Analysis of Anti-blocking Functionality in Control Valves

Blockage in control valves is a common problem in industrial applications. It is especially severe when handling media like slurries, pulp, mining slurry, and caustic soda. These media often contain many impurities, which can cause frequent blockages during valve operation. In addition to unclean media, solid particles such as welding slag and metal shavings in the pipeline can also lead to blockages. To ensure the long-term stability and reliability of control valves, good anti-blocking functionality is necessary. Despite technological advancements, there is still no valve that is completely blockage-free. However, experts believe that by optimizing valve designs, materials, and operating conditions, anti-blocking performance can be significantly improved.

Causes of Control Valve Blockage

The causes of valve blockage are varied. They can be summarized as follows.

Unclean Media: Media like slurries, mining slurry, and pulp often contain solid particles that can accumulate inside the valve, leading to blockages.

Pipeline Contaminants: Solid particles such as welding slag and metal shavings may enter the valve from the pipeline. These particles can get stuck in the valve core or plug, causing blockages.

Improper Valve Design: Some valve designs have complex flow paths that can create vortex dead zones at bends. These dead zones trap media, increasing the chance of blockage.

Flow Path Design and Anti-blocking Performance

The flow path design directly affects a valve's anti-blocking performance. The more complex the flow path, the more likely it is for dead zones and sedimentation to occur inside the valve. Different types of valves have different flow path characteristics.

1. Straight-through Valves

In single-seat control valves, the media flows horizontally into the valve, undergoes vertical throttling, and exits horizontally. This design is complex, and bends in the flow path can create vortex dead zones where impurities accumulate. Increased resistance from these bends and the small internal gaps make it easier for unclean media to cause blockages.

2. Traditional Single-seat and Double-seat Valves

These valves often have sedimentation dead zones at the valve's lower cover guide. Impurities can collect here, making it difficult for the valve core to move downward. This can cause leakage and blockages.

3. Angle-Acting Valves

Angle-acting valves have simpler flow paths, allowing media to flow in almost a straight line. This avoids the complex dead zones and accumulation of impurities. Examples include O-shaped ball valves, which have a straight-flow path and strong anti-blocking performance. Other valves, like full-function ultra-light valves and butterfly valves, also show good anti-blocking effects.

Throttling Port Design and Anti-blocking Performance

The throttling port design is another key factor in anti-blocking performance. Smaller throttling gaps make it easier for larger solid particles to cause blockages. Larger throttling gaps allow cleaner media to flow more smoothly, reducing the risk of blockage.

Plunger-Type Valve Cores: In plunger-type valves, the throttling area is distributed around the circumference. Due to the small throttling gap, media with particles can easily block the valve.

Window-Type Valve Cores: In window-type valves, the throttling area is distributed on the window. This provides a larger throttling gap, which allows particles to pass through and improves anti-blocking performance.

V-Shaped Ball Valves: In practical applications, V-shaped ball valves have throttling areas concentrated at the V-shaped tip. The relatively large throttling gap reduces the risk of blockage, especially at low opening degrees.

Preventive Measures for Special Media

When handling media like concentrated slurries, mud, and mining slurry, control valves face stricter anti-blocking requirements. These media have higher viscosity, poorer flowability, and are prone to sedimentation. Therefore, special designs and measures are necessary to address these challenging media.

1. Smooth Flow Path Design

For viscous media, the valve body should have a smooth flow path with gradual transitions. This reduces media retention and sedimentation. Using through-type valve bodies helps ensure that the internal cavity diameter increases progressively, reducing flow resistance and preventing blockages.

2. Optimized Valve Seat Diameter

For concentrated slurries and other high-concentration media, the valve seat diameter should not be too large. Reducing the valve seat diameter increases throttling speed, which improves the valve's self-cleaning ability and reduces blockage.

3. Purge Interface Design

Adding purge interfaces inside the valve body allows for cleaning using high-pressure air or water. This effectively removes accumulated impurities and simplifies maintenance, reducing downtime caused by blockages.

4. Enhanced Actuator Rigidity and Thrust

For high-viscosity media, the valve actuator needs sufficient rigidity and thrust (torque) to ensure stable operation. For concentrated slurries, a strong actuator can overcome operational resistance and prevent blockages.

Common Anti-blocking Products and Their Features

For media containing impurities or those with higher viscosity, the anti-blocking performance of the control valve is crucial. Different types of valves offer varying degrees of anti-blocking effectiveness based on their design features. Below are some common anti-blocking valve products.

V-Shaped Ball Valves: These valves are ideal for applications that require high anti-blocking performance. Their throttling gap design reduces the risk of blockage, especially in small opening operations.

Full-function Ultra-light Control Valves: These valves provide strong anti-blocking capabilities. They are especially effective for handling concentrated slurries and mining slurries, with smooth flow paths and well-designed throttling ports that prevent blockages.

Rotary Motion Control Valves (e.g., O-Shaped Ball Valves): These valves have simple flow paths and straight-line media flow, making them ideal for anti-blocking applications in liquid and gas flow regulation.

Conclusion

Control valve blockage is a common issue in industrial systems, especially when handling media with solid particles or high sedimentation. By optimizing flow path design, throttling port design, and implementing targeted anti-blocking measures, the anti-blocking capability of control valves can be significantly improved. For special media such as concentrated slurries, mud, and mining slurry, measures like smooth flow path design, valve seat optimization, and purge interfaces can prevent blockages and improve equipment stability. Designers must consider the actual operating conditions and select suitable anti-blocking technologies to ensure long-term stable operation of the system.