Selection and Use of Pneumatic Control Valves in Chemical Valves

With the advancement of China’s technological level, the automated valves produced by ChemChina have also been implemented swiftly, which can complete the accurate control of flow, pressure, liquid level and temperature. In the chemical automatic control system, the regulating valve belongs to a major The actuator, its model and the quality of the device have a major impact on the conditioning quality of the conditioning circuit. If the selection and use of the regulating valve is improper, it will seriously threaten the service life of the regulating valve, and even if the condition is serious, it will even cause the system to cause parking problems. . With the development of industrial automation, the pneumatic control valve has also been widely used as an outstanding actuator. This kind of control valve has the characteristics of reliable action and simple structure. It has a very important meaning for ensuring the safety of the system. The following In-depth analysis on the selection and application of pneumatic control valves in the process of chemical automatic control.

1. The selection of pneumatic control valve in the process of chemical automatic control 1. The selection of control valve type and structure is based on the difference of its stroke. Pneumatic control valve can be divided into two different types, namely straight stroke and angular stroke, according to the structure In terms of points, pneumatic control valves can be divided into butterfly valves, angle valves, sleeve valves, ball valves, diaphragm valves, and straight-through single-seat valves. Meanwhile, the straight-through single-seat regulating valve is the regulating valve with the smallest leakage in the application process. The flow function is ideal and the structure is simple. It can be used in areas with severe leakage requirements, but its flow path is relatively messy, which is also restricted to a certain extent. To improve the scale of its application. The straight-through double-seat control valve is the opposite of the straight-through single-seat control valve. There is no strict requirement for leakage. It is suitable for use in areas with large operating pressure differences. Now, the straight-through double-seat control valve is the most widely used in China. A kind of regulating valve. Sleeve valves can be divided into two types, namely double-sealed sleeve valves and single-sealed sleeve valves. Sleeve valves have outstanding stability, low noise, and convenient disassembly and assembly. However, their quotations are relatively high and repair requests are also high. Therefore, the scale of application is also subject to some constraints. The flow path of the diaphragm valve is simple, and it also produces and uses PT-FE and PFA with high corrosion resistance, which is very suitable for use in strong alkali or strong acid environments, but the conditioning function is relatively poor. 2. Selection of control valve raw materials The use of control valves has almost harsh requirements for corrosion resistance, pressure rating and temperature. Therefore, current control valves mostly use cast iron materials, which can effectively improve the corrosion resistance of the control valve. And compressive strength; stainless steel materials are mostly used in the raw materials of the internal components of the control valve. If the system has low requirements for leakage, you can choose soft seals. If the system has high requirements for leakage, you need to use Hastelloy . In the selection of corrosion-resistant materials, it is necessary to summarize and consider the liquid concentration, temperature and pressure, and make selection in connection with mechanical shock. 3. Operation principle and advantages of pneumatic control valve (1) Analysis of the operation principle of pneumatic control valve The position valve and other components can complete the effect of driving the valve, and can also complete the proportional adjustment of the switch, and then use various control signals to complete the setting of the pipeline medium temperature, pressure, flow rate and other parameters. Pneumatic control valve has the characteristics of quick response, simple control, and intrinsic safety, and there is no need to install explosion-proof devices. After the air chamber has a certain pressure signal, the membrane will show thrust, pulling the thrust plate, valve stem, push rod, compression spring, and valve core to move. After the valve core is separated from the valve seat, the compressed air will circulate. After the signal pressure reaches a certain value, the valve will remain at the corresponding opening. Pneumatic control valve has high reliability, simple structure, and will not show electric spark in the process of work. Therefore, its application scale is very wide, and it can also be used in gas transmission stations with explosion-proof requirements.
 2. Analysis of the flow characteristics of the control valve The flow characteristics of the control valve include operating flow and ideal flow. Under the condition that the pressure difference between the inlet and the outlet is constant, the flow through the mediation valve is the ideal flow. This ideal flow has a straight line, Parabola, quick opening, percentage characteristics. In terms of conditioning quality, the chemical automatic control process mainly relies on the principle of characteristic compensation for production. The production of the system has strict rules on the characteristics of the regulating valve. According to this element, when selecting, it is necessary to analyze the amplification factor of the regulating valve. Prevent the conditioning coefficient from changing. In terms of flow characteristics, the control valve will show changes in flow during the operation process, which is very simple to cause vibration questions. When the large opening operation is implemented, the control valve will appear to be slow, and it is very simple to show that the adjustment is not timely and the adjustment is not sensitive. Considering this element, the linear flow control valve should not be used in a system with large changes.
 3. Precautions when installing the regulating valve Before installing the regulating valve, the regulating valve needs to be analyzed carefully and informatively. After the pipeline is thoroughly cleaned, the installation can be carried out. During the installation process, it is necessary to maintain a straight or upright condition. At the same time, it is also necessary to set up brackets in the front and rear positions of the regulating valve to ensure the safety and stability of the regulating valve operation. In addition, in the process of the installation, it is also necessary to analyze the flow direction. In order to ensure the quality of the device, the device should be installed under the condition of less stress. It is also necessary to ensure that the length of the straight pipe section in the inlet direction meets the requirements of the specification. If the installation requires a small-diameter valve, it needs to strictly comply with the planning norms. Under normal circumstances, the straight pipe section in the outlet direction needs to be 3 to 5 times larger than the valve diameter. During the installation, it is necessary to leave enough space to facilitate subsequent protection and operation, and to control the pipeline diameter. When selecting the pipeline connection method, various influencing factors should be summarized and analyzed. 4. In conclusion, the control valve is the main component of the chemical automatic control loop. The selection, device and protection of the control valve will affect the work of the chemical system. Therefore, the operator must strictly abide by the relevant device guidelines and summarize To analyze various types, always select the regulating valve. With the development of science and technology, chemical automatic control has also put forward higher requirements for regulating valves. This requires in-depth research on regulating valves to continuously improve the reliability and stability of regulating valves.

Post time: Nov-27-2021