Hand-held power tools play a very important role in our manufacturing operations and are widely used in our manufacturing operations. For example, we often use: impact drill, angle grinder, electric drill, electric drill, manual edge bander and so on.
These tools make our work much more efficient. But in the process of using it, it can also harm us for various reasons. Electric shock due to the use of these tools is also one of the common workplace accidents.
What should we do in case of electric shock accidents caused by the use of power tools? Can we effectively prevent such accidents?
■First of all, you need to understand the classification of power tools.Hand-held power tools can be divided into 3 categories based on electrical protection.
Class I equipment: conventional power tools with a rated voltage greater than 50 V. Class 1 power tools not only rely on basic insulation to protect against electric shock, but also contain additional safety precautions. The method consists in connecting the accessible conductive parts to the protective conductor installed in the fixed line, so that the accessible conductive parts do not become charged bodies in case of damage to the basic insulation. For tools equipped with non-removable plugs, the ground terminal inside the tool must be connected to the main protective earth conductor in the flexible cable or cord.
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ⅡClass II equipment: Double insulated power tools whose rated voltage exceeds 50V. Double insulation structure is a form of double insulated insulation or reinforced insulation or both. In addition to the basic insulation, double insulation also has a separate layer of additional insulation. Double insulated or reinforced insulated equipment is marked with a “return” type on the nameplate.
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Class III equipment: safety voltage tools whose rated voltage does not exceed 50V, protection against electric shock depends on the safety voltage power supply and inside the tool, no voltage above the safety voltage will be generated. The electric shock protection of the three types of tools uses a strong base insulation, the power supply is isolated from the ground, and the so-called "triple protection" of the extra-low voltage below 50V is used, so that the tools have a higher safety. performance. The second and third types of tools allow you to ensure electrical safety and reliability in use, while no protective earthing or protective neutral connection is allowed.
■Choose the right power tool for different conditions of use
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- In general areas, class II tools should be chosen for safety. When using class 1, in addition to proper grounding or neutral connection, additional protective measures should be taken: use insulating equipment (gloves, shoes, platforms, platforms); Install a leak protection device; protective isolation transformer.
- In damp locations or on metal structures and other highly conductive work areas, Class II or Class III tools must be used. If class I is selected, it is necessary to install a leakage protection device with an operating leakage current below 30 mA and a trip time within 0.1 second.
- Use class III tools in narrow and highly conductive areas such as boilers, metal containers and pipes. If class II is selected, it is necessary to install a leakage protection device with an operating leakage current of less than 15 mA and a response time of less than 0.1 second. And install a safety transformer, the leakage protection device must be placed outside, and someone must monitor it from the outside.
■ Precautions for safe use
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- The tool body cannot be broken, and the mechanical safety device is complete and secure; After the switch, lead wire, plug, body earth protective device, etc. are in good condition, connect the power supply and make sure the body is not charged before use. In the event of damage to the insulation, damage to the flexible cable or sheath of the flexible wire, loss of the protective neutral connection or earth wire, cracked plug and socket, mechanical damage that impairs safety, etc., the malfunction must be repaired immediately.
- Insulation resistance of power tools should be measured after long-term storage and maintenance of power tools;
- If you need to move tools or stop working, leave people behind, or turn off the power suddenly during use, you must turn off the power switch or remove the plug from the outlet.
- Wear face shields, goggles, and other protective equipment when using power tools.
- The soft cable or tool cord should not be too long, and the power switch should be located in a prominent place, and there should not be any objects around to facilitate work.
We cannot be careless in the use of hand-held power tools. Proper use and maintenance are a guarantee of long-term safety.