Wednesday, March 31, 2010

Am I In Danger?

Due to the dynamic, rugged nature of construction work, normal use of electrical equipment at your site causes wear and tear that results in insulation breaks, short-circuits, and exposed wires [for additional information, see Flexible Cords and Power Tools]. If there is no ground-fault protection, these can cause a ground-faultthat sends current through the worker's body, resulting in electrical burns, explosions, fire, or death.

How Do I Avoid Hazards?
  • Use ground-fault circuit interrupters (GFCIs) on all 120-volt, single-phase, 15- and 20-ampere receptacles, or have an assured equipment grounding conductor program (AEGCP).
  • Follow manufacturers' recommended testing procedure to insure GFCI is working correctly.
  • Use double-insulated tools and equipment, distinctively marked.
  • Use tools and equipment according to the instructions included in their listing, labeling or certification.
  • Visually inspect all electrical equipment before use. Remove from service any equipment with frayed cords, missing ground prongs, cracked tool casings, etc. Apply a warning tag to any defective tool and do not use it until the problem has been corrected.

Saturday, March 27, 2010

Cords & Appliances

Cords & Appliances

Cords & Appliances

Cords, Equipment, and Tool Grounding

  • Make sure all equipment and extension cords bear the mark of an independent testing laboratory such as UL, CSA, ETL or MET Labs.

  • Protect flexible cords and cables from physical damage. Check cords for cut, broken, or cracked insulation.

  • Keep slack in flexible cords to prevent tension on electrical terminals.

  • Make sure the insulating qualities of a splice are equal to or greater than the original cord.

  • Extension cords are for temporary use. Install permanent wiring when use is no longer temporary.

  • Verify that all three-wire tools and equipment are grounded.

  • Water, electrical equipment, and power cords do not mix! Use GFCI protection in wet or damp environments.

  • Ground exposed parts of fixed equipment that could be energized.

  • Use non-conductive tools whenever possible.

  • Always double check the operation of your voltage testers by testing a live circuit.

Thursday, March 25, 2010



An explosion or fire can cause all sorts of havoc in any company's operations. Rebuilding, after a fire, can take a company years. One of the major causes of explosions and fire in industry is from electrical sources. Potential losses from these fires can be reduced by having proper electrical installations and equipment.

Hazardous locations require specially designed electrical equipment to protect people and property against increased fire potential. Certain electrical components and instruments are engineered specifically for locations designated as hazardous due to the possible presence of ignitable quantities of flammable liquids, gases, vapors, combustible dusts, or ignitable fibers.

Hazardous locations are classified as Class I, Class II, or Class III. The class is dependent on the physical properties of the combustible materials which may be expected to be present.

  • Class I locations are those in which flammable vapors or gases may be present.
  • Class II locations are those in which combustible dusts may be found.
  • Class III locations are those in which there are ignitable fibers and filings.

Each of these three classes are divided into two hazard categories, Division 1 and Division 2. The divisions identify the degree of potential for an ignitable atmosphere to exist. Class and Division explanations are detailed in Articles 500 - 503 of the National Electric Code (NEC), and in OSHA 29CFR 1910.39.

Before selecting electrical equipment and the associated wiring for any hazardous location, the exact nature and concentrations of the flammable materials must be determined. An electrical fitting or device which is safe for installation in an atmosphere of combustible dust may not be safe for operation in an atmosphere containing flammable vapors or gases. These electrical fittings are specifically designed for each hazard.

Class I electrical wiring applications are commonly referred to as "Explosion Proof." Properly installed and maintained class I equipment will not ignite the dangerous atmosphere surrounding it, and is approved for use in specific hazardous areas. Explosion proof fittings are designed to contain any arcing, intense heat, and explosions. These fixtures are distinctive in appearance. Class II locations may require "Dust-ignition proof" fixtures. These fixtures are designed in such a manner that their construction prohibits ignitable amounts of dust from entering the devices.

Hazardous areas that must have approved electrical installations include, but are not limited to: locations where volatile flammable liquids are transferred from one container to another; interiors of spray booths; in the vicinity of spray painting operations where volatile flammable solvents are used; locations where dangerous concentrations of suspended dust are likely, such as in grain elevators; and gasoline fueling stations. Remember to think electrical safety when proposing any electrical systems that will be located in a hazardous location.