Pneumatic valve actuator

In the previous picture, let’s show it to you; if the picture isn’t there, how can you know?

It wasn’t explained very clearly. Generally, changing actuators requires personnel with specific expertise or the manufacturer of the control valve to carry out the task.

I also wonder that, regarding changes to the fault status of control valves, it seems impossible to make such changes on-site when the valve has a lining; however, I have seen manufacturers make changes on-site for single-seat control valves made of ordinary stainless steel or carbon steel.

It is crucial to understand, from a safety perspective, what the valve status should be in the event of a failure. There are several ways to modify pneumatic actuators; one of them is to change the air intake from the top to the bottom, and this requires the manufacturer to provide the corresponding accessories. The second method involves modifying the DCS configuration; in some DCS systems, the AO output signals can be set to operate in forward or reverse mode. For example, previously a forward output configuration meant that 0% valve opening corresponded to 4 mA, but with a reverse output setting, 0% valve opening corresponds to 20 mA, thereby allowing the valve state to be changed. In one word, safety of the personnel operating the process equipment must be ensured first.

I’m not sure if I understand correctly. For example, the three holes are labeled A, B, and C respectively; B is the middle hole (which serves as the inlet), while A and C are the outlets. Currently, there is no flow of fluid through A and B, while flow occurs through C and B. Is it intended to change this so that there is no flow through B and C, with flow instead occurring through A and B? If that’s the case, it can be done on-site by removing the actuator from the valve body, manually rotating the valve core to its initial position where flow occurs through C and B; after rotating it 90 degrees, flow will occur through A and B. Then, the actuator can be reinstalled.

The actuator rotates counterclockwise; after manually adjusting the valve core, it needs to be rotated clockwise to achieve this effect

Remove the actuator, rotate it 90°, and then reinstall it.

For stewing, is it to change the gas setting from off to on, or from on to off?

That’s right. How do I change this? Please help

First, it’s necessary to know what model of actuator you have. For example, if it’s an older-style HA head, the actuator’s push rod needs to be replaced, as the lengths of the push rods for air-operated and air-locked actuators are different. If it’s a VA head or a Fisher model, the internal switching mechanism of the actuator needs to be disassembled and replaced. For HA and regular VA heads, be sure to check whether they have pre-tensioning. If they do, use a long screw to loosen the pre-tensioning, otherwise it can easily cause injury. If it’s Fisher’s, there’s no need to worry about pre-tensioning; his pre-tensioning mechanism releases force from the bottom of the bracket. When changing the direction of action, it is also necessary to consider whether a spring replacement is needed, as the way in which force is applied may affect whether the spring’s travel distance is sufficient. This is just an approach based on the equipment; there are other ways of switching as well, such as using smart positioner commands or making changes in the control room. It depends on what exactly you need. If you need it, you can send me photos and I’ll show them to you. My email address is: wyhb@vip.sina.com