#Follow Longzhong across the sea: Beijing Public Research Unit -THE END-
Last time I explained the vacuum grading and the equipment for creating a vacuum environment, today we will talk about the operation process of the whole case.
In the beginning, we planned to control the cryopump interface through the PLC program, and use the RS-232 communication method to connect the control. Although RS-232 is the main serial communication interface at present, it has some shortcomings in this case because it is a relatively early interface standard. In addition to the low transmission rate and poor anti-interference ability, RS-232 transmission is limited to a distance of only 15 meters. In addition to the location that is not conducive to the on-site construction environment, the point-to-point communication method is also inappropriate.
Therefore, we convert the RS-232 equipment network server into an Ethernet network to connect the PLC, and then communicate with the cryopump through the network.
It has been mentioned before that the operating principle of the cryopump is to obtain a vacuum environment by adsorbing particles. Therefore, after the limit of adsorption of particles by the cryopump has been reached, we need to regenerate and reduce it.
The regeneration of the cryopump is a process of desorption and desorption of the gas stored in the adsorption and condensation of the pump. There are various regeneration methods, and the required time and regeneration effect are also different. In principle, the gas captured by the cryopump can be removed in a solid, gaseous or liquid state. Due to the technical difficulty of removing the condensate in a solid state, most cryopumps currently use the gaseous or liquid state. Two ways.
According to the different heating methods, the regeneration methods are generally divided into three types: natural heating regeneration, gas flushing regeneration, and electric heating regeneration.
●Natural heating regeneration: It is the simplest regeneration method of cryogenic pump. It uses the heat exchange between the pump wall and the surrounding air to heat up the pump. At the beginning of regeneration, due to the high vacuum degree in the pump, it mainly relies on the pump wall. The heat radiation from the radiator and the heat conduction in the pump heat up the cold plate gradually, and the heating process is quite slow. Natural heating regeneration is generally only used in some occasions that do not require high pump performance.
●Gas flushing regeneration: It is a very commonly used method. It uses room temperature or heated dry inert gas (nitrogen N2 or argon Ar) flushed into the pump to heat the pump. It has two methods: constant pressure method and pulse flushing method. form. Because of effective convective heat exchange, the regeneration time can be shortened, and the gas flushing is beneficial to the desorption of water vapor from the activated carbon, which improves the regeneration quality of the cryopump. In addition, it can also dilute the toxic and explosive stored in the pump. gas.
●Electric heating regeneration: It is an economical regeneration method. At present, there are two different heating methods, one is to use a heating tape wrapped on the surface of the pump wall for heating, and the other is to use the heating plate on the cold head in the pump for heating. Since some components in the cryopump cannot withstand high temperatures, the heating process needs to be controlled.
(Data source of cryopump regeneration: Vacuum Technology Network)
We mainly use liquid nitrogen to regenerate cryopumps, and send back the operations and data required for regeneration to SCADA to fully upgrade the system to automation. Because the owner of this case needs to monitor more and more complex data, we integrated 4 monitors into one host, so that the owner can easily grasp the whole picture and understand the data at a glance.
The case of the Beijing public research unit came to an end here.
From the very beginning, our personnel frequently traveled back and forth between Taiwan and mainland, and actively held many discussions with the owner, in order to ensure that both parties reached a consensus on the direction of the case. Although the local climate and various factors continue to increase the difficulty of this project, it is also a good opportunity to test our crisis handling ability. As the saying goes, real gold is not afraid of fire, we Longzhong rely on years of experience to complete it all the way! The most important thing is to thank the customers for their trust and support, and also for the cooperation and encouragement of the teams of both sides, to be able to write this new milestone for Longzhong.