Office or Environmental Health and Safety

Electrical Safety

Introduction

OSHA's electrical standards address concerns that electricity has long been recognized as a serious workplace hazard, exposing employees to such dangers as electric shock, electrocution, burns, fires, and explosions. In 1992, for example, the Bureau of Labor Statistics reported that more than 6,210 work-related deaths occurred in private sector workplaces. Six percent of the fatalities, or around 347 deaths, were the direct result of electrocutions. What makes these statistics more tragic is that, for the most part, these fatalities could have been easily avoided.

The danger of injury (or worse) by electrical shock is present whenever electrical power is used.All electrical equipment should be adequately insulated, grounded, orisolated to prevent bodily contact with any source of dangerouspotentials. Under certain conditions people can be injured severely even from relatively low voltages coupled with high current flows. OSHA'S electrical standards help minimize these potential hazards by specifying safety aspects in the design and use of electrical equipment and systems.

The primary effects of electric shock are due to current actually flowing through the body. Electrical burns occur when the body, or apart of it, completes a circuit connecting the power source with theground. Although the resistance of dry, unbroken skin to electriccurrent is relatively high, the amount of current necessary to kill aperson is small. Therefore, it is easy to exceed lethal levels ofcurrent flow, especially if the skin is broken, wet, or damp with sweat.

Check all equipment regularly and wear the proper protective equipmentwhen working with high voltages or currents]

If your equipment runs erratically or if you feel an electrical "tingle"when you touch it, stop using the tool, tag it, and have it repaired.Whenever the risk of electrocution is high, wear the proper protective clothing, insulated gloves, eye protection, boots, and head gear. If you are not sure what to wear, ask your supervisor or your Safety Committee representative for assistance.

General Electrical Safety

• Never modify a plug by bending or removing the prongs. When plug prongs are bent, loose or missing, replace the device.

• Cord adapters used to defeat the ground connection (i.e. 3-prong to 2-prong adapters) should not be used.

• All receptacles and any electrical conductors must be sufficiently grounded, and if uncertain whether or not this is true, call Facilities for assistance.

• If plug prongs break off and remain in the receptacle slots after insertion or withdrawal, do not attempt to remove them. Call Facilities for assistance.

• Receptacles should be mounted firmly in their enclosures and should not move when the plug is inserted. Loose receptacles can cause short circuits.

• If you discover loose receptacles or other faulty electrical equipment, it should be removed from service or tagged out until a qualified electrician from Facilities can make repairs.

• Damaged electrical enclosures such as switch or plug receptacles and junction boxes should be reported immediately to Facilities.

• Extension cords should be used only when necessary and only on a temporary basis. Extension cords should not be used in place of permanent or fixed wiring.

• Make sure all extension cords are the right size or rating for the tool you're using. EXAMPLE: The diameter of the extension cord being used should be equal to or greater than the cord of the appliance being used.

• Keep all electrical cords away from areas where they may be pinched, such as off the floor, out of walkways, and out of doorways. Where possible, move the electrical appliance closer to the outlet.

• Do not use any appliance or extension cord that exhibits signs of wear, such as frayed insulation or exposed wiring. To insure safe operation, all electrical equipment should be visually inspected before use.

• Never staple, nail or otherwise attach extension cords to a surface.

• Never unplug an appliance by pulling on the cord, always remove by the plug.

• Keep the floor in your workplace completely dry.

• Keep all electrical equipment away from any source of water unless the appliance is rated for use around water, such as a wet-dry shop vacuum.

• Ground fault circuit interrupters (GFCI's) should be used as much as possible. In any wet, damp or moist environment, GFCI's are required.

• All electrical panels shall be unobstructed, have a minimum clearance of 36", and shall be easily accessible.

• Keep dust and lint off electrical panels, receptacles, and appliances.

• Electrical panel doors should be closed and latched when not in use.

• Separate all combustible materials away from electrical equipment.

• Attempt to limit one appliance per outlet. However, if more than one appliance is to be used for each circuit, an approved plug strip with circuit breaker should be used.
• Always turn off a tool or appliance before disconnecting it to avoid exposure to live electrical parts.

• Proper illumination shall be provided in all areas where electrical hazards are apt to be encountered and an emergency lighting system should be in place as well.

• All energized parts of electrical circuits and equipment shall be guarded against accidental contact by approved cabinets or enclosures.
• Employees who regularly work on or around energized electrical equipment shall be trained in the proper methods of cardio- pulmonary resuscitation.

• Where electrical shock hazards exist, first-line and backup protection shall be provided to prevent access to energized circuits and parts. This protection includes using lockouts, grounding hooks, barriers and rubber mats.

• In places where electrical hazards exist, there shall be conspicuous visual indications of ON and OFF conditions, the type of hazard and its exact location.

• Bench tops and bench edges in the immediate work area should be non-conductive and only a minimum of connected equipment should be on the bench tops. Rubber matting of adequate breakdown voltage should be used.
• Adequate and workable lockout-tag out procedures shall be used (see Lockout-Tag out section).
• When any equipment may produce sparks or arcing during normal operation, safety glasses must be used at all times.

• Proper personal protective equipment, such as a hard hat, safety glasses, arm mats and gloves should be worn when maintaining any electrical equipment.

• When using tools near electrical hazards, all tools must have a double insulated casing to prevent contact with energized parts.

• Never work alone on a live circuit - always have an observer.

• Be acquainted with all electrical hazards that may be encountered in your work area.

• Notify your supervisor of any potential electrical hazard that may be going unnoticed.

High Voltage Electrical Safety

In addition to the recommendations for general electrical safety, there are more stringent rules that apply to high voltage operations. High voltage is defined as electrical equipment that is operating at more than 600 volts in terminal to terminal operation, or at more than 300 volts in voltage to ground operation. Low voltage, high current AC or DC power supplies are also considered to be high voltage.

1. Prior to operation, inspect the power supply and check all protective devices.

2. Employees are prohibited from working alone on energized lines or equipment over 600 volts.

3. Ensure that all PPE (Goggles, face shield, hearing protection rubber gauntlets

Before entering power supply or associated equipment enclosure, take the following precautions:

• De-energize the equipment.
• Open and lockout the main input power circuit breaker.
• Check for auxiliary power circuits which could still be energized.
• Inspect automatic shorting devices to verify proper operation.
• Short the power supply from terminal-to-terminal, and terminal- to-ground with grounding hooks.

4. Label equipment to identify input power sources; and label input power sources to identify their connected power supply loads.

5. Equipment that is remotely controlled or unattended while energized should be labeled with emergency shutdown instructions and identification of personnel to contact in case of emergency.

Arc Flash Hazards

Besides the obvious electrocution hazard, high voltage electrical equipment also poses a risk for "Arc Flashing." An arc flash is essentially a short circuit through the air. When insulation or isolation between electrified conductors is breached or can no longer withstand the applied voltage, an arc flash occurs. As employees work on or near energized conductors or circuits, movement near or contact with the equipment, or a failure of the equipment, may cause a phase-to-ground and/or a phase-to-phase fault.

The temperature of an arc can reach more than 5000 F as it creates a brilliant flash of light and a pressure wave. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment. This explosion can damage hearing, eyesight and can cause severe burns to exposed parts of the body. The fast-moving pressure wave also can send loose material such as pieces of equipment, metal tools, and other objects flying, injuring anyone standing nearby.

Regulations require the calculation of the “flash protection boundary” inside which qualified workers must be protected when working.

OSHA and NFPA 70E require equipment be in an electrically safe work condition before employees work on or near it. Equipment, therefore, should be de-energized before any work is done. In some cases, however, work cannot be done on de-energized systems, such as in a hospital or a 24 hr continuous operation.

There are specific steps NFPA 70E dictates to ensure an electrically safe working condition exists:

• Determine all possible sources of supply.
• Open disconnecting device(s) for each source.
• Where possible, visually verify device is open.
• Apply lockout/tagout devices.
• Test voltage on each conductor to verify that it is de-energized.
• Apply grounding devices where stored energy or induced voltage could exist or where de-energized conductors could contact live parts.

Establishing these safety procedures is part of the company safety plan that must be in effect for each facility:

• Employers must formalize procedures and practices such as the qualification of employees to work in hazardous areas, tasks they may perform, steps needed to secure management approval for work to be done, and audits.
• Employers must provide training for employees in the skills and techniques needed to work with electrical equipment, equipment details, and emergency procedures.
• Employees must implement the practices according to the training.
• Companies must perform a flash hazard analysis before work is done on any energized equipment.

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