The electric control valve is generally composed of actuator and valve system. By adjusting the control signal, the electric power receiving unit outputs the control signal to change the flow rate, pressure, temperature of process medium, and the operation parameters of the liquid level of the final control element. It is a control valve of the known electronic control valve in industrial automation and process control. Because of its heavy weight, it is difficult to find the right problem, which is often hard to please. It also involves system operation, system integrity, quality of laws and regulations, environmental pollution and so on.
1. Method of changing the action direction of unbalanced force
When the stability analysis shows that when the unbalance force is closed in the same direction as the known valve, the valve tends to close and the differential valve is stable. On the valve staff
When the above unbalanced force conditions, change the direction of the action selection method, the closed type usually flows to the open flow type, generally, the problem of valve stability can be easily solved.
2. Avoid working in unstable area of valve itself
Some valves are limited by their own economic structure, and their stability is relatively poor when they are improved in some opening. When the opening of the double seat valve is less than 10%, the upper ball flow rate is open and the lower ball flow rate is closed, resulting in instability; 2. The slope of unbalanced force change is close to alternating, and its stability is poor. Butterfly valve, alternating at point 70 degrees; 80? 90% opening in double seat valves. In the case of such valves, the development in the unstable area is bound to have poor stability, so the staff in the unstable area can be avoided.
3. Replace the valve with good stability
The stability of unbalance force is the change of small valve, which has good guidance. Commonly used ball valve, sleeve valve has our big characteristics. When the stability of single and double seat valve is poor, the stability of replacing complete set of cylinder valve will be improved.
4. Increase the spring stiffness
The ability to resist the impact load variation of the actuator stroke depends on the stiffness of the spring, the greater the rigidity, the smaller the stroke, and the better stability of the valve. Increasing the spring structure stiffness is a common simple analysis method to improve the stability of the valve. For example, the spring with 20-100kpa spring working range can be changed to a spring with 60-180kpa large stiffness. This method is mainly used for the valve with positioner in the enterprise, otherwise, the valve used should be equipped with a positioner.
5. Reduce the response speed
When the system design requires that the response or regulation development speed of the control valve should not be too fast, the response and regulation speed of the valve is relatively fast. For example, the flow management needs to be fine tuned, but the social change of the flow regulation of the regulating valve is great, or the information system itself is a rapid response analysis system, and the regulating valve is equipped with a locator to speed up the action of the valve It's all bad. This will develop into overshoot and affect vibration. Therefore, the response speed should be reduced. Measures include:
Firstly, the linear characteristic is changed into logarithmic characteristic;
The device with positioner can be changed into converter and relay.