Selection of pneumatic control valves

1. It is appropriate to choose a pneumatic diaphragm single-seat control valve. For the gas source pressure you mentioned (0.5 to 0.8 MPa), diaphragm control valves are suitable, as common diaphragm control valves can withstand pressures within this range. 2. Film-type single-seat control valves generally come in two types: single-acting and double-acting, with the single-acting type usually being air-operated open or air-operated closed. When making the specific selection, it is necessary to decide whether to choose a gas-open or gas-close type based on your process requirements and safety needs. Fail Open means that the valve opens when the signal pressure is lost ； Fail Close refers to the valve closing when the signal air pressure is lost. .

This post was last edited by CHANGBAISHI on 2024-6-28 07:36. 1. Is it appropriate to choose a pneumatic diaphragm single-seat control valve? Some people say that the pressure of my air source is not suitable for membrane-type control valves. ——It should be possible, as the pressure difference flow rate isn’t very high. The pressure of your instrument air supply is sufficient to drive the pneumatic diaphragm control valve. 2. Are membrane-type single-seat control valves only single-acting? ——I don’t know what ‘single or double’ means. ——Should it specify open gas or closed gas? ——The selection between gas open/gas closed is determined by the state required of the valve in an emergency situation. Typically, solenoid valves are used to control the instrument air supply by turning power on and off. For reference. Note: The valve port diameter selected may need to be reduced depending on the gas flow rate.

Thank you, I understand that a single-acting type has air intake on only one side, while a double-acting type has air intake on both sides

The specifications state that when the pressure difference between the front and back is low, a single-seat valve is advisable. I consulted a manufacturer, who said that in my case the pressure before the valve could reach 0.7 MPa while it might be 0.2 MPa behind the valve; if the pressure difference exceeds 0.4 MPa, then a sleeve valve could be considered

I consulted a manufacturer, who said that when the pressure difference is greater than 0.4 MPa, they recommend using sleeves, as there have been instances in the past where it wasn’t possible to open the device

There is such a saying; it is related to the type of membrane head used in the configuration. It is recommended to choose a well-known brand, and that should work. For reference.

Ordinary valves are directional, which is related to their structure. But it’s not absolute; if there is such a need, butterfly valves and ball valves can both be used for this purpose.

1. It’s fine to choose a pneumatic diaphragm single-seat control valve. But the pressure of the gas supply for this gauge is the supply pressure; it needs to pass through a control device when used to control membrane control valves ； 2. The diaphragm-type single-seat control valve is only single-acting ； 3. Whether the valve should be in the open or closed position depends on the process requirements – that is, whether you want the valve to remain open or closed in the event of a loss of instrument air supply. It is recommended to consider choosing a \"self-acting diaphragm control valve\"; such valves do not require additional instrument air or control devices, and their control accuracy is usually satisfactory in situations where pressure fluctuations are not severe (such as at the inlet of a piping network) ； The downside is that pressure adjustment behind (or in front of) the valve is a bit cumbersome (for those who have not used it before).