Tuesday, January 5, 2010

Electrical injury pictures

I found these pictures of electrical injuries from one of the NIOSH websites. They were classified as in public domain and free for re-publishing. So I put them here for those who need them but have no time or the internet skills to go around digging inside those massive websites themselves.

How did these injuries occur? How did it happen? Visit this post, How you get electric shocks. I have made a few simple diagrams and easy to understand descriptions of the mechanics that can lead to these sort of electrical injuries.

Picture 1 - Entrance Wound

When electric shock happens, the current enter the body at one point and then leave the body at another point of contact. So there are two points of the body where there are electrical contact happens to complete the electrical circuit that will allow the shock current to flow through.

At each of the points of contact there is resistance. The human body itself also presents resistance but this normally very low compared to the resistances at the two points of contact. Because of these resistances, the flow of the shock current is converted into heat at these two locations which can cause severe burns.

What the image in Picture 1 shows is the burn injury on the body at the location where the shock current flows in. The dark spot in the center of the wound is the entrance point. This man was lucky. The shock current narrowly missed his spinal cord.

Picture 2 shows the injuries where the current leaves the body. Usually this is under the feet where they touch the ground. The magnitude of the current when it enters the body is the same as when it leaves the body. If both feet touch the ground at the moment of the shock, then it is the total of the exiting currents at both feet.

In the case of Picture 2, it didn’t say whether or not both feet were injured. The foot shown here suffered massive internal injuries that is not visible in the picture here. However it was so bad that the foot had to be amputated a few days later.

Picture 2 – Exit wound

Picture 3 – Arc or flash burn

Don’t be there if you are not supposed to be there. That is what we usually say to bystanders who are waiting to witness the Energization of a newly completed electrical system. It is always dangerous to be anywhere near the place because one of the most common types of accident there is electrical explosions.

The image in Picture 3 is one example of injuries from electrical explosions. The NIOSH site said that man was near an electrical panel when the accident happened. He did not touch the electrical panel.

However the electricity arched through the air. An example of electric arcs through the air is what we call lightning strikes. Surprised? So you can consider this an injury from an extremely small lightning strike.

The man happened to be in the path of the arcing electrical current, so the current punched into his body. You may wonder why the injury is located at the armpit. That is because there were perspiration on his body at the time and perspirations are very conductive. So his armpit presented a very conductive (and therefore “very attractive”) path for the electric arc current.

Picture 4 - Thermal Contact Burns

Electric current not only heats up electrical wires that burn houses. If and when it travels through a human body, the points of contact where it enters and leaves the body can generate enough heat (due to skin contact resistances) to cause fire and burns the victim’s clothes.

That was what happened to the victim in this picture. The current exited the victim’s body at the knee. It caused fire at the skin there which then catches his clothing and burned his upper leg.

Picture 5 – Internal injuries

This is an example of an electric tool accident. The worker was shocked by the electric tool he was holding. You can see from the picture the thermal burn injury at the entry point of the shock current.

However the wound was even more severe that what can be seen here. Massive internal tissue damages have occurred that subsequently caused severe swelling to the hand.

The swelling usually peaks 24 – 72 hours after the electric shock. In this case, the hospital needed to cut open the skin on the arm in order to relieve the pressure that resulted from the swelling which could have damaged nerves and blood vessels. This image in Picture 6 below was after the skin was cut open a few days later.

Picture 6 – A few days later

Picture 7 - Involuntary Muscle Contraction

This worker was working above overhead electrical cables. For some reasons he fell and grabbed the bare cables in order to save himself. The resulting electric shock mummified his first two fingers, which later had to be removed.

The acute angle of the wrist was caused by the burning of the tendons, which had contracted, drawing the hand with them.
That is all I have the time for today. I wish I could write more on these pictures but that will have to wait until some other time.

You can see a number of pictures I uploaded on electrical installations that could have caused these sorts of accidents. See this post, Temporary electrical installations. There are some lessons to be learned.

How much current does it take to cause the kind of injuries that you see in the above pictures? Read my other post, ELCB - Home Electric Shock Protection, to know them in details.

See you again.

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1 comment:

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