Solenoid valves are used in conjunction with on/off valves, while limit switches are used with control valves
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I’m a beginner who’s just starting to work with instruments. I have a question. Does every pneumatic on-off valve necessarily require a solenoid valve? What role does the solenoid valve play here? Can using the solenoid valve alone achieve the goal? In my understanding, limit switches are used in conjunction with control valves to determine the position of the valve stem; I’m not sure if this understanding is correct. I would appreciate some guidance from those who are more knowledgeable.
Generally, solenoid valves are used as air source switches for controlling the flow of air in and out of valves, while limit switches are employed to transmit signals from the field back to the control room, enabling the control room to know the position of the valves on site.
Thank you to the friend above. I have another question: are the solenoid valves used in conjunction with on/off valves the same as those used independently? Are there other valves that can be used to control the air supply switch as well? In what other situations are solenoid valves used?
Electromagnetic valves are used to control the gas flowing in and out of the cylinder, thereby enabling it to open and close. I’m not sure what you mean by using an electromagnetic valve alone
Solenoid valves are generally used in conjunction with pneumatic on-off valves; their function is to control the opening and closing of the air path in the pneumatic valve by switching the solenoid valve on or off, thereby enabling the valve to open or close. The function of the limit switch is to transmit signals to the DCS indicating whether the valve is in the open or closed position. The control solenoid valve is a DO signal, while the valve position feedback is a DI signal.
Some very small pipelines are controlled for opening and closing directly by solenoid valves; for example, the solenoid valve used to ignite natural gas is not connected to a cylinder. Solenoid valves can also be installed on control valves, serving to quickly open or close the control valve during interlock operations.
Generally, solenoid valves are used as air source switches for controlling the flow of air in and out of valves, while limit switches are employed to transmit signals from the field back to the control room, enabling the control room to know the position of the valves on site. Some very small pipelines are controlled for opening and closing directly by solenoid valves; for example, the solenoid valve used to ignite natural gas is not connected to a cylinder. Solenoid valves can also be installed on control valves, serving to quickly open or close the control valve during interlock operations. For certain hazardous media and critical valves, the solenoid valve ensures that these valves remain in a safe open or closed position when the power is cut off, thereby serving as a safety mechanism.
Thank you very much to everyone for your replies; I now have a general understanding.
Thank you very much for your reply. My understanding is that solenoid valves can be considered a type of valve alongside control valves and on/off valves; they can also be used as on/off valves on their own. So how should one make a choice – when to use on/off valves and when to use solenoid valves? In what other situations can solenoid valves be utilized? Thank you.
Seeing the OP’s question, I felt frustrated – what kind of beginner is this OP?
Uh, I’m sorry for the inconvenience to those upstairs