The Solutions For The Poor Stability Of Control Valve

The Solutions For The Poor Stability Of Control Valve

01 Change the direction of unbalanced force

In the stability analysis, when the unbalanced force is known to act in the same direction as the valve closing direction, that is, when the valve is closed, the valve stability is poor. When the valve is working under the above-mentioned unbalanced force conditions, the method of changing its direction of action is usually selected to change the flow closed type to the flow open type. Generally speaking, the stability problem of the valve can be easily solved.

02 Working method to avoid the unstable zone of the valve itself

Some valves are limited by their own structure and have poor stability when working at certain openings. The double-seat valve has an opening degree of less than 10%, because the upper ball is open and the lower ball is closed, which brings instability problems; near the change slope of the unbalanced force, its stability is poor. Such as butterfly valve, the alternating point is around 70 degrees; double seat valve is at 80-90% opening. In the case of this kind of valve, working in the unstable zone will inevitably have poor stability, just avoid working in the unstable zone.

03 Replace the valve with good stability

The valve with good stability has less unbalanced force change and good guidance. Among the commonly used ball valves, the sleeve valve has this major feature. When the stability of single and double seat valves is poor, the stability of replacing them with sleeve valves will definitely be improved.

04 Method of increasing spring stiffness

The ability of the actuator to resist the impact of load changes on the stroke depends on the spring stiffness. The greater the stiffness, the smaller the impact on the stroke and the better the valve stability. Increasing the spring stiffness is a common and simple way to improve valve stability. For example, change the spring range of 20～100KPa to a high stiffness spring of 60～180KPa. This method is mainly used for valves with positioners. Otherwise, use The valve should be equipped with a positioner.

05 Reduce response speed method

When the system requires the response of the regulating valve or the regulation speed should not be too fast, the response and regulation speed of the valve is relatively fast. For example, the flow needs to be fine-tuned, but the flow regulation of the regulating valve changes greatly, or the system itself is already responding quickly The system and the regulating valve have a positioner to speed up the action of the valve, which is disadvantageous. This will cause overshoot, vibration, etc. In this regard, the response speed should be reduced. The methods are: The linear characteristic is changed to logarithmic characteristic; the one with positioner can be changed to converter and relay.