Installing PVC-Coated Conduit
Pipe Wrenches and Pliers
PVC-coated conduit requires special wrenches to protect the coating. Pipe wrenches specially designed with fine teeth are available for use with PVC-coated conduit. Strap wrenches can also be used. Slip-joint pliers of the Channel-LockTM type, specially equipped with wide jaws, are also available to protect the coating. (NOTE: For PVC-coated conduit, wrench sizes are the same. However, the jaw of the wrench must be specially designed for PVC-coated conduit. If not available, a strap wrench should be used.) Do not use ordinary slip-joint pliers or standard pipe wrenches with PVC coated conduit.
Sleeves on Couplings and Fittings
- Sleeves on PVC-coated conduit couplings and fittings are provided to ensure continuous coating protection. There is added protection because the coating is separate, not continuous, between a section and fitting. This makes the coating more resistant to corrosion penetration.
- To make the sleeve softer in cold weather applications, soak the coupling or fitting in warm water.
- To make installation easier, a silicon sprays can be applied to the inside diameter of the sleeve
Threadless fittings cannot be used with PVC-coated RMC or IMC.
Engagement of Threads
Since the threads are not visible because PVC sleeves cover them, take extra care to be sure that the threads are fully engaged and made wrench tight.
Patching Damaged Areas
Even when following recommended practices, the PVC coating can sometimes become damaged during installation. This destroys the coating protection and provides the potential for exposure to corrosive elements. Damaged areas can be patched, following manufacturers’ instructions.
Equipment Grounding and Bonding
When expansion joints are used in PVC-coated conduit systems, an external bonding jumper should be used. Typically, this requires removing a portion of the PVC coating from the conduit where the jumper will be attached, installing the jumper and repairing the surrounding coating with touch up compound provided. For proper installation, follow the instructions from the PVC-coated conduit manufacturer.
The Process of Manufacturing PVC-Coated Conduit
The process begins with 20-foot lengths of raw steel shell. The steel shell is cut, threaded and prepared for the hot dip galvanizing process. The threaded shell is submerged in a molten zinc bath. This hot-dip galvanizing process allows the zinc to penetrate the steel and provide the best possible protection. After the conduit is removed from the zinc bath, super-heated steam is blown through the interior and over the outside of the conduit to remove any slag. The ends of the conduit are heated enough to blow excess zinc from the threads before the exterior PVC coating, 2 mils (nominal) urethane is applied to the inside diameter and the threads of the conduit. After priming, the conduit is heated and then rolled through liquid plastic obtaining 40 mils thickness
Two Keys to Proper Bonding:
- Surface preparation is the key to a good bond.
- The quality of the bond determines the quality of the corrosion protection