Milling Journal - Q1 2008 - (Page 26)

Protecting Electrical Workers Hazards and effective electrical safety in the workplace This article is based on a presentation by David Frazelle, divisional environmental, health, and safety manager for ADM Milling Co., Decatur, IL (217-451-4406). He spoke in May 2007 at the International Association of Operative Millers Conference and Expo in Overland Park, KS. The numbers tell a sobering story. Every year, U.S. workplaces report an estimated 30,000 nonfatal electrical shock incidents. More than 2,000 people are admitted to burn centers with severe electrical burns. Electrical incidents kill between 600 and 1,000 people annually. More than half of those deaths involve voltages under 600 volts. The three main hazards of electricity are: • Electrical shock. • Electrical arc. • Electrical blast. Electrical Shock Electrical shock is caused by a difference in potential that causes a flow of electrons across the human body. The amount of electrical current flow depends on a number of factors, including type of circuit, voltage, resistance of the body, amperage, pathway through the body, and the duration of contact. It doesn’t take a lot of amperage to cause injury or death. Table 1 shows the effects of various levels of electrical current through the body. A current as low as 25 mA can be fatal to some people. The most damaging pathways through the body pass through the lungs, heart, or brain. Amperage can be calculated by using Ohm’s Law, which states that amperage equals volts divided by resistance. For example, the average human body offers 1,000 ohms of resistance. Exposure to the standard U.S. voltage of 120v yields 120mA in amperage. According to the chart, that’s twice as much amperage as it takes to produce ventricular fibrillation, which is usually fatal. Electrical Arc An electrical arc occurs when current 35,000 degrees F or four times hotter than the surface of the sun. (By contrast, exposure to as little as 205 degrees for a tenth of a second can cause an incurable thirddegree burn.) Electrical Arc Blast The most dangerous effect of an electrical arc is an arc blast, which can occur when electrical equipment is exposed to arc temperatures and is vaporized. Copper wire exposed to an electrical arc instantly expands 67,000 times by volume. Between 80% and 90% of electrical injuries can be traced to unsafe acts by employees. These include: • Failure to de-energize electrical equipment for repair or inspection. • Use of improper, defective, or unsafe tools. • Use of conductive tools or equipment too close to energized parts. • Horseplay. Regulatory Standards Both the Occupational Safety and Health Administration (OSHA) and the National Fire Protection Association (NFPA) have established electrical safety standards to provide practical safeguarding of employees in the workplace. OSHA. Underlying all of OSHA’s safety standards is Section 5, the socalled “General Duty Clause,” which requires all employers to furnish employees with a workplace free from recognized hazards that could cause death or physical harm. However, OSHA standards 1910.332 through 1910.335 specifically address electrical safety in the workplace. • Only qualified personnel may work on exposed, energized electrical equipment or circuit parts using proper procedures and personal protective equipment (PPE). • Live parts to which an employee may be exposed must be de-energized before the employee works on or near them, unless it can be demonstrated that de-energizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. suddenly leaps across the air from energized equipment to a nearby ground, in this case a human body. Approximately half of serious electrical injuries involve burns from electrical arcs. The number one way to prevent injuries from electrical arcs is to allow only trained people wearing arc protection equipment to approach energized electrical equipment. Spectators must stay away. Fatalities can occur as far as 10 feet or more from the equipment generating the arc. The temperature of an electrical arc is The number one way to prevent injuries from electrical arcs is to allow only trained people wearing arc protection equipment to appoach energized electrical equipment. Spectators must stay away. Fatalities can occur as far as10 feet or more from the equipment generating the arc. 26 First Quarter 2008 MILLING JOURNAL

Table of Contents Feed for the Digital Edition of Milling Journal - Q1 2008

Milling Journal - First Quarter 2008 Contents First Break Examining Fortification Standards IAOM 2008 Milling Short Courses 2008 IAOM Conference and Expo Melinda Farris Interview Designing a Purifierless Millflow Dirk Maier Named KSU Dept. Head NAMA’s 2008 Division Meetings Protecting Electrical Workers Miller Profiles Todd Bastean Interview Safety: How Serious Are We? Product Quality/Gwirtz Product Roundup: Magnets Pest Management/Subramanyam Explosion Protection Supplier Interview: Darin Stutler Product Reviews New IAOM Safety Award Criteria Don’t Forget OSHA Form 300A Milling Notes Great Lakes Regional Conference 4th Quarter 2007 Flour Production IAOM Reference Guide Hammermills Brushes Aspirators Level Indicators Product Reviews Magnets Mixers Packaging Purifiers Safety Equipment Screeners Separators Sifter Accessories Ad Index

Milling Journal - Q1 2008

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