In my last column, I identified the parts of a cable determine where faults could happen: 1) the end junctions or terminations, 2) in the length of the cable where there is damage, 3) splices in the cable, and 4) in the length of the cable where there is no damage. Let&#;s get to the last one, No. 4.
It is far more common to have an
internal fault in the length: possibly a manufacturer&#;s defect, but much more
likely from external abuse. We have one client with many decades of operation, and
we know its operators often abuse the cables during moving. Their procedure calls for safety hooks or
loops to be put in at least two places on the cable a certain distance apart
but, for ease and speed, the will often just put one loop around the cable and
start pulling with the machine. I have
had operators describe seeing the cable twisting and looping back on itself as
this is happening, though the cable does not fail immediately.
The difficulty this creates is
that the operators know that the cable can take a tremendous amount of abuse
and so, for their own speed and efficiency, they will abuse the cable. Abuse such as this will typically end up
creating internal damage, as the flexing will eventually cause the cable to
break down. It is difficult to convince
a person to quit abusing cables when they&#;ve been doing it for years with no
immediate failure.
Interestingly, although the
acceptance test voltage might be 36kV on a 5kV cable, trying to intentionally
fail the cable with either an AC or DC hipot would actually take well over
100kV. As we train mine operators about
the dangers of these, we explain the type of damage that can happen in a cable,
and what they should be watching for. It
is a lot easier to do this in the day light, but they should be concerned
anywhere close to a junction box or a splice.
When faults are in the length of the cable, and operators do a visual
inspection, moving a high-voltage trailing cable by hand would have a higher
safety factor built into it than either a 120V or 600V cable.
It&#;s important to evaluate the
literature and the accidents and determine where the accident occurred. Many accidents have occurred where the victim
has been working at the junction box.
Contact with a live system at the junction box does not apply to a risk
in moving a mine trailing cable or touching it.
A failure of a splice because it was poorly done also does not impact
the danger of moving a perfectly good, undamaged cable in the length.
When I have had operators tell me
they have seen cable flashes (and they describe a huge flash), I always ask
them &#;How long ago was that?&#; I
typically get the response, &#;About ten years&#;, which is a lifetime of
technological change. Most clients now have
very sensitive, high-speed relays that operate fast enough to minimize the arc
flash.
Companies have to make the
decisions on how they are going to operate their system, but at minimum, there
should be the fastest relays as possible on the system, then train the operators
on the dangers and how to perform inspections.
Then, they have to ensure inspections are done properly.
Where operators occasionally
hand-bomb mine trailing cables, there are many protective products
available. Some companies require rubber
gloves and, while you cannot go wrong with them, they are truly annoying for
continuous heavy work, worse in hot weather, and contaminants such as tar sand
can quickly destroy them. Many companies
require ropes, slings and saddles properly spaced apart, but the abusers will
continue to abuse them. There are
D-rings that counter this with the proper bending radius in the design. Other companies will use insulated hook
sticks or tongs, but dry conditions will quickly marginalize the insulating
value.
We get both emotional and
rational responses in our own instructor group.
We have one very experienced substation electrician/electrical
technologist who is absolutely adamant he would never touch the outside of a
live 15kV cable. We have another
instructor with the same credentials who just shakes his head and says it&#;s
just a big extension cord. Both of these
men each have over 40 years of high-voltage field experience. Who is right?
Actually, both.
The bottom line is, there is a
tremendous amount of danger when you are dealing with high voltages and high
currents. At the same time, there are
large extension cords, and when they are installed correctly and treated
properly, then there is no more danger to them than touching a low-voltage
cable. But hey&#; that&#;s a rational
response.
Until next time, be ready, be careful and be safe.
Every workplace has some types of health and safety hazards that people need to be aware of. When it comes to the mining industry, however, there are significantly more hazards to be concerned with. To make matters worse, the hazards in this industry are often far more dangerous than they are in most other workplaces.
According to Mine Safety and Health Administration,
&#;Safety and health in America&#;s mining industry made significant strides during the 20th century and over the last 35 years in particular. In , the first year the Mine Safety and Health Administration (MSHA) operated under the new Federal Mine Safety and Health Act of , 242 miners died in mining accidents. MSHA continues to work to reduce injuries, illnesses and death through strong enforcement as well as active outreach, education and training, and technical support to the mining industry.&#;
This is why it is so important for all mining companies to take their workplace safety very seriously. The following 10 mining health and safety tips will help you to identify risks and take steps to address them as soon as possible. When implemented properly, this can help make the workplace safer for everyone involved.
When working in or near mines, it is critical to take care of your lungs. For generations there were people who would get &#;black lungs&#; after working in coal mines or other similar areas. This is because as you are breathing, you are bringing the dust and debris from the air into your body.
In order to keep your lungs healthy, everyone that is working in a mine should make sure they are using the proper (and provided) respiratory protection. In some cases this may simply be a face mask that will keep any dust out of your lungs. In others, you&#;ll need to wear more advanced protection. The mining company should evaluate the specific needs in each situation, and provide the proper protection to ensure mining health and safety.
When there is a hazard in an area, it is essential that people know about it. In order to ensure everyone is aware of any potential danger, the mining company should focus on improving hazard communication throughout the workplace.
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Visual hazard communication would include things like hazard signs, safety labels and much more. The idea is to always make it as easy as possible for people to be aware of any potential danger. Because the atmosphere and chemicals found in a mine shaft can be extremely dangerous, ensure you are staying in compliance with federal and local regulations.
Unlike many workplaces, the actual mine that people are working in will be constantly changing. As the miners work, the tunnels may change and even the requirements for structural integrity can be shifted. Keeping everyone aware of what changes are being made is absolutely essential.
This is especially important when major changes are made. Having an industrial label printer for updating signs, labels and verbal communication can help to maximize the mining health and safety related to the physical layout of the mines where people are working.
The use of explosives in mining is quite common. In fact, it can become so common that some people are tempted to take safety shortcuts because they think they have the experience and knowledge to perform these actions.
The fact is, however, that every mining company should have detailed safety policies in place when it comes to how explosives are handled, stored and used. There should never be any situation where people decide to go around the safety regulations because even a small mistake can lead to serious injuries, cave-ins or even fatalities.
When most people think of mining health and safety, they don&#;t really think about the risk of falling. This is because mining is commonly done on or even under the ground. The fact is, however, that falls can take place in any environment, so you need to plan for them.
Depending on the type of mine, there are likely a variety of different fall hazards that are present. This could include falling down a mining shaft, or even just slipping down a steep side of a hill or mountain. Whenever working in a location where falling is a possibility, make sure that the proper safety equipment is in place.
Most mining environments have many different pieces of electrical equipment that are used on a regular basis. The issue is, these devices may need to be moved to all different locations both inside and out of the mine itself.
This often means that there will be electrical cords stretched along many areas of the mine. This can cause electrocution hazards, as well as trip and fall risks. You should always have policies in place about how and when extension and other electrical cords should be used so people are aware of them and can take the proper electrical safety precautions.
Another major safety issue with mining is that of fires. Fires can come from a variety of sources at mining sites. For example, there may be natural gas that begins to seep into the mine. The fuel used to power specific machinery could ignite too. There are many other potential sources for fire, so you need to do all you can to minimize this risk.
Due to the nature of this type of workplace, you may not be able to have a traditional fire suppression system installed, which makes it even more important to take fire safety seriously. Watching out for fire hazards at all times is a key component of the overall mining health and safety program.
When working in or around mines there are two primary things to be concerned about. The first is a cave-in. This occurs when rocks or other debris become unstable and fall into the mine. When this occurs miners can get crushed by the debris, or trapped deep within the mine.
The other issue, which can be directly related, is a collapse. This occurs when the ground around the mine is not properly supported, and it collapses in. This can be especially dangerous when driving heavy equipment over areas where there are tunnels deep below.
Most mining sites will have many different vehicles that are used throughout the area. This could be cement trucks, cranes, tractors or any number of other things. These large vehicles often don&#;t have the best visibility, which can make it very dangerous for those working around them.
Taking the time to identify specific areas where these vehicles should be traveling, and making sure that people don&#;t walk in those areas, can help to keep people safe. A well planned out vehicle traffic area should be an essential component of any mining health and safety strategy.
Miners are well known for being big, strong individuals who work in some of the most rugged areas on earth. While this is necessary in many situations, it doesn&#;t mean that they don&#;t have to take precautions when lifting heavy objects.
Those working in mines should know how to properly lift things to avoid leg and back injuries, and how to determine when it is best to ask for help or get some type of lifting equipment to help. Related to this, miners need to know how to carry these items safely so they don&#;t trip and fall or run into other people in the area.
There are many other things you can do to help improve mining health and safety at the workplace. These ten tips are a great place to start, but you should always be looking for new ways to keep people safe while on the job site. With some hard work and participation by management and employees, mining accidents and injuries can continue to become less and less common every year.
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