Electrical Hazards

To prevent electrical shock insure that all equipment is properly grounded
The danger of injury through electrical shock is present
whenever electrical power is used. All electrical equipment
should be adequately insulated, grounded, or isolated to
prevent bodily contact with any source of dangerous
potentials. Under certain conditions people can be injured
severely even from relatively low voltages coupled with high current flows.
[To reduce the risk of shock, do not contact any electrical components, and keep your work area dry]
The primary effects of electric shock are due to current actually
flowing through the body. Electrical burns occur when the body, or a
part of it, completes a circuit connecting the power source with the
ground. Although the resistance of dry, unbroken skin to electric
current is relatively high, the amount of current necessary to kill a
person is small. Therefore, it is easy to exceed lethal levels of
current flow, especially if the skin is broken, wet, or damp with sweat.
[Check all equipment regularly and wear the proper protective equipment
when 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 right 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.
ELECTRICAL SAFETY TIPS
* 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 switches 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 TIPS
* In addition to the recommendations for general electrical safety,
there are more stringent rules that apply to high voltage operations.
* High voltage pertains to 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. In addition,
low voltage, high current AC or DC power supplies are also
considered to be high voltage applications.
* All switches, circuit breakers, and other control devices that
are in high voltage equipment shall be labeled as such.
* For a more comprehensive listing of proper high voltage
maintenance and operation, check the Code of California
regulations, Title 8, High Voltage Electrical Safety Orders
and/or the National Electrical Code. These references are
available in the Environmental Safety Facility library.
Hazards of Working With High Voltage
1. Care must be taken to insure that unknown parties do not come in
contact with energized parts. This can occur when there is a remote
on/off switch relative to the energized conduits.
2. Insure that terminal voltage ratings can withstand any surges that
may occur due to electrical faults or switching transients.
3. Overload or improper cooling can cause excessive temperature rises,
resulting in equipment damage.
4. Be aware of output circuits even after input power is turned off to
the system. Parallel power sources and energy storage devices such as
capacitors can cause damage.
5. When power supplies serve more than one experiment, switching errors
can result in energizing the wrong equipment or load, creating
possible hazards for nearby personnel.
6. Over-current protective devices such as fuses and circuit breakers
may not adequately limit or interrupt the total inductive energy and
fault currents in highly inductive dc systems.
Pertinent Design and Construction Considerations
1. Provide isolation devices or physical barriers to prevent high
voltage stored energy from being dissipated in a low voltage supply
and/or control circuits.
2. Provide a switch and/or fixed bleeder resistor in the output circuit
to discharge the power supply when the input power is turned off.
3. Equip all power supplies with lockout capability.
4. Provide alarms, signs or lights to warn personnel when the supply is
energized.
5. Minimize the number of control stations for each power supply
(preferably only one), and provide emergency stop controls at all
remote power supply locations.
Safe Operating Procedures
1. Prior to operation, inspect the power supply and check all protective
devices.
2. Employees shall be prohibited from working alone on energized lines
or equipment over 600 volts.
3. 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.