I kindly ask fellow sailors to provide an answer
Thread Content
Dear sea friends, once the feedback rod of the positioner on the control valve comes loose, what state will the air-on and air-off valves be in respectively?
The last edit to this post was made by ylb913 on 2016-8-13 at 11:18. When the feedback rod of the positioner on the control valve comes loose, it results in a decrease in the air pressure output by the positioner; as a result, the valve operated by air cannot be opened further to a certain extent, but it won’t close completely； When the air shut-off valve is closed to a certain extent, it can no longer be closed further, but it also doesn’t open completely. ——I think it’s been reversed.
Could you please explain in more detail why the wind pressure decreases, and why it’s not possible to maintain the original valve position?
This post was last edited by ylb913 on 2016-8-13 at 12:09. I think it was reversed somehow. The feedback from the locator should come with a baffle corresponding to a nozzle inside the locator. For example, in the case of a wind shut-off valve, when the actuator sends a signal to close it, the pressure output by the actuator is initially high; then the feedback rod moves the baffle away from the nozzle, reducing the back pressure inside the nozzle. As a result, the air pressure output by the actuator also decreases, and the distance between the baffle and the nozzle gradually decreases… until equilibrium is reached. ——By this inference, the feedback rod of the locator has come loose; as a result, the distance between the baffle and the nozzle remains at its minimum, and therefore the air pressure output by the locator is at its highest.
Well, I think that’s the case too. If the feedback rod comes loose, in valves that don’t have valve position retention, FC will be fully open and FO will be fully closed, right?
May I ask, under normal circumstances, does FC/FO refer to the forward/reverse action of the actuator or that of the positioner?
May I ask, in a control valve with valve position holding, does the situation where the feedback rod comes loose behave the same as in FC/FO valves?