The importance of pneumatic control valve selection and principles

A, A pneumatic control valve selection, control of pneumatic valve type selection of the importance of regulating pneumatic valve actuator in automatic control system, its application quality direct response on system control quality. As terminal in the process control element, a updated understanding of its importance, compared with the past. Adjust the stand or fall of pneumatic valve application, in addition to product quality, the user is correct installation, use, maintenance, calculation, selection is very important to correctly. System due to on the selection of calculation error, starting and stopping, some even can't putting-in-service proactively, so for the user and the system design personnel should know the importance of the pneumatic valve at the scene, must cause enough attention to adjust the pneumatic valve selection. B, the principle of pneumatic control valve selection, according to the process conditions, select the appropriate structure and materials. , according to the characteristics of the process object, select the control flow rate characteristics of pneumatic valve. According to process operating parameters, select the appropriate control of pneumatic valve diameter size. , according to the requirement of the process, select the desired auxiliary device. Actuator, the reasonable choice. Response speed of the actuator should be able to meet the requirements of process to control the travel time: chooses the control of pneumatic valve actuator can should be of sufficient pneumatic valve stroke and the technique requirement to the leak amount level. In some occasions, such as selection pressure pneumatic control valve ( Including object completely valve, should consider the actual possible differential proper amplification, which can provide larger force required for actuators. Otherwise, may be when the abnormal situation on craft, pneumatic control valve before and after the actual pressure difference is bigger, will happen dangerous don't or can't open it. Second, the control of the pneumatic valve accessories in the process of production, control system makes all kinds of special requirements for pneumatic valves, pneumatic control valve, therefore, must be with all kinds of accessory device ( Hereinafter referred to as attachments to meet the needs of the production process. Pneumatic control valve accessories include: pneumatic valve, pneumatic valve is used to improve the positioning control regulation performance of job characteristics, realize the correct positioning. Pneumatic valve, pneumatic valve position switch according to the working position of upper and lower stroke. Pneumatic valve, pneumatic pneumatic valve when the position control of the air supply failure occurs, keep the pneumatic valve opening position in front of the breakdown in the air. Pneumatic valve, electromagnetic gas path of electromagnetic switch, ensure pneumatic valve when power failure the valve is in the desired security opening position. , the handwheel institutions controller failure occurs when the control system, pneumatic valve can be switch to manual mode operation. , pneumatic relay actuator movement speed, reduce the transmission time. , air filtration pressure is used to purify air, adjust air pressure. , storage tanks to guarantee when there is a failure in the air, make work without spring cylinder piston pneumatic valve actuator to control action to the fail safe position. Its size depends on the size of the cylinder, pneumatic valve action time of the pneumatic valve working conditions and requirements. In conclusion, the role of the attachment is to control the function of the pneumatic valve more perfect, more reasonable and more complete. Three, the maintenance of pneumatic control valve; Control characteristics of pneumatic valve has simple structure and reliable operation, but because of its direct contact with the process medium, its performance directly affect the quality system and environmental pollution, so to control the pneumatic valve must be regularly maintenance and preventive maintenance, especially to use conditions and important occasions, more should pay attention to maintenance work. Key inspection area, the pneumatic valve body wall for use in high pressure and corrosive medium occasion control pneumatic valve, pneumatic valve body wall, pneumatic diaphragm valve diaphragm often hit from the medium and corrosion, must review the situation of stress and corrosion. Pneumatic valve, pneumatic valve seat control work, because of the medium infiltration, fixed pneumatic seat with the thread surface are susceptible to corrosion and make the pneumatic valve seat is loose, should be careful when checking. To work under high pressure difference of pneumatic valve, pneumatic valve seat sealing surface should also check whether the broken to pieces. Pneumatic valve, pneumatic valve core core is adjust the moving parts of the job, by the medium of erosion and corrosion is most serious, maintenance carefully check whether all parts of the pneumatic valve core corrosion, wear and tear, especially under the condition of the high pressure difference of pneumatic valve core wear more serious ( Because of the cavitation phenomenon) , should be pay attention to. Pneumatic valve core is badly damaged should be replaced when, also should pay attention to whether the pneumatic valve stem has a similar phenomenon, loose or connected to the pneumatic valve core, etc. , 'O' ring of diaphragm and other gasket. Applicants should control pneumatic valve diaphragm, 'O' shaped sealing cushion is aging, crack damage. Should be paid attention to, packing ptfe packing, sealing grease is aging, mating surface is damaged, it should be replaced when necessary.