Possible Causes And Solutions for Control Valve Failures

Control valves are critical components in industrial automation control systems and are widely used in various industrial process controls. 

control valve jamming or blockage is a common issue in these systems. When a control valve gets stuck or blocked, it can affect the normal operation of the control system and even lead to equipment damage. Understanding the causes and treatment methods is essential for ensuring industrial production safety.

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Causes of Jamming or Blockage

1. Debris Blockage

When debris or foreign matter gets stuck between the valve plug and seat, it can be due to particles in the medium depositing on the seat and plug during flow, causing adhesion and resulting in valve failure. This is particularly problematic when the medium contains salts, organic materials, acidic substances, etc., which may penetrate into the valve seat and plug, exacerbating adhesion. Moreover, in high-pressure, high-temperature environments, debris and foreign matter can more easily damage the valve plug and seat, leading to valve failure.Click to view Pneumatic Diaphragm Control Valve supplied by FLOWX.

2. Excessive Pressure and Wear Damage

Excessive pressure and wear damage are two critical issues for controlvalves. They directly impact the valve's performance and lifespan, subsequently affecting the entire system's normal operation.Click to view Pneumatic Diaphragm Control Valve supplied by FLOWX.

3. Packing Gland Not Tightened

If the packing gland of the controlvalve is not tightened, it may cause leakage and other failures, affecting the entire system's normal operation. This typically manifests as the medium leaking through the gap between the packing and valve stem, leading to resource waste, potential pollution of the working environment, and even safety issues.Click to view Pneumatic Diaphragm Control Valve supplied by FLOWX.

Treatment Methods for Jamming or Blockage

1. Cleaning Method

For control valves blocked by debris, the cleaning method can be used. First, close the inlet and outlet valves of the control valve, then clean the controlvalve with a cleaning agent. After cleaning, rinse with clean water and then open the inlet and outlet valves to restore normal operation.Click to contact us to get personalized valve solutions.

2. External Flushing Method

For media prone to sedimentation or containing solid particles that commonly block throttling ports and guide areas, external flushing with gas or steam can be employed. When a blockage or jamming occurs, opening the external gas or steam valve allows cleaning without moving the controlvalve, thus ensuring normal operation.Click to contact us to get personalized valve solutions.

3. Installing Pipeline Filter Method

For small-diameter control valves, especially ultra-small flow control valves with tiny throttling gaps, a filter should be installed on the pipeline before the valve to ensure smooth medium flow and prevent blockages caused by debris.

For controlvalves with positioners, improper functioning is often due to clogged air pathways. Therefore, it is essential to manage the air source properly by installing an air filter pressure regulator on the air source pipeline before the positioner.Click to contact us to get personalized valve solutions.

4. Increasing Throttling Gap Method

If solid particles in the medium or debris like weld slag and rust from the pipeline cause blockage or jamming due to inability to pass through the throttling port, use a throttling component with a larger gap. For example, replace the cylindrical valve plug with a "V" shaped plug or a sleeve valve, as they have a concentrated throttling area instead of a circular distribution, making it easier to resolve the issue.

For instance, a chemical plant had a dual-seat valve that frequently got stuck. After replacing it with a sleeve valve, the problem was immediately solved.Click to contact us to get personalized valve solutions.

5. Medium Flushing Method

Utilize the medium's own flushing energy to remove and carry away sediment and blockages, enhancing the valve's anti-blocking capability. Common methods include:

① Using the valve in a flow-to-close configuration.

② Adopting a streamlined valve body.

③ Placing the throttling port at the most flushed area, while ensuring the throttling components' material can withstand erosion.

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6. Convert Straight-Through to Angle Type

A straight-through valve has a complex flow path and numerous dead zones in the upper and lower chambers, providing places for medium sedimentation. Converting to an angle type valve, where the medium flows through a 90° bend, enhances flushing performance and minimizes dead zones. Therefore, if a straight-through controlvalve experiences slight blockage, it can be replaced with an angle type valve.Click to contact us to get personalized valve solutions.

Preventive Measures

1. Regular Inspection:

Conduct regular inspections of control valves to identify and address potential issues timely.

2. Maintain Cleanliness:

Keep the control valve and its surrounding environment clean to prevent debris from entering the valve.

3. Proper Selection:

Select the appropriate type and specification of control valve based on actual working conditions to avoid jamming or blockage due to improper selection.

4. Routine Maintenance:

Perform routine maintenance on control valves to ensure their normal operation.

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