Generally, medium frequency induction furnace safety protection can be divided into furnace equipment safety protection and operator safety protection. Only the safety measures taken in terms of equipment structure are introduced here.
Aluminum shell medium frequency induction furnace
Steel shell medium frequency induction furnace
1. Cooling water system
Intermediate frequency power supply, induction coil, water cable, etc. all need water for cooling, so water is essential for furnace equipment. The probability of furnace equipment damage due to cooling water failure is high. Since the cooling devices are mostly electrically charged, such as thyristors, induction coils, water cables, etc., the cooling water for direct cooling of these devices must have a lower conductivity than the specified value, and the connection hose must be carbon-free.In addition, the inlet temperature, outlet temperature, water pressure, and flow rate of cooling water must conform to the design regulations. The cooling water system of the electric furnace is equipped with various sensors to monitor the relevant parameters of cooling water. When the cooling water parameter is abnormal or exceeds the set value, it will alarm or stop the operation of the equipment.
The intermediate frequency electric furnace cooling water pump station shall be equipped with two main water pumps of the same specification (one for use and one for standby) and shall be equipped with an emergency cooling water system. When the power supply interruption of the power grid causes the main pump to be unable to work, the emergency cooling water system can provide cooling for the furnace body to avoid furnace body damage.
2. Hydraulic system
The hydraulic system of an intermediate frequency coreless induction furnace is used to dump molten metal in the furnace and to open and close the furnace cover. To ensure reliable operation, the hydraulic station of the electric furnace should be equipped with two main pumps with the same specifications (one for use and one for standby).
The inlet end of the tilting furnace hydraulic cylinder shall be equipped with a throttle valve to prevent the furnace body from falling down suddenly due to the loss of pressure of the hydraulic system.
The molten metal in the furnace may cool and solidify when the power supply is interrupted for a long time, which may damage the lining of the furnace. It is very dangerous to melt and solidify the metal in the furnace by running the furnace. Therefore, the hydraulic system of the furnace should be equipped with an emergency system. If necessary, this emergency system can be used to pour out the molten metal in the furnace to prevent it from solidifying in the furnace when the power supply of the grid is interrupted.
3. Monitor and alarm the floor drain furnace
In the operation of a coreless medium frequency induction furnace, if its lining damage will lead to furnace leakage accident. If molten metal leaks from the lining, it can damage the insulation of the induction coil, the coil stanchion, and the yoke, causing serious leakage if not detected in time. If the molten metal will coil copper pipe burn leakage, then the water inside the tube and molten metal contact may cause an explosion, causing serious accidents. It can be seen that it is absolutely necessary to set up an alarm system for furnace lining leakage. At present, the better is the DC injection leakage furnace alarm system.
The center point on the secondary side of the transformer is ungrounded, so the AC supply circuit of the induction coil can be connected in parallel with a DC circuit. The molten metal in the furnace is grounded by the bottom electrode, and the induction coil is connected to the DC power supply and the milliammeter in series and grounded, so that the liquid metal, the furnace lining, the coil, and the milliammeter are connected into a DC circuit. When the furnace lining is in good condition, the milliammeter display value is very small due to the great resistance of the furnace lining. If the lining condition is poor when molten metal penetrates into the lining and is close to the induction coil, the lining resistance will be reduced and the milliammeter indication value will be increased. When the current value exceeds the set value, an alarm will be issued and the main power will be cut off, so as to prevent the occurrence of furnace leakage accidents.
4. Automatic troubleshooting
The modern induction furnace is equipped with a computer management system. This system has an automatic fault diagnosis function. The system scans each set point of the equipment. When the parameter of the setpoint is found abnormal, an alarm will be issued and the fault information can be displayed and recorded. Because of the speed of the scans, which can be hundreds of times per minute, faults can be detected in their initial state without causing serious equipment damage. Information about the failure is stored in the computer for future reference.
In addition to the above listed, there are some other safety measures, such as when the cabinet door of intermediate frequency power is opened, through the mechanical chain will automatically cut off the power supply into the line; For example, each capacitor is equipped with a pressure switch. When the internal pressure of the capacitor exceeds the set value, an alarm will be given and the power will be cut off to prevent the capacitor from exploding due to excessive internal pressure.
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