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#Follow Longzhong across the sea to Beijing: PLC integrated vacuum equipment system control overseas engineering technical support part-2

Longzhong vacuum system vacuum valve operation


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In this case of overseas engineering and technical support for vacuum system control integration, Longzhong planned for the owner to use PLC programming to design the vacuum degree, vacuum gauge, vacuum pump, vacuum valve, temperature, vacuum pressure sensing, etc. of the automatic control system, considering the vacuum of a wide variety of components. The performance of mechanical transmission, sealing and sealing quality, power signal introduction and connection between systems are well designed and correctly designed. PLC is used to implement the automatic regeneration program of the cryopump. The system automatically monitors the information in the cryopump and judges the operation time. The vacuum degree of the overall vacuum equipment system can be maintained at ultra-high vacuum.

The size and technology of the vacuum equipment workpiece are complex. The owner requires that the vacuum degree of the vacuum system must reach the environment below 1×10−8Pa. To achieve the ultra-high vacuum system, different types of vacuum pumps are required to cooperate with each other for pumping/exhausting. Longzhong controls the requirements of the owner. The temperature in the chamber and the pressure change system program response, and the PLC automatic control is designed to achieve the control of automatic technology to avoid damage to the vacuum equipment.

Longzhong vacuum system molecular pump

Vacuum extraction equipment usually uses a vacuum pump to evacuate, and one of the vacuum pumps used in this case is : Molecular Pump

The molecular pump uses the high-speed rotating rotor to transfer momentum to the gas molecules, so that they can obtain a directional speed, and then use the front stage to extract the compressed and driven air to the exhaust port to achieve a vacuum environment.

Longzhong vacuum system screw pump

screw pump

Dry screw pumps are suitable for low to medium vacuum related applications, where oil-free vacuum areas are required, and the bearings and seals are protected by internal compression to achieve a high vacuum environment.

Longzhong vacuum system cryopump


A cryopump is a vacuum pump that utilizes a low temperature surface to condense gas, also known as a condensate pump. The cryopump can obtain a clean vacuum with the largest pumping rate and the lowest ultimate pressure by means of adsorption, so as to reach the ultra-high vacuum environment. In this environment, all matter becomes a quiescent ionic state (ionization is like freezing)

The general process of vacuum pumping designed by Longzhong is as follows: use a screw pump to pump into a vacuum, the pressure value measured by the vacuum meter is reached, the vacuum valve is opened and closed, and when the control pressure reaches a balance, it is pumped into a high vacuum environment with a molecular pump, and the ultra-high vacuum is Need to cooperate with cryopump. Through PLC logic integration and control of the vacuum pump, vacuum gauge and vacuum valve operating system, according to the requirements of the pumping system with different vacuum degrees according to the needs of customers in different experimental stages, the process of switching vacuum degrees of each vacuum pump or vacuum valve can still maintain an orderly and smooth automatic operation. System, step-by-step vacuum, high vacuum, ultra-high vacuum switching. Next, let's talk about the operation process of the overall PLC control vacuum system case!

Longzhong HMI man-machine interface vacuum system integration

Longzhong's engineers planned to control the cryopump interface through Siemens S7-1500PLC program, and planned to use 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.

So later, the RS-232 was connected to the S7-1500 PLC program by converting the equipment networking server into an Ethernet network, and then communicated with the cryopump through the network. In this way, the control system of the vacuum system is composed of PLC program design and programming, which can automatically adjust the vacuum degree according to the customer's test environment requirements.

The operating principle of the cryopump has been mentioned before, which is to obtain a vacuum environment by adsorbing particles. Therefore, after the limit of adsorption of particles by the cryopump has been reached, it needs to be regenerated and reduced.

The regeneration of the cryopump is a process of desorption and desorption of the gas stored in the pump by adsorption and condensation. 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 regeneration methods.

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 degree of vacuum in the pump, the pump wall mainly relies The heat radiation and heat conduction in the pump gradually heat up the cold plate. This heating process is quite slow, and natural heating regeneration is generally only used in some occasions that do not require high pump performance.

● Gas flushing regeneration: It is a widely used method. The pump is heated by room temperature or heated dry inert gas (nitrogen N2 or argon Ar) flushed into the pump. There are two kinds of constant pressure method and pulse flushing method. form. Because of the effective convective heat exchange, the regeneration time can be shortened, and the gas flushing is conducive to the desorption of water vapor from the activated carbon, which improves the regeneration quality of the cryopump, and also dilutes the toxic and explosive gases stored in the pump. .

Electrical heating regeneration: It is an economical regeneration method. There are two different heating methods. One is to use the heating tape to wrap the surface of the pump wall for heating, and the other is to use the heating plate on the cooling 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)

Longzhong mainly uses liquid nitrogen to regenerate the cryopump, and transmits the operation and data required for regeneration to SCADA through PLC programming. The powerful integrated control force of Siemens S7-1500 can comprehensively improve the vacuum system for automation. In this case, the owner needs to monitor more and more complex data, so Longzhong engineers PLC integrated the vacuum equipment system control, and integrated the information of 4 screens into one host, so that the owner can easily grasp the whole data and understand it at a glance.

The case of the Beijing public research unit came to an end here.
From the very beginning, Longzhong engineering personnel frequently traveled back and forth between Taiwan and mainland, and they also actively conducted many cross-sea calls and discussions with the owner in order to ensure that both parties reached a consensus on the direction of the vacuum system control case. Although the local climate and various factors continue to increase the difficulty of this PLC integrated vacuum equipment system control project, this is also a good opportunity to test Longzhong's crisis handling capabilities.

As the saying goes, real gold is not afraid of fire. We, Longzhong, relying on many years of automatic control experience, have overcome difficulties and completed the PLC logic control vacuum system case that has never been touched before, and achieved the first successful overseas engineering technical support! 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.


To Be Continued⋯⋯

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