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Common faults and treatment methods of vacuum furnace

Time:2022-03-18
  If the vacuum furnace is not used for a long time or has been used for many years, some failures will inevitably occur. The following briefly introduces the common failures of vacuum furnaces and the corresponding treatment methods.
1. Electrical failure
A. Abnormal temperature, including over-temperature alarm, or the displayed temperature cannot reach the set value.
(1) The method of removing the fault of the high temperature alarm:
1. First check whether the parameters of the thermostat in the working area are normal, and check all parameters with reference to other thermostats in normal use.
2. Check whether the solid state relay output terminal of the corresponding working area is broken down according to the circuit diagram,
With this method: after a power failure, use the multimeter resistance gear to measure the resistance between the two points of the output end of the solid state relay. Normally, the resistance will be more than a few megohms. If it is broken down, there will be almost no resistance, and it must be replaced according to the same model. new.
3. When the power is turned on, shake the thermocouple probe in the corresponding working area by hand to see if the corresponding thermostat shows a large jump. If this phenomenon occurs, it means that the thermocouple probe is in poor contact and needs to be replaced with a new one. of.
(2) The displayed temperature is too low to reach the set value:
1. Similarly, first check whether the parameters of the thermostat in the working area are normal and whether there is an output signal.
2. Check whether the thermocouples in the corresponding working area are damaged. In order to check whether these thermocouples are in good condition, you can exchange them with the thermocouples on the normal thermostat and connect them to the thermostat to observe the temperature display. If the thermocouple is indeed damaged, it must be replaced. (Note: If the replaced thermocouple is in the inner cavity, the vacuum sealing performance will also be involved, and the details will be explained separately)
3. If there is no problem with the thermostat and thermocouple, you need to test whether the heating tube is energized and working normally. Method: After the power is turned on, start the heating. According to the circuit diagram, directly use a test pen to test the wire connected to the heating tube in the corresponding working area (the white high temperature line on the solid-state output end) to see if there is electricity. If there is electricity, it is also necessary to use a clamp meter to measure whether the current is different from other working areas. Under normal circumstances, the difference is not large.
4. If no electricity arrives, you must check the circuits one by one according to the circuit diagram to see at which link the electricity is cut off and whether any components are burned out?
 
B. Abnormal phenomenon of vacuum
The vacuum cannot be pumped up or is too low:
1. First, confirm whether the vacuum air source is normal (above -95KPa), and whether the compressed air pressure is normal (the normal use range is 0.4-0.6 MPa).
2. Check whether the vacuum gauge is in good condition, and check whether the parameters are normal against the vacuum gauge in normal use?
3. Check whether the door is closed tightly, whether the sealing film at the door is damaged or deformed, and whether there is foreign matter on the door panel? please check carefully!
4. If there is no problem with the door, you need to check the pipelines, pneumatic valves, thermocouple penetration ports, etc. in the corresponding work area. Usually there are more cases at the entrance of the thermocouple, because if the thermocouple is replaced, the sealing performance of the vacuum is often destroyed, and AB glue must be re-applied for sealing.
 
2. Mechanical structure failure
1. If the door is not closed tightly, check whether the hinge of the door is loose, whether the buckle is deformed, whether the door sealing strip is damaged, and whether the door panel is deformed?
2. There is abnormal noise in the fan, please check carefully whether there is any foreign matter entering the fan wheel of the fan, or whether the screw fixing the motor is loose.
3. If the pneumatic valve cannot operate, first check whether the corresponding solenoid valve can work normally, and whether the compressed air pressure meets the working requirements? If the air pressure is normal and the solenoid valve is also good, the pneumatic valve itself must be broken and must be replaced with a new one.
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