In the steam turbine electro-hydraulic control system, the servo valve G771K201 plays an extremely critical role, and its performance is directly related to the control accuracy and stability of the entire system. However, the zero bias drift phenomenon is like a potential “ghost”, which always threatens the normal operation of the servo valve, and then affects the performance of the steam turbine electro-hydraulic control system. Therefore, it is of great practical significance to have a deep understanding of the zero bias drift phenomenon of the servo valve G771K201 and master the precise detection and calibration methods.

1. Analysis of the zero bias drift phenomenon of the servo valve G771K201

The zero bias of the servo valve G771K201, in simple terms, refers to the situation where the output flow or pressure is not strictly zero when there is no control signal input. The zero bias drift refers to the uncontrollable change of this zero bias value with the change of time, temperature, system pressure and other factors.

There are many factors that cause zero bias drift. From the internal factors, the wear of the internal components of the servo valve is an important reason. For example, after long-term use, the matching clearance between the valve core and the valve sleeve may change, resulting in a change in the amount of fluid leakage, which in turn causes zero bias drift. In addition, the elastic fatigue of the spring cannot be ignored. During the long-term expansion and contraction process, the elastic coefficient of the spring may change, affecting the initial position of the valve core, thereby causing zero bias drift. From the perspective of external factors, temperature changes have a significant impact on zero bias drift. Temperature fluctuations will cause different thermal expansion coefficients of the components in the servo valve, causing the relative positions of the parts to change, thereby causing zero bias changes. In addition, the instability of the system pressure may also cause zero bias drift. The fluctuation of pressure will produce additional force on the valve core, causing it to deviate from the initial zero position.

2. Detection method of zero bias drift of servo valve G771K201

(I) Static detection method

The static detection method is a relatively basic and commonly used detection method. When the system is in a static state, professional detection equipment, such as high-precision pressure sensors and flow sensors, are used to measure the output pressure and flow of the servo valve when there is no control signal input. First, reliably connect the servo valve to the detection system to ensure that the system is in a stable initial state. Then, record the pressure and flow data measured by the sensor at this time, which are the initial values ​​of the zero bias. Under different environmental conditions, such as different temperatures and humidity, measure multiple times and compare the measured data. If there is obvious fluctuation in the data, and the fluctuation range exceeds the specified error range, then it can be preliminarily determined that the servo valve has zero bias drift.

(II) Dynamic detection method

The dynamic detection method can more truly reflect the zero bias drift of the servo valve during actual operation. During the operation of the system, the control signal, output flow and pressure parameters of the servo valve are collected in real time using the data acquisition system. By analyzing these dynamic data, observe whether the output flow and pressure fluctuate around a fixed value when the control signal is zero. Signal processing methods such as spectrum analysis can be used to analyze the frequency and amplitude of the fluctuation. If the fluctuation amplitude is large and the frequency shows a certain regularity or irregularity, then it indicates that the servo valve may have zero bias drift. For example, after the system has been running stably for a period of time, it is found that the output flow has periodic small fluctuations when the control signal is zero. After analyzing and excluding other interference factors, it is likely that the zero bias of the servo valve has drifted.

(III) Model-based detection method

With the development of modern control theory and computer technology, model-based detection methods have gradually been widely used. First, establish an accurate mathematical model of the servo valve G771K201, which should be able to accurately describe the input and output characteristics of the servo valve under different working conditions. Then, compare the actual collected servo valve input and output data with the model prediction value. If the deviation between the two exceeds the set threshold, it means that the servo valve may have zero bias drift. For example, use a neural network model to model the characteristics of the servo valve, input the real-time collected data into the model for prediction, and judge the zero bias drift by comparing the difference between the predicted value and the actual value. This method has high accuracy and intelligence, but requires a large amount of experimental data to train the model to ensure the reliability of the model.

3. Calibration method for zero bias drift of servo valve G771K201

(I) Mechanical adjustment calibration

Mechanical adjustment calibration is a more direct calibration method. For zero bias drift caused by mechanical reasons such as valve core position offset, calibration can be performed by adjusting the initial position of the valve core. First, open the outer shell of the servo valve and find the valve core adjustment mechanism. Then, use professional tools, such as precision screwdrivers, to adjust the position of the valve core in the specified direction and amplitude. During the adjustment process, combine the static detection method to measure the zero bias value of the servo valve in real time until the zero bias value reaches the specified range. After the adjustment is completed, ensure that the valve core adjustment mechanism is firmly fixed to prevent displacement during operation.

(II) Electrical compensation calibration

Electrical compensation calibration uses electrical signals to compensate for the influence of zero bias drift. By adding a compensation circuit or software algorithm to the control system, the output signal of the servo valve is corrected in real time. For example, in terms of hardware, a compensation circuit based on an operational amplifier can be designed to generate a compensation signal opposite to the zero bias according to the detected zero bias value, which is superimposed on the control signal of the servo valve to offset the influence of zero bias. In terms of software, PID control algorithms can be used to dynamically adjust the compensation amount according to the real-time collected zero bias data to make the output of the servo valve more stable.

(III) Replacement of key components for calibration

If it is found through detection that the zero bias drift is caused by damage or aging of certain key components inside the servo valve, then replacing these components is an effective calibration method. For example, if the spring has elastic fatigue, resulting in zero bias drift, then a new spring needs to be replaced. When replacing parts, ensure that the selected parts are of reliable quality and are completely consistent with the specifications of the original parts. After the replacement is completed, the servo valve is fully tested and debugged again to ensure that its performance returns to normal levels.

By adopting appropriate detection methods, zero bias drift problems can be discovered in a timely and accurate manner. For zero bias drift caused by different reasons, the servo valve can be effectively calibrated by using mechanical adjustment calibration, electrical compensation calibration, and replacement of key components calibration to ensure that it works stably and reliably in the turbine electro-hydraulic control system. Only by doing a good job in the detection and calibration of the zero bias drift of the servo valve G771K201 can the efficient operation of the entire turbine electro-hydraulic control system be guaranteed, providing a solid guarantee for the stability and development of industrial production.

When looking for high-quality, reliable servo valves, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:

E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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