Working with Electricity
Electricity has long been recognized as a serious workplace hazard. OSHA's electrical standards are designed to protect employees exposed to dangers such as electric shock,
electrocution, fires, and explosions.
The following hazards are the most frequent causes of electrical injuries in construction:
- contact with power lines
- lack of ground-fault protection
- missing or discontinuous path to ground
- equipment not used in manner prescribed
- improper use of extension and flexible cords
Control of Hazardous Energy (Lockout/Tagout)
The employer must establish a program consisting of energy control procedures, employee training, and periodic inspections. The purpose is to ensure that equipment is isolated
from the energy source and made inoperative before any employee performs any service or maintenance where the unexpected energizing, start up, or release of stored energy could occur.
Sequence of a Lockout/Tagout Procedure
The following are the steps to lockout/tagout equipment:
- Notify all affected employees that service or maintenance is required on a piece of equipment. An affected employee is one who normally works on the machine that is being locked or
tagged for service. This action also applies to employees who are working in the area of the locked/tagged piece of equipment.
- Authorized employees should refer to the company procedure to identify the type and magnitude of the energy that the machine uses, understand the hazards of the energy and know the
methods to control the energy.
- If the equipment is operating, the authorized employee will shut it down by the normal stopping procedure (depress stop button, open switch, close valve, etc.).
- De-activate the energy-isolating device(s) so the equipment is isolated from the energy source(s).
- Lockout/tagout the energy-isolating device(s) with assigned individual lock(s).
- Dissipate or restrain stored or residual energy (such as springs; elevated or suspended equipment parts; hydraulic systems; air, gas, steam or water pressure; electricity in capacitors; etc.)
by methods such as grounding, repositioning, blocking or bleeding down.
- Remove all other employees from the area before the equipment is disconnected from the energy source(s). Verify the isolation of the equipment by attempting to restart the equipment under
its normal operations. Remember to return operating control(s) to the neutral or “off” position after attempting to restart the equipment.
- At this point the equipment should be in locked-out condition.
Restoring Equipment to Service
The following are procedures for restoring equipment to service:
- Check the equipment and immediate area around the equipment to ensure nonessential items such as tools have been removed and equipment components are operationally intact.
- Check the work area to ensure all employees have been safely positioned or removed from the area.
- Verify the controls are in neutral.
- Remove the lockout device(s) and start the equipment. The removal of some forms of blocking may require starting the equipment before safe removal.
- Notify affected employees that the service or maintenance is completed and the equipment is ready for use.
In the steps outlined in the previous section, one person should place his or her lock on each piece of an energy-isolating device. There may be occasions when more than one person
needs to work on a piece of equipment. When this occurs, each person involved in the service or maintenance will be required to place his or her own lock on the energy- isolating device.
- A single authorized employee must assume the overall responsibility for the control of hazardous energy for all members of the group while the servicing or maintenance work is in progress.
- A multi-hasp lock is required if the energy-isolating device does not have enough places for each employee to place his or her own lock.
- Each employee must affix his/her personal lockout or tagout device to the group lockout device, group lockbox, or comparable mechanism, before engaging in the servicing and maintenance operation.
- When the activities involving group lockout or tagout extend into another workshift, or there is a change of authorized employees, the provisions for shift or personnel changes must also be followed.
Ground Fault Circuit Interrupters (GFCI)
- All 125-volt, single-phase, 15-, 20-, and 30-ampere receptacles on construction sites that are for temporary power and are available for use by employees, must have approved ground-fault circuit
- GFCI protection must be located at the outlet end of the circuit. Extension cords or other devices with listed ground-fault circuit interrupter protection are acceptable.
- Receptacles more than 125-volt, single phase, 30-amperes must have protection that complies with GFCI protection above, or an assured equipment grounding conductor program.
Working Near Overhead High-voltage Lines and Equipment
Overhead and buried power lines at your site are especially hazardous because they carry extremely high voltage. Fatal electrocution is the main risk, but burns and falls from elevations are
also hazards. Using tools and equipment that can contact power lines increases the risk.
Examples of Equipment That Can Contact Power Lines
- aluminum paint rollers
- concrete pumpers
- long-handled cement finishing floats
- metal building materials
- metal ladders
- raised dump truck beds
Restricted Space Precautions
Important general electrical safety precautions when working around high voltage power lines in construction include:
- No person is allowed to perform any construction activity within the restricted space surrounding an overhead high-voltage line or equipment unless:
- that person is the owner, an authorized employee, or authorized (in writing) agent of the overhead high voltage system,
- proper notification is provided and the line and/or equipment is de-energized and visibly grounded by the owner of the high-voltage system or authorized agent, or accidental contact is
prevented by use of insulating barriers or guards,
- insulated power lines (not tree wire) and equipment designed and engineered to allow only incidental contact are installed by the owner of the high-voltage system or authorized agent.
- For high voltage power lines rated more than 600 Volts (V) and up to 50 kilovolts (kV), restricted space extends 10 feet in all directions from the surface of the line or equipment.
- For high voltage power lines rated over 50 kV, restricted space extends 10 feet plus 0.4 inch for each one kV over 50 kV, or twice the length of the insulator (but never less than 10 feet)
in all directions from the surface of the line or equipment.
- For equipment or structures in transit, on level surfaces, restricted space extends:
- four feet in all directions from lines or equipment rated 50 kV or less,
- 10 feet in all directions for lines or equipment rated more than 50 kV, and
- 16 feet in all directions for lines or equipment rated more than 345 kV up to and including 750 kV.
Follow these general electrical safety precautions on construction sites:
- Secure electric equipment firmly to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials must not be used.
- Do not work on new and existing energized (hot) electrical circuits until all power is shut off and grounds are attached.
- Make sure an effective Lockout/Tagout system is in place.
- Promptly replace frayed, damaged or worn electrical cords or cables.
- Ensure all extension cords have grounding prongs.
- Protect flexible cords and cables from damage. Sharp corners and projections should be avoided.
- Use extension cord sets used with portable electric tools and appliances that are the three-wire type and designed for hard or extra-hard service. (Look for some of the following letters imprinted on the casing: S, ST, SO, STO.)
- Maintain all electrical tools and equipment in safe condition and regularly check for defects and take the tools out of service if defects are found.
- Do not bypass any protective system or device designed to protect employees from contact with electrical energy.
- Locate and identify overhead electrical power lines.
- Ensure that ladders, scaffolds, equipment or materials never come within 10 feet of electrical power lines.
- Properly ground all electrical tools unless they are of the double insulated type.
- Do not allow multiple plug adapters.
Real World Accident
Scaffold Too Close To Power Line
Seven employees of a masonry company were erecting a brick wall from a tubular, welded-frame scaffold approximately 24 feet high. The scaffold had been constructed only 21 horizontal
inches across from a 7,620-volt power line. A laborer carried a piece of wire reinforcement (10 feet long by 8 inches wide) along the top section of the scaffold and contacted the power line with it.
The laborer, who was wearing leather gloves, received an electric shock and dropped the wire reinforcement, which fell across the power line and simultaneously contacted the metal rail of the scaffold,
energizing the entire scaffold. A 20-year-old bricklayer standing on the work platform in contact with the main scaffold was electrocuted.
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