Vacuum brazing furnace daily failure and troubleshooting methods:
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Failure phenomenon |
Causes of the failure |
Troubleshooting solution of vacuum brazing furnace |
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Temperature control Failure |
1、Thermocouple broken wire
2、Temperature control instrument failure |
1、Replace the new thermocouple
2、According to the temperature control instrument manual maintenance |
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The vacuum brazing furnace does not reach the ultimate vacuum or time is too long |
1、vacuum brazing furnace vacuum system failure
2、Vacuum brazing furnace body leakage, vacuum brazing furnace heat exchanger leakage.
3、 The vacuum gauge resistance gauge and the ionization gauge damage
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1、Check, Exclude
2 、Check the vacuum brazing furnace heat exchanger
3、Replace the regulation of the vacuum gauge |
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The heating power does not reach the rated value |
1、Magnetic voltage regulator failure
2、Graphite heating tube pollution, resistance increased
3、The new graphite tube resistivity does not match. |
1、Maintenance of magnetic voltage regulator
2、Replace the new graphite heating tube
3、Check the graphite tube resistivity |
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The surface of the processing part is not bright |
1、The cooling gas is not pure
2、the vacuum is too low |
1、 to ensure that nitrogen (argon) gas purity of more than 99.9996%. Water content, oxygen content less than 5ppm
2、Check the vacuum system and cooling system of vacuum brazing furnace. |
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Thermocouple burned down |
1、thermocouple and carbon felt touch
2、thermocouple is not sealed |
1、Excluding vacuum brazing furnace heater
2、Check the sealing ring
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Insulation resistance<1000 Ω
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The electrodes are surrounded by carbon fibers |
Remove the fly copper, oven treatment, clean up the carbon fiber |
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Vacuum valve switch failure |
Compressed air pressure is insufficient
2、Solenoid valve Failure (Vibration caused by the relative movement of the electromagnet and the shell)
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1、 Ensure that air pressure is not less than 0.5 MPa
2、Maintenance, plus rubber pad and tighten |
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Mechanical pump failure |
1、Can not start
2、 The direction of rotation reversed
3、The operation is not flexible
4、Low pumping efficiency
5、Can not reach the degree of vacuum |
1、Check the motor starter switch position and overload protection device and cooling water switch
2、Replace the two phase wiring in the motor three phase
3、Repair according to the instructions
4、Oil pollution, for new oil, if no change to check the other parts of the vacuum system.
5、The exclusion of oil pollution; replace shaft end oil seal；open the gas ballast valve |
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The transmission parts Running fault |
Limit failure |
Put the limit and impact devices in harmony |
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Mechanical booster pump failure |
1、No action
2、Abnormal noise
3、Not reach the degree of vacuum |
1、Check whether the motor starter switch and overload protector work
2、 Eliminate the gear accuracy is not enough, the rotor dynamic balance is not good; bearing deflection error or damage; coupling different shafts
3、 Replace the shaft seal, adjust the rotor and rotor, rotor and stator, rotor and end cover gap |
Common Faults and Treatment of Thermocouple in Vacuum Brazing Furnace
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Failure phenomenon |
Possible causes |
Processing method |
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The thermoelectric potential is smaller than the actual value (display instrument indication value is low) |
Thermal electrode short circuit |
To find out the cause of short circuit, such as due to moisture，it needs to be dry; If the insulator is damaged, the insulator must be replaced. |
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The junction of the thermocouple is accumulated dust, causing a short circuit |
Cleaning of dust in vacuum brazing furnace |
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Short circuit between compensation conductor line |
Find the short circuit poi, nt, strengthen insulation or replace compensating wires |
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Thermocouple thermal electrode metamorphism |
In the range of allowable length, cut off the metamorphic section re-welding, or replace the new thermocouple |
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The compensation conductor wire is reversed with the thermocouple polarity |
Re-connect correctly |
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Compensation wire and thermocouple are not matched |
Replace the matching compensation wire |
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Thermocouple installation location is incorrect or insertion depth does not meet requirements |
Re-install Thermocouples as required |
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Thermocouple cold junction temperature compensation does not meet the requirements |
Adjust the thermocouple cold junction compensator |
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Thermocouple and display instruments are not matched |
Replace thermocouple or display instrument to make it match |
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The thermoelectric potential is larger than the actual value (display instrument indication value is high) |
Thermocouple and display instruments are not matched |
Replace thermocouple or display instrument to make it match |
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Compensation wire and thermocouple are not matched |
Replace the matching compensation wire |
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There is a DC interference signal to enter |
Eliminate DC interference |
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Thermoelectric output is unstable |
Compensating conductor is in poor contact with the hot electrode |
Tighten the terminal screws |
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Thermocouple measuring line insulation damage, causing intermittent short circuit or grounding |
Find fault points and repair insulation |
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Thermocouple installation is not strong or external vibration |
Tighten the thermocouple, eliminate vibration or take shock measures |
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The thermal electrode will be broken |
Repair or replace thermocouple |
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External disturbance (AC leakage, electromagnetic induction, etc.) |
Detection of interference sources, the use of shielding measures |
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Large error of thermocouple thermoelectric potential |
Thermoelectrode metamorphism |
Replace the hot electrode |
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Improper installation position of Thermocouple |
Change the installation location |
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Thermocouple protection tube surface dust |
Clear dust |
Vacuum brazing furnace pressure rise rate unqualified
First, the Leak
A. Seal damage leakage, priority check vacuum brazing door seal ring, electrode seal ring, thermocouple sealing ring and other interface seals, generally by water pressure due to vacuum brazing furnace sealing ring aging.
B. Vacuum brazing furnace shell welding cracks resulting in internal leakage or external leakage, poor welding quality caused, If it's an internal leak, it's not detectable by helium mass leak detector.
C. Connection heat exchanger leakage, caused by poor welding quality of heat exchanger in the latter part of vacuum brazing furnace. Need to separate leak detection for vacuum brazing furnace heat exchanger.
D. Valve leakage,vacuum brazing furnace commonly used butterfly valve, baffle valve, flashboard valve, ball valve, solenoid valves, membrane valves and other valves, the valve seal ring in the dirty environment is easy to damage, in a polluted environment should be filtered and then into the valve and pump.
Second, the vacuum brazing furnace internal material deflated
A. The inner wall of the shell, in the south more humid weather, moisture absorption, easy to cause leakage of the illusion.
B. Thermal insulation materials deflated, vacuum brazing furnace insulation is generally metal, carbon materials and ceramic fiber, ceramic fiber in low-temperature insulation effect is good, but inspiratory large,carbon material and second.
C. Vacuum brazing furnace heat exchanger deflation, mainly because the heat exchanger fin area is particularly large, adsorption gas is not easy to release.
D. With the furnace brazing fixture deflated, to be brazed product material deflated, especially the car EGR system products Ni-based solder assembly after the product did not dry into the vacuum brazing furnace.To solve the above problems need to bake oven. But the bake oven does not have much effect on the heat exchanger, and needs to be dried separately before the product enters the vacuum brazing furnace. The vacuum brazing furnace needs to be filled with gas after the oven, start the fan for hot air circulation can be resolved.
E. Virtual welding deflated and assembly threaded hole is deflated, vacuum brazing furnace shell inner wall welding is bad, graphite electrode and the copper electrode did not leave a vent hole, etc., this problem should be solved during design and manufacture, it's hard to meet in practical use.
Third, the instrument readings
A. This is mainly for the domestic vacuum brazing furnace vacuum gauge, the domestic vacuum gauge reading is the original logarithmic relationship using the segmentation of the interpolation of the linear relationship between the line, which will result in test pressure rise rate, a section of qualified and a section of unqualified.
B. Vacuum gauge used resistance gauge effective measurement value is 0.1 ~ 2500 Pa, the domestic instrument should be used before the full and zero adjustment, if there is no tune, had only 0.1Pa changes may become 1Pa changes.
C. The foreign vacuum recorder measurement is not complicated and generally does not need to be adjusted, and if the display is not allowed, generally can be reset at atmospheric pressure can be.
D. If there are several measuring instruments on the device, they can be compared with each other, McLeod gauge is an absolute amount of vacuum gauge with a measuring range of 0.1~500PA, you can use McLeod gauge to calibrate the electronic vacuum gauge.
Regular maintenance table for vacuum brazing furnaces
In the factory
|
Day |
1.Check the cooling tower and the storage tank and replace the filter as needed |
2.Move the coarse pump oil filter to the next pump in turn ,replace the filter as needed |
3.Check the crude pump oil level and oil temperature, listen to the mechanical problems |
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Weekly |
1. All vacuum furnace to do cold leakage inspection, the maximum 0.5Pa / H |
2.Check diffusion pump, roots pump and maintain pump oil level |
3.air compressor release air |
4.Check all vacuum furnace control systems |
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Monthly |
1.Check all temperature instruments |
2.Replace all air filters in the control cabinet |
3.Put the oil and butter on the main valve of the furnace |
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Every three months |
1.Calibration instrument for calibration instrument |
2.Check all vacuum instruments |
3.Replace the thermocouple for inspection |
4.Vacuum furnace temperature uniformity test |
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Six months |
1.Argon pipeline system pressure test |
2.Vacuum furnace thermal leakage test |
3. Check the dew point meter, change oil for vacuum pump |
4. Replace the crude pump oil and the valve |
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Every year |
1. Check and brush all circuit boards |
2. Argon Purity Calibration |
3.Check the main transformer oil level, replace the crude pump oil separator |
4.Calibration test of each meter |
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