Strong winds, ice or unintentional contact with equipment may cause trees or tree limbs to fall into powerlines. This may cause wires to break and fall to the ground. Should this happen, notify the electric utility company immediately.
A fallen wire can create hazards for workers and the general public. Objects touched by a fallen wire - fences, vehicles, buildings or even the surrounding ground - must be considered energized and should not be touched.
It is impossible to tell simply by looking whether a downed wire is energized. Consider all downed wires energized and dangerous until the electric utility personnel notify you otherwise.
Where a power line has fallen across a vehicle, occupants should remain within the vehicle. If they must leave the vehicle because of a life-threatening situation, such as fire or potential explosion, they should jump clear of the vehicle without touching either the vehicle or wire and the ground at the same time.
Once clear of the vehicle, they should shuffle away, taking small steps and keeping both feet in contact with the ground.
Remember, electricity can be transmitted from the victim to you. If a switch is accessible, shut off the power immediately. Otherwise, stand on a dry surface and pull the victim away with a dry board or rope. Do not use your hands or anything metal.
Use a C02 or dry chemical extinguisher to put out an electrical fire. Water should be used only by trained firefighting personnel. In an emergency involving power lines or electrical equipment, call the electric utility company immediately.
Training Workers
Ensure that workers assigned to operate cranes and other boomed vehicles are specifically trained in safe operating procedures. Also ensure that workers are trained (1) to understand the limitations of such devices as boom guards, insulated lines, ground rods, nonconductive links, and proximity warning devices, and (2) to recognize that these devices are not substitutes for de-energizing and grounding lines or maintaining safe clearance.
Workers should also be trained to recognize the hazards and use proper techniques when rescuing coworkers or recovering equipment in contact with electrical energy. CSA guidelines list techniques that can be used when equipment contacts energized power lines [CSA 1982]. All employers and workers should be trained in cardiopulmonary resuscitation (CPR).
THE USE OF GROUND FAULT CURRENT INTERRUPTER (GFCI) IN SAFE ELECTRICAL SYSTEM
A groundfault circuit interrupter (GFCI) is an electrical device which protects personnel by detecting potentially hazardous ground faults and immediately disconnecting power from the circuit. Any current over 8 mA is considered potentially dangerous depending on the path the current takes, the amount of time exposed to the shock, as well as the physical condition of the person receiving the shock.
GFCIs should be installed in such places as dwellings, hotels, motels, construction sites, marinas, receptacles near swimming pools and hot tubs, underwater lighting, fountains, and other areas in which a person may experience a ground fault.
A GFCI compares the amount of current in the ungrounded (hot) conductor with the amount of current in the neutral conductor. If the current in the neutral conductor becomes less than the current in the hot conductor, a ground fault condition exists.
The missing current is returned to the source by some path other than the intended path (fault current). A fault current as low as 4 mA to 6 mA activates the GFCI and interrupts the circuit.
Once activated, the fault condition is cleared and the GFCI manually resets before power may be restored to the circuit. GFCI protection may be installed at different locations within a circuit.
Direct-wired GFCI receptacles provide a ground fault protection at the point of installation. GFCI receptacles may also be connected to provide GFCI protection at all other receptacles installed downstream on the same circuit. GFCI CBs, when installed in a load center or panelboard, provide GFCI protection and conventional circuit overcurrent protection for all branch-circuit components connected to the CB.
Plug-in GFCls provide ground fault protection for devices plugged into them. Plug-in devices are generally utilized by personnel working with power tools in an area that does not include GFCI receptacles.
HOW GFCI WORKS? THE OPERATING PRINCIPLE OF GFCI
A GFCI compares the amount of current in the ungrounded (hot) conductor with the amount of current in the neutral conductor.
GFCI operation diagram is found below:
GFCIs should be installed in such places as dwellings, hotels, motels, construction sites, marinas, receptacles near swimming pools and hot tubs, underwater lighting, fountains, and other areas in which a person may experience a ground fault.
A GFCI compares the amount of current in the ungrounded (hot) conductor with the amount of current in the neutral conductor. If the current in the neutral conductor becomes less than the current in the hot conductor, a ground fault condition exists.
The missing current is returned to the source by some path other than the intended path (fault current). A fault current as low as 4 mA to 6 mA activates the GFCI and interrupts the circuit.
Once activated, the fault condition is cleared and the GFCI manually resets before power may be restored to the circuit. GFCI protection may be installed at different locations within a circuit.
Direct-wired GFCI receptacles provide a ground fault protection at the point of installation. GFCI receptacles may also be connected to provide GFCI protection at all other receptacles installed downstream on the same circuit. GFCI CBs, when installed in a load center or panelboard, provide GFCI protection and conventional circuit overcurrent protection for all branch-circuit components connected to the CB.
Plug-in GFCls provide ground fault protection for devices plugged into them. Plug-in devices are generally utilized by personnel working with power tools in an area that does not include GFCI receptacles.
HOW GFCI WORKS? THE OPERATING PRINCIPLE OF GFCI
A GFCI compares the amount of current in the ungrounded (hot) conductor with the amount of current in the neutral conductor.
GFCI operation diagram is found below:
THE DECIBEL SCALE - UNDERSTANDING SAFETY NOISE
A sound consists essentially of a moving series of pressure fluctuations, and the normal unit of pressure is the pascal (abbreviated to Pa). However, it is not normal to measure sound in pascals; instead the decibel (abbreviated to dB) scale is used.
The decibel scale is a logarithmic one, which compresses a large range of values to a much smaller range. For example, the range of sound pressures from 0.00002 to 2.0 Pa is represented on the decibel scale by the range 0 to 100 dB. Two justifications are normally given for using a decibel scale.
1. The range of values involved in measuring the amplitude of sound is inconveniently large.
2. The human ear does not respond linearly to different sound levels and the decibel scale relates sound measurement more closely to subjective impressions of loudness.
Neither of these explanations really stands up to scrutiny. We cope with larger ranges of values when measuring other quantities (length and money are just two examples of this). It is certainly true that our ears do not respond linearly to changes in sound pressure. In other words doubling the sound pressure does not double the apparent loudness of a sound.
However, they do not respond linearly to the decibel scale either, so little has been gained in this respect by using a decibel scale. Whatever the original reasons for adopting a decibel scale, it is now used universally, so there is no alternative but to do so.
The use of a logarithmic scale dates from the days before electronic calculators when many calculations were carried out with the help of a book of logarithms, or ‘log’ tables. As a result, logarithms were much more familiar to anyone who needed to carry out calculations regularly.
Many fewer people are nowadays familiar with them. Fortunately, with the help of a calculator, decibel calculations can be carried out without any great understanding of how logarithms work.
In other fields, different logarithms – called natural logarithms and abbreviated to either loge or ln – are used.
In workplace noise calculations, all logarithms will be the more familiar system based on the number 10. They are sometimes called ‘logs to base 10’, abbreviated to log10, log or simply lg.
The decibel scale is a logarithmic one, which compresses a large range of values to a much smaller range. For example, the range of sound pressures from 0.00002 to 2.0 Pa is represented on the decibel scale by the range 0 to 100 dB. Two justifications are normally given for using a decibel scale.
1. The range of values involved in measuring the amplitude of sound is inconveniently large.
2. The human ear does not respond linearly to different sound levels and the decibel scale relates sound measurement more closely to subjective impressions of loudness.
Neither of these explanations really stands up to scrutiny. We cope with larger ranges of values when measuring other quantities (length and money are just two examples of this). It is certainly true that our ears do not respond linearly to changes in sound pressure. In other words doubling the sound pressure does not double the apparent loudness of a sound.
However, they do not respond linearly to the decibel scale either, so little has been gained in this respect by using a decibel scale. Whatever the original reasons for adopting a decibel scale, it is now used universally, so there is no alternative but to do so.
The use of a logarithmic scale dates from the days before electronic calculators when many calculations were carried out with the help of a book of logarithms, or ‘log’ tables. As a result, logarithms were much more familiar to anyone who needed to carry out calculations regularly.
Many fewer people are nowadays familiar with them. Fortunately, with the help of a calculator, decibel calculations can be carried out without any great understanding of how logarithms work.
In other fields, different logarithms – called natural logarithms and abbreviated to either loge or ln – are used.
In workplace noise calculations, all logarithms will be the more familiar system based on the number 10. They are sometimes called ‘logs to base 10’, abbreviated to log10, log or simply lg.
HARD HAT DESIGN - RECOMMENDED BASIS FOR HEAD PROTECTION OF ELECTRICAL WORKERS
An eye injury can put you out of work for days or weeks, but a head injury can put you out of work permanently, and can even be terminal. Think about this seriously for a minute. Your brain is inside your head and it controls everything your body does.
Some worker injuries that have resulted from not wearing a hardhat include permanently blurred vision, memory loss, and lack of coordination. Your neck and spine are connected to your head and an injury to these vital structures can leave you paralyzed for life.
OSHA 1910.135 requires that anytime there is the chance of falling overhead objects, tight construction areas where workers could bump their heads on surrounding objects, or the possibility that a worker’s head could accidentally come in contact with EHs, an employer must make sure that workers wear head protection.
A hardhat’s design includes a suspension harness that provides impact protection and ventilation.
That criteria covers just about any worksite condition.
Hardhats have a hard outer shell and a shock-absorbing lining with a headband and straps that suspend the shell from 1 to 1¼ inches away from your head. The basic design provides ventilation during normal wear and shock absorption in the event of an impact.
When you wear a hardhat, the force of a falling object is transmitted and distributed, reducing the impact by approximately 75%. The force of a falling object can be calculated from the weight of the object and the distance that it falls.
For example, a metal washer falling about 30 feet will generate a force of 6½ pounds on impact! Now imagine that you are pulling wire in a new construction house and someone working on the trusses two stories above you drops his hammer and it hits your hardhat.
This kind of accident has happened more than once, resulting in nothing more than a startled electrician with a few choice words for the carpenter above him. However, without your hardhat to dissipate and absorb that kind of shock, you could end up with a fractured skull or an injury that is so severe it kills you.
Some worker injuries that have resulted from not wearing a hardhat include permanently blurred vision, memory loss, and lack of coordination. Your neck and spine are connected to your head and an injury to these vital structures can leave you paralyzed for life.
OSHA 1910.135 requires that anytime there is the chance of falling overhead objects, tight construction areas where workers could bump their heads on surrounding objects, or the possibility that a worker’s head could accidentally come in contact with EHs, an employer must make sure that workers wear head protection.
A hardhat’s design includes a suspension harness that provides impact protection and ventilation.
That criteria covers just about any worksite condition.
Hardhats have a hard outer shell and a shock-absorbing lining with a headband and straps that suspend the shell from 1 to 1¼ inches away from your head. The basic design provides ventilation during normal wear and shock absorption in the event of an impact.
When you wear a hardhat, the force of a falling object is transmitted and distributed, reducing the impact by approximately 75%. The force of a falling object can be calculated from the weight of the object and the distance that it falls.
For example, a metal washer falling about 30 feet will generate a force of 6½ pounds on impact! Now imagine that you are pulling wire in a new construction house and someone working on the trusses two stories above you drops his hammer and it hits your hardhat.
This kind of accident has happened more than once, resulting in nothing more than a startled electrician with a few choice words for the carpenter above him. However, without your hardhat to dissipate and absorb that kind of shock, you could end up with a fractured skull or an injury that is so severe it kills you.
SAMPLE OF GENERAL REQUIREMENTS OF SAFETY IN WORKSHOP POLICY
The following rules apply to all workshop personnel, whether they are permanently employed in the workshop or just occasional users:
• Keep the workshop clean and tidy at all times.
• Always seek instruction before using an unfamiliar piece of equipment.
• Only use tools and machines for their intended purpose.
• Report all damaged equipment and do not use it until it has been repaired by a qualified person.
• Where machine guards are provide they must be kept in place.
• Never distract the attention of another staff member when that person is operating equipment and never indulge in horseplay.
Always use the appropriate personal protective devices and check that they are clean and in good repair before and after use.
Long hair needs to be restrained by either a tie or hat. Never use compressed air for cleaning clothing and machinery.
Report all hazards and unsafe conditions and work practices
• Keep the workshop clean and tidy at all times.
• Always seek instruction before using an unfamiliar piece of equipment.
• Only use tools and machines for their intended purpose.
• Report all damaged equipment and do not use it until it has been repaired by a qualified person.
• Where machine guards are provide they must be kept in place.
• Never distract the attention of another staff member when that person is operating equipment and never indulge in horseplay.
Always use the appropriate personal protective devices and check that they are clean and in good repair before and after use.
Long hair needs to be restrained by either a tie or hat. Never use compressed air for cleaning clothing and machinery.
Report all hazards and unsafe conditions and work practices
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