Consulting about ABB double-acting positioners
Thread Content
ABB double-acting actuator: there is no issue with the upward movement. When a 75% command is given for the downward movement, the shutter gets stuck at around 76% of its position (it doesn’t get stuck completely); an exhaust sound can be heard, but the shutter doesn’t move (this occurs occasionally). When a command to close it fully is given, an exhaust sound is heard continuously as the shutter approaches its fully closed position, yet the shutter hardly moves. After some time, when all air pressure is released, the shutter finally closes completely – this also happens occasionally. There have been instances where it took a very long time before the shutter closed fully. What could be the problem?
The function of the positioner is to continuously send adjustment signals as long as the stroke does not reach the desired level (it can be considered a proportional + differential control system). Therefore, the baffle of a pneumatic (electro/pneumatic) double-acting positioner does not stop at its static position when the valve has not reached the corresponding travel distance ； Therefore, during inspection, first check whether the stroke has reached the proper position ； If the phenomenon disappears after it persists for a while and the process reaches the intended state, focus on checking whether the exhaust pipeline (including the pipelines inside the locator) is unobstructed ； Gently move the baffle back and forth; if the issue disappears quickly, there may be a jam in the pneumatic amplifier.
In addition to the above, please check whether there are leaks in the cylinders, whether the air supply pressure is sufficient, whether the bearings are moving freely, and whether the feedback rod is loose； Also, if the baffle has an eccentric structure, it is difficult to close it completely.