A Switch in Time

Edison Welding Institute realized efficiency and safety gains from installing combination plug/receptacle and disconnect switches at more than 100 of its workstations.

• By Bill Fortman
• Jul 01, 2010

A continual need to move welding equipment between more than 100 different workstations at Edison Welding Institute made it difficult to disconnect electrical power quickly and safely each time. By installing a combination plug/receptacle and disconnect switch at each location, EWI has been able to save time, gain greater flexibility, and improve safety. The awitch-rated plugs and receptacles now used at the facility allow workers to safely make and break electrical equipment connections, even under full load.

EWI is the leading engineering and technology organization in North America dedicated to the applied research and development of materials joining and welding. It provides expert materials joining assistance, as well as research, consulting, and training, to its members in the aerospace, automotive, government, energy and chemical, heavy manufacturing, medical, and electronics industries. Its 40,000-square-foot high-bay laboratory provides the space to set up individual workstations for a large number of projects simultaneously. Three 1,600 amp bus bars provide 480 volt power throughout the laboratory, with more than 100 separate power drops for welding power supplies.

Because of the nature of EWI's assignments, workspace layouts and equipment are constantly being rearranged. "We have nearly every one of the recognized welding processes commonly used today, and they all require electricity," said Andy Joseph, manager, Welding and Testing Labs. "The equipment for all these different procedures takes space, but we're not using them all at the same time, so we need to be able to change them out."

Previously, fused disconnects were attached directly to the overhead bus bars, with pin-and-sleeve connectors at the workstations. Safety was a concern because the disconnects were located at the ceiling level. "We had to use a 20-foot pole with a hook on the end to turn off the power to a plug. Disconnecting live would have been an unsafe option," Joseph explained. From a safety standpoint, there was no way to disconnect quickly if someone were getting hurt.

As a remedy, EWI first considered installing disconnect switches at ground level for each location. This still would have required the pin-and-sleeve plugs to connect the equipment, and the switch boxes would have taken up valuable space. Joseph said with 120 of the old connectors, "we would have had to buy 120 disconnect boxes that would have required extra wiring."

Instead, he selected the switch-rated plugs and receptacles, which combine the two functions. They are installed at more than 100 locations in the lab and make disconnecting power a simple and safe operation. Pressing a push-button off-switch on the receptacle breaks the circuit and ejects the plug to its rest position. The plug then can be withdrawn from the receptacle in complete safety because the circuit is already dead. When the plug and receptacle are separated, de-energization can be visually verified, and a safety shutter on the receptacle prevents access to live contacts.

Easier 70E Compliance
Safety was the key factor in the decision to use the switch-rated plugs and receptacles. Joseph said simplified compliance to the NFPA 70E standard was an additional benefit from using the devices. "With the disconnects overhead, we would have had to suit up with PPE because there was no way to verify that the power was disconnected without someone going up in a manlift. Having the disconnect switch right in the plug eliminates the need for an arc flash hazard assessment or suiting up."

In addition to safety, the Meltric Decontactor Series switch-rated plugs and receptacles provide greater flexibility in EWI's operations. "We have a limited amount of space and are continually changing out equipment for different projects," said Joseph. "When we start or finish a project, we can pull out one set-up and bring in another, quickly and safely." Approximately half of the laboratories are set up for systems welding, with the other half divided between arc welding and laser welding. Moving one technology into another area is very simple with the devices in place, he said.

Another benefit is easier installation of the Decontactors (which were provided through Meltric distributor Johnson Electric Supply of Columbus, Ohio) compared to the previous pin-and-sleeve connectors, and there is a relative cost savings because of the inconvenience of installing the former connectors. "They required soldering," Joseph noted, "and we are constantly swapping equipment in and out."

In addition to the welding power supplies, EWI uses auxiliary equipment such as hoists, wire feeders, fume extractors, welding positioners, robotics, and travel carriages. Joseph said he purchased 20 each of Meltric's 20 amp and 30 amp Decontactors for these applications, all rated for 480 volt operation. "Probably the biggest benefit for us has come from efficiency improvements," he said. "Previously, because of the difficulty with making disconnects during a changeover, we would leave workstations set up because it was hard to take them apart and put them back together. This made floor space hard to come by. It also caused some turf wars on how space was being used. Now, changeouts are easier to accomplish, we have a more presentable area, and the engineers and technicians don't have to worry about someone else tearing down their workstation because it is easy to set up again."