Every day MIDWEST’s Switchgear Division receives interesting calls, mostly about technical stuff. Often just plain old problem solving. And sometimes an emergency request for a replacement bus plug. Every once in a while we are asked whether the bus plug we sold was new or used. They couldn’t tell the difference. An example is a call about a Square D PQ3603G bus plug. The customer thought we made a mistake and sent them a new bus plug instead of a used PQ3603G. He was a bit surprised when we told him it was used, but had been reconditioned by MIDWEST. The reconditioning process is a full detailed disassembly, reconditioning of components, reassembly and final quality control testing and inspection. Thirty years ago, the common practice for some companies may have been to just wipe a used bus plug off and send it out the door. Those days should be long gone. Unfortunately there are suppliers that still don’t do much more than cosmetics. MIDWEST has a huge advantage.We are a full service electrical testing and switchgear maintenance company and have been for over 30 year. In addition to high current and high voltage test equipment, we have test stations to simulate normal installation and operation of electrical equipment. Reconditioning a used Square D PQ3603G bus plug to look like new is routine work at MIDWEST.But it is always nice to get a compliment from our customers.We passed it on to the Switchgear Services Shop.We have received similar compliments about other equipment, such as fused panel board switches, circuit breakers, transformers, etc.
We asked MIDWEST’s Switchgear Shop for an example of a replacement bus plug problem or defect that would not be picked up by standardized reconditioning and testing procedures.Procedures that might be found in published data. We were looking for something that went directly to the value of experience. The value of quality workmanship.Here’s a quick example from one of MIDWEST’s switchgear Engineering Technicians.
He spoke of a Federal Pacific bus plug, catalog number LSP 1436SN, 600 volt, 400 amp, just as an example. He said it could just as well be a Cutler Hammer Bus Plug catalog number HD 1364N, or a replacement Square D bus plug or Westinghouse bus plug. It didn’t make a difference.A service company could simply test, or repair or completely recondition a bus plug. Then perform the tests that look for current or voltage related problems. Do the quality control physical and mechanical inspection. The reconditioned Square D bus plug could look and perform so well that you might think it was brand new. But as part of the quality control, veteran Engineering Technicians
Cutler Hammer HD1364N Bus Plug For Sale by MIDWEST
know to double check the nameplate of the reconditioned bus plug with what they actually have. They said this could very easily be missed, because the nameplate is always correct, almost. The last error he found was a bus plug that had a neutral indicated in the catalog number on the nameplate, like the two just mentioned, but actually did not have the neutral bus. It had been removed. It came into the Switchgear Shop that way, as was determined by inspecting other bus plugs in the same lot. Just a detail, a really big detail. So standardized tests can not replace experience and quality workmanship.
Sometimes you couldn’t write the script for the strange things that happen in the real world.At least in our world of reconditioning old used bus plugs and selling them to folks that tell us they couldn’t tell the difference from new.The technical world seems so boring to outsiders, but MIDWEST has its share of action. For example, a large food processing facility called at 6:15 PM on a Monday night, in a screaming panic, because they needed a replacement 200 amp bus plug and they needed it right away. They couldn’t get a new one immediately and the electrical suppliers for most of the US were already closed for the day.The cracking in his voice changed to audible relief when we told him we had a fully reconditioned Square D PQ3620G bus plug, boxed and ready for shipping pickup. It was set to go to another customer, but it was part of an order for over 100 bus plugs and there was no urgency for it to ship. It was a shipping scramble but the food processing plant had their like new Square D bus plug the next morning. What’s the chance MIDWEST would have a Square D PQ3620G bus plug sitting at the shipping dock, ready to go, and someone calls and needs it “right now.”The answer to that question is that it’s much more common than one would ever guess. It seems improbable, but it happens fairly often. The odds may be higher because of the number of bus plugs, transformers and circuit breakers we ship.But it’s always a nice thrill for MIDWEST to defy the odds. And it gives the Engineers something to argue about, the odds versus reality.
MIDWEST had an emergency call from a manufacture because they blew up a large 800 amp bus plug and their production was down. They were the primary ‘just in time’ supplier of some parts to a larger manufacturer. They couldn’t afford a major loss of production because they would then become the secondary supplier or even worse.We had a replacement reconditioned bus plug but they wanted someone to look at their bus duct system and the other old bus plugs because something just didn’t seem right when the 800 amp bus plug failed.
When we inspected the bus duct, we had to do a double take on what we saw. The brackets supporting the splice connection at the ends of each section of bus duct were melted away in some areas. And some of the hangers and supports also had damage. It was as if someone had taken a welder or cutting torch and melted away parts of the bus duct support brackets and other supports and bolts along the length of the bus duct. This was a four wire system.But you might think of it as a five wire.A, B, and C phase, plus neutral, and ground.It was apparent they had an unprotected fault from phase to ground, a ground fault. The ground, in this case, was the metal enclosure and supports for the bus duct. The bus duct was protected by an old 2000 amp fused bolted pressure switch. There was no ground fault protection on the old system. Before the 2000 amp fuse blew, a lot of welding and melting took place.Fortunately only one replacement bus plug was needed and one section of bus duct had to be replaced. The arcing and melting damage to steel brackets and supports, although visually dramatic, was not enough to prevent them from getting back on as soon as the damaged section of bus duct and damaged bus plug were replaced. They intended to complete other structural repairs later, maybe. At the time, their only concern was to get production back up as soon as possible, even if it was only temporarily. We all know how stressful production schedules can be. The cause of the problem was failed supports on their old obsolete bus plug. It lasted a long time, but eventually it sagged enough for one phase to go to ground, the metal enclosure.And after a few moments of 277 volt arc welding, they had a mess.
