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Showing posts with label Electrical Hazards. Show all posts
Showing posts with label Electrical Hazards. Show all posts

Wednesday, April 7, 2021

April 07, 2021

Electrical Safety

Electrical Safety

Electrical Hazards and How to Control it.




Electricity - The Dangers

 About 5 workers are electrocuted every week.
 Causes 12% of young worker workplace deaths.
 Takes very little electricity to cause harm.
 Significant risk of causing fires.

Whenever you work with power tools or electrical circuits there is a risk of electrical hazards, especially electrical shock. Risks are increased at construction sites because many jobs involve electric power tools.

Electrical trades workers must pay special attention to electrical hazards because they work on electrical circuits. Coming in contact with an electrical voltage can cause current to flow through the body, resulting in electrical shock and burns. Serious injury or even death may occur.

Electricity has long been recognized as a serious workplace hazard, exposing employees to electric shock, electrocution, burns, fires, and explosions. In 1999, for example, 278 workers died from electrocutions at work, accounting for almost 5 percent of all on-the-job fatalities that year, according to the Bureau of Labor Statistics. What makes these statistics more tragic is that most of these fatalities could have been easily avoided.

Electricity – How it Works

 Electricity is the flow of energy from one place to another.
 Requires a source of power: usually a generating station.
 A flow of electrons (current) travels through a conductor.
 Travels in a closed circuit.

Operating an electric switch is like turning on a water faucet.

Behind the faucet (or switch) there is a source of water (or electricity) with a way to transport it, and pressure to make it flow. The faucet’s water source is a reservoir or pumping station. A pump provides enough pressure for the water to travel through the pipes. For electricity the source is the power generating station. A generator provides the pressure (voltage) for the electrical current to travel through electric conductors (wires).

Volts – the electrical pressure (measure of electrical force).

Amps – the volume or intensity of the electrical flow.

Watts – the power consumed.

Electrical Terms

Current -- electrical movement (measured in amps).

Circuit -- complete path of the current. Includes electricity source, a conductor, and the output device or load (such as a lamp, tool, or heater).

Resistance -- restriction to electrical flow.

Conductors – substances, like metals, with little resistance to electricity that allow electricity to flow.

Grounding – a conductive connection to the earth which acts as a protective measure.

Insulators -- substances with high resistance to electricity like glass, porcelain, plastic, and dry wood that prevent electricity from getting to unwanted areas.

Resistance – Measured in ohms.

Four factors determine the resistance of a material to the flow of electricity:

- What it is made of (silver is best, copper is most common).
- Its diameter (smaller diameter = more resistance).
- Its temperature (higher temperature = higher resistance).
- Its length (longer = higher resistance).

Electrical Injuries 

There are four main types of electrical injuries:

Direct

 Electrocution or death due to electrical shock.
 Electrical shock.
 Burns.

Indirect

Falls

When an electrical shock enters the body it may produce different types of injuries. Electrocution results in internal and external injury to body parts or the entire body – often resulting in death. After receiving a ―jolt‖ of electricity all or part of the body may be temporarily paralyzed and this may cause loss of grip or stability. A person may also involuntarily move as a result of receiving an electrical shock, resulting in a fall. Internal or external burns may result from contact with electricity.

Electrical Shock

An electrical shock is received when electrical current passes through the body. You will get an electrical shock if a part of your body completes an electrical circuit by:

 Touching a live wire and an electrical ground.
 Touching a live wire and another wire at a different voltage.
 Electricity travels in closed circuits, and its normal route is through a conductor. Electric shock occurs when the body becomes a part of the circuit.

Grounding is a physical connection to the earth, which is at zero volts.

The metal parts of electric tools and machines may become energized if there is a break in the insulation of the tool or machine wiring. A worker using these tools and machines is made less vulnerable to electric shock when there is a low-resistance path from the metallic case of the tool or machine to the ground. This is done through the use of an equipment grounding conductor—a low-resistance wire that causes the unwanted current to pass directly to the ground, thereby greatly reducing the amount of current passing through the body of the person in contact with the tool or machine.

Shock Severity

Severity of the shock depends on:

— Path of current through the body.
— Amount of current flowing through the body (amps).
— Duration of the shocking current through the body.

LOW VOLTAGE DOES NOT MEAN LOW HAZARD

Other factors that may affect the severity of the shock are:

- The voltage of the current.
- The presence of moisture.
- The general health of the person prior to the shock.

Low voltages can be extremely dangerous because, all other factors being equal, the degree of injury increases the longer the body is in contact with the circuit.

The resistance of the body varies based on:

- The amount of moisture on the skin (less moisture = more resistance).
- The size of the area of contact (smaller area = more resistance).
- The pressure applied to the contact point (less pressure = more resistance).
- Muscular structure (less muscle = less resistance).

Dangers of Electrical Shock

Currents above 10 mA* can paralyze or “freeze” muscles.

Currents more than 75 mA can cause a rapid, ineffective heartbeat -- death will occur in a few minutes unless a defibrillator is used 75 mA is not much current – a small power drill uses 30 times as much.

For example, 1/10 of an ampere (amp) of electricity going through the body for just 2 seconds is enough to cause death.

Currents above 10 mA can paralyze or ―freeze‖ muscles. When this ―freezing‖ happens, a person is no longer able to release a tool, wire, or other object. In fact, the electrified object may be held even more tightly, resulting in longer exposure to the shocking current. For this reason, hand-held tools that give a shock can be very dangerous. If you can’t let go of the tool, current continues through your body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). You stop breathing for a period of time. People have stopped breathing when shocked with currents from voltages as low as 49 volts. Usually, it takes about 30 mA of current to cause respiratory paralysis.

Burns

Most common shock-related injury Occurs when you touch electrical wiring or equipment that is improperly used or maintained Typically occurs on hands Very serious injury that needs immediate attention Shock-related injuries include burns, internal injuries, and injuries due to involuntary muscle contractions.

The most common shock-related injury is a burn. Burns suffered in electrical incidents may be one or more of the following three types.

Electrical burns cause tissue damage, and are the result of heat generated by the flow of electrical current through the body. These are one of the most serious injuries you can receive and require immediate attention.

Arc or Flash burns are caused by high temperatures near the body produced by an electrical arc or explosion. Attend to them immediately.

Thermal contact burns occur when skin comes in contact with overheated electric equipment, or when clothing is ignited by an electrical incident.

Falls

Electric shock can also cause indirect injuries Workers in elevated locations who experience a shock may fall, resulting in serious injury or death.

Electrical Hazards and How to Control Them

Electrical accidents are caused by a combination of three factors:

- Unsafe equipment and/or installation.
- Workplaces made unsafe by the environment, and
- Unsafe work practices.

Electrical shocks, fires, or falls result from these hazards:

— Exposed electrical parts.
— Overhead power lines.
— Inadequate wiring.
— Defective insulation.
— Improper grounding.
— Overloaded circuits.
— Wet conditions.
— Damaged tools and equipment.
— Improper PPE.

Hazard – Exposed Electrical Parts
Control – Isolate Electrical Parts

- Use guards or barriers.
- Replace covers

Except as required or permitted elsewhere in the subpart, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by cabinets or other forms of enclosures, or by any of the following means:

* By location in a room, vault, or similar enclosure that is accessible only to qualified persons.
* By partitions or screens so arranged that only qualified persons will have access to the space within reach of the live parts. Any openings in such partitions or screens shall be so sized and located

that persons are not likely to come into accidental contact with the live parts or to bring conducting objects into contact with them.

* By location on a balcony, gallery, or platform so elevated and arranged as to exclude unqualified persons.
* By elevation of 8 feet or more above the floor or other working surface and so installed as to exclude unqualified persons.

Control – Isolate Electrical Parts - Cabinets, Boxes & Fittings

Conductors going into them must be protected, and unused openings must be closed

Conductors entering boxes, cabinets, or fittings shall be protected from abrasion, and openings through which conductors enter shall be effectively closed. Unused openings in cabinets, boxes, and fittings shall also be effectively closed.

Covers and canopies. All pull boxes, junction boxes, and fittings shall be provided with covers. If metal covers are used, they shall be grounded. In energized installations each outlet box shall have a cover, faceplate, or fixture canopy. Covers of outlet boxes having holes through which flexible cord pendants pass shall be provided with bushings designed for the purpose or shall have smooth, well-rounded surfaces on which the cords may bear.

Control – Close Openings

- Junction boxes, pull boxes and fittings must have approved covers.
- Unused openings in cabinets, boxes and fittings must be closed (no missing knockouts).
Hazard - Overhead Power Lines
- Usually not insulated.

Examples of equipment that can contact power lines:

— Crane
— Ladder
— Scaffold
— Backhoe
— Scissors lift
— Raised dump truck bed
— Aluminum paint roller

Overhead and buried power lines are especially hazardous because they carry extremely high voltage. Fatal electrocution is the main risk, but burns and falls from elevation are also hazards. Using tools and equipment that can contact power lines increases the risk.

More than half of all electrocutions are caused by direct worker contact with energized power lines. Power line workers must be especially aware of the dangers of overhead lines. In the past, 80% of all lineman deaths were caused by contacting a live wire with a bare hand. Due to such incidents, all linemen now wear special rubber gloves that protect them up to 34,500 volts. Today, most electrocutions involving overhead power lines are caused by failure to maintain proper work distances.

Overhead power lines must be de-energized and grounded by the owner or operator of the lines, or other protective measures must be provided before work is started. Protective measures (such as guarding or insulating the lines) must be designed to prevent contact with the lines.

PPE may consist of rubber insulating gloves, hoods, sleeves, matting, blankets, line hose, and industrial protective helmets.

Control - Overhead Power Lines

- Stay at least 10 feet away.
- Post warning signs.
- Assume that lines are energized.
- Use wood or fiberglass ladders, not metal.
- Power line workers need special training & PPE.

How Do I Avoid Hazards?

-- Look for overhead power lines and buried power line indicators. Post warning signs.
-- Contact utilities for buried power line locations.
-- Stay at least 10 feet away from overhead power lines.
-- Unless you know otherwise, assume that overhead lines are energized.
-- Get the owner or operator of the lines to de-energize and ground lines when working near them.
-- Other protective measures include guarding or insulating the lines.
-- Use non-conductive wood or fiberglass ladders when working near power lines.

Hazard - Inadequate Wiring
Hazard - wire too small for the current.

Example - portable tool with an extension cord that has a wire too small for the tool

— The tool will draw more current than the cord can handle, causing overheating and a possible fire without tripping the circuit breaker.

— The circuit breaker could be the right size for the circuit but not for the smaller-wire extension cord.

An electrical hazard exists when the wire is too small a gauge for the current it will carry. Normally, the circuit breaker in a circuit is matched to the wire size. However, in older wiring, branch lines to permanent ceiling light fixtures could be wired with a smaller gauge than the supply cable.

Note that wire-gauge size is inversely related to the diameter of the wire. For example, a No. 12 flexible cord has a larger diameter wire than a No. 14 flexible cord.

Choose a wire size that can handle the total current. Remember: The larger the gauge number, the smaller the wire!

American Wire Gauge (AWG)

Wire size          Handles up to

#10 AWG             30 amps

#12 AWG             25 amps

#14 AWG             18 amps

#16 AWG             13 amps

Control – Use the Correct Wire

- Wire used depends on operation, building materials, electrical load, and environmental factors.
- Use fixed cords rather than flexible cords.
- Use the correct extension cord.

The OSHA standard requires flexible cords to be rated for hard or extra-hard usage. These ratings are to be indelibly marked approximately every foot of the cord. Since deterioration occurs more rapidly in cords which are not rugged enough for construction conditions, the National Electric Code and OSHA have specified the types of cords to use in a construction environment. This rule designates the types of cords that must be used for various applications including portable tools, appliances, temporary and portable lights. The cords are designated HARD and EXTRA HARD SERVICE.

Examples of HARD SERVICE designation types include S, ST, SO, STO, SJ, SJO, SJT, & SJTO. Extension cords must be durably marked as per 1926.405(g)(2)(ii) with one of the HARD or EXTRA HARD SERVICE designation letters, size and number of conductors.

Hazard – Defective Cords & Wires

Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside. If you touch damaged power tools or other equipment, you will receive a shock. You are more likely to receive a shock if the tool is not grounded or double-insulated.

Hazard – Damaged Cords

Cords can be damaged by:

— Aging.
— Door or window edges.
— Staples or fastenings.
— Abrasion from adjacent materials.
— Activity in the area.

Improper use can cause shocks, burns or fire

Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside. If you touch damaged power tools or other equipment, you will receive a shock. You are more likely to receive a shock if the tool is not grounded or double-insulated.

Control – Cords & Wires

- Insulate live wires.
- Check before use.
- Use only cords that are 3-wire type.
- Use only cords marked for hard or extra-hard usage.
- Use only cords, connection devices, and fittings equipped with strain relief.
- Remove cords by pulling on the plugs, not the cords.
- Cords not marked for hard or extra-hard use, or which have been modified, must be taken out of service immediately.
- Insulation is the most common manner of guarding electrical energy.
- Extension cords must be 3-wire type so they may be grounded, and to permit grounding of any tools or equipment connected to them.
- Extension cords when exposed to "normal" construction use can experience rapid deterioration. When this happens, conductors with energized bare wires can be exposed. Conductors can break or come loose from their terminal screws, specifically the equipment grounding conductor. If that occurs, the equipment grounding for the tool in use is lost.

Permissible Use of Flexible Cords Other use examples:

- Elevator cables.
- Wiring of cranes and hoists.
- Prevention of the transmission of noise or vibration.
- Appliances where the fastening means and mechanical connections are designed to permit removal for maintenance and repair.

DO NOT use flexible wiring in situations where frequent inspection would be difficult, where damage would be likely, or where long-term electrical supply is needed. Flexible cords cannot be used as a substitute for the fixed wiring of a structure.

Flexible cords must not be . . .

- Run through holes in walls, ceilings, or floors;

run through doorways, windows, or similar openings (unless physically protected);

attached to building surfaces (except with a tension take-up device within 6 feet of the supply end);

hidden in walls, ceilings, or floors; or hidden in conduit or other raceways.

Grounding

Grounding is a secondary method of preventing electrical shock.

Grounded electrical systems are usually connected to a grounding rod that is placed 6-8 feet deep into the earth.

Grounded - connected to earth or to some conducting body that serves in place of the earth.

Grounded, effectively (Over 600 volts, nominal.) Permanently connected to earth through a ground connection of sufficiently low impedance and having sufficient capacity that ground fault current which may occur cannot build up to voltages dangerous to personnel.

Grounded conductor. A system or circuit conductor that is intentionally grounded.

Grounding conductor. A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.

Hazard – Improper Grounding

- Tools plugged into improperly grounded circuits may become energized.
- Broken wire or plug on extension cord.

Some of the most frequently violated OSHA standards:

The most frequently violated OSHA electrical regulation is improper grounding of equipment and circuitry. The metal parts of an electrical wiring system that we touch (switch plates, ceiling light fixtures, conduit, etc.) should be grounded and at 0 volts. If the system is not grounded properly, these parts may become energized. Metal parts of motors, appliances, or electronics that are plugged into improperly grounded circuits may be energized. When a circuit is not grounded properly, a hazard exists because unwanted voltage cannot be safely eliminated. If there is no safe path to ground for fault currents, exposed metal parts in damaged appliances can become energized.

Extension cords may not provide a continuous path to ground because of a broken ground wire or plug.

Electrical systems are often grounded to metal water pipes that serve as a continuous path to ground. If plumbing is used as a path to ground for fault current, all pipes must be made of conductive material (a type of metal). Many electrocutions and fires occur because (during renovation or repair) parts of metal plumbing are replaced with plastic pipe, which does not conduct electricity.

Control – Ground Tools & Equipment

- Ground power supply systems, electrical circuits, and electrical equipment Frequently inspect electrical systems to insure path to ground is continuous.
- Inspect electrical equipment before use.
- Don’t remove ground prongs from tools or extension cords.
- Ground exposed metal parts of equipment.

A typical extension cord grounding system has four components:

- A third wire in the cord, called a ground wire;

a three-prong plug with a grounding prong on one end of the cord;

a three-wire, grounding-type receptacle at the other end of the cord; and a properly grounded outlet.

Two kinds of grounds are required by the standard:

1. Service or system ground. In this instance, one wire, called the neutral conductor or grounded conductor, is grounded. In an ordinary low-voltage circuit, the white (or gray) wire is grounded at the generator or transformer and again at the service entrance of the building. This type of ground is primarily designed to protect machines, tools, and insulation against damage.

2. For enhanced worker protection, an additional ground, called the equipment ground, must be furnished by providing another path from the tool or machine through which the current can flow to the ground. This additional ground safeguards the electric equipment operator if a malfunction causes the metal frame of the tool to become energized.

Control – Use GFCI (ground-fault circuit interrupter)

- Protects you from shock.
- Detects difference in current between the black and white wires.
- If ground fault detected, GFCI shuts off electricity in 1/40th of a second
- Use GFCI’s on all 120-volt, single-phase, 15- and 20-ampere receptacles, or have an assured equipment grounding conductor program.

GFCI

- Matches the amount of current going to an electrical device against the amount of current returning from the device.
- Interrupts the electric power within as little as 1/40 of a second when the amount of current going differs from the amount returning by about 5 mA
- Must be tested to ensure it is working correctly.

NEC requires GFCI’s be used in these high-risk situations:
- Electricity is used near water.
- The user of electrical equipment is grounded (by touching grounded material).
- Circuits are providing power to portable tools or outdoor receptacles.
- Temporary wiring or extension cords are used.

There is one disadvantage to grounding: a break in the grounding system may occur without the user's knowledge. Using a ground-fault circuit interrupter (GFCI) is one way of overcoming grounding deficiencies.

Control - Assured Equipment Grounding Conductor Program Program must cover:

— All cord sets.
— Receptacles not part of a building or structure.
— Equipment connected by plug and cord.

Program requirements include:

— Specific procedures adopted by the employer.
— Competent person to implement the program.
— Visual inspection for damage of equipment connected by cord and plug.

Assured Equipment Grounding Conductor Program (AEGCP).

The employer shall establish and implement AEGCP on construction sites covering all listed above which are available for use or used by employees. This program has the following minimum requirements:

- Daily visual inspections,
- Periodic test inspections (3 months at most for temporary cords and cords exposed to damage, 6 months for fixed cords not exposed).
- Written description.
- A competent person to implement the program, and Record of the periodic tests.

When portions of the building(s) or structures(s) which have been completed and no longer expose employees to weather or damp and wet locations, or to other grounding hazards, GFCIs or an assured equipment grounding program may not be required when approved extension cords are plugged into the permanent wiring at construction sites.

Hazard – Overloaded Circuits

Hazards may result from:

- Too many devices plugged into a circuit, causing heated wires and possibly a fire.
- Damaged tools overheating.
- Lack of overcurrent protection.
- Wire insulation melting, which may cause arcing and a fire in the area where the overload exists, even inside a wall.

If the circuit breakers or fuses are too big (high current rating) for the wires they are supposed to protect, an overload in the circuit will not be detected and the current will not be shut off. A circuit with improper overcurrent protection devices – or one with no overcurrent protection devices at all – is a hazard.

Control - Electrical Protective Devices

Automatically opens circuit if excess current from overload or ground-fault is detected – shutting off electricity.

Includes GFCI’s, fuses, and circuit breakers.

Fuses and circuit breakers are overcurrent devices. When too much current:

 Fuses melt
 Circuit breakers trip open

To prevent too much current in a circuit, a circuit breaker or fuse is placed in the circuit. If there is too much current in the circuit, the breaker ―trips‖ and opens like a switch. If an overloaded circuit is equipped with a fuse, an internal part of the fuse melts, opening the circuit. Both breakers and fuses do the same thing: open the circuit to shut off the electrical current.

The basic idea of an overcurrent device is to make a weak link in the circuit. In the case of a fuse, the fuse is destroyed before another part of the system is destroyed. In the case of a circuit breaker, a set of contacts opens the circuit. Unlike a fuse, a circuit breaker can be re-used by re-closing the contacts. Fuses and circuit breakers are designed to protect equipment and facilities, and in so doing, they also provide considerable protection against shock in most situations. However, the only electrical protective device whose sole purpose is to protect people is the ground-fault circuit-interrupter.

Power Tool Requirements

• Have a three-wire cord with ground plugged into a grounded receptacle, or Be double insulated, or Be powered by a low-voltage isolation transformer.
Common Examples of Misused Equipment = OSHA Violations
* Using multi-receptacle boxes designed to be mounted by fitting them with a power cord and placing them on the floor.
* Fabricating extension cords with ROMEX® wire.
* Using equipment outdoors that is labeled for use only in dry, indoor locations.
* Attaching ungrounded, two-prong adapter plugs to three-prong cords and tools.
* Using circuit breakers or fuses with the wrong rating for over-current protection, e.g. using a 30-amp breaker in a system with 15- or 20-amp receptacles. Protection is lost because it will not trip when the system's load has been exceeded.
* Using modified cords or tools, e.g., removing ground prongs, face plates, insulation, etc.
* Using cords or tools with worn insulation or exposed wires.

Tool Safety Tips

Avoid accidental starting. Don’t hold fingers on switch button while carrying a plugged-in tool.

Tag damaged tools: "Do Not Use."

Hazards of portable electric tools:

- Currents as small as 10 mA can paralyze, or ―freeze‖ muscles: person cannot release tool.
- Tools are held tightly, resulting in longer shock exposure.
- Power drills use 30 times as much current as what will kill.

Preventing Electrical Hazards - Tools

* Use tools and equipment according to the instructions included in their listing, labeling or certification.

* Visually inspect all electrical equipment before use. Remove from service any equipment with frayed cords, missing ground prongs, cracked tool casings, etc. Apply a warning tag to any defective tool and do not use it until the problem has been corrected.

Temporary Lights Protect from contact and damage, and don’t suspend by cords unless designed to do so.

Clues that Electrical Hazards Exist

- Tripped circuit breakers or blown fuses.
- Warm tools, wires, cords, connections, or junction boxes.
- GFCI that shuts off a circuit.
- Worn or frayed insulation around wire or connection.

There are ―clues‖ that electrical hazards exist. For example, if a GFCI keeps tripping while you are using a power tool, there is a problem. Don’t keep resetting the GFCI and continue to work. You must evaluate the ―clue‖ and decide what action should be taken to control the hazard.

There are a number of other conditions that indicate a hazard.

Tripped circuit breakers and blown fuses show that too much current is flowing in a circuit. This could be due to several factors, such as malfunctioning equipment or a short between conductors. You need to determine the cause in order to control the hazard.

An electrical tool, appliance, wire, or connection that feels warm may indicate too much current in the circuit or equipment. You need to evaluate the situation and determine your risk.

An extension cord that feels warm may indicate too much current for the wire size of the cord. You must decide when action needs to be taken.

A cable, fuse box, or junction box that feels warm may indicate too much current in the circuits.

A burning odor may indicate overheated insulation.

Worn, frayed, or damaged insulation around any wire or other conductor is an electrical hazard because the conductors could be exposed. Contact with an exposed wire could cause a shock. Damaged insulation could cause a short, leading to arcing or a fire. Inspect all insulation for scrapes and breaks. You need to evaluate the seriousness of any damage you find and decide how to deal with the hazard.

A GFCI that trips indicates there is current leakage from the circuit First, you must decide the probable cause of the leakage by recognizing any contributing hazards. Then, you must decide what action needs to be taken.

Lockout and Tagging of Circuits

(a) Controls. Controls that are to be deactivated during the course of work on energized or de-energized equipment or circuits shall be tagged.
(b) Equipment and circuits. Equipment or circuits that are deenergized shall be rendered inoperative and shall have tags attached at all points where such equipment or circuits can be energized.
(c) Tags. Tags shall be placed to identify plainly the equipment or circuits being worked on.
(d) Lockout and tagging. While any employee is exposed to contact with parts of fixed electric equipment or circuits which have been de-energized, the circuits energizing the parts shall be locked out or tagged or both.

Case study

An electrician was removing a metal fish tape from a hole at the base of a metal light pole.

(A fish tape is used to pull wire through a conduit run.) The fish tape became energized, electrocuting him. As a result of its inspection, OSHA issued a citation for three serious violations of the agency’s construction standards.

If the following OSHA requirements had been followed, this death could have been prevented.

- De-energize all circuits before beginning work.
- Always lock out and tag out de-energized equipment.
- Companies must train workers to recognize and avoid unsafe conditions.
- Apply locks to power source after de-energizing.
- Tag deactivated controls.
- Tag de-energized equipment and circuits at all points where they can be energized.
- Tags must identify equipment or circuits being worked on.

Safety-Related Work Practices

To protect workers from electrical shock:

— Use barriers and guards to prevent passage through areas of exposed energized equipment.
— Pre-plan work, post hazard warnings and use protective measures.
— Keep working spaces and walkways clear of cords.

Safety-Related Work Practices

- Use special insulated tools when working on fuses with energized terminals.
- Don’t use worn or frayed cords and cables.
- Don’t fasten extension cords with staples, hang from nails, or suspend by wire.
- Employees must not work near any part of an electric power circuit that the employee could contact in the course of work, unless the employee is protected against electric shock by de-energizing the circuit and grounding it or by guarding it effectively by insulation or other means.

* In work areas where the exact location of underground electric power lines is unknown, employees using jack-hammers, bars, or other hand tools which may contact a line shall be provided with insulated protective gloves.

* Before work is begun, inquire or observe by instruments whether any part of an energized electric power circuit is so located that the performance of the work may bring any person, tool, or machine into physical or electrical contact with the electric power circuit. Post and maintain proper warning signs where such a circuit exists. The employer shall advise employees of the location of such lines, the hazards involved, and the protective measures to be taken.

Preventing Electrical Hazards - Planning

- Plan your work with others.
- Plan to avoid falls.
- Plan to lock-out and tag-out equipment.
- Remove jewelry.
- Avoid wet conditions and overhead power lines.

Make your environment safer by doing the following:

- Lock and tag out circuits and machines.
- Prevent overloaded wiring by using the right size and type of wire.
- Prevent exposure to live electrical parts by isolating them.
- Prevent exposure to live wires and parts by using insulation.
- Prevent shocking currents from electrical systems and tools by grounding them.
- Prevent shocking currents by using GFCI’s.
- Prevent too much current in circuits by using overcurrent protection devices.

Avoid Wet Conditions

If you touch a live wire or other electrical component while standing in even a small puddle of water you’ll get a shock.

Damaged insulation, equipment, or tools can expose you to live electrical parts.

Improperly grounded metal switch plates & ceiling lights are especially hazardous in wet conditions.

Wet clothing, high humidity, and perspiration increase your chances of being electrocuted.

A damaged tool may not be grounded properly, so the housing of the tool may be energized, causing you to receive a shock.

Improperly grounded metal switch plates and ceiling lights are especially hazardous in wet conditions. If you touch a live electrical component with an uninsulated hand tool, you are more likely to receive a shock when standing in water. But remember: you don’t have to be standing in water to be electrocuted. Wet clothing, high humidity, and perspiration also increase your chances of being electrocuted.

Use extra caution when working with electricity when water is present in the environment or on the skin. Pure water is a poor conductor, but small amounts of impurities, like salt and acid (both are in perspiration), make it a ready conductor.

Preventing Electrical Hazards - PPE

Personal protective equipment (PPE) should always be the last line of defense against a hazard. If the hazard is unavoidable, and cannot be addressed in any other safe manner, then employees must be fitted with proper PPE.

Safety shoes should be non-conductive and protect your feet from completing an electrical circuit to ground. They can also protect against open circuits of up to 600 volts in dry conditions. These shoes should be used with other insulating equipment and in connection with active precautions to reduce or eliminate the potential for providing a path for hazardous electrical energy.

When it is necessary to handle or come close to wires with a potential live electrical charge, it is essential to use proper insulating PPE to protect employees from contact with the hazardous electrical energy.

Specific types of hard hats are needed when performing electrical work.

A ―Class B‖ Electrical/Utility type hard hat protects against falling objects and high-voltage shock and burns.

Preventing Electrical Hazards – Proper Wiring and Connectors

If the polarity is reversed on a GFCI, the lights will test good, but the press to test button will not trip the circuit.

Training

De-energizing Electrical Equipment.

Accidental or unexpected starting of electrical equipment can cause injury or death. Before ANY inspections or repairs are made, the current must be turned off at the switch box and the switch padlocked in the OFF position. At the same time, the switch or controls of the machine or other equipment being locked out of service must be securely tagged to show which equipment or circuits are being worked on.

Employees shall be trained in and familiar with the safety-related work practices that pertain to their respective job assignments.

Summary – Hazards & Protections Hazards

Inadequate wiring.

Exposed electrical parts.

Wires with bad insulation.

Ungrounded electrical systems and tools.

Overloaded circuits.

Damaged power tools and equipment.

Using the wrong PPE and tools.

Overhead power lines.

All hazards are made worse in wet conditions.

Protective Measures

Proper grounding.

Use GFCI’s.

Use fuses and circuit breakers.

Guard live parts.

Lockout/Tagout.

Proper use of flexible cords.

Close electric panels.

Training.

Summary.

Electrical equipment must be:

— Listed and labeled.
— Free from hazards.
— Used in the proper manner.

If you use electrical tools you must be:

— Protected from electrical shock.
— Provided necessary safety equipment.


مخاطر الكهرباء وطرق الوقاية منها

أسباب الإصابات الكهربائية كثيرة منها

1- لمس أجزاء ناقلة لأى خطوط للتيار الكهربائى غير معزولة .
2- عدم قطع التيار الكهربائى عن الآلة أو الجهاز أو الخطوط الكهربائية التى يقوم العامل على إصلاحها .
3- جهل بعض العاملين بالدوائر الكهربائية و التوصيلات فى الأجهزة أو الأدوات أو اللوحات التى يقوم بالكشف عليها أو إصلاحها .
4- توصيل التيار الكهربائى لموقع العمل عن طريق الخطأً بوجود عمال يعملون فيها وعدم تعليق لوحة تدل على قطع التيار الكهربائى.
5- استعمال أدوات غير معزولة بشكل جيد .
6- عدم استخدام العامل أجهزة الوقاية اللازمة.
7- عدم تأريض (توصيل بالأرضى) الآلات و المعدات الكهربائية أو الخطوط بشكل جيد .

الإسعافات الأولية في حالة حدوث حوادث

الصعق الكهربائي :
الإسعاف:

- قطع التيار الكهربائي أو إبعاد الشخص المصاب عن الموصل الكهربائي و ذلك بدفعه بشدة و بسرعة بواسطة شيء عازل (قطعة خشبية حبل...).
- إجراء التنفس الصناعي للمصاب لفترة طويلة لا تفل عن 4 ساعات.
- تدفئة المصاب ببطانية و باستخدام زجاجة ماء ساخن.

تخليص المصابين من التيار الكهربائى

- من الضرورى تخليص العامل المصاب بالصدمة الكهربية من التيار الكهربائى بأسرع وقت ممكن لأنه كلما طالت فترة تأثير التيار الكهربائى كلما كانت الصدمة أقوى.
- ويجب أن نعرف أن المساس بناقل فيه تيار كهربائى يجعل عضلات العامل تتقلص بشكل عام وتنكمش الأصابع على الناقل بشكل غير ارادى.
- ولذلك فإن عملية إنقاذ المصاب يجب أن تبداً بفصل التيار الكهربائى.
- وعلى المنقذ أن يكون مرتديا لأدوات الوقاية الازمة لأن لمسه للمصاب يعرضه لخطر التكهرب إذا لم يتم فصل التيار الكهربائى.
- إذا كان المصاب على إرتفاع عالى فإن فصل التيار قد يؤدى إلى سقوط المصاب لذا يجب اتخاذ الإجراءات الكفيلة بحماية المصاب من السقوط وعدم تعريضه لخطر اإضافى.
- فى حالة تعذر فصل التيار الكهربائى يجب اتخاذ الإجراءات لفصل المصاب عن الأجزاء الناقلة التى تلامسه.

أقل من 1000 فولت

1. يتم تخليص المصاب من التوتر باستعمال الملابس الجافة أوالحبال أو عصا أو لوح خشب أو أى مادة أخرى جافة غير ناقلة للتيار ولايسمح باستعمال الأدوات المعدنية أو المواد الأخرى الرطبة .
2. يمكن تخليص المصاب بجره من ملابسه إذا كانت جافة وغير ملتصقة بجسمه على أن يتنبه المنقذ لعدم لمس الأجزاء المعدنية المحيطة بالمصاب .
3. ينصح المنقذ بعدم جر المصاب من قدميه إذا إذا لم يكن مرتديا لكفوف عازلة لأن هناك أنواع من الأحذية بها واقية فولازية أو مسامير فتكون بمثابة نواقل للتيار الكهربى .
4. إذا اقتضت الضرورة سحب المصاب من جسده العارى فيجب على المنقذ أرتداء جوانتيات وبوط عازل أو لف الأيدى لملابس جافة .
5. يمكن للمنقذ أن يعزل نفسه بالوقوف على لوح جاف من الخشب أو لوح بلاستيكى .
6. ينصح عند تخليص المصاب من التيار الكهربائى استعمال يد واحدة فقط قد الاستطاعة .
7. إذا تعذر فصل التيار الكهربائى وكان المصاب يمسك بالناقل فيمكن فصل أو رفع قدميه عن الأرض بواسطة حبل أو ملابس جافة
8. يمكن للمنقذ أتباع أسلوب قطع النواقل بواسطة فأس أو ساطور بيد خشبية جافة أو أى وسيلة أخرى على أن يتم ذلك بحذر وقطع كل ناقل على حده وأن يكون المنقذ مرتديا لوسائل الأمن الصناعى من كفوف وحذاء عازل .

أكثر من 1000 فولت

1. يجب استخدام وسائل الأمن الصناعى مثل الجوانتيات العازلة و الحذاء المعزول و العصا العازلة الخاصة بالفولتات العالية بهدف عزل المصاب عن الأرض أو تخليصه من النواقل التى يمر بها التيار الكهربى.
2. عندما يكون العامل المصاب يعمل على خطوط التوتر العالى يصعب عزله لذلك يجب اجراء دائرة أرضى (تأريض) على الخط لفصله كليا عن التوتر ويتم ذلك بإلقاء سلك متصل بالأرضى على الخط مع المراعاة الدقيقة لقواعد الأمن الصناعى والإنتباه إلى الخطر الناجم عن ملامسة سلك التأريض (الأرضى) لجسم المصاب أو جسم المنقذ مع مراعاة ما يلى:

أ- يجب الإنتباه لعدم تعريض المصاب لخطر السقوط إذا كان على ارتفاع عالى .
ب إذا كان المصاب يمس أحد النواقل فقط فإنه يمكن الأكتفاء بتأريض هذا الناقل .
ج_ يجب تأريض السلك (وصله بالأرضى الرئيسى) فى البداية ثم رميه على الناقل المراد تأريضه.
د. بهد فصل الخطوط المحملة بالتوتر العالى يمكن أن تبقى فيها شحنة كبيرة خطرة على الحياة ولا يمكن تفادى هذا الخطر إلا بالتأريض الجيد لها.

للوقاية من وقوع حوادث الصعق الكهربائى

1- يجب إجراء الصيانة الدورية للمعدات والأجهزة الكهربائية ووقايتها من التلف.
2- تنبيه العمال الذين يعملون فى الإنارة وصيانة وخطوط التوتر العالى وكافة العمال الكهربائيين إلى الأخطار الناجمة عن التيار الكهربائى وإعطائهم تعليمات الأمن الصناعى والوقاية التى يجب مراعاتها بشكل دائم.
3- يجب أن تكون كافة العدد و الأدوات الكهربائية مجهزة بغلاف عازل لمنع تسرب التيار الكهربائى .
4- يجب عزل نهايات الكابلات و الوصلات حين إصلاح المعدات والأجهزة الكهربائية وتمديد الكابلات .
5- يفضل استخدام الأدوات والأجهزا التوترات الخفيفة أى بإستعمال بطاريات أو محولات كهربائية صغيرة .
6- يجب تأريض هياكل العدد و الأدوات الكهربائية بواسطة سلك أرضى ذو مقاومة ضعيفة أو تجهيزها بفيوزات بحيث يحترق الفيوز أو ينفصل القاطع للدائرة الكهربائية عندما يزداد التيار الكهربائى عن الحد المسموح به فى حالة حدوث دائرة قصر مع الأرض فتنقطع الدائرة الكهربائية .
7- يفضل استخدام الأجهزة و المعدات التى تكون مجهزة أصلا بسلك ثالث للتأريض.
8- يمكن استخدام قواطع تفاضلية للوقاية من التسرب الكهربائى ويقوم القاطع بفصل الدائرة عند وجود قصر مع الأرض .
9- على العامل الكهربائى أن يذكر دوما أن التجهيزات أو الخطوط التى انقطع عنها التوتر فجأة يمكن أن توضع تحت التوتر بدون إعلام سابق .
10- عند تنفيذ بعض الأعمال على خطوط التوتر الكهربائى وضرورة العمل دون قطع التيار يجب استخدام أجهزة الوقاية اللازمة بالأضافة للأدوات المساعدة مثل (العصا المعزولة - مؤشر التوتر ... ) .
11- فى حالة مد شبكات جديدة لخطوط التوتر العالى أو المتوسط أو المنخفض و حين تقاطع هذه الخطوط مع خطوط محملة بالتيار الكهربى يجب عدم البدء بالمد إلا بعد الحصول على وثيقة تفيد بقطع التيار الكهربائى عن هذه الخطوط وتصريح عمل محدد بالتاريخ والزمن وساعة البداية و ساعة النهاية إذا أمكن ذلك .
12- فحص خطوط التوتر المحملة بالتيار الكهربائى والتى تم قطع التيار عنها والمراد تمرير الخطوط الجديدة من فوقها أو تحتها يجب تفريغ الشحنات الكهربائية بواسطة بندقية التأريض أو أى وسيلة أخرى معروفة ؛ وأن يتم تأريض الخطوط فى المنطقة التى يتم العمل فيها كأمان إضافى منعا للأخطاء التى يمكن أن تحصل بإعادة التيار الكهربائى على هذه الخطوط