Preventing Electrical Hazards
There are various ways of protecting people from the hazards caused by electricity, including insulation, guarding, grounding, and electrical protective devices. Laboratory workers can significantly reduce electrical hazards by following some basic precautions:
1) Inspect wiring of equipment before each use. Replace damaged or frayed electrical cords immediately
2) Use safe work practices every time electrical equipment is used
3) Know the location and how to operate shut-off switches and/or circuit breaker panels. Use these devices to shut off equipment in the event of a fire or electrocution
4) Limit the use of extension cords. Use only for temporary operations and then only for short periods of time. In all other cases, request installation of a new electrical outlet
5) Multi-plug adapters must have circuit breakers or fuses
6) Place exposed electrical conductors (such as those sometimes used with electrophoresis devices) behind shields
7) Minimize the potential for water or chemical spills on or near electrical equipment.
How do OSHA's standards minimize electrical hazards?
OSHA standards focus on the design and use of electrical equipment and systems. The standards cover only the exposed or operating elements of an electrical installation such as lighting, equipment, motors, machines, appliances, switches, controls, and enclosures, requiring that they be constructed and installed to minimize workplace electrical dangers. Also, the standards require that certain approved testing organizations test and certify electrical equipment before use in the workplace to ensure it is safe.
Insulation
All electrical cords should have sufficient insulation to prevent direct contact with wires. In a laboratory, it is particularly important to check all cords before each use, since corrosive chemicals or solvents may erode the insulation.Damaged cords should be repaired or taken out of service immediately, especially in wet environments such as cold rooms and near water baths.
Types of Insulation
Insulation on conductors is often color coded. Insulated equipment grounding conductors usually are either solid green or green with yellow stripes. Insulation covering grounded conductors is generally white or gray. Ungrounded conductors, or “hot wires,” often are black or red, although they may be any color other than green, white, or gray. Before connecting electrical equipment to a power source, it’s a good idea to check the insulation for any exposed wires for possible defects. Insulation covering flexible cords such as extension cords is particularly vulnerable to damage.
Guarding
Electrical systems must be guarded to prevent inadvertent contact with live conductors. The following are requirements for guarding live electrical parts:
1) Live parts to electrical equipment operating at 50 volts or more above ground must be guarded against accidental contact;
2) Proper guarding can be achieved by use of an approved cabinet or other approved enclosure or by location in a room or vault that is accessible to qualified persons only
3) If electrical equipment is located in an area where it is potentially exposed to physical damage, the enclosure or guard must be of sufficient strength to prevent such damage.
Grounding
Electrical Grounding or "Grounding" originally began as a safety measure used to help prevent people from accidentally coming in contact with electrical hazards. Only equipment with three-prong plugs should be used in the laboratory. The third prong provides a path to ground for internal electrical short circuits, thereby protecting the user from a potential electrical shock.
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Circuit Protection Devices
Circuit protection devices are designed to automatically limit or shut off the flow of electricity in the event of a ground-fault, overload or short circuit in the wiring system. Ground-fault circuit interrupters, circuit breakers and fuses are three well-known examples of such devices.
Fuses and circuit breakers prevent over-heating of wires and components that might otherwise create fire hazards.
Fuses
A fuse is the simplest circuit protection device. It derives its name from the Latin word "fusus," meaning "to melt." Fuses have been used almost from the beginning of the use of electricity. The earliest type of fuse was simply a bare wire between two connections. The wire was smaller than the conductor it was protecting and, therefore, would melt before the conductor it was protecting was harmed. Some "copper fuse link" types are still in use, but most fuses no longer use copper as the fuse element (the part of the fuse that melts). After changing from copper to other metals, tubes or enclosures were developed to hold the melting metal. The enclosed fuse made possible the addition of filler material, which helps to contain the arc that occurs when the element melts. For many low power uses, the finer material is not required. A simple glass tube is used. The use of a glass tube gives the added advantage of being able to see when a fuse is open. Fuses of this type are commonly found in automobile lighting circuits.
Circuit Breaker
Electrical Circuit Breaker is a switching device which can be operated manually as well as automatically for controlling and protection of electrical power system respectively. As the modern power system deals with huge currents, the spacial attention should be given during designing of circuit breaker to safe interruption of arc produced during the operation of circuit breaker.
The ground-fault circuit interrupter, or GFCI, is designed to shutoff electric power if a ground fault is detected, protecting the user from a potential electrical shock. The GFCI is particularly useful near sinks and wet locations. Since GFCIs can cause equipment to shutdown unexpectedly, they may not be appropriate for certain apparatus. Portable GFCI adapters (available in most safety supply catalogs) may be used with a non-GFCI outlet.