The heating equipment often used in laboratories is a common heating equipment such as muffle furnace, high temperature furnace, tube furnace, etc. In which most of the research on metal, ceramic, polymer and other raw materials must be vacuumed to carry out experiments, in which the tube furnace is vacuumed. The performance index is stronger. However, the operation procedure of most laboratory workers is not necessarily reasonable. It may lead to the low vacuum value inside the tube furnace and excessive residual air, which may lead to the decrease of the accuracy of the experiment and the failure to reach the test. Standard conditions.
Tubular vacuum furnace
In response to such phenomena, Zhengzhou Nuotai technology technicians summarized the vacuuming phenomenon of tubular furnaces, listed in the key issues and reasonable practical methods.
In order to improve the accuracy of vacuuming, we first summarize the significance and function of vacuuming the tube furnace. First, the significance of vacuuming is to reduce the air inside the tube furnace, so that the test raw materials are in an oxygen-free environment, thus eliminating the experimental raw materials. Redox reactions.
Why is the vacuum value low? Why is the experiment not achieving the ideal situation?
The low vacuum value has the following phenomena;
First, the vacuum pump is aging, and the vacuum value originally achieved is low;
Second, the vacuum line is aging, the pipeline is leaking, and the interface is leaking;
The sealing ring of the third tube furnace is aged and the assembly method is incorrect.
The solution is as follows: Firstly, the aging pipe and the sealing ring are replaced, and the interface part is checked for air leakage. In particular, many manufacturers use the quick-connecting air pipe interface to fail to meet the vacuuming regulations, and the hidden leakage is difficult to check. Secondly, the sealing ring is coated with vacuum silicone grease to improve the sealing of the sealing ring part, and the sealing sealing effect of the flange part assembly is mainly checked.
The vacuum pumping performance index of the tube furnace vacuum pump is not good, and it is possible to carry out experiments with a vacuum pump with higher precision. The price of the vacuum pump commonly used in the tube furnace ranges from 1,000 to 3,000, and the price of the molecular pump is several tens of thousands.
However, in order to save costs, we rely on the vacuum to exclude oxygen. We can fill the inside of the tube furnace with inert gas such as nitrogen and argon to reduce the oxygen concentration and thus the experimental raw materials are not prone to redox phenomenon. The operation flow is as follows;
First, we connect the tube furnace to the vacuum pump and the nitrogen bottle, then close all the valves, open the vacuum pump and vacuum valve, observe the pressure gauge, wait until the vacuum pump vacuum value is stable, close the vacuum valve and vacuum pump; then open the cylinder to open the intake air. Valve, wait until the pressure gauge returns to normal pressure, close the intake valve, at this time the air concentration in the tube furnace is reduced, but the air remains. We repeat the steps to obtain higher purity nitrogen and then exclude air, such as The step may be repeated multiple times for a more pure experiment. Pay attention to the sequence of opening and closing the pump valve cylinder.
Some laboratory tube furnaces must be tested in a vacuum. The vacuum pump has high precision, but it does not meet the experimental requirements. It may be that the vacuum pump is turned off directly after vacuuming, and the vacuum valve is not closed, because the vacuum pump will return to the air when it is not working, which may result in When the air enters the tube furnace tube, we can completely solve this phenomenon by simply closing the vacuum valve after vacuuming.
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