MCC innovations reducing the risk of arc flash incidents

With a pressure wave similar to a hand grenade and the potential to produce heat nearly four times the temperature of the sun, arc flash hazards pose serious danger. That’s why manufacturers across all sectors of industry are implementing techniques and practices designed to reduce these hazards and help protect workers.



With a pressure wave similar to a hand grenade and the potential to produce heat nearly four times the temperature of the sun, arc flash hazards pose serious danger. That’s why manufacturers across all sectors of industry are implementing techniques and practices designed to reduce these hazards and help protect workers.

The causes of arc flash are usually accidental %%MDASSML%% for example, maybe a rodent or water accidentally enters electrical equipment or an employee accidentally forgets to tighten a connection. When this happens, an arc fault superheats the air around it, expands and creates a pressure wave within the electrical enclosure.

This arc plasma vaporizes everything it comes in contact with %%MDASSML%% copper, insulating materials, bolts and the steel enclosure %%MDASSML%% and can cause serious injury to workers. Injuries can include severe burns from the burning and vaporized materials, damaged hearing from the sound waves and impaired eyesight from the high-intensity flash.

Intensifying the focus

Historically, electric codes and safety standards did not directly address arc-flash hazards; they only addressed protection from fire, electrocution and shock hazard. But standards such as “NFPA 70E%%MDASSML%%Electrical Standard for Safety in the Workplace” are putting more focus on arc-flash risks and helping reduce the associated hazards in North America.

As codes and standards evolve, users are looking for leading-edge products capable of delivering higher levels of safety. Arc-resistant motor control centers and intelligent control systems are fulfilling that need in many applications. Such solutions offer improved safety features along with remote operation and monitoring capabilities.

Creating an effective design

An arc-resistant MCC is designed and built to provide a complete structural solution, with the ability to contain and redirect the arc energy away from personnel and capable of providing Type 2 accessibility. Type 2 accessibility, as defined within IEEE standard C37.20.7-2007, helps shield personnel on the front, rear and sides of an enclosure from the effects of an internal arcing fault. Core features should include:

  • Structural integrity through a solid, robust design

  • Two side sheets on every section

  • Well-isolated horizontal bus and vertical bus insulated in a nonconductive labyrinth support

  • Automatic vertical bus shutters

  • Unit isolation

  • Dedicated unit ground stab and vertical ground bus.

    • Rugged structural design and a well-supported, isolated and insulated bus system are critical for an MCC to withstand the effects of an arc-flash event. Two side sheets on every section and a robust bus support design contribute significantly to the ability of the equipment to contain and redirect the arc-flash energy.

      To help isolate and protect users from potentially hazardous voltages, the MCC should employ a solid grounding system, along with a well-isolated and insulated horizontal bus and vertical bus. For added safety, spaces which accommodate plug-in units should include automatic shutters that immediately isolate stab openings when units are removed.

      One of the newest features in MCC technology is the use of built-in networking and preconfigured software. By including a built-in industrial network, based on an open protocol like DeviceNet, along with MCC monitoring and configuration software, users can remotely monitor, configure and troubleshoot the MCC, minimizing the need for personnel to enter an arc-flash boundary zone.

      Clearing the confusion

      In considering an arc-resistant MCC, it’s important that users understand the performance criteria that must be met before the MCC can be classified as an arc-resistant design. “Arc-resistant,” as it applies to electrical equipment like low voltage MCCs, is a recognized industry term defined by IEEE C37.20.7-2007. The standard defines the test requirements that must be met and the expected performance equipment must deliver in the event of an arc flash.

      Some vendors may use terms like “arc flash-resistant” to describe their product with the implication that it offers substantiated arc-resistant capabilities. However, “arc flash-resistant” is not a standard industry term and has no relevant meaning behind it.

      Another area of confusion centers on the claim that keeping the doors of an MCC closed during insertion and removal of power stabs provides a lower risk, and therefore allows users to adhere to a reduced level of required PPE. The reality is no industry standard allows users to reduce the risk category of an MCC application just because the door is closed.

      Diligence pays off

      Ultimately, the best prevention against exposure to an arc flash is an in-house safety program that complies with the NFPA 70E standard. Beyond that, the most important advice is “shut it off.”

      Because of high-production volumes and the use of multiple and differing automation systems in a single plant, identifying and significantly reducing potential hazards can be a complex task. This means end users and employers must be diligent in their training practices and highly selective in their technology choices to increase workplace safety.

      The good news is advances in control technology make it easier with an expanded array of solutions designed to deliver improved safety, increased productivity and greater cost-savings.

      Employers must be diligent in their training practices and highly selective in their technology choices to increase workplace safety.

      Good maintenance practices can help lower maintenance costs by 60%.

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
The true cost of lubrication: Three keys to consider when evaluating oils; Plant Engineering Lubrication Guide; 11 ways to protect bearing assets; Is lubrication part of your KPIs?
Contract maintenance: 5 ways to keep things humming while keeping an eye on costs; Pneumatic systems; Energy monitoring; The sixth 'S' is safety
Transport your data: Supply chain information critical to operational excellence; High-voltage faults; Portable cooling; Safety automation isn't automatic
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Synchronizing industrial Ethernet networks; Selecting protocol conversion gateways; Integrating HMIs with PLCs and PACs
Why manufacturers need to see energy in a different light: Current approaches to energy management yield quick savings, but leave plant managers searching for ways of improving on those early gains.

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.