Analysis and preventive measures of electric shock

Analysis and preventive measures of electric shock accident of electroslag pressure welding machine

with the rapid development of urban construction, high-rise and super high-rise buildings have sprung up. For each additional floor of high-rise buildings, a large number of steel bars need to be welded vertically with electroslag pressure welding machines. Due to the complexity and particularity of the power environment on the construction site, a variety of operation procedures are crossed, and most of the front-line operators are migrant workers, with weak awareness of safe power use and poor self-protection ability, electric shock accidents sometimes occur during welding

I. Analysis of electric shock accident of secondary no-load voltage of electroslag pressure welding machine

1. The secondary no-load voltage of electroslag pressure welding machine is generally about 65v-80v, its working time is about 20%, and the no-load time is about 80%. The longer the no-load time is, the greater the risk of personal electric shock is

2. One of the secondary wires of the electroslag pressure welding machine is the grounding wire, and the other is the welding handle wire. The grounding wire is connected to the reinforcement of the building and is connected with the metal of the whole building. The welded reinforcement is dense, the operation site is narrow, and the ground reinforcement is stacked. The operators work for a long time. Once they touch the power supply of the welding handle wire, there is a risk of electric shock

3. The vertical welding is all brand-new deformed steel bars, which are hard and heavy. The gloves and shoes used for labor protection are damaged quickly. If the labor protection articles are not replaced in time, hands and feet may directly contact the reinforcement, which is prone to electric shock

4. In wet and hot weather, the degree of sweating is serious, and the human body resistance decreases significantly. Once you get an electric shock, it is not easy to get rid of, and its risk is greater

5. The construction schedule in the construction industry is generally tight. Thousands of reinforcing bars need to be welded on the first floor, and the welding of reinforcing bars needs to be completed at one time. It is normal to work continuously for more than ten hours. In hot weather, long-time physical labor and open-air work make the human body very tired, and the risk of electric shock is also high

II. Weak safety awareness

the construction industry is an important industry for the development of the national economy. With the rapid development of the national economy, the capital construction projects are increasing year by year, and the construction workforce is expanding. The front-line construction workers in the construction industry are mainly migrant workers. Their working environment uses energizer, which belongs to high-altitude, open-air, underground and grade separation operations. Some operators have not received professional training, their operation skills are unfamiliar, and their safety awareness and self-protection ability are poor

the market price competition in the construction industry is fierce. A project is subcontracted layer by layer. The proportion of the subcontracting amount of vertical welding of reinforcement is very small, and the safety procedures are not complete. The price has fallen from 5 yuan per welding point in the 1990s to less than 2 yuan per welding point now. Due to price competition, the investment in labor protection products has been reduced, and the labor intensity has increased, resulting in an increase in the hidden danger of electric shock accidents

the JGJ inspection standard issued by the Ministry of construction requires that electric welding machines should be installed with secondary voltage reduction protection devices, which is to ensure the safety production of front-line construction operators. However, the standard has been issued for more than 3 years, and various anti electric shock devices for arc welding machines have been put into use for more than 3 years, but secondary no-load voltage injuries of electroslag pressure welding machines and electric welding machines still occur frequently. The reasons are as follows: ① pass the power line through the anti electric shock device of arc welding machines, directly connect it to the incoming power end of electric welding machines, and give up all functions of the device; ② Connect the incoming line and outgoing line of the power supply to the same end in the device and use it as a bridge box, which has no protective effect at all; ③ At present, there are many manufacturers producing secondary voltage reduction protection devices for welding machines in the market, with mixed advantages and disadvantages. Some products are of poor quality. Some manufacturers put them into production, sales and use without testing equipment, not to mention 3C certification, which has no protection function at all; Some users install such equipment only to cope with safety inspection; ④ The anti electric shock device of the arc welding machine with manual adjustment can instantly have about 3 times of the impulse current when its voltage is converted. In order to avoid the impulse current, it can only be adjusted too much in this regard, so the arc starting resistance is low, and it is difficult to start the arc. The user will adjust it to the working state (red light) and lose the protection function under no-load condition. When the safety inspection is carried out, it will be switched back to standby (green light), which is only to cope with the safety inspection; ⑤ The power line is not selected according to the current. Some incoming lines of the 500 electric welding machine use 4mm2 and 6mm2, while the safety carrying capacity of the 6mm2 wire can only reach 50A current, and the joint will heat up and burn out the equipment within 30 minutes; ⑥ The capacity of electric welding machine is not matched with the selected anti electric shock device, which has potential safety accidents; ⑦ For AC arc welding machines with two gears of rough adjustment, the no-load performance parameters of the two gears are very different, which increases the risk of electric shock

III. preventive measures

1. Operators of electroslag pressure welding machines must be equipped with special labor protection articles (gloves, which means and insulating shoes), because they are in contact with brand-new deformed steel bars with hard burrs, which are damaged quickly and are easy to cause electric shock accidents

2. Electroslag pressure welding machine is equipped with arc welding machine anti electric shock device (secondary voltage reduction protector). According to the technical requirements of the national standard GB for arc welding machine anti electric shock device: ① the no-load safety voltage is less than 24V, and there is no danger of personal electric shock in any wet place, so as to ensure the personal safety of operators; ② The starting time is less than 0.06s, and there is no starting response time for electroslag pressure welding; ③ The starting sensitivity is less than 500O, which will not start when the human body contacts two-phase electricity in any wet place to achieve safety protection; ④ The standby delay time is less than 1s. When the secondary no-load voltage is 80V, it will be reduced to less than 24V within 1s, effectively preventing the danger of personal death from electric shock. The above four are the scientific basis to effectively prevent the secondary no-load voltage of electroslag pressure welding machine from hurting people. Users must purchase the arc welding machine anti electric shock device with national compulsory 3C certification when purchasing

3. The operators of electroslag pressure welding machines must be trained in professional skills. In addition to the special operation certificate of electric welders, they also need to pass the safety operation training in the construction industry, take up their posts with two certificates, and make supervision records during operation. Each electroslag pressure welding machine is operated in a group, and one person in each group must have the knowledge of supervision and rescue, or multiple sets (groups) have a specially assigned person monitoring system

4. For electroslag pressure welding machines and electric welding machines entering the construction site, the on-site safety supervisors must install arc welding machine anti electric shock devices before operation, and must provide 3C certification. According to the regulations of the national quality certification center and the State Bureau of technical supervision, products without 3C certification are not allowed to enter the site for use. The secondary no-load voltage shall be tested irregularly, and the safety voltage shall be lower than 24V

IV. social and economic benefits

electroslag pressure welding machine operation and electric welding machine operation, secondary no-load voltage electric shock accidents occur from time to time. Every electric shock accident will bring great misfortune to a family, great pressure to an enterprise and negative impact on society. The main cost lies in life span. According to the technical conditions of the national GB standard of arc welding machine anti electric shock device, it is effective to prevent the secondary no-load voltage electric shock accident of electroslag pressure welding machine and electric welding machine, and its benefits to the society are immeasurable

in a construction project, if the arc welding machine anti electric shock device is not used, once the electroslag pressure welding machine and the electric welding machine have a secondary no-load voltage electric shock accident, the family members of the deceased will come to arrange reception work and settling in expenses will not be less than 300000 yuan. Even if the construction area of the site is 20000 square meters, the shutdown and rectification for about ten days will bring considerable human, material and economic losses to the enterprise. Electroslag pressure welding machine is a high leakage reactance transformer, and the power factor is generally only 0 4. 0 at no load 2. The no-load loss of electric energy is large. Each electroslag pressure welding machine consumes about 2000kwh of no-load power every year. According to the data provided by the Shanghai electric welding machine industry association, there are about 120000 construction units in Shanghai, about 120000 in the city, and about 1.2 million AC welding machines in the country, which consumes considerable power