Butterfly valve leakage is one of the most common problems in piping systems. In actual engineering applications, leakage is not always caused by valve quality itself. In many cases, it is related to valve selection, installation methods, operating conditions, and long-term maintenance.
In general, butterfly valve leakage can be divided into two main types:
- Internal Leakage
This occurs when media continues to pass through the valve even after it is fully closed.
- External Leakage
This refers to leakage from the stem area, flange connections, or outside of the valve body.
Below are the most common causes of butterfly valve leakage found in real engineering applications.
This is one of the most common causes of butterfly valve leakage.
After long-term operation, the seat of a soft-seated butterfly valve may gradually develop:
- Aging
- Deformation
- Cracking
- Wear
- Permanent indentation
Seat wear tends to accelerate under conditions such as:
- Frequent opening and closing
- High temperatures
- Media containing particles or debris
Common examples include:
- EPDM becoming harder after long-term exposure to high temperatures
- NBR swelling when exposed to oil-based media
- PTFE gradually wearing due to continuous friction
Once the seat can no longer maintain proper sealing contact with the disc, leakage is likely to occur even when the valve is fully closed.
2. Incorrect Valve Selection
Many butterfly valve leakage problems are not actually caused by valve quality, but by selecting the wrong valve type for the application.
For example:
- Using soft-seated butterfly valves in high-temperature applications
- Operating beyond the valve’s pressure rating
- Using seat materials that are not resistant to the media
- Using standard concentric butterfly valves for high-pressure throttling service
All of these situations can eventually lead to sealing failure.
Even a new butterfly valve can develop leakage problems if it is installed incorrectly.
Common installation issues include:
- Flange misalignment
- Uneven bolt tightening
- Excessive pipeline stress
- Incorrect gasket installation
- Welding slag left inside the flange or pipeline
These problems may result in:
- Valve body deformation caused by excessive compression
- Disc misalignment
- Seat damage
Ultimately, these issues can affect the sealing performance of the butterfly valve.
4. Debris or Particles Inside the Pipeline
In wastewater systems, circulating water systems, or older pipelines, it is common to find:
- Welding slag
- Rust
- Sand or sediment
- Solid particles
Once these materials enter the butterfly valve, they may become trapped between the disc and the seat.
Even if the valve is fully closed, the trapped debris can prevent proper sealing and cause leakage.
This problem is especially common in:
- Water treatment systems
- Cooling water systems
- Wastewater systems
5. Stem or Disc Misalignment
After long-term operation, internal components of the butterfly valve may gradually develop problems such as:
- Bent stems
- Disc offset
- Bushing wear
- Assembly deviation
These issues can prevent the disc from making even contact with the seat.
In large-diameter butterfly valves, insufficient stem rigidity can make sealing surface misalignment more likely to occur.
6. Operating Beyond Temperature or Pressure Limits
High temperature and high pressure can significantly affect the sealing performance of a butterfly valve.
High temperatures may cause:
- Thermal deformation of the seat
- Rubber aging
- Uneven thermal expansion
High pressure may:
- Increase stress on the sealing surface
- Accelerate seat wear
- Cause structural deformation
For this reason, high-temperature and high-pressure applications are usually better suited for:
- Double eccentric butterfly valves
- Triple eccentric butterfly valves
- Metal seated butterfly valves
7. Actuator or Operating Mechanism Problems
In some cases, leakage is not caused by the valve itself, but because the actuator or operating mechanism cannot fully close the valve.
For example:
- Insufficient torque from the electric actuator
- Incorrect pneumatic actuator stroke
- Excessive gearbox backlash
- The handle not being fully closed
These issues can prevent the disc from properly compressing the seat, resulting in leakage.
8. Lack of Regular Maintenance
Although butterfly valves have a relatively simple structure, a lack of long-term maintenance can still lead to problems such as:
- Corrosion on the sealing surface
- Stem sticking or difficult operation
- Seat aging
- Internal scale buildup
Butterfly valves that remain in the same position for long periods without operation are especially more likely to develop leakage problems when opened or closed again.
How to Reduce Butterfly Valve Leakage
In actual engineering applications, most butterfly valve leakage problems can be prevented in advance.
Proper valve selection, correct installation, and regular maintenance can significantly reduce the risk of leakage and help extend the service life of the butterfly valve.
1. Correctly Select the Valve Type and Seat Material
Different operating conditions require different butterfly valve types and seat materials.
For example:
- EPDM is generally more suitable for normal-temperature water systems
- NBR is more suitable for oil-containing media
- PTFE is better suited for corrosive media
- Metal seated butterfly valves are more suitable for high-temperature and high-pressure applications
If the valve selection does not match the actual working conditions, leakage may occur quickly even with a new butterfly valve.
2. Avoid Exceeding Pressure and Temperature Limits
Long-term operation under excessive pressure or temperature can accelerate:
- Seat aging
- Sealing surface wear
- Valve body deformation
For this reason, the operating pressure, temperature, and media conditions should always remain within the valve’s design range.
3. Ensure Proper Installation
Improper installation is one of the major causes of butterfly valve leakage.
During installation, attention should be paid to:
- Keeping the flanges properly aligned
- Tightening bolts evenly
- Removing welding slag and debris
- Avoiding excessive pipeline stress
Otherwise, problems such as disc misalignment or seat damage may occur.
4. Keep the Pipeline Clean
Welding slag, rust, and solid particles can easily become trapped between the disc and the seat, affecting sealing performance.
It is recommended to:
- Clean the pipeline before installation
- Install strainers when necessary
- Flush the system regularly
This is especially important in water treatment and cooling water systems.
5. Perform Regular Inspection and Maintenance
It is recommended to regularly inspect:
- Seat wear condition
- Stem operating condition
- Actuator performance
- Changes in operating torque
- Overall sealing performance
Butterfly valves that remain in the same position for long periods should also be operated periodically to help prevent internal sticking or scale buildup.
How to Repair Butterfly Valve Leakage
When a butterfly valve starts leaking, the first step is to identify the leakage location and determine the actual cause before selecting the appropriate repair method.
1. Replace the Damaged Seat
If the seat has developed:
- Aging
- Cracking
- Deformation
- Severe wear
it is usually necessary to replace the seat with a new one.
At the same time, the edge of the disc should also be inspected for scratches, corrosion, or other damage.
2. Clean the Sealing Surface
If the leakage is caused by debris, the valve can be disassembled and cleaned to remove:
- Welding slag
- Rust
- Scale buildup
- Solid particles
In many cases, minor leakage problems can be resolved after cleaning the sealing surfaces.
3. Adjust the Actuator or Operating Mechanism
If the valve cannot fully close, the following items should be checked:
- Electric actuator torque
- Pneumatic actuator stroke
- Gearbox backlash
- Limit switch settings
In some cases, simply recalibrating the actuator or operating mechanism can solve the leakage problem.
4. Repair or Replace Worn Internal Components
If the valve has problems such as:
- Bent stem
- Worn bushings
- Disc misalignment
the affected components usually need to be adjusted, repaired, or replaced.
5. Replace the Valve if Necessary
If the butterfly valve has already developed:
- Severe corrosion
- Valve body deformation
- Serious sealing surface damage
- Or has been operated beyond its design conditions for a long period
then replacing the valve with a more suitable butterfly valve is usually the more reliable solution.
Butterfly valve leakage is often related to valve selection, installation quality, operating conditions, and long-term maintenance.
Understanding the actual cause of leakage can help reduce system downtime, improve sealing reliability, and extend the service life of the butterfly valve.
As a professional industrial valve manufacturer, TFW Valve supplies a wide range of butterfly valves for HVAC systems, water treatment, cooling systems, and industrial piping applications, including both soft-seated and metal seated butterfly valves for different operating conditions. Feel free to contact us anytime.
