Proper safety precautions should assume all mechanical devices have failed to operate properly until proper operation is verified.

The following information is a good example of why safety procedures are so important for even simple tasks like opening and closing switches and breakers. The Square D, HVL switch, in some cases, may not properly open all blades even though the mechanism is operated properly and appears to be in the “open” position. As indicated on the Square-D HVL warning label, you should verify that all blades are cleared before proceeding with any work. The HVL switch design may go back several years, but the warning labels appear to be relatively recent.

A colleague reports that during a recent HVL maintenance procedure, the switch mechanism was opened and the electrician proceeded to attach a ground strap. The crew called him the human cannon ball as he was blown back from the blast. Thankfully, the electrician was wearing PPE level #4 and was not injured. Review of four (4) subsequent HVL switches at the facility showed that all four did not open properly.

The above safety precautions should not be construed to single out just Square D and their HVL switch. Again, proper safety precautions should assume all mechanical devices have failed to operate properly until proper operation is verified!

In a very unfortunate, similar incident, a death caused by a medium voltage switch is reported here.

Overview

With industry adopting NFPA 70E, and Canada’s Z462 as the consensus electrical safety standard, North American facilities and many of their counterparts worldwide are performing arc flash hazard studies to label their electrical equipment for safety. The requirement for arc flash hazard labeling is found in the National Electrical Code, Article 110.16 for new equipment, NFPA 70E-2009 Article 130.3(C) for existing equipment, and OSHA 1910.335(b)(1) for general safety hazards.

There are as many different ways to label equipment as there are engineers and electricians in industry. Unfortunately, many of the methods being used are incorrect and may actually decrease worker safety, while increasing your company’s liability should an accident occur. This article supplies a safe-approach reference developed through years of experience working with engineers and electricians on their arc flash hazard projects. The viewpoints expressed in this paper are provided as a guide to industry, recognizing that the NEC, NFPA, and OSHA set the standards but do not cover the myriad of questions associated with labeling the different types of electrical equipment in industry.

Common Terms: AFH (arc flash hazard), NFPA 70E (National Fire Protection Association – Standard for Electrical Safety in the Workplace), OSHA (Occupational Safety and Health Administration), CSA Z462 (Canadian Standards Association - Standard for Electrical Safety in the Workplace), PPE (Personal Protective Equipment), NEC (National Electrical Code), ANSI (American National Standards Institute).

To download the entire arc flash labeling article, Click Here.

2009 IEEE IAS Electrical Safety Workshop
February 2 - 6, 2009
St Louis, Missouri USA

If you have an interest or responsibility in workplace electrical safety, mark you calendars and register for the 16th Annual IEEE Industry Applications Society Electrical Safety Workshop, February 2-6, 2009 at the St Louis Union Station Marriott in St Louis, Missouri. Full details and on-line registration are available at www.ewh.ieee.org/cmte/ias-esw