ISHN February 2012 : Page 49
49 infrared viewing windows and finger-safe component barriers, are just a sample of the available options that help provide further protection and reduce the risk of personnel making contact with energized components. One of the newest features in LV and MV MCC technology is the use of built-in networking and pre-configured software. By including a built-in indus-trial network, based on an open protocol, along with MCC monitoring and configuration software, users can remotely monitor, configure and troubleshoot the MCC, minimizing the need for personnel to enter into an arc-flash boundary zone. is not rated as arc resistant. Even if reducing the risk category by keeping the door closed on a LV MCC were allowed, the real question is: Will the door stay closed in the event of a fault in the unit? The reality is that during an internal arcing fault, the doors of equipment that is not arc-resistant may come open, even if they were properly closed and latched per the manufacturer’s specifications. implements arc-resistant control equipment. 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 manu-facturers must be diligent in their training practices and highly selective in their technology choices to increase workplace safety in compliance with present safety standards. John Kay is senior product specialist, Institute of Electrical and Electronics Engineers (IEEE) Fellow, Rockwell Automation. Diligence pays off Ultimately, the best prevention against exposure to an arc flash is a safety program that complies with the requirements outlined in the NFPA 70E standard and Clearing the confusion Understand performance criteria that must be met before the equipment can be classified as an arc-resistant design. “Arc-resistant,” as it applies to electrical equipment like MV 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 expect-ed performance the equipment must deliver in the event of an arc flash. In many cases, motor controls that are not arc-resistant simply cannot withstand the effects of internal arcing faults for the tests prescribed in the IEEE standard. Instead of achieving the advanced level of protection being sought, many users instead are relegating their strategy (perhaps unknowingly) to one based solely on preventive measures. This limited approach may not fully address arc-flash dangers and may only protect a small scope of users. A fundamental approach to arc-flash safety must include all personnel, electrically quali-fied and nonqualified. Arc faults can occur during normal operation without any specific human action and affect someone simply “minding their own business,” such as walking by the equipment or sweeping the floor in the equipment room. Arc-resistant control products are designed to contain the arc energy and direct it away from personnel. Sticking to the standards In the case of LV MCCs, 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. According to NFPA 70E, PPE levels are to be determined by either using the “default” hazard/risk category tables contained in the standard or by calculating the expected arc-flash incident energy using one of the methods described in the standard. For the closed-door activities described in the default tables, the hazard/risk category assumes that no abnormal condition (like an arc fault) will occur, or if it does, the unit door will remain closed. This is a potentially fatal assumption if the equipment To: Carol Paulsen From: Ted Jordan $100 Best Buy ® e-Gift Card Carol: Thanks for participating in our program. We truly appreciate your involvement. Please enjoy this reward — you deserve it! -Ted Introducing Best Buy ® e-Gift Cards ISHN FEBRUARY 2012 Take a moment to make someone’s day with Best Buy e-Gift Cards. Just order, add a personal message and get quick, online delivery. They’re redeemable at any Best Buy store in the U.S. or online at BestBuy.com ® . Learn more at CorporateGiftCards.BestBuy.com/ISHN . No fees. No expiration dates. Just happiness ™ — at exactly the right moment. www.ishn.com BEST BUY, the BEST BUY logo, the tag design and BESTBUY.COM are trademarks of BBY Solutions, Inc. © 2011 BBY Solutions, Inc. All Rights Reserved. 11023 CIRCLE 236 FOR FREE INFO