Class I tools: Tools not only rely on basic insulation for protection against electric shock, but also include an additional safety precaution. The method is to connect accessible conductive parts to the protective (grounding) wire in the installed fixed circuit, so that accessible conductive parts do not become charged in the event of basic insulation damage accidents.
Class II tools: their rated voltage exceeds 50V. Tools not only rely on basic insulation for protection against electric shock, but also provide additional safety precautions such as double insulation or reinforced insulation, as well as measures without protective grounding or relying on installation conditions. There are two types of tool casings for this type of tool: metallic and non-metallic, but the handheld part is non-metallic, with a "return" symbol at the non-metallic part.
Class III tools: their rated voltage does not exceed 50V. Powered by an ultra-low voltage power supply, the tool does not generate a voltage higher than the safe ultra-low voltage inside. The shells of these tools are all made of plastic.
matters needing attention
1. Before using handheld electric tools, the shell, handle, load bearing, plug, switch, etc. must be intact and undamaged. Before use, a no-load test must be conducted, and after acceptance by the equipment and safety management department, it must be determined that it meets the requirements and issued a permit or acceptance procedures before use. Hang a qualified tag on the equipment.
2. When using Class I handheld electric tools, it is necessary to wear insulation equipment or stand on insulation pads according to regulations. And ensure that there are good grounding or grounding measures, separate the protective neutral line from the working neutral line, and use 1.5mm or more multi stranded soft copper wire for the protective neutral line. Install a leakage protector with a leakage current not exceeding 15mA and an action time not exceeding 0.1s.
In general places, to ensure safety, Class II tools should be used and leakage protectors with a rated leakage current of no more than 15mA and an operating time of no more than 0.1s should be installed. The insulation resistance of Class II tools shall not be less than 7M Ω.
4. Class II or III tools must be used in outdoor, damp places or when working on metal structures, and splash proof leakage protectors must be installed. The use of Class I handheld electric tools is strictly prohibited.
5. In narrow areas (boilers, metal containers, trenches, pipelines, etc.), Class III handheld electric tools with isolation transformers should be selected. Isolation transformers and leakage protectors should be installed outside narrow areas and supervised during operation.
6. The negative load of handheld electric tools must use weather resistant rubber sheathed copper core flexible cables, and there must be no joints.
7. Electric tools should not be replaced with plugs arbitrarily during use, and the wires should not be inserted directly into the socket without the plug. When electric tools are not in use or need to be replaced, the plug should be unplugged in a timely manner. When inserting the plug, the switch should be in the disconnected position to prevent sudden start-up.
8. During use, it is necessary to check regularly. If insulation damage, power cord or cable sheath rupture, grounding wire detachment, plug socket cracking, poor contact, and intermittent operation are found, the machine should be immediately shut down for repair. When moving electric tools, it is necessary to hold the handle of the tool and not use the rubber cord to move the tool. Pay attention to prevent the rubber cord from being scratched, cut, or punctured at all times to avoid accidents.
9. For electric tools that have been unused for a long time, the insulation resistance value between the winding and the casing must be measured with a 500V megohmmeter before use, which should not be lower than 7M Ω. Otherwise, drying treatment is required.
10. Electric tools are not suitable for use in special environments containing flammable, explosive, or corrosive gases, and should be stored in a dry, clean, and non corrosive environment. For motors and appliances with non-metallic shells, they should avoid contact with solvents such as gasoline during storage and use.
