Selection of accessories related to control valves

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Valve positioner: A valve positioner is a key accessory for pneumatic actuators. It is used in conjunction with these actuators to improve the accuracy of the valve’s position, to counteract the effects of friction on the valve stem and uneven forces from the medium, thereby ensuring that the valve is positioned correctly according to the signals sent by the regulator. Positioners are required in the following situations: 1. When the medium pressure is high and the pressure difference is large ； 2. When the diameter of the control valve is large (DN>100) ； 3. High-temperature or low-temperature control valves ； 4. When it is necessary to increase the operating speed of the control valve ； 5. When operating actuators with non-standard springs using standard signals (for spring ranges other than 20–100 KPa) ； 6. For step control ； 7. When causing the valve to operate in reverse (switching between air-operated shut and air-operated open modes) ； 8. When it is necessary to change the flow characteristics of the valve (the positioner cam can be adjusted) ； 9. For springless actuator or piston actuator systems, to achieve proportional operation ； 10. When using electrical signals to operate pneumatic actuators, a power-to-pneumatic valve positioner is necessary. Solenoid valve: When the system requires program control or two-position control, a solenoid valve is needed. When selecting a solenoid valve, in addition to considering the AC/DC power supply as well as voltage and frequency, it is necessary to pay attention to the relationship between the function of the solenoid valve and that of the control valve; it can be used in either a \"normally open\" or \"normally closed\" configuration. If it is necessary to increase the capacity of the solenoid valve in order to reduce the actuation time, two solenoid valves can be used in parallel, or the solenoid valve can be used as a pilot valve in combination with a high-capacity pneumatic actuator. The control valves produced by our factory are typically used in conjunction with solenoid valves manufactured by Dandong Solenoid Valve Factory. Dandong Solenoid Valve Factory has localized the advanced solenoid valve technology from German company HERION. Among them are direct-acting 2/3-way solenoid valves with single control (including explosion-proof types) ； A101ED-SB024000 series (specifications: 3, 5, 8, 10, 12, 15, 20, 25, 40, 50mm) ； Two-position four (five) way solenoid valves with single electrical control, A102ED-SF025000 series (sizes: 5, 8, 12, 15, 20, 25 mm). Advantages of direct-acting type: 1. The working medium can start operating at 0 MPa ； 2. It can be installed and used freely ； 3. The working medium is suitable for water, gas, and oil ； 4. Agile in operation, reliable in performance ； 5. Low power consumption, long lifespan, high operating frequency ； 6. The explosion-proof head combines an enhanced mounting type with an explosion isolation type, facilitating wiring for users. Pilot-type 2/3-way solenoid valves with single or dual control, series P411EI-WFM80200 (sizes: 6, 12 mm) ； Two-way five-port solenoid valves with single or dual control, P413EI-WFM2630 series (sizes: 6, 12 mm). For the technical parameters when making a selection, please refer to the product catalog of Dandong Solenoid Valve Factory. Pneumatic relay: A pneumatic relay is a type of power amplifier that enables the transmission of air pressure signals over long distances, eliminating the delays caused by longer signal lines. It is primarily used between field transmitters and control instruments in the central control room, or between controllers and field control valves. Another function of it is to amplify or reduce signals. Converters are divided into gas-to-electric converters and electric-to-gas converters; their function is to establish a certain relationship between gas and electrical signals, enabling conversion between them. They are primarily used to convert 0–10mA or 4–20mA electrical signals, or 0–100KPa gas signals, into 0–10mA or 4–20mA electrical signals when controlling pneumatic actuators with electrical signals. Air filter pressure regulator: The air filter pressure regulator is an accessory used in industrial automation instruments. Its main function is to filter and purify the compressed air coming from air compressors, as well as to stabilize the pressure at the desired level. It can be used as a power supply and pressure stabilization device for various pneumatic instruments, solenoid valves, cylinders, spraying equipment, and small pneumatic tools. Self-locking valve (positioning valve) A self-locking valve is a device used to maintain the valve position. In the event of a failure in the air supply, the pneumatic control valve can cut off the air supply signal, thereby keeping the pressure signal in the diaphragm chamber or cylinder at the level it was just before the failure. This ensures that the valve position remains at its value before the failure, thus serving a position-maintaining function. A valve position transmitter is necessary when the control valve is located far away from the control room; it allows for an accurate understanding of the valve’s open or closed position without having to go to the site. This transmitter converts the mechanical displacement of the valve’s opening degree into electrical signals that are sent to the control room. Such signals can be continuous signals reflecting any degree of valve opening, or they can be considered as the reverse action of a valve positioner. Travel switch (feedback device): A device that detects the two extreme positions of a valve’s opening and closing state, and simultaneously sends out a signal; the control room can use this signal to determine the valve’s status and take appropriate action.