Leak Sealing Techniques for Valve Bodies Under Pressure

Leakage in valve bodies is a common issue in industrial production. If not addressed promptly, it can lead to medium loss, environmental pollution, equipment failure, and safety hazards. Therefore, developing effective leak sealing techniques under pressure is essential. This approach allows for sealing without halting production, significantly enhancing equipment efficiency and safety. Below, we will explore several leak sealing methods for industrial valve bodies under pressure, along with their suitable scenarios and implementation details.

Basic Principles of Leak Sealing Under Pressure

When performing leak sealing, a thorough assessment of the leak's nature, medium pressure, temperature, size, and location is crucial. Based on this information, the appropriate sealing method can be selected. The core objective of leak sealing under pressure is to quickly and safely reduce or stop the leakage while ensuring the safety of the personnel involved. Key principles include:
Quick Response: Timely assessment and action are necessary to prevent the leak from worsening.
Safety First: Ensure the safety of personnel during the process to avoid injuries related to the leakage.
Effectiveness: Sealing measures should yield rapid results while production continues.

Adhesive Method

The adhesive method is a common leak sealing technique suitable for small leaks, especially under low pressure. Using the right adhesive can quickly form a seal.

1. Small Leak Point Treatment

For treating small leaks, the following steps are usually taken:
Preparation: Clean the area around the leak, using sandpaper or grinding tools to polish the metal surface, ensuring good adhesion for the adhesive.
Use of Tapered Pins: Align a tapered pin with the leak point and apply the right amount of force to drive it in, reducing leakage or achieving temporary sealing. Choosing the correct length and diameter of the pin is critical for effective sealing.
Applying Adhesive: Apply a fast-curing adhesive around the pin to create a new solid sealing structure, effectively stopping the leak.

2. Large Leak Point Treatment

For high-pressure media and significant leakage, follow these steps:
Secure the Pressure Tool: Fix the pressure tool on one side of the valve, using a high-speed pressure screw to align with the leak point, ensuring stability.
Apply Pressure: Rotate the pressure screw, using the end of the screw to apply pressure on the leaking area, forcing the leak to stop. Monitor the leakage closely to maintain effective pressure control during the process.
Use of Soft Metal Gaskets: If the area of the screw tip is smaller than the leak point, place a soft metal sheet under the screw to enhance sealing. The choice of soft metal should consider the chemical properties and temperature of the medium.
Cleaning and Curing: Once the leak stops, clean the metal surface around the leak point to remove rust and grease, ensuring good adhesion for the adhesive. Then, apply the prepared adhesive and allow it to cure fully.
Remove the Pressure Tool: After the adhesive has cured, remove the screws that secure the pressure tool and take off the mechanism. For added pressure resistance, reinforce the treated leak area with materials like fiberglass to create a more robust seal.

3. Internal Diameter Nut Method

For low-pressure, small leak scenarios, the following method can be employed:
Install Nut: Use a nut with an internal diameter at least twice the size of the leak point, allowing the leaking medium to flow out from within the nut.
Weld the Nut: Weld the nut onto the valve body, ensuring a good seal at the weld to prevent future leaks.
Install Bolts: Use bolts of the same specifications as the nut, placing a rubber or asbestos gasket at the bottom of the nut. Wrap the top of the bolt with sealing tape and screw it into the nut to stop the leak.

Welding Method

The welding method is suitable for valve leaks under high temperature and pressure conditions, particularly for larger valves with minor leaks. Welding provides a long-lasting solution.

Treatment Steps

Seal the Gap: First, weld the gaps on the valve body related to the leak point, avoiding welding directly on the leak point to prevent further damage.
Prepare the Pipe: Use a pipe that matches the working conditions (temperature and pressure), typically around 200mm in length, with a diameter larger than the leak point to ensure complete coverage.
Weld the Valve: Weld a valve that matches the pipe at one end and fully open it to ensure smooth flow.
Align for Welding: Align the other end of the pipe with the leak point and weld it securely. During the welding process, carefully monitor the temperature and time to ensure quality.
Close the Valve: After welding, close the valve to effectively stop the leak.

Wrapping Method

When traditional methods are challenging, the wrapping method provides an effective solution, especially for emergencies, quickly sealing leak points.
 

1. Treatment Steps

Create a Box: Use materials that match the working conditions to create a box that can wrap around the entire valve or the area with a leak to enhance sealing performance.
Weld the Box: Weld the box onto the valve, ensuring it covers the leak point to create a sealed space that prevents medium leakage.
Drilling and Welding: If difficulties arise while welding the box, drill holes in the box for venting, combining methods from drainage welding to install vent valves and other devices for easy sealing.

2. Application Scenarios

This welding method has been effectively used in the main steam path drainage of units, high-pressure heater drainage systems, and other high-pressure conditions. The wrapping method not only effectively resolves leakage issues but also enhances overall equipment safety and stability. In routine maintenance, the wrapping method is widely adopted and proves to be a significant leak sealing technique that is essential for valve repair professionals to master.

Conclusion

Handling valve body leaks through pressure-sealing techniques is a complex yet vital process. By assessing leak points and selecting appropriate sealing methods, the risks associated with leaks can be significantly reduced, ensuring the safety and normal operation of equipment. Whether through adhesive methods, welding techniques, or wrapping methods, each approach has its unique application scenarios and advantages. Mastering these techniques can greatly enhance maintenance efficiency, reduce production downtime, and provide robust support for industrial operations.