In the “Simple Solutions” section of the July 2000 issue, the suggestion for using floor wax on the threads of aluminum conduit is a violation of the 1999 National Electric Code. Section 110-2 requires items to be approved for the use. Section 110-3 sets out guidelines for this approval.
Aluminum conduit is approved for use as an equipment grounding conductor, and the use of wax on the threads could compromise the joint, no longer maintaining the electrical continuity of the system, and also affecting the bonding requirements for conduit. Grounding and bonding are covered in section 250 of the Code.
The use of wax on the threads can also permit overtightening of the joint, thus weakening fittings, causing them to split and break. The floor wax could also harden and seal the threads, which would represent a problem if used in a hazardous classified area. Threads on fittings are designed to allow explosive gases to escape in the case of an explosion inside the enclosure or conduit. Gases are cooled so that by the time they get out into the raceways, they will not cause a fire or explosion there. If threads are sealed, conduit and enclosures may turn into pipe bombs.
The local electrical supply store should be able to offer a lubricant approved for this purpose. It must be remembered that if a lubricant is used, the installer must be careful not to overtighten the joints.-Mike Hunsaker, Maintenance Coordinator, Thiokol Propulsion, Brigham City, UT
Tip contributor’s reply: Mr. Hunsaker makes some good points. As far as the floor wax compromising the grounding of the conduit, it is common knowledge that when you tighten conduit, the threads eat right through the wax and into the aluminum, which is why I suggested wax in the first place. The threads become hot and the aluminum seizes and you cannot screw the pipes all the way together.
As far as overtightening the conduit, you can do that with or without the wax. Common sense has to come into play.
The point about a pipe bomb doesn’t hold up. Have you ever heard of an aluminum pipe bomb? No, because it splits before it fragments. If using aluminum conduit, or any conduit in a hazardous location, there are sealoff fittings no farther away than 18-in. before any box or spark creating device, and the box and/or switch are explosionproof to keep the spark from getting into the hazardous area. The spark should not go into the conduit either. If the conduit run is large, say 500 MCM and at 480 V, 300 amps, and the conductors short to the conduit or together inside the conduit, you will blow a hole in the aluminum with or without the wax because the aluminum melting point is less than regular rigid conduit, which will probably do the same thing.-Dave White, Titan Intl., Inc., Quincy, IL
Focus on training
As a former plant operator, turned training instructor, I think your Editorial, “The wheels are coming loose” (PE, July 2000, p 12), is right on the mark.
Serious problems develop when personnel are not specifically trained in all areas of plant responsibilities. Every time we read about an accident or other catastrophe in a plant operation, it can almost always be linked to a lack of communication and training.
The Gulf Coast Process Technology Alliance is trying to correct this problem. This group of industry members and educational institutions are working together to standardize training for plant personnel. Find out more at www.
processtech.org/gcptahome.htm.-Martha McKinley, Eastman Chemical Co.