Arc Flash & Electrical Safety: December 2007

Friday, December 21, 2007

Top Safety Story of 2007

Occupational Hazards E-News has put out their list of the top ten most read news stories on their web site in 2007. The #1 most read story was about OSHA issuing a final rule on electrical standards.

Here is the February 13th press release from OSHA:

OSHA Issues Final Rule on Electrical Installation Standard

WASHINGTON -- The Occupational Safety and Health Administration will publish a final rule in tomorrow's Federal Register for an updated electrical installation standard.

"These are the first changes to the electrical installation requirements in 25 years, so it is important the standard reflects the most current practices and technologies in the industry," said Assistant Secretary for Occupational Safety and Health Edwin G. Foulke Jr. "The revised standard strengthens employee protections and adds consistency between OSHA's requirements and many state and local building codes which have adopted updated National Fire Protection Association (NFPA) and National Electrical Code provisions."

Changes to OSHA's general industry electrical installation standard focus on safety in the design and installation of electric equipment in the workplace. The updated standard includes a new alternative method for classifying and installing equipment in Class I hazardous locations; new requirements for ground-fault circuit interrupters (GFCIs) and new provisions on wiring for carnivals and similar installations.

The final rule updates the general industry electrical installation requirements to the 2000 edition of the NFPA 70E, which was used as the foundation of the revised standard. The final rule also replaces the reference to the 1971 National Electrical Code in the mandatory appendix to the powered platform standard with a reference to OSHA's electrical installation standard.

Under the Occupational Safety and Health Act of 1970, employers are responsible for providing a safe and healthful workplace for their employees. OSHA's role is to assure the safety and health of America's working men and women by setting and enforcing standards; providing training, outreach, and education; establishing partnerships; and encouraging continual process improvement in workplace safety and health. For more information, visit www.osha.gov.

Labels: Electrical Hazards, OSHA

posted by Steve Hudgik | This Arc Flash Post and 0 Comments | Add Comment | links

Wednesday, December 19, 2007

Isolating the Risk of Catastrophic Arc Flash Explosions

Betty Jackson, of Hoffman, has publish a white paper titled "Isolating the Risk of Catastrophic Arc Flash Explosions" that is available online. This paper makes that point that arc flash incidents will happen and that a solution is the Hoffman SEQUESTR™ External Disconnect Enclosure.

The paper begins by providing an overview of arc flash, its causes and the damage that can result. It gives this summary of arc flash hazards:

"According to NFPA 70E Standard for Electrical Safety in the Workplace, 2004 Edition, pages 12 and 28, the two most important numbers to remember are 1.2 and 40. Incident energy levels greater than 1.2 calories per centimeter-squared can produce second degree burns. The NFPA 70E requires that workers wear personal protective equipment (PPE) when working with 50 volts or more. Arc flash levels above 40 calories per centimeter squared can be fatal and usually result in a massive pressurized blast with sound pressure waves and projectiles. The PPE is available for exposures up to 100 calories per centimeter-squared; however, the force from the pressurized blast can be fatal regardless of the PPE."

The white paper then goes on to point out that in spite of best efforts, because of the large number of variables--some of which may be unknown--the true extent of the arc flash hazard can never be known. In addition, the paper points out something I know to be true from personal experience:

"During private discussions, electrical engineers have revealed that, despite their compliance training, they sometimes skirt the PPE rules because the bulky, fire retardant suit, gloves, face shield/goggles and other gear is hot, uncomfortable and makes service and maintenance time-consuming and cumbersome."

The second half of the white paper dicusses the SEQUESTR™ External Disconnect Enclosure.

"The SEQUESTR™ External Disconnect Enclosure attaches to the side of a main control enclosure and houses only the disconnect switch or circuit breaker, physically removing it from the main enclosure."

"Live power is no longer present in the main control enclosure when power is turned off at the disconnect switch. It completely shuts down the power in the main cabinet, and there is no hazard of power coming into the box. Its system also interlocks the doors of the main control cabinet when the disconnect switch is powered on. This allows users to comply with the disconnect door interlocking requirements of UL 508A, NFPA79, IEC 60204, and HS 1738, the most common electrical standards for industrial machinery."

Use the link above to read the entire white paper.

Labels: Arc Flash, Preventing Arc Flash Accidents

posted by Steve Hudgik | This Arc Flash Post and 0 Comments | Add Comment | links

Free Online Electrical Formulas

The following web sites provide general purpose electrical formulas and information:

Search Electrical provides a range of electrical formulas and resources available as Excel spreadsheets or PDF files. They include an Arc Blast Calculator available as an Excel spreadsheet. A Fault Current spreadsheet and planning documents. Plus there are links to free online conversion utilities and other resources.

MC² is a company that provides estimating services for contractors. They provide a page with electrical formulas for estimators. The following formulas are provided: AMPERES when KVA is known; AMPERES when horsepower is known; AMPERES when kilowatts are known; KILOWATTS; KILOVOLT/AMPERES; HORSEPOWER and WATTS.

ConWeb provides a variety of technical tables, including Electrical & Mechanical Formulas . These include: OHMS Law; Power - AC Circuits; Power - DC Circuits; and formulas for fan, blower and pump motors.

BOWest Party, Ltd. - Electrical & Project Engineering has a library with a wide variety of electrical information and formulas such as Electrical Circuit Theorems; Electical Circuit Formulas; and Electrical System Formulas. All of the formulas are indexed at the bottom of their page.

Labels: Electrical Information

posted by Steve Hudgik | This Arc Flash Post and 0 Comments | Add Comment | links

Thursday, December 13, 2007

The Myths and Realities of Arc Flash Protection

Electric Energy Online has an excellent article that is mostly about Personal Protective Equipment (PPE) used for arc flash protection. It discusses 10 myths about arc flash.

MYTH 1: Arc Flash explosions do not happen… I have never seen one.
MYTH 2: There is nothing anyone can do to protect against an Arc Flash explosion
MYTH 3: Will Street Clothes made of cotton or other natural fibers protective me?
MYTH 4: Spectacles and Sunglasses will protect me from the heat of an Arc Flash exposure
MYTH 5: I wear a face shield… that should be enough
MYTH 6: I wear a face shield… when would I need a hood?
MYTH 7: FR Clothing is all the same.
MYTH 8: ATPV = 100% Protection
MYTH 9: Aluminized clothing is an effective choice for protection from Arc Flash hazards.
MYTH 10: I am confused by the Table 3.3.9.3 in NFPA 70E. What exactly is a Hazard/Risk Category?

It is a good, practical real-word article that provides explanations demonstrating that all of the above are myths.

Labels: Arc Flash PPE

posted by Steve Hudgik | This Arc Flash Post and 1 Comments | Add Comment | links

Wednesday, December 12, 2007

Every Industry Needs To Address Arc Flash Hazards

Last Friday members of the International Association of Operative Millers' (IAOM) Wheat State District met in Wichita, KS. This is an international organization for grain millers. GrainNet reports that "Protecting millers against the dangers of an arc flash comprised the bulk of the technical session."

It is great to see industry paying attention to and addressing the need to implement arc flash safety. Although establishing safe work practices and labeling equipment that presents an arc flash hazard has been required by NFPA 70E for a number of years, many are still not aware of the hazards of arc flash.

To help increase arc flash awareness we have just published a new page on our web site that provides an overview and introduction to the dangers of arc flash. We will be publicizing this page in the materials we distribute to our customers.

Labels: Arc Flash

posted by Steve Hudgik | This Arc Flash Post and 0 Comments | Add Comment | links

Monday, December 03, 2007

To De-Energize or Not to De-Energize

One of the most important decisions in planning an electric task is whether to de-energize. Whenever possible, live parts to which you might be exposed should be put into an electrically safe work condition, unless your employer can demonstrate that de-energizing creates more or worse hazards, or is not practical because of equipment design or operational limitations.

You might need to work live to avoid interrupting life-support systems, deactivating emergency alarm systems, or shutting down ventilation equipment for hazardous locations, for instance. And de-energizing would not be practical during testing of live electric circuits or work on circuits that are part of a continuous process that cannot be completely shut down.

De-Energizing
An Electrically Safe Work Condition

The most important principle of electric safety is, assume electric circuits are energized unless you make sure they are not. Test every circuit and conductor every time you work on them. The National Fire Protection Association lists six steps to ensure conditions for electrically safe work.

1. Identify all sources of power to the equipment.

2. Interrupt the load current, then open the disconnecting devices for each power source.

3. Where possible, visually verify that blades of disconnecting devices are fully open or that drawout-type circuit breakers are fully withdrawn.

4. Apply lockout/tagout devices in accordance with a formal, written policy.

5. Test each phase conductor or circuit part with an adequately rated voltage detector to verify that the equipment is de-energized. Check the voltage detector before and after each test to be sure it is working.

6. Properly ground all possible sources of induced voltage and stored electric energy (such as, capacitors) before touching. If conductors or circuit parts that are being de-energized could contact other exposed conductors or circuit parts, apply ground-connecting devices rated for the available fault current.

The process of de-energizing is "live" work and can result in an arc flash due to equipment failure. When de-energizing, follow the procedures described below in "Working On or Near Live Circuits."

The above was taken from a NIOSH article that also covers lockout/tagout and information about working on or near live circuits.

Labels: Construction, NIOSH

posted by Steve Hudgik | This Arc Flash Post and 0 Comments | Add Comment | links