What pressure of instrument air should be used for the control valve?

Add a low-power pressure reducing valve before the electric converter, and then check the actuator of the valve to reduce the air pressure~~

Generally, the pressure for instrument air is 5-6 kilograms; what the poster is referring to is the pressure of the instrument air main pipeline. As for how to reduce the pressure to that required by the valve, «it certainly isn’t what the original poster suggested, which is to convert a 4–20mA signal into a wind pressure of 0.2–1 kilogram in order to drive the actuator». The first step is to use a filter regulator «or it could simply be a regular regulator». The second step involves the signal conversion function of the positioner, which is what the IP unit is responsible for. As for the exact output pressure required, it varies depending on the size of the valve.

This post was last edited by ylb913 on 2014-12-31 at 22:09. 1. Earlier, ordinary control valves of the diaphragm type used a pressure range of 0–1.4 kg/cm2; later on, more cylinder-type valves were seen, which required instrument air at a pressure of at least 3 kg/cm2. Even later, diaphragm control valves required an air pressure of at least 3 kg/cm2. 2. The air pressure requirements specified for control valves over the past few years have generally been in the range of 3.0 to 8.0 kg/cm2. The low-pressure value refers to the instrument air pressure sufficient to drive the valve to operate properly, while the high-pressure value is related to the pressure tolerance rating of the instrument’s diaphragm head and cylinders. 3. For the air pressure of the control valve, a pressure reducer is still needed to keep it at the normal maximum pressure, such as 3.5 kg/cm2, which is the low-pressure value mentioned in the second point above. 4. For the cylinder valves of switches, the requirements regarding pressure are not so strict. ——The minimum value must be met (otherwise it won’t be possible to drive it, or it won’t close or open fully); a higher value is also fine (as long as it doesn’t exceed the designed pressure of the cylinder).

Bro, do you have a schematic diagram for this?

Hey, do you have a schematic diagram of this unit that includes the filter pressure reducer as well as the control valve? Thanks

The guy is as professional and meticulous as ever. . Could you recommend any books that are better for understanding the structure of control valves? Happy New Year, haha

Don’t regulation valves and shut-off valves come equipped with pressure reducers? For the regulation valves in our unit, those with small diameters operate at a pressure of around 2 kilograms, while those with larger diameters operate at a pressure of 4 kilograms

Do you know where I can find the schematic diagrams of these control valves? Or would it be possible for you to take some photos of them? Thank you

　Here, three pressure levels for instrument air are involved: 1. The instrument air pressure in the plant (unit) air supply network. The national standard specifies two grades: 500–800 KPa and 300–500 KPa. 　　2. The operating air pressure for pneumatic instruments. The national standard specifies several specifications for its nominal value, namely 140,260,350,550,700 KPa (with a 10% tolerance). 3. Pneumatic analog signal pressure. The national standard specifies 20–100 KPa, while the supply pressure for instruments using this signal is 130–150 KPa ； 　When the control valve is in operation, the air supply comes from the instrument air supplied by the plant’s air distribution network; this air is then reduced to the pressure required for the valve actuator’s operation using a pressure reducing device such as a filter pressure regulator, before being supplied to the actuator ； 　The valve positioner sends pneumatic analog signals based on the standard signals of 4-20mA or 20-100KPa to control (drive) the operation of the control valve. 　It should be noted that many pneumatic instruments today allow for a wide range of operating air pressure levels, and can often adapt to the pressure in the pipeline system without the need for pressure reduction. 　At the same time, many control valves treat the actuator and the positioner as a single unit, and the pneumatic signals between the positioner and the control valve do not meet the requirements of standard signals.