Buckles-Smith's Tech Blog

Allen-Bradley Centerline 2100 Motor Control Center

Allen-Bradley Centerline 2100 Motor Control Center

with ArcShield, Arc Flash Protection

The use of multiple and differing automation systems in a single plant brings its own unique set of potential hazards and training requirements – forcing companies to work proactively and diligently to increase workplace safety. One rapidly growing area of focus is on reducing risk in situations where workers must enter an area with arc flash potential by creating arc flash protection boundaries.

Arc flashes – the concentrated radiant energy that explodes inside electrical equipment following an arc fault – are responsible for about 80 percent of all electrical-related injuries. In North America, five to 10 arc flash events occur every day. What makes an arc flash such a dangerous event is the extreme temperatures involved, which in some cases can reach 35,000 degrees Fahrenheit – almost four times the surface temperature of the sun. Moreover, the pressure wave from the blast is equivalent to that of a hand grenade.

Arc Flash

The causes of arc flash are usually accidental. Air is typically used as an insulating material in many electrical equipment designs. If that air space is compromised (via water infiltration or a misplaced tool), the electrical energy will try to pass from point A to point B through the air. This could ignite an electrical arc, resulting in an arc flash event.

An in-house safety program that complies with the NFPA 70E standard offers protection against exposure to an arc flash. Companies also can install arc-resistant motor control equipment and intelligent control systems, which offer enhanced safety features and remote operation and monitoring capabilities. Arc resistant equipment can't prevent an arc flash, but it is designed to control arc flash exposure by either extinguishing the arc, controlling the spread of the arc or by channeling the arc energy away from personnel.

As new standards continue to raise the awareness of arc flash hazards, users are looking for leading-edge products capable of delivering these higher levels of safety. To meet these needs, Rockwell Automation developed the Allen-Bradley CENTERLINE® 2100 motor control center (MCC) ArcShield™ . This version of the CENTERLINE 2100 MCC provides unmatched arc flash protection in a low-voltage MCC (up to 600 volts). Rockwell Automation is the first equipment manufacturer to apply arc-containment features to features to low voltage NEMA MCCs.

ArcShield features a reinforced enclosure and special arc-containment door latches that, when properly engaged, allow internal pressure relief and help keep the doors from unlatching during an arcing fault. By containing the arc fault, the potential of worker exposure to hazardous conditions can be reduced. ArcShield also helps contain arc faults by using a lower horizontal bus rating (maximum 1,200 ampere bus) and smaller main disconnects, which help reduce the amount of let-through energy within the MCC.

ArcShield Latch

ArcShield is available with several optional features, including blown fuse indicators, windows on unit doors and infrared inspection ports, which allow hands-off inspection of unit status. Optional finger-safe barriers help minimize the chance of a potential arc-flash being initiated by accidental contact with energized parts. These added features to the MCC meets Type 2 protection requirements (in accordance with IEEE C37.20.1 ), which are designed to shield personnel from arc exhaust materials on the front, rear and sides of the enclosure.

Rockwell Automation also offers an ArcShield medium-voltage (up to 7,200 volts) arc-resistant MCC. The design redirects arc flash energy out relief vents at the top of the unit and away from personnel through an overhead plenum. To contain the pressure blast, the ArcShield controller's cabinet is heavily reinforced with additional support members and plates and uses 12-gauge steel for all doors, as well as side, roof and back sheets. Extra strength, multipoint latches and robust door hinges add to the security of the unit's main doors.

A key differentiator of the medium-voltage ArcShield MCC is that it maintains Type 2 protection (in accordance with IEEE C37.20.7 ) even with the low voltage door open for maintenance purposes. The controllers are compartmentalized and the low-voltage panel is reinforced and sealed to prevent arc flash materials from entering it.

Both low and medium-voltage ArcShield products are equipped with built-in DeviceNet wiring and can incorporate Intelligent Motor Control capabilities – such as real-time monitoring – thanks to IntelliCENTER® software.

This technology allows users to monitor, configure and troubleshoot the MCC via DeviceNet, helping to further minimize exposure to hazardous voltages. When an Ohio-based scrap metal recycler wanted to improve the safety of its MCCs and reduce the amount of protective equipment its workers needed to wear, it relied on ArcShield medium-voltage MCC technology to meet its needs.

With compartmentalized and sealed low-voltage compartments, workers can perform certain troubleshooting in the low-voltage compartment with a reduced risk of exposure to arc flashes, allowing them to wear a lower class of protective equipment. "I was most impressed by the medium-voltage ArcShield enclosure," said the company's reliability team leader. "The latching mechanism on the door goes around the entire perimeter of the door, whereas most of our older MCCs only have latches on the opening side. The separated low-voltage compartment also reduces exposure to the high-voltage. We really feel like we are keeping our employees safer."

To assess arc flash hazard risk, Buckles-Smith provides Arc Flash Analysis service. The Buckles-Smith Services Team will review your facility’s existing electrical system, perform an onsite inspection, and determine arc flash energy levels, boundaries, and required personal protective equipment (PPE). You can learn about the whole scope of the Arc Flash Analysis on our Arc Flash webpage: Arc Flash Analysis, including an example proposal outlining specific deliverables.

If you want to know more about Rockwell Automation's line of MCCs, contact Buckles-Smith and we will put you in touch with the appropriate technical specialist.

Buckles-Smith is an electrical distributor with multiple stocking locations throughout Northern California and the San Francisco Bay Area. Contact us today for any questions you may have and we'll help you out.

Contact Buckles-Smith      800-833-7362

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Posted: Mar 3, 2014,
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Author: Chris Mahler
Chris Mahler

Chris MahlerChris Mahler

Working with the customers Motor Control Center specification, Chris will provide the optimal solution for the MCC requirements. Chris partners with Rockwell Automation to provide parts repair, engineering services and training for Allen Bradley Motor Control Centers.

Other posts by Chris Mahler

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