For the solenoid valve in the pneumatic circuit of a control valve, should it be a direct-acting type or a pilot-operated type?
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For the solenoid valve in the pneumatic circuit of a control valve, should it be a direct-acting type or a pilot-operated type? There are different opinions regarding the breakdown; some say that a straight-through type should be used for control valves, while a pilot-operated type should be used for on/off valves, and this combination cannot be changed. Some say they are all the same. But according to information available online, the direct-acting type is faster and seems more suitable for on/off valves
For solenoid valves used in gas pipelines, pilot-operated types are sufficient; direct-acting solenoid valves are only suitable for pipeline systems where the operating pressure is below 0.1 kilograms
This post was last edited by liuyuqian on 2022-8-2 at 14:30. The solenoid valve on the control valve cannot be a pilot-type one. A direct-through type is used to ensure the valve’s response speed.
Do the control valves you mentioned include regulating valves and on/off valves?
Why are the statements above so absolute? For control valves, both pilot-operated and direct-acting types can be used. If emergency shutdown is required, the direct-acting type is a bit faster than the pilot-operated type, but the difference isn’t very significant； Regulating valves that come equipped with solenoids indicate a need for rapid shut-off; in such cases, a direct-acting type should be chosen. A pilot-operated type, when installed behind the positioner, can affect the valve’s ability to open to small degrees, while it can still be used if installed in front of the positioner. If rapid shut-off is required, it is best to avoid using pilot-operated types.
The CV value of the direct-acting type is too small, while that of the pilot-type is large
This post was last edited by liuyuqian on 2022-8-2 18:12. Yes
Solenoid valves are used solely to control the air circuit; pilot-operated types are fully sufficient for this purpose. Solenoid valves can be used to control pneumatic directional valves, thereby regulating the degree of valve opening. If there are requirements regarding the speed at which the valve operates, an air circuit quick-release valve or an air circuit flow amplifier can be installed.
All of them can be used; as mentioned above, it depends on the usage scenario.
The selection of solenoid valves requires taking many factors into account, such as flow capacity, properties of the medium, explosion-proof requirements, installation requirements, and so on. For pneumatic control valves specifically, the key considerations are flow capacity, as well as the dimensions and installation methods determined by explosion-proof requirements; these valves can be used alone or in combination, and speed has little impact on them