The valve of the double-acting cylinder FC has opened accidentally

Your question relates to chemical processing equipment and control systems, which is a rather complex issue. To the best of my knowledge, the following is some preliminary analysis and possible solutions to your question: 1. If the valve remains fully open due to a failure of the positioner that results in no output, and an excessive differential pressure causes the valve to stay open, then switching it to flow-closing mode could be a viable solution. In this case, you may need to replace or repair the locator to ensure it functions properly. If the valve operates with low inlet and high outlet pressure, changing it to a flow-shutting mode may reduce the pressure difference, thereby preventing the valve from opening fully. 2. If the valve is fully open due to a fault in the piezoelectric module of the positioner, which results in air intake only at the lower part of the cylinder, replacing it with a mechanical positioner could be a viable solution. In this case, a mechanical positioner may be able to better control the air intake to the cylinder, thereby preventing the valve from opening fully. However, I recommend that you have a professional engineer inspect and evaluate your equipment and system before making any changes. This ensures that the true cause of the problem is identified, and it also guarantees that the chosen solution is safe and effective. It should also be noted that these are only preliminary suggestions; the actual solutions may need to be determined based on the specific conditions of the equipment and the requirements of the manufacturing process. .

This post was last edited by liu530014416 on 2023-9-24 21:56. 1. As per the original design, nothing needs to be changed. 2. The locator is faulty; replacing it with a locator of the same model will suffice. This valve cylinder has a spring, and a double-acting actuator is used; the air circuit diagram is unclear. Please upload the images above (including those of the on-site control valve’s air circuit) in file form for further analysis. Was the control valve automatic or manual at the time of the accident?

Replace the nozzle baffle locator (all smart machines have this); it’s durable and robust

1. The double-acting cylinder is equipped with a spring; what pressure can this spring withstand? The differential pressure is high; how much is it? Generally, the valve is selected based on the closing pressure differential, and a cylinder is chosen for that purpose; a double-acting design with a spring is used to prevent high pressure differentials. It’s necessary to check the design data and selection criteria. It’s unlikely that this is the issue; if so, there might be a problem with the valve selection. 2. The locator’s piezoelectric module is faulty – why is air entering the lower cylinder? Is the maximum fault output set? 3. Are there any other interlocks or something like that? 4. Which pressure gauge is broken?

This post was last edited by zergvs on 2023-9-26 at 19:39. A cylinder with a return spring is of the single-acting type, not double-acting; if it were double-acting, there would be no spring, so there is an issue with what FS provided and with the schematic diagram. Single-acting: Under normal conditions, if it is of the FC type, then the force of the return spring must be greater than the force exerted on the valve disc by the medium. Double-acting: Under normal conditions, if it is FC, the force at the upper end of the cylinder must be greater than the force exerted by the medium on the valve disc.

1. Mechanical pneumatic (electro-pneumatic) valve positioners can be classified as fail-open or fail-close types. But the intelligent locator seems to be able to only achieve gas on and gas off ； 2. When the valve is changed to a flow-blocking mode, the driving force will increase, which needs to be taken into consideration. .

This Foss locator is simply terrible