The role of regulating pneumatic valve in industrial process control

put much manpower and material resources. Relatively, 7 fast detecting element and transmitter, controller and other development. Is generally thought that regulating pneumatic valve has simple structure, therefore, to adjust the pneumatic valve is put into research and development of the relative lack of manpower and material resources.
the role of regulating pneumatic valve in industrial production process control
. Basic composition of the control system of
such as simple control system, a complex control system, industrial production process control system has a variety of different types. Figure l control system of two simple examples. The diagram, each control system including the controlled variable, control variable and the corresponding control law. Controlled variable is the need to control the process variables, such as, the outlet temperature of the heat exchanger, pump inlet pressure, etc. The controlled variables to make consistent with the desired set point, need a control means, for example, in the steam flow in the figure, the bypass flow pump, etc. Controlled variable deviates from the set existed in the production process is the cause of interference, for example, the change of the shake of steam pressure, pump speed, etc. Usually, called the variables used to adjust the control variables.
figure l simple control system example
a temperature control system

b pressure control system will detect signal is converted into a standard signal. For example, a simple control system by detecting element and transmitter, controller, actuator and the controlled object. Detecting element and transmitter ( Sensorandtransmitt controlled variables used to test. Thermal resistor converts the temperature change resistance, temperature transmitter converts resistance signal to the standard air pressure, voltage or current signal, etc.
deviation, signal controller, Control will detect variable to match the standard signals and setting of the output signals. In a certain control rule of the deviation signal ( Errorsign for operations, operations to actuator. Controller can be used to simulate the instrument, also can use of the microprocessor digital controller implementation, such as DCS and FCS adopted PID control function module, etc.
so, also known as the final element ( Finalel execution is used to receive the output signal of the controller, actuator, Actuat at the final location of the control loop. And controls the dominant variable changes. Most of the industrial production process control applications, the actuator adopts pneumatic valve adjustment. In recent years, with the application of frequency control of motor speed technology, some of the control system had been using frequency converter and motor ( Pump equipment of actuators. This page is introduced to adjust the contents of the pneumatic valve, don't discuss the inverter and other actuators.
by detecting element and transmitter detection and transmitting, the production process of load change or operating conditions change. Will send controller, the controlled variables of the process of the control law operation after the output of the actuator, the corresponding fluid flow in the process of change, make the controlled variable and set point. Visible, the role of detecting element and transmitter is similar to people's eyes, the role of the controller is similar to the human brain, the role of the executor is similar to the man's hands and feet. A control system of quality is affected by the various components of control system, mainly depends on the influence of the most vulnerable part of the control system components. The importance of regulating pneumatic valve adjusting pneumatic valve ( Controlvalv used for regulating the flow of control variables, therefore, also called before pneumatic valve adjustment. From the overall control system, a control system control is good, should be done by adjusting the pneumatic valve. Adjust the pneumatic valve for the following reasons, becomes very important.
belong to the moving parts, (1) regulating pneumatic valve is a throttling device. And detecting element and transmitter, controller, control process, adjust the pneumatic valve needs to change from time to time of throttling flow area, the dominant variable change, to adapt to the load changes or changes in operating conditions. Therefore, to adjust the pneumatic valve pneumatic valve components of seal, pressure, corrosion, etc. Put forward higher requirements. Seal, for example, can make the control pneumatic valve friction increase, adjust the pneumatic valve dead-zone, caused the control system control quality becomes poor.
not only wastes the resources or materials, (2) regulate the activity of the pneumatic valve parts is a 'run' running 'drops' 'the main reason for the leakage. Also pollute the environment, cause an accident.
and detecting element and the differences in contact with the medium process is as follows (3) regulating pneumatic valve pneumatic valve in direct contact with the process medium.
to adjust the pneumatic valve corrosion resistance, strength, stiffness, materials have higher requirements. Adjust the pneumatic valve pneumatic valve components of the contact medium may contact with detecting element of different media. Methods of detecting element spacer can be used with dielectric isolation process. It is difficult to adopt the method of isolation and dielectric isolation process.
so, (4) to adjust the throttle of pneumatic valve to make energy is consumed within the pneumatic trims. Reduce the energy consumption and reduce the pressure loss of regulating pneumatic valve, and ensure a better control quality and to reasonable choice between both.
when the pneumatic valve inlet pressure below the vapor pressure of liquid, (5) regulating pneumatic valve throttling of fluid at the same time also cause noise. For example. Cause flash; When the downstream pressure is higher than liquid vapor pressure pneumatic valve and cause cavitation. Regulating pneumatic valve caused by noise and adjust the design of the pneumatic valve flow, operating pressure, was charged with characteristic of medium etc, therefore, to reduce the noise, reduce the pressure loss on regulating pneumatic valve put forward higher requirements.
the production process of low temperature, high temperature, high pressure, large flow, small flow need to adjust the operating conditions, such as pneumatic valve has a variety of functions, and adjust the strong adaptability of pneumatic valve. Be installed in a variety of different production process. Adjust the pneumatic valve should be able to adapt to the requirements of different applications.