May 1, 2011
By Jack Smith
For nearly 10 years now, trade publications, manufacturers, consultants, and electrical training organizations have been providing a tremendous amount of information about arc flash. This increasing arc flash awareness is a good thing - it’s as it should be. However, without diminishing the risk of arc flash, let’s not ignore the fact that those who work with and around electricity also face electrical shock and electrocution hazards.
At the “Manufacturing and Automation Summit”
I recently attended the “Manufacturing and Automation Summit” in Chicago, hosted by Plant Engineering and Control Engineering magazines. Two of the session speakers were H. Landis “Lanny” Floyd, principal consultant for electrical safety and technology at DuPont Engineering; and Joe Weigel, product manager for Square D Services at Schneider Electric.
Weigel and Floyd discussed how a growing industry has been built around companies providing arc flash hazard analysis, training, personal protective equipment (PPE), and arc mitigating equipment. Floyd said that when some people offer seminars on “NFPA 70E,” the agenda lists only arc flash related topics. “‘NFPA-70E’ is not just about arc flash, it’s about electrical safety,” he said. “The biggest hazard is still electrical shock.”
According to Electrical Safety Foundation International (ESFI):
Each May, ESFI sponsors National Electrical Safety Month. ESFI (www.electrical-safety.org) is a joint effort between Underwriters Laboratories Inc., the U.S. Consumer Product Safety Commission, and the National Electrical Manufacturers Association (NEMA).
The immediate effects of electrical shock include muscle contraction, tingling, pain, labored breathing, disorientation, and dizziness. Long-term effects include memory loss, nervous disorders, chemical imbalances, vital organ damage, and death in some cases.
How to guard against electrical shock injuries or electrocution
De-energizing electrical circuits before working on the equipment they energize is the best way to guard against electrical shock injuries or electrocution. According to “NFPA 70E: Standard for Electrical Safety in the Workplace,” the first step in preventing electrical shock is placing circuits in an electrically safe working condition by locking out and tagging out all electrical energy sources.
Just because the circuits have been locked out and tagged out, never assume that the equipment or system is actually de-energized. Merely shutting off the power is not enough because hazardous conditions can still exist. There could be a tie breaker in the system that never made it onto the electrical documentation. Also, some systems are configured so that removing power automatically kicks in a backup generator. Therefore, the next step, according to “NFPA 70E,” is to verify that no electrical energy is present. In addition to identifying all possible energy sources that could feed the circuit, test the circuit to ensure that all power has been removed.
At a minimum, use a non-contact voltage detector to verify that each circuit is de-energized. Ideally, don full PPE and test each circuit first with an electrical test tool. Of course, until it’s determined that the equipment is de-energized and in a safe work condition, PPE appropriate to the potential hazard level must be worn. Also, ensure that the test equipment used for the verification process is working properly both before and after use. Using high-quality test equipment designed specifically for the intended task is critical. Test tools must hold the correct CAT rating for the task.
You’ll find useful application notes about safety, from “10 Dumb Things Smart People Do When Testing Electricity” to “Preparing for Absence of Voltage Testing.”
Both lock-out/tag-out and verification are covered in “NFPA 70E” Chapter 1, Section 120.2(D).
NFPA 70E acknowledges that it is not always feasible to de-energize electrical circuits prior to performing work. There are some justifications to working on energized systems, according to Weigel. “Infeasibility would be tasks such as voltage testing, troubleshooting, diagnostics, and infrared thermography,” he said. “However, it still has to be done safely. There’s way too much work that goes on energized than there should be.”
When work must be done on live circuits, it must be authorized using an “Energized Electrical Work Permit” signed by a person at the facility with the authority to do so. This permit describes the work to be performed and why it must be performed while energized. There must also be a written detailed job plan for the specific tasks to be performed safely. Each person who will be doing the work must verify that they understand the job plan.
Another tool is common sense
When working around electricity, another tool is common sense. There’s an excellent Application Note on the Fluke website titled “Ten dumb things smart people do when testing electricity.” It was developed to be a quick reminder of what not to do when taking electrical measurements. Not only does it give good advice that electrical workers should follow every day, it also lists the hazard/risk categories described in “NFPA 70E” and the overvoltage CAT ratings. It continues to be one of the most-visited pages on the Fluke website.
Although electric shock injuries and electrocution fatalities have declined significantly over the past 15 years, there are still too many. Be safe - don’t become a statistic.
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Until next time, keep standing on “Solid Ground.”