Key Strategies for Enhancing Control Valve Lifespan

 
Control valves play a crucial role in industrial automation systems, as their lifespan and stability directly impact the safety and efficiency of the entire production process. However, during prolonged operation, control valves often suffer from performance degradation or even failure due to issues such as cavitation, erosion, and corrosion. Implementing effective maintenance and optimization measures can significantly enhance the service life and operational efficiency of control valves. Below are several key methods for improving the lifespan of control valves.

Optimizing Initial Opening Management

 
During the initial operation, control valves should operate at a relatively large opening to focus the damaging effects of cavitation and erosion on the valve head. This strategy ensures that initial wear is concentrated in a controllable area. As damage progresses, the valve opening can be gradually reduced, allowing for full utilization of the entire valve stem until the stem root and sealing surface are completely worn out and can no longer be used. In contrast, if the valve operates at a medium or small opening from the beginning, the damage to the valve stem and sealing surface will be more severe, significantly shortening the valve's lifespan.

Reducing Pressure Drop Across the Control Valve

 
Proper pressure drop allocation during system design can minimize control valve losses. Reducing the pressure drop across the control valve can effectively lessen the destructive power of cavitation and erosion. Specific measures include:
Installing an Orifice Plate Downstream of the Valve: An orifice plate can absorb part of the pressure drop, reducing the pressure drop across the control valve, thereby increasing the valve opening and reducing the impact of cavitation and erosion.
Adjusting Manual Valves: Closing manual valves in series with the control valve until the desired opening is achieved. This method is particularly suitable for oversized control valves, allowing quick and effective adjustment of valve opening, improving operational efficiency and lifespan.
These methods can extend the valve's service life by more than double, significantly reducing maintenance frequency due to cavitation and erosion.

Adjusting Valve Diameter

 
Increasing the working opening by adjusting the valve diameter is also an effective method. Specific operations include:
Replacing with a Smaller Diameter Valve: For example, replacing a DN32 control valve with a DN25 valve can allow the valve to operate at a larger opening, reducing internal cavitation and erosion.
Replacing Valve Plug and Seat: Without changing the valve body, using a smaller diameter valve plug and seat can increase the working opening, thereby extending valve lifespan.

Improving Throttling Channel Design

 
Extending the throttling channel or changing the geometry of the throttling component can effectively shift the damage location, protecting the sealing surface and throttling surface of the valve stem and seat. Examples include:
Thickening the Valve Seat: Increasing the thickness of the valve seat extends the throttling channel, delaying the point where the fluid expands abruptly after throttling, avoiding direct impact on the sealing surface.
Designing Special Throttling Channels: Designs such as stepped or wave-like throttling channels can increase flow resistance and reduce pressure recovery, thereby mitigating cavitation damage. This method is often used in high-pressure valves and equipment retrofits, with significant results in reducing cavitation and extending valve life.

Optimizing Flow Direction Design

 
When selecting the flow direction of control valves, flow-to-close structures should be prioritized. Compared to flow-to-open designs, flow-to-close flow direction effectively protects the stem root and sealing surface:
Flow-to-Open: Fluid flows in the opening direction, with cavitation and erosion mainly acting on the sealing surface, leading to rapid damage to the sealing surface and stem root.
Flow-to-Close: Fluid flows in the closing direction, with cavitation and erosion occurring below the valve seat sealing surface, effectively protecting the sealing surface and stem root. For flow-to-open valves experiencing severe lifespan issues, simply adjusting the flow direction can extend the valve life by 1 to 2 times.

Using Special Materials

 
Selecting suitable materials with resistance to cavitation, erosion, and corrosion based on specific working conditions can significantly extend the valve's lifespan:
Cavitation and Erosion Resistant Materials: Materials such as 6YC-1, A4 steel, Stellite alloy, and hard alloys effectively resist damage caused by cavitation and erosion.
Corrosion Resistant Materials: Non-metallic materials such as rubber, PTFE, and ceramics, as well as metal alloys like Monel and Hastelloy, offer excellent corrosion resistance and mechanical properties, making them suitable for corrosive environments.

Improving Valve Structure

 
For complex conditions, multi-stage control valves, anti-cavitation valves, or corrosion-resistant valves can be considered. These valves, through multi-stage throttling or special internal structural design, reduce internal flow velocity and pressure fluctuations, minimizing cavitation and erosion damage to the stem and seat. For example, multi-stage control valves can effectively disperse pressure in high-pressure drop and high-flow conditions, reducing damage caused by single-stage throttling and thereby extending service life.

Conclusion

 
By optimizing opening management, pressure drop distribution, diameter adjustment, flow direction design, material selection, and structural improvements, the service life of control valves can be significantly enhanced. Applying these methods flexibly based on specific working conditions not only extends the valve's lifespan but also improves the overall reliability and operational efficiency of the system. Choosing the right measures is crucial for achieving optimal performance and maximum lifespan of control valves in practical applications.