Class hour "Electrical safety of schoolchildren". Electrical safety lesson, elementary school Electrical safety lesson in elementary school
Electrical safety lesson in elementary school
Target: teach children safe behavior at home
Lesson goals.
Educational : 1. Expand the question: what is electric current
2. Formulate ways to solve the problem of saving electricity.
Developing: 1. To promote the development of students' creative abilities, the ability to work with scientific information, analyze, compare, and express their point of view.
Educational: 1. To form a positive attitude towards the problem of saving energy costs, a sense of responsibility in the operation of electrical appliances.
Tasks : To introduce children to electric current, using it in everyday life;
Teach careful handling of electricity to prevent injury;
Familiarize yourself with the rules of electrical safety;
Cultivate a caring attitude towards electricity;
Equipment: rubber balls, pieces of woolen cloth according to the number of children, posters with electrical safety signs.
Problem: Each of us is a consumer of electricity. Can we contribute to solving the problem? Can electricity consumption be reduced without sacrificing comfort levels? What safety precautions should be observed when using electrical appliances?
Teacher: Hello guys! Today we have an unusual lesson with you, and try to guess what we are going to talk about by listening to the poem.
My grandfather is a big fan of fables.
Tells me about this, about this,
And so that the meaning is always clear,
I myself read about everything.
Long ago it was time
Food was cooked by the fire
As soon as the sun rises,
Lights out - as darkness comes.
But times have changed
And the life of miracles is now full.
Can we turn on the computer
And call a distant city
Catch the waves moving
To treat people in a new way,
Do not heat the stove with firewood,
Surprise with a new fireplace
And warm and feed
What needs to be brightly lit.
After all, electricity is our friend.
But you have to be smart to suddenly.
Didn't turn into an enemy.
To the detriment did not take a step.
The moral of this story is -
The head should work.
And you have to do everything wisely
To not shed tears later.
Teacher:
So, what are we going to talk about today? Presentation #1 (slide #1)
(children's answers ) That's right, about the electric current. Do you know what it is and where does the electric current come from? (children's answers ) and now we will conduct an experiment.
Experience with a balloon and cloth. When you rub objects on a fabric, they receive energy, so they begin to attract lighter objects, rubbing the balls on a woolen cloth, we saw that small, small pieces of paper) objects are attracted to the ball.
This happens because the ball has received energy, in other words, it has become electrified.
There is safe electricity, as in the case of balls dangerous, that goes through the wires.
Please give examples of electrical appliances that a person uses.
(children's answers)
Teacher:
For the first time, the ability of rubbed bodies to attract light objects to themselves was discovered by ancient Greek weavers. They drew attention to the fact that individual parts of the machines made of amber, when rubbed against wool, attracted fluffs, dust particles, straws and other light objects. This property was attributed only to amber. from the name of which the word "electricity" originated, which comes from the Greek word "electron" - amber.
Poem
We are twin sisters
We are called parts.
We come to help you
When we get charged.
We run along thin and thick wires,
And at the right moment we get to you.
Which sisters are you talking about?
What are their names?
And they are called the smallest charged particles. (slide number 2)
Electricity is a stream of tiny charged particles - electrons. Each electron carries a small charge of energy. When these electrons accumulate a lot, an electrical voltage occurs.
How do you think electricity gets into our house?
(children's answers)
Right on the wires. (slide number 3)
Just as water runs through a hose, so electricity enters our home through wires. And it comes to the wires from power plants, and the very first power plants were wind turbines (slide number 4)
What do you think is the importance of electricity for us?
(children's answers)
And tell me, is there a profession in the world that could do without electric current?
Who invented electricity?
(slide number 5)
How did the first light bulb come about?
First, in the ancient era, an oil lamp appeared - a clay or metal teapot with oil, through the spout of which a wick was passed (slide No. 6)
The lamp smoked for many centuries, then in the middle of the 19th century kerosene was obtained from oil, a kerosene lamp appeared (slide number 7)
At the same time, they invented and mastered gas, and gas burners came to our house (slide No. 8)
Now guess the riddles (riddles about the light bulb)
She looks like a pear on the outside,
Whist idle during the day.
And lights up the house at night.
Spent under the ceiling
Amazing lace.
Screwed on the bubble
The fire has lit up!
A pear tree hangs from the ceiling.
And do not think to eat a pear,
Shine like the sun
Drop it - it will break!
Leading:
The lamp will burn for a day
One hundred kilos of coal will burn!
If she shines in vain,
Where is the savings in raw materials?
Who invented the light bulb?
(slide number 9 photo of Thomas Edison)
Guys, what do you think, is it possible to save electricity?
(children's answers)
But as?
(children's answers)
(slide number 10 "Rules of economical and thrifty guys)
(slide number 11)
(slide number 12)
(slide number 13)
(slide number 14)
(slide number 15)
(slide number 16)
(slide number 17)
(slide number 18)
(slide number 19)
TOK comes in
Hello, friends! I'll give you a riddle. and you guess who I am.
On the path I run
I can't do without a path
Where am I guys not-
The lights won't turn on in the house! (children's answers)
CURRENT: That's right, my name is electric current. What do you know about me (children's answers)
TOK: Right guys. Now I will make riddles, and you will guess them. For each correct answer, I will give you a token, the one who collects more tokens will be awarded the title of chief electrician.
*Beware of dust and debris,
I'll deal with you live!
And don't hide in the corners
I’ll still find you there! (slide number 20) (vacuum cleaner)
*This device is ideal
Heats up water instantly.
Just turn it on
Soon we can drink tea! (slide No. 21) (teapot)
* The whole universe lives in it
And the thing is extraordinary (slide number 22) (TV)
*Perform the magic circle
And my friend will hear me! (slide number 23) (phone)
* In the summer, our dad brought
Frost in the white box
And now the frost is gray
Houses in summer and winter.
Protects products
Meat, fish, fruits (slide number 24) (refrigerator)
* to distant villages-cities
Who goes to the cities?
Light Majesty-
This……. (-ELECTRICITY)
CURRENT:
You guys are great! Let's count the tokens earned (winner's ribbon award)
TOK: Now let's play a game. I will name the object, and if it is electric, you sit, and if it is not electric, get up (TV, plate, light bulb, tree, plane, chair. refrigerator. fork. iron, etc.)
TOK: Well done guys! I am sure that you have learned what an electric current is, I can safely leave you and go to other guys! Goodbye!
Host: Electricity helps us a lot. but he demands respect for himself: he wants to be treated as it should be. (presentation No. 2 "Electrical safety rules")
Leading:
Guys. Do not upset your parents with your rash actions! Warn your comrades against dangerous pranks near electrical objects! this will save his life!
This lesson - the conference was held as the final lesson on the topic: "Electrical phenomena" in grade 9 (according to the textbook Gromov S. V.); as an extracurricular activity during Physics Month; as an integrated physics lesson - life safety; part of the material was used in grade 11 when studying the topic: "Production, transmission and use of electricity" "Development of communications." With a two-hour program, it is convenient to consider these topics in the form of defending projects in different sections of the topic, paying attention not only to high matters, but to the reality of this phenomenon in everyday life, developing and maintaining interest in physics among students with a humanitarian mindset, on specific problems and features of life situations .
Preparatory work
At the beginning of the study of the topic in the classroom, the topic of the lesson is voiced - the conference "Electrical Safety"; groups are formed, leaders are appointed, topics of speeches are determined.
Students get acquainted with the forms of performing creative work: a poster on electrical safety, slogans, a story, a message on the topic. In the library and office there is a folder on this topic, a list of references, a presentation. All students should discuss their work with the teacher during the study of the topic.
Lesson objectives:
- To teach students to work independently with additional literature and Internet resources on this topic.
- To develop in students the ability to compose and make reports, messages on a given topic and design information stands.
- To develop in students the ability to explain the observed phenomena.
- Develop students' interest in physics.
- Familiarize yourself with the rules of conduct during a thunderstorm.
- In a non-standard form, introduce students to the rules of electrical safety.
Lesson Objectives:
- Educational - to teach students to highlight the main thing, draw conclusions, apply knowledge in practice, give knowledge about precautions when dealing with electric current, acquire knowledge about the effects of electric current on a person.
- Educational - education of the ability to listen and analyze the speeches of classmates; teaching students to take care of their health.
- Developing - the development of logical thinking and cognitive activity, the development of cooperation.
Plan of the lesson-conference:
I Introductory speech of the teacher.
II Reports of class students
- Lightning
- History of lightning research
- lightning rod
- Rules of conduct during a thunderstorm
- First aid for victims of lightning
- The effect of electric current on living organisms
- Electrical safety rules in everyday life
During the classes:
Introduction by the teacher.
Dear children, our today's lesson will be unusual and your classmates will lead it. For three weeks, we have been working on messages, reports, drawings on electrical safety in nature, everyday life and technology. They wrote stories, composed slogans, poems and ditties. Today, at a generalizing lesson, we will sum up the results, name the best ones, listen to their reports, and evaluate the results of the work of our groups.
Let me introduce you to today's speakers
(There is a presentation of the guys who prepared the messages)
Speaker #1
We all have seen lightning more than once - it is a beautiful and unsafe phenomenon of nature. It is estimated that about 100 lightning strikes occur in the Earth's atmosphere every second.
Lesson on electrical safety
in 1 B class
"The World of Electricity"
During the classes
I.Organizing time
Introduction by the teacher.
Guys, listen carefully to the riddle and guess it:
I run along the paths
I can't live without paths.
Where am I, guys, no,
The lights won't turn on in the house. ( electricity)
Do you think a person needs electricity? Yes.
What are the benefits of electricity to humans? Refrigerators, washing machines, kettles, computers, TVs, trolleybuses work from electricity.
Doctors, accountants, teachers, installers, trolleybus drivers will not be able to work without electricity. Because many of the appliances that people need are powered by electricity. Without electric current, a dentist will not be able to treat a tooth, a trolleybus driver will not be able to transport passengers, an installer will not be able to grind a part on a machine.
Conclusion:But every person must remember that electric current is needed, but it is not safe for life.
(Knock on the door. Forest animals enter the class: a hare and a fox)
Hare: Oh trouble, oh trouble
Help us friends!
Teacher: What's happened? What's happened?
Scene (squirrel ironing ribbons)
Fox: Anyuta the squirrel was stroking the ribbon
And I saw my friends through the window
And I completely forgot about the iron.
Hare: This is no joke!
That's what three minutes means
There is no tape, there is waste all around,
Almost started a fire.
Teacher: Guys, why did the squirrel almost start a fire?
(Answers of children). The squirrel threw the included iron on a ribbon.
Teacher: How to be? How can we be?
How to help the animals?
Teacher: I know one secret.
So that there are no more troubles
We invite all the animals
Hurry up to the lesson.
Pass the forest dwellers, sit down with the guys.
II . Presentation of the topic and objectives of the lesson.
The topic of our lesson is “In the world of electricity”.
Game: "What can be dangerous"
Now we are going to play a game. I will name objects, and if you hear something dangerous, raise your hand.
(electric stove, book, electric socket, soccer ball, washing machine, table, plate, vacuum cleaner, iron)
III. Learning new material A
Today we will talk about electric current, about the rules for using electrical appliances.
Teacher: Guys, what do you know about electric current? Where is he located?
(Children's answers) In the wires of the TV, refrigerator, computer, sockets.
Teacher: Electricity is also “pipes”, only through them energy enters our house. And just as water finds a hole in a pipe and an accident occurs, so does electricity become dangerous if the wires are faulty.
A person can accidentally touch the wire with his bare hand, and he will be shocked. The wires can connect and short circuit (lights go out) or even a fire can occur. Therefore, if you see a bare wire, a faulty switch or socket, you must immediately tell an adult about it!
The history of the emergence of electricity dates back to 550 BC.
For the first time, the phenomena now called electrical were seen in ancient China, India, and later in ancient Greece.
The surviving legends say that the ancient Greek philosopher Thales of Miletus already knew the property of amber, rubbed with fur or wool, attract scraps of paper, fluff and other light bodies.
And you, more than once, I think, have observed that a fountain pen or a comb rubbed on your hair attracts pieces of paper.
Let's do this experience with you. You have pens and small pieces of paper on your desk. They took pens, rubbed them on their hair and brought them to the papers. What are you observing? Yes, papers are attracted to a fountain pen. This phenomenon is called electrification.
But where to our house comes electricity? (children's answers)
Electricity comes through wires.
Teacher: Electricity enters the house through wires, and it comes to the wires from power plants.
The very first power plants were windmills. (slide 2-3)
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Then they began to build solar power plants. (slide 5)
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and nuclear power plants
III.Fizkultminutka.
Tilly - boom! Tilly - boom!
The cat's house is on fire!
The cat's house caught fire
There is a column of smoke!
A chicken runs with a bucket
Fill the cat's house
A horse with a lantern
And a dog with a broomstick.
Once! Once! Once! Once!
And the fire went out!
IV.Continued work on new material.
Teacher: Guys, so that such a disaster as a cat does not happen, what should every person know? (children's answers)
What safety rules with electrical appliances do you know?
(children's answers)
VWorking out the rules for safe handling of electrical appliances
Now we will solve riddles, and explain in what cases things are dangerous.
1. Button on the head,
A sieve in the nose
One hand
Yes, it's on the back. (Kettle.)
- When Is the kettle dangerous?
(When the kettle is turned on,not filling water into it, stick a plug into a faulty outlet, touch a working electric kettle with wet hands; they forget to turn off an ordinary kettle after it has boiledwater, etc.)
2. There is a steamer -
Back, then forward
And behind him such a smooth surface -
Not a wrinkle to be seen Iron.)
In what cases do people risk using this necessary device?
(The electric iron is left on unattended, handled with wet hands, etc.)
3. Masha messed up her jacket.
But I didn't wash it by hand.
There is a special machine -
Washes from the heart to us. (Washing machine.)
Guys, when does this irreplaceable thing for any housewife become dangerous for children? (When it is turned on without parental permission, holding the electric plug with wet hands, opening the lid during operation, etc.)
Well done! And remember: you can not stick your hand into the washing machine during operation, trying to pull something out of it. The hand can tighten and cripple. For most modern models, the hatch is blocked during operation, but if not, be vigilant yourself.
4. That's the house, one window.
Every day in the window - a movie. (TV.)
(Children and teacher discuss the rules for using the TV.)
-Generalization: So, all these things belong to the group of dangerous things - electrical appliances. They pose a threat for two reasons:
First, these items can cause a fire.
Secondly, an electric current passes through them, which can hit.
Teacher: Let's sum up our statements. What are the basic safety rules with electrical appliances?
VI.Working with proverbs about dangerous situations.
No wonder people have put together such proverbs:
"Fear is half salvation"
"Beware of troubles while they are not"
How do you understand the meaning of these proverbs?
(Student answers: you need to be careful, know and follow the rules of safe behavior so as not to get into difficult situations)
VII. Viewing the presentation "Electrical safety rules
at home and on the street »
Presentation. Rules for handling electrical appliances.
1. First rule (slide)
Never enter transformer substations.
THIS IS VERY DANGEROUS FOR LIFE!
2. Second rule (slide)
Do not use electrical appliances in bathrooms, baths, pools and saunas.
3. Third rule
Do not insert the plug into the socket with wet hands.
4. Fourth rule (slide)
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Never approach or touch a bare wire. May be electrocuted.
5. Fifth rule (slide)
When pulling out the plug from the socket, never pull the electric wire with your hands, a short circuit may occur.
6. Sixth Rule
Never wipe switched on appliances with a damp cloth.
7. Seventh Rule
Do not extinguish fired electrical appliances with water.
Household appliances at school, at work. Electric current is a true friend and helper of man. And we must treat electricity carefully and carefully. And we have already talked about the dangers of handling electrical appliances.
Student: Everyone knows that iron -
A kind but serious friend.
The one who is familiar with the iron,
Doesn't play with iron.
Student: Who studies science
So appliances does not include:
Overheated outlet
It lights up frequently.
Teacher: Very often, we plug several electrical appliances into the outlet at once. For example: TV, iron, washing machine, refrigerator, computer. And this cannot be done. Because an overheated outlet can also cause a fire or short circuit.
VI.Summing up the lesson.
Teacher: Well done boys! You did a good job in class today. I think our forest guests learned what electric current is and how dangerous it is for life, where electricity comes from in our house, got acquainted with the rules for the safe handling of electrical appliances.
Hare: Oh trouble, oh trouble
Help us friends!
Fox: Anyuta the squirrel was stroking the ribbon
And I saw my friends through the window
Distracted for only three minutes
And I completely forgot about the iron.
Hare: This is no joke!
That's what three minutes means
There is no tape, there is waste all around,
Almost started a fire.
There is a booth in Sasha's yard
There is a drawing on the door.
If you want to be healthy
Don't go into this booth!
Electricity is useful
Electricity is great
But if you climb a pole -
Electricity is dangerous!
If you see - the wire is broken -
Step aside:
Because the electric charge
Dangerous for a child!
Know that the wire is bare
Not a toy at all
Nearly died once
Our neighbor Andryushka!
You can brush your teeth in the bathroom
You can wash your head
Only there we are unlikely to be
Dry hair with a hair dryer.
Student: We would shiver from the cold
It would be dark without him.
Didn't know a lot
Well, of course it would be bad.
Student: TV would not know
Neither eat nor drink
They wouldn't play Dandy either,
In general, it would be bad to live.
Student: Everyone knows that iron -
A kind but serious friend.
The one who is familiar with the iron,
Doesn't play with iron.
Student: Who studies science
So appliances does not include:
Overheated outlet
It lights up frequently.
Every year in Russia, due to ignorance of safety rules, personal negligence and attempts to steal wires and non-ferrous metal, about 70 people die and 130 are injured from exposure to electric current. Think about these numbers - these people were victims of their own carelessness, violating the rules of elementary safety. Summer is coming, and on the eve of the holidays, schoolchildren need to remember the rules that everyone should know. We continue a series of lessons on electrical safety.
How dangerous is electricity?
Electrical appliances you use at home and at school, electrical networks and substations that you pass in the yard and on the street are safe during normal operation. Power engineers took care to exclude accidental contact with live parts. All electrical installations have a fence, warning signs and safety posters and are locked. However, with various insulation damages, wire breaks, climbing poles, penetration into substations and electrical panels, a real threat to life arises.
The magnitude of the current is greater, the higher the voltage under which the person turned out to be.
The safe voltage is 12 volts. The most widespread in industry and agriculture and everyday life are electrical networks with a voltage of 220 and 380 volts: the first - for lighting and household appliances, the second - for three-phase electric motors of machines and mechanisms. This voltage is economically beneficial, but very dangerous for humans.
Rules for handling electricity in everyday life
1. Do not use electrical appliances without adult permission.
2. You must not replace light bulbs and fuses, repair electrical wiring and household appliances, open the back covers of televisions and radios, install bells, switches and sockets yourself. Let an adult or a qualified electrician do it.
3. Do not use switches, sockets, plugs, bell buttons with broken covers, as well as household appliances with damaged, charred or twisted cords. And do not pass by such facts, especially do not break the covers of switches, bells, sockets out of mischief, damaging the electrical wiring. By doing so, you are committing an offense equal to a crime, since this can lead to the death of people.
4. Do not use faulty electrical appliances. If the TV, refrigerator or vacuum cleaner smells of burnt rubber, if sparks are visible, you must immediately unplug the device from the mains and tell adults about the faulty device.
5. When turning off the appliance, do not pull on the cord. Grab the plug and gently pull it out of the socket.
6. Remember: electricity does not tolerate proximity to water (in order not to get an electric shock, do not touch the included electrical appliances with wet hands or wipe electrical appliances with a damp cloth).
Rules of conduct near power facilities
Power facilities are overhead and cable power lines, substations, transformer substations, distribution points.
Overhead power lines with a voltage of 35, 110 kilovolts and above are responsible for the power supply of cities and towns. Overhead and cable power lines with a voltage of 6 and 10 kilovolts are responsible for power supply within cities and towns, as well as rural settlements. Power lines with a voltage of 380 volts provide electricity to apartment buildings, and 220 volts - individual apartments.
Substations are designed to reduce the voltage in the AC network and to distribute electricity. Transformer substations are located in every settlement and, due to their ubiquity, pose a particular danger to the population!
1. In no case should you touch or even approach broken wires hanging or lying on the ground.
2. It is deadly dangerous to climb high-voltage power lines, play under them, make fires, break insulators on supports, throw wires and other objects on wires, and fly kites under wires.
3. In no case should you open stair switchboards located in the entrances of houses, climb onto the roofs of houses and buildings where electrical wires pass nearby, go into transformer boxes, switchboards and other electrical rooms, touch electrical equipment, wires with your hands.
4. If you see a broken wire, open or damaged doors of transformer boxes or electrical panels, do not touch anything and inform an adult immediately.
5. In the summer, when going camping or fishing, it is dangerous to stop to rest near overhead power lines or substations and fish under the wires of the power line.
What is step voltage?
An electric shock can also be received a few meters from a broken, lying on the ground or sagging wire, due to step voltage. Therefore, let's agree to consider any wire or electrical appliance as being energized! Even if two dozen people touched it before you. And suddenly, at the very moment when you picked up the wire, someone a few kilometers away from you turned on the switch or pressed the switch!
If, nevertheless, a person got into the zone of "" step voltage, it is impossible to tear off the soles from the surface of the earth. You should move away from the wire with a “goose step” - the heel of the walking leg, without leaving the ground, is attached to the toe of the other leg. Remember, when you see a broken wire lying on the ground, in no case approach it at a distance closer than 8 meters.
How does electric current affect the human body?
The danger of electric current lies in the fact that without special devices it is impossible to feel whether a given part of the electrical installation is energized or not: electricity has no taste, smell and operates silently. Therefore, people often do not realize the danger and do not take the necessary protective measures.
A person, touching the current-carrying parts of electrical installations and uninsulated wires under voltage, is included in the electrical circuit. Under the influence of voltage, an electric current flows through his body, which disrupts the normal functioning of the body. The most unfavorable outcome of the lesion will be in cases where the touch occurred with wet hands in a damp or hot room. In addition, it matters which way the current passes in the human body, whether it touches the heart, chest, brain and spinal cord.
The immediate causes of death of a person struck by an electric current are the cessation of the work of the heart, respiratory arrest due to paralysis of the muscles of the chest, and electric shock.
Why are electric shocks among the most severe types of injuries?
Electric shocks are one of the most severe types of injuries. The human body is 80% water. And she conducts electricity well. Damage from electric current is determined by the strength of the current and the duration of its impact. The lower the resistance of the human body, the higher the current. Resistance decreases under the influence of the following factors:
High voltage;
skin moisture;
Long exposure time;
Lowering the partial pressure of oxygen in the air: in the mountains, in poorly ventilated rooms, a person becomes much more vulnerable;
Increasing the content of carbon dioxide in the air;
High air temperature;
Carelessness, mental unpreparedness for a possible electric shock.
The central nervous system suffers most from the action of electric current. Due to its damage, breathing and cardiac activity are disturbed.
Electrical burns are much more difficult to heal than conventional thermal burns. Some consequences of an electrical injury may appear after a few hours, days, months. The victim must live in a "sparing" mode for a long time and be under the supervision of specialists.
CHECK YOURSELF!
Task 1
You went fishing on a pond. There is a power line nearby. The distance from where you are is 7 - 10 meters. How long should the fishing rod be so that fishing does not end with an electric shock, given that the fishing rod is made of carbon fiber - a conductor of electric current, and there is high humidity near the reservoir?
Answer: The length of the fishing rod with fishing line should be such that it does not accidentally touch the wires. Otherwise, fatal injury cannot be avoided.
Task 2
You were playing with a friend at home and he suddenly got electrocuted. He has convulsions, but he cannot unhook from the wire. What are your actions?
Answer: If a person has fallen under the influence of an electric current, it is necessary, first of all, to quickly (every second is precious!) Release the victim from the action of an electric current, since a person who is under voltage cannot, due to convulsions or loss of consciousness, independently break away from the wire , body of the device. If this happens indoors, turn off the wire or device by turning off the switch, unplugging the plug from the socket, turning off the circuit breakers at the electricity meter, unscrewing the fuses at the electricity meter. But in real conditions, this is quite difficult to do. Adults will do it better, or energy specialists. Call them for help!
Task 3
A storm has come. Thunder rumbles and lightning flashes are visible. How do you know how close a thunderstorm is to where you are?
Answer: The speed of light is faster than the speed of sound. Therefore, we often see a flash of lightning, and only a few seconds later we hear thunder. It is known that sound propagates in air at a speed of 330 m/s. Therefore, it is enough to multiply this figure by the seconds by which the sound "lags behind" the flash of light - and you will get the distance to the epicenter of the thunderstorm.
IMPORTANT!
How is theft from power facilities punished?
Theft of wire from a line or equipment from a substation is a criminal offense, and adults, in order to avoid punishment, offer children to take part in the theft of non-ferrous metals from energy facilities. As a result, children receive serious burns and injuries.
Remember that it is deadly dangerous to agree to illegal actions to steal equipment from energy facilities that adults or even friends can push you to. In addition, theft of power equipment entails punishment under Part 2 of Art. 158 of the Criminal Code of the Russian Federation - "Theft of another's property" in the form of imprisonment for up to 5 years and compensation for material damage caused.
On the eve of the summer holidays, we hope that our electrical safety lesson will be useful in the work of counselors and teachers of children's health and school camps. Send us stories and photo reports about the most interesting lessons to the address: 454091, Chelyabinsk, st. Red, 4, office 606.
We're talking to you guys! Remember: electricity is dangerous! Do not forget about simple safety rules that can save the life of you, your friends and loved ones!
Preview:
Technological map of the lesson
Discipline: Labor protection
Group: SP-08
Lesson type: a lesson in learning new material Teacher: Dyachenko E.G.
Type of lesson: Combined lesson
Topic: "Electrical safety during welding"
Stages | Lesson Component | Teacher activity | Student activity | Realization of the goal and objectives |
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Organizing time 2 minutes | Greetings, the psychological attitude of students to learning activities. | Checking students' readiness for the lesson. | Perception of information | Development of mindfulness, discipline, creating an atmosphere of emotional uplift |
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Update of reference knowledge 4 min Goal setting and learning objectives | Survey of students using the method of "brainstorming" Reporting the topic, goals and objectives of the lesson | Organizational and controlling; teacher explains AOZU: Task for students: List in the notebook "Sources of electrical hazards in the workplace associated with your future profession" Attitude to gain new knowledge; Statement of the problem by showing a fragment of the cartoon "electrical safety" | Repetition of the previously passed in the production practice Perception of information. | To promote the development of thinking, the ability to analyze, compare and draw conclusions To promote I realize the importance of the acquired knowledge in further professional activity and in life. |
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Learning new material Control over the primary assimilation of the studied material Homework message. Reflection, summing up | introductory conversation; Lecture with elements of problem presentation Lecture with elements of advanced learning Independent work with the textbook Student presentation "Electric Strike" Frontal conversation. Workshop. Practicing resuscitation actions with a demonstration on the simulator. Performing test work in the form of a test. Mutual control of students Recording homework. Lesson conclusions. Satisfaction with the lesson | conversation Explaining new material, creating problem situations presentation of student speakers Issuing a task Write out - What are electrical injuries. Coordination of work and explanation of difficult moments. Slideshow conversation Demonstration of ventilator and NMS actions Testing instructions. Grading Criteria Explained Brief instruction on homework. Summarizing the results of the lesson and grading. | Perception of information Compose lesson outline Students make presentations on "electrical safety when performing welding work" Performing independent work, students answer questions Student presentation. Perception of information. Outlining of the most important provisions. They answer questions. Outline the main points. Closely monitor the actions of the teacher and remember the order of performing resuscitation. Perform verification work. Check out a friend's work. Write down homework. Listening to homework instructions Answer questions | Development of cognitive interest, activity of thinking. Ability to draw analogies and match. Development of activity of thinking, attentiveness, sociability. Ability to analyze, draw analogies, highlight the main thing. The development of mindfulness. To promote the formation and assimilation of new knowledge among students. The development of attentiveness, a serious attitude to ongoing actions. Awareness of the need for acquired knowledge to save lives in cases of emergency. Application of knowledge to solve the test. The ability to analyze. The development of responsibility. The development of mindfulness, responsibility. The ability to do personal self-assessment. |
Preview:
Topic: Electrical safety in production
Lesson Objectives:
Educational : Introduce students to the main causes of electric shock. The action of electric current on the human body. First aid for electric shock
Developing: Instilling interest in the subject
Nurturing: Rules of conduct for welding work
Type of lesson : Learning new material
Lesson type : Combined, designed for 80 minutes
Equipment: computer, overhead projector
Software:powerpoint program
Lesson structure, methods and time consumption Stages of the lesson Content of the stage Lesson time
Organization Preparing students for the lesson, checking those present at the lesson 0 - 3
Motivation Explanation of the topic, purpose, lesson plan 3 - 6
Actualization of basic knowledge and methods of action Testing students' knowledge on the previous topic (Independent work) 6-20
Formation of new concepts and methods of action Plan for presenting new material 20-50
Consolidation of the acquired knowledge Taking notes of new knowledge with a parallel presentation, students' answers to the teacher's questions, completing assignments, compiling algorithms, etc. 50-75
Summing up the lessons, homework Reporting by the teacher of grades, students recording homework 75-80
Attached to the abstract:
a brief summary of new knowledge;
card with assignments for independent work;
Electronic presentation
Plan for presenting new material:
The main causes of electric shock
The effect of electric current on the human body and types of electrical injuries
First aid for electric shock.
Presentation of new material:
1. The main causes of electric shock
The main causes of electric shock are: exposure to electric current passing in the welding circuit; touching open live parts and wires (accidental, not caused by production necessity, or due to erroneous voltage supply during repairs and inspections); touching current-carrying parts, the insulation of which is damaged; touching current-carrying parts through objects with low insulation resistance; touching the metal parts of the equipment that accidentally become energized (as a result of the absence or damage of protective devices); contact with building parts of structures that accidentally become energized, etc.
Danger, electric shock also creates a variety of equipment: welding current sources, electric drive, (including ballasts), electrical equipment for hoisting and transport devices, electrified vehicles, high-frequency and lighting installations, electric hand-held machines, etc.
The danger of electric shock is associated with deficiencies in the design and installation of equipment, violations of the rules for its operation, unsatisfactory organization of workplaces, insufficient instruction, etc.
2. The effect of electric current on the human body and types of electrical injuries
The impact of electric current on the human body can cause various electrical injuries (electric burn, skin plating, electric sign and electric shock).
An electric burn can be caused by an electric arc (arc burn) or contact with a live part (current burn) due to the conversion of electric current energy into heat.
Metallization of the skin can occur as a result of mechanical and chemical effects of current, when vaporous or molten metal particles penetrate deep into the skin and the affected area acquires a hard surface.
An electrical sign is a consequence of thermal exposure when a relatively large current flows through a small surface with relatively high resistance at a temperature of 50 - 115 0 C and good contact.
As a result of such a lesion, parched or charred areas of the skin or its swelling appear, as well as an imprint from the touch of the current-carrying part.
An electric shock leads to the excitation of living tissues of the body and is accompanied by involuntary convulsive muscle contractions when an electric current passes through the human body.
Electrophthalmia leads to inflammation of the outer membranes of the eyes, resulting from exposure to a powerful stream of ultraviolet rays from an electric arc. Under the action of an electric current, tissues can be damaged, or it can also act reflexively, that is, damage the nervous system. The reflex effect is expressed very sharply, since when passing through the body, an electric current affects a huge number of sensitive nerves. A very significant effect is exerted by the action of an electric current on the skeletal muscles, causing convulsions, and especially on the heart, causing its fibrillation.
Fibrillation is a condition of the heart when it ceases to contract as a whole in a certain sequence, and separate uncoordinated “twitches” of the fibers of the heart muscle occur; at the same time, the pumping function of the heart ceases and death may occur.
The cause of death, in addition to fibrillation, may be respiratory arrest or burns.
The severity of electric shock to a person depends on a number of factors: body resistance; magnitude, duration of action, type and frequency of current; current paths in the body; state of the body and environmental conditions.
body resistance. The human body, being included in an electrical circuit, is a combination of active and capacitive resistances, the value of which depends on many conditions and consists of the resistance of internal organs and the resistance of the outer integument of the body, mainly the outer layer of the skin.
The resistance of the internal organs is 800 - 1000 ohms and depends on the applied voltage and also on the body temperature.
The magnitude of the current. The current at which the initial sensation of it is fixed is the initial irritating current, and as the initial current increases, the body's reactions intensify (Table 1)
Tab. 1 Sensations arising from the action of an electric current of various sizes
Dangerous for the body is the current at which it is impossible to break away from the conductors on its own, so the breakdown of the skin occurs very quickly, and the magnitude of the current passing through the body increases rapidly.
Alternating current greater than 25-30 mA is a serious danger; a current of more than 50 mA leads to electrical injury and can cause death; a current of 100 mA causes a lethal outcome;
The duration of the current. The duration of current flow through the human body affects the degree of physiological effects and, with a fairly low probability of damaging the current value, has the following values:
With prolonged exposure (up to 30 s), which with a margin fit all cases of current flow through the human body when touching parts of the equipment that are energized, the current value should not exceed the threshold value of the releasing current.
Type of current. The effect on the human body of alternating and direct current is different.
For voltages less than 500 V, industrial frequency alternating current is more dangerous than direct current equal to it in voltage. At voltages of about 450 - 500 V, the danger of alternating and direct current is the same. At voltages over 500 V, direct current is more dangerous.
Current frequency. The outcome of electric shock also depends on its frequency (the most dangerous frequency is 50-60 Hz).
In the frequency range 50-:-500 Hz, the danger of alternating current not only does not decrease, but also increases somewhat. With a further increase in the frequency of the current, the danger decreases; at frequencies of hundreds of thousands of hertz, alternating current is not dangerous in relation to electric shock (but the risk of burns remains).
Path of electric current in the body. Essential for the outcome of the impact of the current is its path (“current loop” of the lesion). The longer this path and the closer it is to the vital organs, the more severe the outcome of the lesion.
The most probable current flow paths are: arm - arm, arm - leg, leg - leg.
Body condition. The outcome of the impact of the current is influenced by the individual characteristics of the organism, its physical and mental state. With diseases of the skin, heart, lungs, nervous, etc., the danger of electric shock increases.
A tired person is more susceptible to electric shock, and due to fatigue, the severity of such an electric shock can be aggravated. Experimental data have shown that with intense attention to the expected event, the degree of damage is weakened. The diseased state of the body, alcohol intoxication reduces the resistance of the body and aggravates the effect of the current.
Any heart disease is a contraindication for access to work associated with the danger of electric shock.
External environment. The risk of electric shock may be exacerbated by environmental conditions.
A decrease in atmospheric pressure increases the risk of exposure to electric current and vice versa.
Protective grounding. The vast majority of electrical injuries occurring at construction and installation sites are due to an irresponsible attitude to strict observance of the rules for the operation of electrical networks, devices, tools and lighting, and sometimes outright negligence due to ignorance of the essence of the danger of electric current exposure to a person. In some cases, protective grounding of the welding machine or other electrical equipment is performed using a single ground electrode (Fig. 1). When one of the welding machines or other electrical equipment is shorted to the body, a potential appears on the ground electrode and in all metal parts attached to it on the body of the device and on the surface of the earth around the earth electrode.
Rice. 1. Graph of change in contact voltage with a single ground electrode
1 - the least dangerous case of a person touching grounded equipment; 2- potential curve; 3, - curve characterizing the change in voltage Upr - when changing the distance from the ground electrode; I3 - current passing through the earth electrode; Rz - ground electrode resistance; Upr - touch voltage; h - grounding potential; os - the potential of the base where the person stands
The most dangerous for a worker is touching electrical equipment; which is located at a distance of 20 m from the ground electrode, and the least dangerous - touching the electrical equipment, which is located directly at the ground electrode.
With a single or group ground electrode, a step voltage may occur (Fig. 2) due to the potential difference. The most dangerous is the approach of a single earthing switch operating to the installation site with a large movement step.
When a worker touches two phases simultaneously, the greatest voltage arises in the network and a large current passes through the worker (Fig. 3). When a worker touches one phase, less voltage arises and less current passes through the worker.
When a worker touches a three-phase three-wire network (Fig. 4) with an isolated neutral during the emergency period, i.e. when one of the phases is shorted to ground, the voltage will be much higher than the phase and somewhat less than the line voltage of the network and therefore is the most dangerous.
When a working person touches a phase in a three-phase four-wire network with a grounded neutral during its normal operation, it is more dangerous than touching a phase of a normally operating network with an isolated neutral, but less dangerous than touching an undamaged phase of a network with an isolated neutral during an emergency period (Fig. 5).
Rice. 5. Scheme of a person touching a phase wire of a three-phase four-wire network with a grounded neutral in normal a and emergency b modes
UФ - phase voltage; Ih - current passing through the human body; ro - neutral grounding resistance; r - wire insulation resistance; c is the capacitance of the wire; Rh is the resistance of the human body; rzm - resistance when the phase is shorted to earth; Iz - current passing when the phase is shorted to earth; Io - current passing through the neutral earthing switch
3. First aid for electric shock
It must be remembered that the victim, who is in the current circuit, is himself a conductor of electric current.
Release the victim from the action of the current
Open the circuit with a switch, breaker, plug, remove plugs or turn off the package or circuit breakers on the panel
If there is no shield, socket or other means of disconnecting the electric current, then you need to cut or cut the wires (each wire separately), while the handles of scissors or other cutting tools must be made of insulating material.
If it is not possible to quickly disconnect the victim from the current with the help of tools, you can wear rubber gloves, or wrap your hands in a dry cloth, and put on rubber boots on your feet. Additionally, put a dry insulating object (rug, board) under your feet. You need to pull the victim with one hand, by the edge of the clothes. You can throw the wire away from the victim with a dry stick or board.
First aid depends on the condition of the victim
Immediately lay the victim on his back, horizontally, create an influx of fresh air, give ammonia a sniff, rub and warm the body;
Unbutton clothing that restricts breathing; Check by the movement of the chest whether he is breathing; check for a pulse (on the radial artery at the wrist or on the carotid artery in the neck). A wide fixed pupil indicates a lack of blood circulation to the brain.
Artificial respiration by inhaling air through the mouth or nose
Provide the victim with free passage of air into the lungs through the respiratory tract. The head of the victim is thrown back, for which they put one hand under the neck, and the other is pressed on the forehead. This ensures the departure of the root of the tongue from the back wall of the larynx and the restoration of airway patency. The victim's mouth usually opens. If there is mucus in the mouth, it is wiped with a handkerchief or the edge of a shirt stretched over the index finger. Then they check again if there are any foreign objects in the pipe that must be removed. Then proceed to blowing air into the mouth or nose. When air is blown into the mouth, the assisting person takes a breath, tightly (possibly through gauze or a handkerchief) presses his mouth to the victim’s mouth and blows air into the victim’s mouth with force, simultaneously with his face (cheek) or fingers located on the forehead, pinching the victim nose to ensure that all the inhaled air enters his lungs.
If it is impossible to completely cover the victim's mouth, inhale air into the nose, while tightly closing the victim's mouth.
External (indirect) cardiac massage
Supports blood circulation both during cardiac arrest and in violation of the rhythm of its contractions. The caregiver kneels on the side of the victim and takes such a position as to be able to bend over the victim. Determine the position of the lower third of the sternum. Put on it the base of the palm (cushion) of the unbent brush. The palm of the second hand is placed on top of the first. And they begin to rhythmically press on the lower edge of the sternum. It is necessary to press on the sternum with sharp jerks: in this case, the sternum moves down (towards the back) towards the vertebra by 3–4 cm. The heart is compressed, and blood is squeezed out of its cavities into the blood vessels. Pressing must be repeated approximately 1 time per second. It is desirable that two people trained in the rules of first aid take part in the revival, alternately, every 5-10 minutes replacing each other during artificial respiration and heart massage.
Independent work
Define terms:
Occupational safety is...
safety engineering is...
Industrial sanitation is...
Work safety is...
hazardous production factor is...
harmful factor of production is...
an accident at work is...
the safety of production equipment is ...
process safety is...
Electrical safety during welding
Electrical safety - a system of organizational and technical measures and means to protect people from the harmful and dangerous effects of electric current, electric arc, electromagnetic field and static electricity
Electrical injury - injury caused by exposure to electric current or an electric arc
Electrical injury is a phenomenon characterized by a combination of electrical injuries
Electrical short to the case - an accidental electrical connection of the current-carrying part with its metal knowing parts of the electrical installation
Electrical short to ground - an accidental electrical connection of a current-carrying part directly to the ground or non-current-carrying conductive structures or objects that are not insulated from the ground
The main causes of electric shock are the impact of electric current passing in the welding circuit, contact with open current-carrying parts and wires (accidental, not caused by production necessity, or due to erroneous voltage supply during repairs and inspections); touching current-carrying parts, the insulation of which is damaged, touching current-carrying parts through objects with low insulation resistance, touching metal parts of equipment that accidentally become energized (as a result of the absence or damage of protective devices), contact with building parts of structures that accidentally become energized, and etc
The danger of electric shock is created by welding current sources, electric drive (including ballasts), electrical equipment of lifting and transport devices, electrified vehicles, high-frequency and lighting installations, electric manual machines, etc.
The action of electric current on the human body can cause various electrical injuries (electric burns, skin plating, electric sign) and electric shock.
Metallization of the skin occurs as a result of mechanical and chemical effects of current, when vaporous or molten metal particles penetrate deep into the skin and the affected area acquires a hard surface.
Electric sign - a consequence of thermal exposure when a relatively large current flows through a small surface with relatively high resistance at a temperature of 50-115 ° C and good contact, resulting in parched or charred skin areas or swelling of it, as well as an imprint from the touch of the current-carrying part
An electric shock leads to the excitation of living tissues of the body and is accompanied by involuntary convulsive muscle contractions when an electric current passes through the human body.
Electrophthalmia leads to inflammation of the outer membranes of the eyes, resulting from exposure to a powerful stream of ultraviolet rays from an electric arc.
Electric current affects the nervous system. Such an effect is expressed very sharply, since when passing through the body, an electric current affects a huge number of sensory nerves. A significant effect is exerted by the action of an electric current on the skeletal muscles, causing a spasm, and especially on the heart, causing its fibrillation (separate uncoordinated "twitches" of the fibers of the heart muscle) . In this case, the pumping function of the heart stops and death can occur.
The cause of death, in addition to fibrillation, may be respiratory arrest or burns.
The severity of electric shock to a person depends on the following factors, body resistance, magnitude, duration of action, type and frequency of current; current paths in the body, the state of the body and environmental conditions.
Technical means of protection. During the operation of electric welding installations, the use of special protective equipment is required, which are divided into insulating, enclosing and auxiliary
Isolating means of protection are divided into basic and additional.
The main insulating means are able to withstand the operating voltage of the electrical installation for a long time, therefore they are allowed to touch live parts under voltage. Such means include: dielectric rubber gloves, tools with insulated handles and current detectors.
Additional insulating means have insufficient electrical strength and therefore cannot independently protect a person from voltage. These items include: rubber shoes, mats and insulating pads.
Rubber shoes and rugs as additional means of protection are used in operations performed with the help of basic protective equipment.
Enclosing means of protection are intended: for temporary fencing of current-carrying parts (temporary portable fencing-shields, fencing-cages, insulating pads, insulating caps); to prevent erroneous operations (warning posters); for temporary grounding of disconnected current-carrying parts in order to eliminate the danger of electric shock to workers in the event of an accidental voltage appearance (temporary protective grounding).
Auxiliary protective equipment is intended for individual protection of the worker from light, thermal and mechanical influences (goggles, special gloves, etc.).
Protective grounding, grounding and shutdown of electric welding installations and posts. Protective earthing - an intentional electrical connection to earth or its equivalent of metal non-current-carrying parts that may be energized
The purpose of protective grounding is to eliminate the risk of electric shock when voltage appears on the structural parts of electrical equipment, i.e., when shorted to the case.
The scope of protective grounding is three-phase three-wire networks with voltage up to 1000 V with isolated neutral.
There are artificial grounding conductors, intended exclusively for grounding purposes, and natural ones - metal objects located in the ground.
As artificial ground electrodes, vertical and horizontal electrodes are usually used. As vertical electrodes, steel pipes with a diameter of 3-5 cm and angle steel measuring 40X40 to 60x60 mm, 2.5-3m long, steel bars with a diameter of 10-12 mm are used. To connect vertical electrodes and as an independent horizontal electrode, use strip steel with a cross section of not less than 4X12 mm or steel of a round cross section with a diameter of at least 6 mm.
Metal pipes laid in the ground are used as natural grounding conductors, with the exception of pipelines of flammable liquids, flammable or explosive gases, as well as pipelines covered with insulation to protect against corrosion.
Nulling - an intentional electrical connection with a neutral protective conductor of metal and conductive parts that may be energized (25 2).
Purpose of grounding - similar to the purpose of protective grounding
Zeroing scope - three-phase four-wire networks with voltage up to 1000 V with dead-earthed neutral.
The principle of zeroing operation is the transformation of a breakdown to the case into a single-phase short circuit (i.e., a short circuit between the phase and neutral wires) in order to create a large current that can ensure the protection is triggered and thereby automatically disconnect the damaged installation from the mains. Such protection are; fuses and circuit breakers installed in front of energy consumers for protection against short circuit currents -2 s when defending with machine guns
Protective shutdown - high-speed protection that provides automatic shutdown of the electrical installation in the event of a danger of electric shock in it
The main parts of a residual current device are a residual current device and a circuit breaker
Residual current device - a set of individual elements that react to a change in any parameter of the electrical network and give a signal to turn off the circuit breaker. Such an element is a sensor - a device that perceives a change in a parameter and converts it into an appropriate signal
Circuit breaker - a device used to turn off and disconnect circuits under load
Providing first aid to the victim from the effects of electric current during welding. First aid in case of accidents from electric shock consists of releasing the victim from the action of the current and providing him with medical care
The release of the victim from the action of the current can be done as follows: turn off the corresponding part of the electrical installation, cut the wires with an ax with a wooden handle or pull the victim away from the current-carrying part, holding his clothes, if it is dry, discard the wire from him with a wooden stick, etc.
If the victim is conscious, but before that he was in a faint or was under current for a long time, he must be provided with complete rest until the arrival of a doctor or urgently taken to a medical facility
In the absence of consciousness, but preserved breathing, it is necessary to lay the victim evenly and comfortably on a soft bedding, unfasten the belt and clothes, provide fresh air, give ammonia to smell, sprinkle with water, rub and warm the body
In the absence of signs of life, artificial respiration and heart massage should be performed.
Artificial respiration should be started immediately after the victim is released from the current and his condition is identified.
External heart massage aims to artificially maintain blood circulation in the body and restore the independent activity of the heart.
The recovery of heart activity in the victim is judged by the appearance of his own regular pulse, not supported by massage.
Electrical safety requirements for welding equipment
An electric welding installation (a welding transformer, a unit, a converter, a rectifier) must have a passport, an operating manual and an inventory number, under which it is recorded in the log book and periodic inspections.
Transformers, rectifiers and DC generators specially designed for this purpose can be used as welding current sources. Direct power supply of the welding arc from the power (or lighting) distribution shop network is not allowed. Welding-type sources can be connected to distribution networks with a voltage not exceeding 660 V. The load of single-phase welding transformers is evenly distributed between the individual phases of a three-phase network.
In mobile electric welding installations, for connecting them to the network, blocking of the circuit breakers should be provided, which excludes the possibility of connecting and disconnecting the wire when the clamps are energized.
Electric welding installations must be connected to the mains and disconnected from it, as well as repaired only by electricians. Welders are not allowed to perform these operations. The length of the primary circuit between the power point and the mobile welding unit should not exceed 10 m.
The current-carrying parts of the welding circuit must be reliably isolated (insulation resistance must be at least 0.5 MΩ) and protected from mechanical damage. The insulation resistance of the electrical circuits of the installation is measured during current repairs in accordance with GOST for the operated electric welding equipment. The terms of current and major repairs of welding installations are determined by the person responsible for the electrical facilities of the enterprise, based on local conditions and operating conditions, as well as instructions from the manufacturer. The unit and its starting equipment should be inspected and cleaned at least once a month. All open parts of the welding installation, which is energized by the mains, are securely fenced.
Insulation resistance must be checked at least once every three months, and for automatic submerged arc welding - once a month. The insulation must withstand a voltage of 2 kV for 5 minutes.
Cases of electric welding equipment are zeroed (grounded). For protective grounding (grounding) of the housing, power sources equipped with special bolts are connected to the wire of the grounding (grounding) device. In this case, each welding installation must be directly connected to the grounding (grounding) wire. Serial connection of installations among themselves and the use of a common grounding (grounding) wire for a group of installations is not allowed. Failure to comply with this requirement may lead to the fact that if the wire connecting the installations in series is broken, some of them will turn out to be non-zero.
Electrical safety rules for welding
Before switching on and off the knife switch, you must make sure that its casing is zeroed and that the handle is insulated. If there is damage, the switch is turned off. Before starting work, it is necessary to tidy up the overalls; inspect the workplace, check the serviceability of electric welding equipment, the presence of sealed electrical measuring instruments; wipe dry the floor if it turns out to be slippery (doused with oil, paint, water); check the serviceability of cables, wires and their connection to the nodes of the welding machine. In the presence of malfunctions, electric welding is prohibited. Make sure that your hands, shoes and clothes are always dry.
At the end of welding, the electric welder must turn off the welding transformer or generator, turn off the welding cable with the electric holder, wind the wires into coils and put them in a specially designated place.
Connection and disconnection from the network of electric welding installations, as well as monitoring their good condition must be carried out by electrical personnel with a qualification group of at least III.
What can be used as a return wire for electric welding?
As a return wire connecting the workpiece to be welded to the welding power source, flexible wires can be used, and also, where possible, steel bars of any profile of sufficient cross section. The return wire must be insulated in the same way as the one connected to the electric holder. The use of a grounding network of metal building structures of buildings, communications and non-welding process equipment as a return wire is prohibited.
The individual elements used as a return wire are carefully interconnected (by welding or using bolts, clamps or clamps). In installations for arc welding, if necessary (for example, when making circular welds), it is allowed to connect the return wire to the workpiece to be welded using a sliding contact.
Features of electric welding in especially dangerous conditions
When welding inside metal structures, boilers, tanks, as well as outdoor installations (after rain and snowfall), the welder, in addition to overalls, must additionally use dielectric gloves, galoshes and a rug. When working in closed containers, a rubber helmet must also be worn. The use of metal shields in this case is prohibited.
Work in closed containers is carried out by at least two persons, and one of them must have a qualification group of at least III and be outside the container being welded to control the safe performance of work by the welder. An electric welder working inside the tank is provided with a safety belt with a rope, the end of which must be at the second person outside.
Open-circuit voltage limitation of the welding transformer
All electric welding machines for manual arc welding with alternating current, intended for welding in especially dangerous conditions (for example, inside metal containers, in wells, tunnels, during normal work in rooms with increased danger, etc.), must be equipped with voltage limiting devices idle up to 12 V effective action with a time delay of not more than 1 s
