dimensions of which are specified in the table given in the standard, thus facilitating the cutting of clean, true threads. Wall thickness must be equal along the length of the pipe. All seams are well welded. There are no metal decorations, sharp edges or sharp protrusions on the inner or outer surfaces of the pipe in the weld seam.

The interior and exterior surfaces of each tube must be free of scale, flashing or other protrusions before the protective coating is applied.

The length of the finished straight pipe and the weight of the finished zinc coated pipe or single coupling coated with a corrosion resistant alternative coating and bare threaded pipe shall comply with the standard. Typical dimensions of the pipe complying with the requirements of this standard are included in the annex of the standard.

It is allowed to produce lengths shorter or longer than the standard length specified in the table in the standard, with or without thread, with or without coupling. Lengths other than standard lengths must have a minimum acceptable weight proportional to the weights specified in the table.

Standard lengths of primary zinc-plated finished pipes are supplied with a threaded coupling attached or have an integral coupling mounted on top. Manufactured from bare threaded pipe fitted with an alternative corrosion-resistant coating, the pipe has a separate coupling.

The outer and inner surfaces of the finished pipe must be free of weak coatings, hard scale, burrs, fins or other defects.

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