Common potential safety hazards and preventive measures for power use on the construction site
in the process of construction, the safety management of temporary power use on the construction site plays a very important role. How to strengthen the safety management of temporary power use on the construction site and reduce the occurrence of on-site power use accidents has become an important link to ensure construction safety
the following describes the common safety hazards and preventive measures taken in the use of electricity at the construction site
I. hidden dangers existing in the nonstandard switch box
during the inspection, it was found that 1. The switch box was made of poor material, and the outgoing line of the box was random. Some entered the box from the side, and some entered directly from the door of the box. 2. The leakage switch failed or did not use the leakage protector, or the leakage protector was not configured according to the specifications
relevant regulations: 8.1.15 distribution box in the technical code for safety of temporary electricity use on construction site The inlet and outlet of wires in the switch box shall be set at the bottom of the box. 8.1.16 the inlet and outlet of distribution box and switch box shall be equipped with fixed line clamps, and the inlet and outlet lines shall be added with insulating sheath and clamped on the box in bundles, which shall not be in direct contact with the box. The incoming and outgoing lines of mobile distribution boxes and switch boxes shall be rubber sheathed insulated cables without joints. 8.2.10 the rated leakage action current of the leakage protector in the switch box shall not be greater than 30mA, and the rated leakage action time shall not be greater than 0.1s.
the switch box on the construction site is the end of the power distribution system. The technical code for safety of temporary electricity use on the construction site requires that the distribution box should be set up in grades, that is, the distribution box should be set under the main distribution box, the switch box should be set below the distribution box, and the electrical equipment should be set below the switch box, forming a three-level distribution and secondary protection, And achieve "one machine, one switch, one leakage and one box". Whether the selection, setting and use of the switch box meet the requirements of the specification directly affects the power safety of the construction site. The installation regulations of the outgoing line are to ensure the integrity of the outgoing line and prevent electric shock accidents caused by electric leakage. Leakage protector (leakage protection switch) is an electrical safety device. When leakage and electric shock occur and reach the action current value limited by the protector, it will immediately act within the limited time to automatically disconnect the power supply, so as to avoid the occurrence of electric shock accidents
II. The mixed use of phase line, working zero line and protective zero line may cause personnel to get an electric shock or burn out the equipment, and the frequently used mold design and preparation can be adopted.
some construction sites have the phase line, working zero line and protective zero line wrongly connected or disorderly connected by non licensed electricians or responsible electricians, Once used improperly, it will cause personnel to get an electric shock or burn out the equipment
relevant regulations: 5.1.11 of the technical code for safety of temporary electricity on construction site stipulates that the insulation color of N line (working zero line) is light blue; The insulation color of PE line (protective zero line) is green/yellow. In any case, the above color marks shall not be mixed and substituted for each other
III. hidden dangers of construction power lines
hidden dangers of the use of power lines at the construction site are mainly manifested in: 1. The power lines are damaged, the insulation is aging, and there are many connectors, which are likely to form electric leakage, short circuit, etc., causing electrical accidents, and even electric shock casualties or electrical fire accidents. 2. The wires used on the construction site are dragged and pulled randomly, messy and mixed. Those that should be overhead are neither overhead nor protective measures are taken. Some wires are even soaked in water or crushed by objects. 3. Private pulling and random connection, and the power line is too long. Especially in the dormitory of construction personnel, non licensed electricians connect and pull power lines without permission, and increase electrical equipment at will. This is very dangerous. First, it is easy to cause a fire. Because you don't know the knowledge of electricity and don't look at the thickness of wires, using multiple electrical equipment on a power socket is easy to produce sparks or wires heating and fire, causing fire. Second, it is prone to electric shock accidents. The technical code for safety of temporary electricity on construction site clearly stipulates that it is strictly forbidden to use aging insulation, damaged power lines, and no joints are allowed for the incoming and outgoing lines of the switch box
IV. hidden dangers of electric welding construction
1. There is no protective grounding as required. 2. The primary line or secondary line is too long. 3. The power line is damaged.
failure to protect the grounding as required may cause consequences: the shell is not grounded. Once the insulation of the electric welding machine is damaged, the shell of the welding machine will have voltage. If the titanium person who produces 3D printing aerospace parts touches the shell of the welding machine, The human body forms a circuit with the earth and the working grounding wire of the neutral point of the power supply, and the current will cause an electric shock accident through the human body. Case grounding: the insulation of the welding machine is damaged. When the welding machine case is energized, the welding machine case is directly connected with the earth through the case grounding wire to form a short-circuit circuit circuit. This short-circuit current will make the protective device of the power supply (automatic switch, fuse or fuse) act and disconnect the power supply of the welding machine. Before the power supply is cut off, even if someone contacts the shell of the welding machine, because the resistance of the grounding wire of the shell is almost zero, almost no current passes through the human body, which can also play a role in protecting personal safety
relevant regulations: GB 3.1.10 of welding and cutting safety stipulates that the shells of various electric welding machines should be grounded according to the requirements of technical specification 1, and the requirements of demand cannot be ignored to prevent electric shock accidents. 3.2.4 "in addition: the cable of the welding machine should use the whole wire, and there should be no connection joint in the middle. 3.2.5 when the welding cable needs to cross the road or passage. Protective measures must be taken. 9.5.2 the length of the primary power line of the transformer of AC arc welding machine shall not be greater than 5m in the technical code for safety of temporary electricity on construction site. Protective cover must be set at the incoming line of the power supply. 9.5.4: the secondary line of the electric welding machine shall adopt waterproof rubber sheathed copper core flexible cable, and the cable length shall not be greater than 30 meters