Exploration and implementation of pneumatic valve positioner innovative application

According to the idea of redundant configuration of positioner, the Siemens single-acting positioner is taken as the research object to conduct in-depth analysis, and the test and research are repeated in the training base.

After research, four innovative applications were finally practiced:

①Replace the positioner online;

②The positioner is used in conjunction with the two-position three-way solenoid valve;

③The positioner is matched with the manual valve combined use;

④ The positioner is used in conjunction with the check valve, and the positioner is used in conjunction with the two-position three-way solenoid valve, which has very great use value and promotion value.

How does the valve positioner work?

Siemens SIPART PS2 series electro-pneumatic valve positioner belongs to the intelligent category, the core component is a microprocessor, and a new type of piezoelectric valve is used to realize the adjustment and control of the output pressure. For the control of the piezoelectric valve, the CPU needs to use 5 processes to achieve the purpose of program control, with high accuracy and fast speed, to achieve effective control of the increase or decrease of the output air source pressure. For its control algorithm, a digital PID adjustment method is introduced, combined with the size of the input signal, and the valve deviation is comprehensively considered. 

Under the premise of clear direction, the PID is calculated to realize the formation of PWM pulse width modulation pulse signal, and achieve the control of piezoelectric valve. Effective control of switches. Since the width of the pulse is closely related to the pressure of the air source output by the positioner, the targeted change of the output value of the air source pressure can be achieved with faster speed and higher accuracy. Once the deviation value is large, the positioner will output a continuous signal, which will cause a large change in the pressure value of the output gas path, showing a fast and continuous state. 

If the deviation is small, the pulse signal output by the positioner is small, showing an intermittent state, and the amplitude is limited. On this basis, the air pressure is changed. At this time, there is no pulse output phenomenon, and the stability of the valve position operation is maintained.

Relying on the piezoelectric valve device, the control precision can be enhanced. Among the piezoelectric valves, the core component is a piezoelectric flexible switch valve, which has a small mass and low inertia, and supports a high switching frequency. Therefore, it is defined as a high-frequency pulse valve, which can effectively control the air pressure, play a driving role in the actuator, and fundamentally improve the accuracy of valve positioning.

The structure of the valve position feedback element is not complicated, with high precision and outstanding reliability. It is an advanced conductive plastic potentiometer, which promotes the conversion of the linear or angular position of the actuator into a resistance signal to meet the needs of accurate valve position determination. Adapt to the positioning requirements of the valve flow characteristic curve.

Intelligent valve positioner debugging method

1. Auto-tuning

Reasonably carry out the movement of the actuator, separate it from the center position, and realize the initialization development.

(1) Press the hand key for 5s, and then build the configuration mode

(2) Operate the mode key for a short time, and then the second parameter will appear. At the same time, the parameter needs to be guaranteed to be consistent with the setting value of the lever ratio switch;

(3) Switching operation, the display is OFF at this time. After the initialization, if you need to borrow mm to represent the stroke amount, this step is essential, and you need to ensure that the display parameter is consistent with the set value driven on the scale rod;

(4) Use the hand key to complete the switching operation and display INITA. At this time, press the "+" key, and the time is less than 5s, and to enter the initialization phase. During this process, "RUN1" to "RUN5" are displayed one by one in the lower part of the display. Initialization needs to be based on the actuator.

It usually takes about 15 minutes. If the word "finish" appears, it means the initialization is over. At this time, you need to press the hand key for more than 5s to prompt the configuration way to end. After 5s, the mode key is released, the manual mode runs, and then the automatic is used according to the situation.

2. Manual tuning

①With the help of manual drive, the linear travel actuator is operated, so that all strokes can be fully covered. That is to say, set the display potential within the interval between P5.0 and P95;

②Press and hold the hand key for 5s, the configuration mode runs, and the display is WAY;

③Press the hand key to switch to the second parameter state by means of short-time operation.

The angle selection is 33° or 90°, and the parameter value needs to match the setting value of the transmission rate selector;

④Using the hand keys, adjust to OFF state, if necessary, use mm

Indicates full stroke, select the same setting value as that of the drive pin on the rod scale in the display;

Press the increase key for more than 5s to start the initialization. Press the increase key for more than 5s to start initialization;

⑥After 5s, the displayed parameter changes to P32.9. At this point, by means of the increase and decrease keys, the actuator is driven to operate until the first position of the target terminal is reached. Then, press the hand key down. In this way, the end position 1 replaces the current position and the next step begins execution. Once RANGE appears, and at the same time in the downward direction, the end position is outside the specified range, and it needs to be corrected by several means: adjust the friction clamping unit until the OK display appears. 

Then, press and hold the hand key again. Adjust to another end position with the aid of the increase and decrease keys. Press the hand key, the initialization operation is interrupted, and the manual mode is formed at this time, and the stroke is corrected in combination with the first step to define the measurement position;

⑦After the above steps are completed, the displayed value is P22.4, and then use the increase (+) and decrease (-) keys to execute the driver program and reach the second end position. Then, press the hand key, the end position 2 replaces the current position;

⑧ For the initialized stop, it is displayed in an automatic way, and at the same time, RUN1 to RUN5 are sequentially displayed on the lower line of the display. FINISH is displayed after the initialization procedure has been completed. If the rod length is set for the 3YWAY parameter input, the specified stroke in mm will appear on the first line. Short press the hand key, and 5INITM will appear again in the lower line, which means that it is in the state of reconfiguring. Press the mode key for more than 5s to exit the configuration mode. At approximately 5s, the soft key display will appear. Once released, it will be in Manual mode.