Siemens integral-proportional control valve

What brand is the valve positioner?

The electric actuator from German Siemens, model SAX61.03, is simply referred to as sax61.03

Check to see if the actuator has reached its limit; also, use a multimeter to measure the input current....

The actuator uses DC0-10V for its input and output signals; a signal generator was used to test the input voltage, but the feedback voltage corresponding to the valve position could not reach 10V – the maximum value measured with a multimeter was only 9.7V. It was observed that the actuator required a movement of 2 mm in order to close. The technician from the distributor left, and thus no solution could be found

It was observed that the gear below the handwheel disengaged before reaching the predetermined (specified signal) position; the actuator only disengages when it reaches its limit value during the power-on self-check

It is recommended to check the PLC’s output to see if there is any voltage drop in the wiring

I tried it with a signal generator; the actuator receives a voltage signal and there is no voltage drift, and the supplier doesn’t understand this either

(1) Slow valve operation. The most likely reasons for this are air leakage in the valve’s air chamber, or the presence of impurities such as mud inside the valve body, which can cause blockages. It may also be necessary to check whether the valve’s packing is too tight. (2) Leaks at the valve connections and packing areas. What needs to be checked here is whether the valve packing has aged or deteriorated; it’s also necessary to examine whether the valve stem is damaged, if there are any issues with the sealing gaskets, whether the valve packing cover is properly tightened, and whether the screws at the connections are loose. (3) Unstable operation of the control valve: Instability in the valve’s performance during operation is often caused by factors such as the pressure of the air supply; it may also be due to unstable output from the positioning device, or it could be caused by other issues. We need to check for leaks in the valve’s pressure reducer and in the pipelines, as well as whether the spring stiffness of the actuator’s execution mechanism is appropriate. The friction force on the valve stem must be high enough. (4) The diaphragm head of the valve sends a signal but the valve does not operate. This issue does not occur by chance; when it happens, we need to check whether there is any sticking in the valve’s spool and bushing, or in the valve seat. Sticking can also occur in the upper and lower guides of the valve, so thorough inspection is necessary. Additionally, any impurities or debris present in the pipelines and valves must be removed promptly. Rust on the gland surrounding the packing can also cause sticking. (5) Oscillation of the valve is accompanied by a buzzing sound. When abnormal noise occurs during operation, it is likely necessary to check whether there are any vibration sources in the vicinity and whether the valve is properly supported. Regarding the medium, it is important to ensure that its flow direction is the same as the direction in which the valve closes. It is also necessary to verify whether the CV value selected for the valve is too high; the pressure difference across the valve should not be excessive. (6) Inadequate sealing after the valve is closed. Problems of this kind usually occur because the output of the valve’s actuator does not reach its maximum value, or because the preload of the zero-point spring is too high or the valve stem is too short. In such cases, it is also necessary to check for any leaks in the bypass system, as well as to determine whether the valve seat has suffered wear or corrosion. Regarding issues related to pressure differences across the valve, it is important to ensure that the output force of the actuator is sufficient. Additionally, it is necessary to check the diaphragm for air leaks; if any leaks are detected, maintenance should be carried out promptly.