Can the pneumatic shut-off valve of FO be modified by removing the spring to turn it into a FL valve?

It’s not necessarily possible. Some cylinders are double-acting, but they also contain springs; the sides of these springs are sealed, and by removing the springs they can be converted into FL type. Most valve springs have an empty side; the cylinder is not designed to be sealed, and there is nothing that can be done to change this.

Remove the spring, take out the 3/2 solenoid valve, and replace it with a 5/2 solenoid valve to turn it into an FL valve; I’ve done this before – it’s a domestic-type cylinder, and it’s simple. I don’t know anything else for now; I’ll first look at the materials to understand the structure before starting work. I need to have all the small parts on hand, as unknown problems may arise after opening it.

The spring has been removed; by adding an air supply port, it should work

Just remove the spring and replace it with a 2/5 solenoid valve; the situation mentioned by the person on the first floor is worth considering – theoretically such a possibility exists. However, generally both the cylinder spring side and the rack side are sealed, so there shouldn’t be any problems. Many units have been modified on-site, and to date the situation described by that person has not occurred.

It depends on the size of your valve and cylinder, as well as whether it uses a gear and rack mechanism or a fork mechanism. If it’s a fork mechanism, the springs used are often too large and stiff, which can cause injury; therefore, it’s not recommended to attempt to disassemble it by yourself. If you simply want to switch it to FL mode, you need to think carefully about this. By \"failure\" we mean a problem with the air supply, that is, a lack of air flow. If there is no air supply, you still need to maintain the valve’s position. In such cases, you can add a check valve in front of the solenoid valve – a one-way valve that allows air to enter but not exit. When the external air pressure drops, the gas inside the cylinder is released outward, and the check valve closes automatically, thereby maintaining the air pressure inside the cylinder and enabling FL mode

Does FL not include power shutdown in case of solenoid valve failure? This valve does indeed have a position holding valve; the foreign drawings indicate it as FL, and the design team selected a configuration that ensures the valve remains in its current position in case of a gas supply failure. Two months ago, there was a problem with one of the cabinet doors in the SIS system – touching the door caused the DO actuator to lose power, which resulted in the valve opening.

As mentioned earlier, the problems of loss of air supply and power outage can be resolved by replacing the solenoid valve with one that is controlled by two signals. For example, when the valve is in the open position, an open command is sent, but no close command is sent. If the power supply for the open command is interrupted, the open command disappears for the solenoid valve, yet since no close command is received, the valve will not close either. By implementing these two measures together, the desired outcome can be achieved

Generally, it’s not possible; the cylinders in FO are usually single-acting

Theoretically, both diaphragm-type and gear-rack-type systems can be implemented as long as proper sealing is ensured; it’s worth exploring this further :)