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Control Principles and Analysis of Typical Accessories of Pneumatic Control Valves

Views: 263     Author: Site Editor     Publish Time: 2021-06-27      Origin: Site


Fierce international competition has promoted the rapid development of modern industrial automation production process control, and pneumatic control valves and their valve actuator accessories are important means to realize industrial automation production processes. In this regard, this article introduces the basic loop of pneumatic technology and typical control schemes, and analyzes and explains typical control loops and corresponding working processes. This also provides a reference and convenient site for modern industrial automation production processes and control valve manufacturers. Technical solutions.



45.industrial ball valve

Valves Are All Reset

A two-position three-way solenoid valve is equipped between the output of the positioner and the actuator. When the gas (electricity) is normal and the solenoid valve is energized in the configuration, the supply (4~20Ma) signal can realize any valve position. When the power supply of the control pneumatic ball valve fails (power loss or power is lower than the minimum limit value) or the control requires emergency interlocking, and the solenoid ball valve itself is poorly contacted, it can be switched. The air source in the diaphragm head of the actuator is quickly evacuated through the R port of its solenoid valve. At this time, the control valve is in the initial position regardless of the signal given by the positioner. This ensures the safe production of related processes and ensures that related equipment is not damaged.



Independent Adjustment and Cut-Off Configuration

According to on-site process production requirements, the same machine needs to be able to achieve both independent adjustment operations and independent shutdown operations at a certain time. When the air (electricity) source is normal, the system sends a 4-20 Ma signal to the positioner, which is amplified by the pneumatic accelerator, and passes through the pneumatic control valve to the single-acting actuator (the pneumatic control valve only functions as a channel at this time). When the gas (electricity) source is normal and the positioner signal is interrupted, the solenoid valve is energized or de-energized. At this time, the two-position three-way gas control ball valve configured with it realizes the reciprocating action, and the corresponding valve position is fully open or fully closed.



45.solenoid ball valve

The Speed of the Control Valve Can Be Changed at Will

If the on-site process production process needs to artificially change the control valve opening or valve closing action speed, and artificially preset the built-in interception area of the one-way throttle valve 1 or the one-way throttle valve 2 according to the control response index, these two one-way throttle valves should be connected in reverse.



Three-Stage Shut-Off Valve

Three-stage pneumatic shut-off valves are composed of three-stage pneumatic actuators and ball valves or butterfly valves. It is a special pneumatic valve that provides a three-stage operation mode of valve initial position, preset position and end position. By presetting the movement displacement of the auxiliary piston, the opening degree of the valve at a certain position is set. It relies on a solenoid valve to control the appropriate position of its valve, and is equipped with quick exhaust or throttling elements, so that the three-stage control valve has very good switching characteristics. The valve opening and closing speed can be adjusted to adapt to various processes, including single or multiple pipelines with unstable flow rates. This prevents the splashing type of liquid, so that the fluid in the pipeline changes smoothly, and the flammable fluid will not explode due to the impact of water hammer, and it will not damage the flowmeter and other instruments in the system due to the impact. It is suitable for petroleum and chemical industries. It is a flow control system for industries such as, light industry and national defense, so it is widely used in media storage, filling, loading and other systems.



In the modern automated production process, the control system puts various special requirements on the valve, so the control polypropylene ball valve must be equipped with various auxiliary devices to meet the needs of the production process. In short, the role of the accessory is to make the industrial ball valve function perfect, reasonable, safe, and convenient to operate.

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