In addition to temperature, pressure is also a crucial factor in the operation of vacuum furnaces. If the pressure is not reached, it can also affect the processing effect of the workpiece. So, how do you set up the pressure program?
1. Pre-compression: It should be carried out before the vacuum furnace heats up, with the pressure setting typically ranging between 1.0-1.5 MPa; pre-compression can be manually completed.
2. Pressure Application: After the vacuum furnace reaches the predetermined temperature, pressure is applied to the sample. Typically, a program is set up to automatically apply pressure to the sample.
a: Manually add the II rotation pressure potentiometer while observing the displacement indicator. If the displacement change is minimal, it indicates that the upper and lower punches have already contacted the sample. After applying pressure, switch the "up-down-down" switch to the stop position, and adjust the pressure potentiometer device to a low setting.
Automatic Pressure Increase: First set the required pressure on the instrument. When the basic and test pressures are almost reached, turn the "up-down-down" switch to "up" and observe the changes in displacement and force II. The pressure will automatically achieve holding and stabilizing functions when it reaches the appropriate position. To stop the pressure increase, simply turn the "rise-stop-fall" switch to the fall position. When it reaches the bottom, rotate the "up-stop-down" switch to stop. Turn off the hydraulic pump.
Note: When pressure is neither increased nor decreased, set the pressure to negative, and the hydraulic pump should cease operation. When the cylinder is not in use, position it to the stop position; otherwise, it may cause incorrect operation.
There are mainly two methods for vacuum furnace leak detection: the injection method and the nozzle method. The injection method is a traditional leak detection technique, where the furnace is evacuated and helium is applied externally (such as connected to a helium mass spectrometer), followed by observing the results.
Another method is the probe inspection technique, suitable when your inspection object cannot be evacuated. When employing this method, a leak gas (such as helium) must be introduced into the inspected item. Examples of inspection objects include heat exchangers, water-cooled flanges, water-cooled fans and shafts, electrical wiring, water jackets, and more. Once the inspected item is filled with the leak gas, a sensor is used to check for any external gas leaks. Helium mass spectrometers can also be utilized for this detection method.
Leak detection of inert gases is also crucial. This is because the entire refilling system—from the liquefied gas storage system to the vacuum furnace—must have zero leakage rate. If inert gases leak from the gas supply system or valves on the furnace body, the vacuum furnace may exhibit signs of poor evacuation, poor sealing performance, inadequate ultimate vacuum, difficulty in releasing normal gases, and backflow, among others.
There are two common methods for detecting inert gas leaks: film (soapy bubble) leak detection and vacuum leak detection. Overall, the film leak detection method is a simple and quick high-pressure inert gas leak detection technique. It involves spraying a certain leak detection fluid in the known suspect area. If bubbles form at any inspection point, you will know a leak has been detected.
During the leak detection process, any leakage points found in the vacuum furnace should be promptly recorded. Upon completion of the inspection, the situation should be reported immediately and appropriate action should be taken.
