ELECTRICITY Archives - HSE INFORMATION DATABASE

EXTENSION CORD SAFETY

2011/04/06

We use extension cords almost every day both at work and at home. These are very useful devices, but they can present a fire or shock hazard when either worn out or used improperly.

Types of extension cords

Extension cords come in either two or three-wire types. Two-wire extension cords should only be used to operate one or two small appliances. Three-wire cords are used for outdoor appliances and electric power tools. The third wire on this cord is a ground and this type of cord should never be plugged into any ungrounded electrical outlet. Only grounded extension cords are to be used with power tools unless the tool is double insulated.

Care and inspection of extension cords

Extension cords must be treated with care and checked regularly for damage or deterioration. The cord itself should never be pulled to disconnect it from an electrical source; remove it by the plug. They should not be placed under rugs or furniture and should never be strung through doorways, windows, walls, ceilings, or floors. Damaged cords present a potential fire or shock hazard and should be destroyed and replaced immediately.

An extension cord should never be used as a substitute for permanent wiring. They should not be fastened to a building or structure, even though staples are sold for this purpose at many hardware stores. Avoid plugging two cords together to make a longer one. It's best to use one cord in a continuous length from the receptacle to the appliance or tool. Extension cords which are either connected together or are too long will reduce operating voltage and operating efficiency of tools or appliances and may cause motor damage.

Extension cords are convenient devices which we often take for granted in our everyday activities, but which need proper care and attention. Use good housekeeping practices at home and at work, to keep extension cords from being a tripping hazards or becoming damaged. Inspect them regularly for wear and replace defective units.

Prevent potential electrical hazards that may lead to someone's injury!

ELECTRICAL SOURCES IN HAZARDOUS LOCATIONS

2010/12/29

ELECTRICAL SOURCES IN HAZARDOUS LOCATIONS

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.

STATIC ELECTRICITY

Most of us are familiar with static electricity. We all have walked across the rug and reached for the door knob, only to have a spark jump from our hand to the knob. We have also seen the effects of "static cling," when our clothes cling together in the dryer.

Static electricity, as a source of ignition for flammable vapors, gases, and dusts, is a hazard common to a wide variety of industries in Alaska. A static spark can occur when an electrical charge accumulates on the surfaces of two materials that have been brought together and then separated (between two solids, between a solid and a liquid, or between two immiscible liquids, i.e., incapable of mixing). One surface becomes charged positively and the other surface becomes charged negatively. If the materials are not bonded or grounded, they eventually will accumulate a sufficient electrical charge capable of producing a static spark that could ignite flammable vapors, gases, and dusts. Some common processes capable of producing a static ignition are as follows:

The flow of liquids (petroleum or mixtures of petroleum and water) through pipes or fine filters.
The settling of a solid or an immiscible liquid through a liquid (e.g., rust or water through petroleum).
The ejection of particles or droplets from a nozzle (e.g. water washing operations or the initial stages of filling a tank with oil).
The vigorous rubbing together and subsequent separation of certain synthetic polymers (e.g. the sliding of a polypropylene rope through PVC gloved hands).

Preventing static electricity as an ignition source can be accomplished through bonding, grounding, or possibly substitution. Bonding is the process of connecting two or more conductive objects together by means of a conductor. Grounding (earthing) is the process of connecting one or more conductive objects to the ground. If grounding or bonding is not possible, substituting may be an alternative. For example: some absorbent pads used in shops can produce a static spark when separated. If the conditions are right a static spark could be a source of ignition for flammable vapors. By substituting a non-conductive pad (3M – HP556) as an alternative, the risk of static spark can be eliminated.

Remember, taking the time to bond or ground when working around flammable vapors, gases, and dusts will help prevent a serious accident.

PORTABLE LIGHT STRINGS

Inspect the wiring and fixtures before stringing the lights or before they are energized or plugged in. Make sure the outer insulation is not damaged, the plug ends are intact, and the fixtures are not cracked.
The light-string must be grounded. Make certain the plug has a ground prong. Never cut one off. The quality of the ground must be tested frequently. A good ground could save your life if an electrical fault develops, especially when working in wet conditions or on metal structures. If a Ground Fault Interrupter (GFI) is available, use it. GFIs should always be used under wet conditions.
Never string lights so they are near any combustible items. You know from experience, that bulbs get hot. Even if they are not in direct contact with the combustible, heat can build up slowly until the ignition temperature is reached.
Make certain that all bulbs have guards installed. Not only will this help prevent the bulb from coming in direct contact with a combustible, it can also protect you (or someone else) from coming in contact with the bulb and getting burned.
All fixtures must have an unbroken bulb installed. The bulb will help prevent you from coming in contact with the exposed electrical conductors that are present when a bulb is missing or broken. When you change a broken bulb, disconnect the power from the light-string and wear gloves to guard against cuts.

Never use an ordinary light string in an area that could contain flammable vapors. When used within an enclosed or confined space, the space must be certified as "Safe for Hot Work" if a conventional string is used. If the atmosphere is not "Safe for Hot Work", then "explosion-proof" lights must be used. Keep in mind, when you place any type of lighting in an area where flammable vapors are present, you are introducing a source of ignition. This could endanger your life. You will want to be especially careful during your inspection to make sure that the cord, all plugs, the fixture and the globe are all in place. Don't forget the gasket at the bottom of the globe. Make sure everything is clean and tight.

HIGH VOLTAGE ELECTRICAL BURNS

2010/12/12

ELECTRICAL HAZARDS – HIGH VOLTAGE ELECTRICAL BURNS

More than 1000 employees are killed and another 30,000 injured each year from electrical shock. Hands are frequently involved in an electrical injury since they are the most common source of contact with the electrical current. However, damage to other parts of the body may be more extensive and life threatening. Severe electric shock can result in cardiac arrest due to ventricular fibrillation, massive fluid loss into swollen tissues, and kidney failure caused by an overload of muscle protein from damaged muscle and infections.

Electrical injuries are often more severe than they appear to be from the outside. Injury occurs not only at the contact site, but also along the path the electricity takes, and at the exit location. Frequently, there is also extensive muscle damage that will not be evident from a visual examination of the skin. These deep tissue injuries cause severe swelling that require a deep incision extending from the hand to the shoulder to relieve the pressure. If this is not done, the mounting pressure from the swelling will shut off the blood supply by compressing the arteries, rapidly destroying any remaining healthy tissue. Extensive dead skin removal is often necessary to prevent massive infection. Deep burns result in unsightly scars that will often continue to enlarge for 12-18 months after the burn occurs. These scars are not only a cosmetic problem, but may seriously interfere with joint function because motion increases the tension across the wound, which tends to produce even more scar tissue.

More than 90% of fatalities occur when contact is made with a "hot" wire, or energized equipment housing by a person who was well-grounded Most of these injuries would probably have been prevented if a GFI — ground fault interrupter — had been installed on the circuit. A GFI is not an overcurrent device, but is placed across the line to continuously monitor the current flowing from the source and compare it to the current returning to the source. If the difference is 6 milliamperes or more, it opens the circuit almost instantly. This is important because it has been determined that 100 milliamperes flowing through the body for only 2 seconds can cause death by electrocution. 100 milliamperes is not much current when you consider that a portable electric drill draws 30 times that much. Incidentally, the "let go" threshold that causes freezing to the circuit is about 20 milliamperes. Make sure that the equipment you are working with has a GFI — it could save your life.

To work on high voltage (over 600 volts), you must have a minimum of two years of training, experience with high voltage circuits, have demonstrated that you are familiar with the work to be performed, and the hazards involved with high voltage work according to OSHA.

Other safety requirements that must be followed include using insulated gloves for current over 300 volts, eye protection, and lockout/tagout if working on energized parts of equipment or systems. Conductive measuring tapes, ropes, or similar devices obviously cannot be used around exposed conductors, and conductive fish tapes cannot be used if they will be entering enclosures with exposed conductors.