Why is another solenoid valve needed on the instrument air pipeline?
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Why is an electromagnetic valve added to the instrument air line that controls the regulating valve? Last edited by marry on 2009-3-25 08:44]
Solenoid valves are used for rapid shutdown; under normal operating conditions, control valves are adjusted by valve positioners, while in emergency situations solenoid valves are used to quickly shut off or open the flow (depending on the process conditions)
The function of the solenoid valve is to quickly cut off the air supply in emergency situations.
Won’t adjusting the valve when in an accident condition cause it to open or close in an emergency? And how can the valve operate if the instrument air is cut off?
Is it usually the case that interlocks are installed in situations like this?
The function of the solenoid valve is to quickly cut off the air supply in the event of a chain reaction, causing the control valve to assume an emergency open or emergency closed position, thereby ensuring the safety of personnel and production equipment. If a control valve that does not require participation in a chain system is used, there is no need to install a solenoid valve.
The on/off state of the control valve during an accident should be selected with the safety of personnel and equipment in mind. If you know something about the structure of control valves, you should be able to answer your own question.
The control valve equipped with a solenoid valve is used to participate in interlocks. Such a valve can be energized and allow the air path to be connected only when all process conditions are met and there are no abnormal conditions, at which point it can be used. Once a process anomaly occurs and the plant enters interlock mode, the solenoid valve loses power, the air circuit is disconnected, and the control valve becomes passive. The on/off state of the control valve is determined by the selected air-open or air-close mode.
This method is generally used in control systems that require rapid shutdown, and is controlled by a interlock system. Automatic adjustment is carried out during normal production, while in the event of an emergency, it is necessary to quickly cut off the medium.
If it’s a chain system, why choose solenoid valves? Aren’t cut-off valves more convenient?
Solenoids and pneumatic actuators are assembled together for use in interlock systems. Under normal conditions, the solenoid valve is energized, the pneumatic signal enters the diaphragm head, and it operates properly. When an accident occurs in the control system, the interlock signal de-energizes the solenoid valve, cutting off the pneumatic signal to it. Thereby keeping the control valve in a safe state.
Solenoid valves are used on control valves to enable fast opening and closing.
Used on control valves to participate in interlocking.
Generally, it is because the valves controlled by instrument air are equipped with interlocks, and solenoid valves are used to implement these interlocks
Valves equipped with solenoids are used for interlocking. The reason for not using a cut-off valve is that, in an emergency, the solenoid valve can automatically and quickly switch the gas circuit, thereby putting the control valve in a safe state (fully open or fully closed). Under normal conditions, the solenoid valve is energized, which connects the control air circuit and enables valve position control. In an accident scenario, the interlock signal causes the solenoid valve to lose power, thereby cutting off the control air supply; this allows the air cylinder to open or close the valve completely as a form of protection.
Should the air supply be connected to the positioner first, then to the solenoid valve, and finally to the actuator? If the solenoid valve is connected first and the positioner later, will it not be possible to achieve rapid shutdown?
The function of the solenoid valve is to quickly cut off the air supply in the event of a chain reaction, causing the control valve to assume an emergency open or emergency closed position, thereby ensuring the safety of personnel and production equipment. If a control valve that does not require participation in a chain system is used, there is no need to install a solenoid valve. Such solenoid valves are used in interlock applications
Solenoid valves are used for interlock purposes, to cut off the supply of instrument air and thereby enable interlock functions