Safe use of hand-held electric tools

Hand-held power tools can be divided into three categories according to the protection against electric shock

　　 The electric shock protection of Ⅰ type tools not only relies on basic insulation, but also has an additional safety protection measure, such as protective grounding, so that the accessible conductive parts will not become live bodies when the basic insulation is damaged.

　　 The protection against electric shock of class Ⅱ tools not only relies on basic insulation, but also includes additional safety protection measures (but does not provide protective grounding or does not rely on equipment conditions), such as double insulation or reinforced insulation. Its basic types are: ①Insulating material shell type, which has a solid and basically continuous insulating shell; ②Metal shell type, which has a basically continuous metal shell, and all use double insulation. When double insulation is not available, use it Reinforced insulation; ③ Combination of insulating material and metal shell.

　　 Class III tools rely on safe and extra-low voltage power supply. The so-called safety extra-low voltage means that the voltage between the phases and the ground does not exceed 42V, and it is powered by a safety isolation transformer.

　　 With the widespread use of hand-held power tools, the importance of electrical safety has become more prominent. The user department should formulate corresponding safety operating procedures for hand-held electric tools in accordance with national standards. Its content should at least include: the allowable use range of the tool, the correct use method, the operating procedure, the inspection site items before use, the possible dangers in use and the corresponding protective measures, the storage and maintenance methods of the tool, and the operator should pay attention Matters etc. In addition, safety technology education and training should be conducted for the use, maintenance, and repair personnel, and attention should be paid to the inspection, use and maintenance of hand-held power tools, and they are shock-proof, moisture-proof and corrosion-proof.

　　Before use, please select hand-held power tools together

　　 In general workplaces, Class I tools should be used as much as possible. When using class I tools, leakage protectors, isolation transformers, etc. should be equipped. Class II or Class III tools should be used in humid places. If Class I tools are used, a leakage protector with an operating current of not more than 30μA and an operating time of not more than 0.1s must be installed. When working in boilers, metal containers, and pipelines, use Class III tools or Class II tools equipped with leakage protectors. The operating current of the leakage protector is not more than 15μA and the operating time is not more than 0.1s. In special environments such as heat and humidity, rain and snow, explosive or corrosive gases and other operating environments, tools with corresponding protection levels and safety technical requirements should be used.

　　 When installing and using, the safety isolating transformer of class Ⅲ tools, the leakage protector of class Ⅱ tools, the control box and power supply device of class Ⅱ and Ⅲ tools should be kept away from the working place.

　　The power lead of the tool should be made of tough rubber-covered wire or plastic sheathed soft copper wire. There should be no joints in the middle, and no extension or replacement is allowed. The protective grounding resistance shall not be greater than 4Ω. During operation, the protective cover of the moving parts must not be disassembled, and the machine should be stopped to replace the tool and abrasive tools.

　　 There should be guardians in cramped workplaces

　　Except for the isolation transformer with a voltage of 36V and below, the secondary winding of the power supply is not grounded, and the power circuit is equipped with a reliable low-voltage leakage protector, the rest are all wearing rubber insulating gloves, and if necessary, wearing insulating shoes or standing on an insulating mat. The operating isolation transformer should be the primary and secondary dual windings, the secondary windings must not be grounded, and the metal casing and core should be reliably grounded. Terminals should be closed or protected. The original winding should be specially equipped with a fuse, controlled by a bipolar switch, the lead length should not exceed 3m, and there should be no joints.

　　 Before and after the tool is used, the custodian must conduct daily inspections, and the user should conduct inspections before use. The contents of the daily inspection include: whether the shell and handle are damaged or cracked, whether the mechanical protection device is intact, whether the rotating part of the tool is flexible, brisk and unimpeded, whether the electrical protection device is good, whether the protection wire is connected correctly and reliably, whether the power switch is normal and flexible, and the power plug And the power cord is intact. Any problem should be repaired or replaced immediately.

　　 At least one full-time inspection should be conducted every year. In areas with frequent changes in humidity and temperature or with harsh conditions, the inspection cycle should be shortened accordingly. It should be checked in time before the rainy season. In addition to the above checks, a 500V megohmmeter should be used to measure the insulation resistance of the circuit to the housing. Tools that have been left unused for a long time must also be tested for insulation before use. Type I tools should be less than 2MΩ, Type II tools should be less than 7MΩ, and Type III tools should be less than 1MΩ; otherwise, they should be dried or repaired.

　　 The maintenance of tools should be carried out by a specially designated maintenance department, equipped with necessary inspection equipment. Do not arbitrarily change the original design parameters of the tool, do not use substitute materials lower than the original performance, and do not replace parts that do not conform to the original specifications. The insulating gasket and casing in the tool shall not be missing or removed at will.

　　 After maintenance, insulation should be tested, and withstand voltage test should be done between the live parts and the shell. The withstand voltage test voltage of class I tools isolated by basic insulation and live parts is 950V, class III tools are 380V, and the test voltage of class II tools isolated from live parts by reinforced insulation is 2800V.