By Grant Laidlaw
It’s seemingly a basic skill, however the dangers are real.
Johann asks: Grant, many refrigeration people work on or near electrical power without any idea to the hazards. I realise that this is the basics, but it should be important. What about electrical safety using arc welders? Any advice?
Hi, Johann. Many refrigeration / air conditioning people do work with electricity as it forms part of the required skills set. But, unfortunately many working in our field do so without any formal training. This then creates a problem as understanding the dangers one is exposed to when working with electricity, is only theoretical in nature. One cannot just learn about the associated dangers from experience.
Let us begin with what happens when you get an electrical shock.
Electric shock occurs when the body becomes part of an electrical circuit. Electrical shock can occur in several ways:
- A person may come in contact with conductors, live and neutral in a single phase circuit, or between lives in a three phase circuit.
- A person may provide a path between a conductor and earth.
- A person may provide a path between earth and a conducting material that is in contact with a live circuit. (For example: A live wire is in contact with a metal casing and you touch the casing.)
We use the terms high and low voltage but the terms high voltage and low voltage are relative.
Typically, we call a circuit low voltage for any circuit below 600 volts. Our colleagues working at the power stations work with 20 000 volts and on the transmission lines South Africa uses 132 000, 275 000 and up to 765 000 volts. Yes, we then work with the relatively low voltages of 230 volts and 400 volts.
Do not be deceived, low voltage does not necessarily mean low hazard. The potential difference is only one factor making up the dangerous effects of electricity.
When applied to 230 and 400 volt circuits, the extent of injury accompanying electric shock depends on several factors.
- The amount of current conducted through the body.
- The path of the current through the body.
- The length of time a person is subjected to the current.
The amount of the current depends on the potential difference and the resistance. The effects of low current on the human body range from a temporary mild tingling sensation to death. An electric shock can injure you in either or both of the following.
- A severe shock can stop the heart or the breathing muscles, or both.
- The heating effect of the current can cause severe burns, especially at points where the electricity enters and leaves the body.
- Other effects include severe bleeding, breathing difficulty, and ventricular fibrillation. In addition, you may fall, or have some other accident as a result of your response to the shock.
In general, when examining current in this context we find the following:
|Less than 1 milliamps||No sensation; Will not feel the effects or very slight tingling.|
|1 to 3 milliamps||Mild sensation not painful.|
|3 to 10 milliamps||Painful shock.|
|10 to 30 milliamps||
Very Painful. Possible loss of muscular control and/or muscle clinching. Inability to pull free from electrical source. Possible death
|30 to 75 milliamps||Respiratory paralysis. Possible death.|
|75 milliamps to 4 amps||Ventricular fibrillation, death.|
|4 amps and over||Heart muscles begin to clinch, cardiac arrest, tissue begins to burn, death.|
As we can see, current (amps) is the fatal factor when dealing with electrical shock. Voltage is important only in that it determines how much current will flow through a given body resistance.
230 volts is more than enough to cause a current to flow which is many times greater than what is necessary to kill.
Proper first aid can mean the difference between life and death. Sufficient circulation can sometimes be maintained by heart compression, which should always be supported with mouth-to-mouth resuscitation, commonly known as CPR.
Safe work practices
It is good practice when developing a safe work environment to have policies and procedures in place which provide the necessary guidelines and rules for employees to work safely. The procedures should help eliminate injuries for people working on or near energised electrical circuit conductors. The policies should address protective equipment, tools, qualifications, as well as other additional cautions and information.
Electrical accidents cause countless injuries and cost the lives of hundreds of people each year. Injuries could be minimised and many lives saved if proper rescue techniques are used.
An electrically related incident occurs, what does one do?
We all know that in this type of situation time is critical. The quicker that medical treatment can occur, the better the outcome will be and the greater the chance for survival.
Questions one can ask. Do you know the proper actions to take? Do you know what dangers could be encountered?
When an electrical incident occurs, due to the effect of muscle clinching, the victim may often be incapable of moving or releasing the electrical conductor. Attempts to rescue an accident victim will pose as great a hazard for the rescuer as it does for the victim.
This is why there should always be an emergency response plan for scheduled electrical maintenance or in fact any electrical work.
Lives can be saved if proper rescue techniques are used.
- What are your primary safety considerations?
- What action will you take when you find an electrical accident victim?
- Who will you call first?
- What tools or protective equipment will you need?
You have come across an electrical incident, now what?
Never rush into an accident situation, approach with caution, analyse the situation.
- Do not place yourself at risk.
- Call for help as soon as possible.
- Visually examine victim to determine if in contact with energised conductors, bearing in mind that metal surfaces, objects near the victim or the earth itself may be energised.
- Do not touch the victim or conductive surfaces while they are energised.
- Turn off electrical circuits if at all possible.
- If you cannot turn off the power source use extreme care.
- Ensure that your hands and feet are dry.
- Stand on a dry rubber mat or other insulating material if possible.
- Wear protective equipment such as low voltage gloves and overshoes if available. Stand on a clean dry surface.
- Use a non-conductive material to remove a victim from the conductor. Hot sticks or wood / plastic poles to remove a victim from energised conductors. In some cases, non-conductive rope or cord may be used to remove a victim from a conductor.
- Do not touch the victim or conductive material near the victim until the power is off or until the victim has been removed away from the hazard.
- Once power is off, examine the victim.
- Give First Aid.
- A victim may require cardio-pulmonary resuscitation (CPR) – only if you are trained to administer this.
- If the victim is breathing and has a heartbeat, give first aid for injuries and treat for shock.
- Ensure the victim gets medical care as soon as possible.
- Stay with the victim until help arrives.
- Provide medical personnel with information on voltage level, shock duration & entry/exit points. It is of great value for the physician to have detailed specific information to properly diagnose and care for the victim.
Basic electrical safety rules
There are two very important basic rules:
The first is not to work on live circuits.
The second point is that even after the power has been turned off, you still should treat the circuit as live. After a circuit has been turned off and locked out you should always test to make sure that the electricity is in fact off.
The safest way to avoid electrical incidents is then to de-energise the conductors to be worked on or near, and, assure that they cannot be turned back on and verify that the power is off. This is then an electrically-safe work condition and should always be your first consideration.
An electrically-safe work condition will be achieved and verified by the following process:
- Determine all possible sources of electrical supply to the specific equipment.
- After properly shutting off the load current, isolate source.
- Visually verify that isolators / circuit breakers are off or fuses removed. Test operation of electrical instrumentation / testing equipment and confirm electrical isolation.
- Apply lockout devices in accordance with a documented and established policy.
- Verify isolation at load. (for example, check for power at motor).
- Where the possibility of induced voltages or stored electrical energy exists (capacitors), ground the phase conductors or circuit parts before touching them.
If at all possible, do not attempt to work on live circuits.
If your situation is such that working on a live circuit cannot be avoided, extreme caution is required.
Testing, fault-finding, or the impracticality of shutting down some continuous industrial processes are examples of where one may have to work on live circuits.
Working on electrical conductors or circuit parts which are or may become live shall only be done by trained employees who can identify electrical hazards and have the knowledge to avoid injury by using safe practices, precautionary techniques and protective equipment.
Johann, I will continue with the second part of your question with regards to electrical safety whilst using an electric arc welder. Keep safe out there.
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