The function of a valve positioner

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Function of electrical valve positioners: 1. When the fluid is viscous or contains solid particles suspended in it, using a positioner can reduce the resistance exerted by the fluid on the movement of the valve stem. 　　2. Improve the flow characteristics of the control valve. 　　3. Electrical valve positioners help overcome the delay in the transmission of control signals, thereby improving the response speed of the valve. 　　4. For control systems with high requirements for control quality, it is necessary to improve the positioning accuracy of control valves and enhance their reliability. 　　5. It should be installed in locations where the pressure difference across the valve is greater than 1 MPa; by increasing the air pressure, the output force of the actuator is enhanced, which helps to overcome the opposing forces exerted by the fluid on the valve core and reduces errors during operation. 　　6. When a single regulator controls two actuators, two positioners can be used – one for low-position operation and the other for high-position operation – to receive low input signals and high input signals respectively, thereby achieving split-range control. 　　7. To prevent external leakage, when the flowing fluid is at high temperature, high pressure, low temperature, or is toxic, flammable, or explosive, the filler is usually compressed very tightly, thereby increasing the friction between the valve stem and the filler; in such cases, an electrical valve positioner can be used to overcome any delay in response. 　　Function of pneumatic valve positioners: 1. Increase the thrust of the actuator. 　　2. Increase the speed of movement of the actuator. 　　3. Improve the flow characteristics of the control valve. 　　4. Achieve step control. In split-range control, two positioners are operated by one regulator, with the operating range of each positioner determined by the split points.