Correct Installation Methods for Valve Sealing Gaskets

Sealing gaskets play a critical role in valve operation by ensuring a tight seal and preventing media leaks. As a key component of valves, the proper installation of sealing gaskets directly affects the sealing performance and operational stability of the valve. Therefore, correct installation techniques and attention to detail are essential for maintaining the normal operation of the valve. This article will provide a detailed guide on the installation process and precautions for valve sealing gaskets.

Preparation Before Installation

Before installing the valve sealing gasket, ensure that all relevant valve components are in good condition.

Check Flange and Threaded Connections: Make sure the valve’s flange or threaded connection is undamaged, and the sealing surface is clean, flat, and free from defects.
Clean the Sealing Surface: Lubricate the sealing surfaces, gasket, threads, and rotating parts of bolts and nuts with graphite powder or a mixture of graphite powder and oil (or water) to facilitate smooth gasket installation.
Keep the Gasket Clean: Ensure the gasket surface is free from dirt or contaminants, as any foreign particles can affect the sealing performance.

Correct Installation of the Gasket

Proper installation of the gasket is crucial to ensure the valve’s sealing efficiency. The following key principles should be followed.

Alignment: Ensure the gasket is properly aligned and placed on the sealing surface without any tilting. The gasket should not extend into the valve cavity or sit on the valve shoulder.
Single Gasket Use: Only one gasket should be used between each sealing surface. Do not stack multiple gaskets, as this can result in poor sealing.
Oval Gaskets: When using oval gaskets, the inner and outer rings should make contact with the sealing surface. The ends of the gasket should not touch the bottom of the groove to avoid leakage.
O-Rings: When installing O-rings, ensure the O-ring and groove dimensions are according to the design specifications, and the compression is appropriate. Minimizing compression distortion increases the O-ring’s service life.

Installation Process: Key Details to Note

During the gasket installation, pay attention to the following details.

Valve Status: The valve should be in the open position before installing the gasket to prevent any damage or sealing issues during installation.
Avoid Pushing or Pulling the Gasket: Ensure the gasket is properly aligned with the sealing surface, and avoid pushing or pulling it during installation to prevent shifting or damage.
Gasket Position: For bolted or threaded connections, the gasket should be installed flat and level. Particularly for threaded valves, avoid using pipe wrenches; instead, use a proper wrench to tighten.

Setting the Correct Pressure and Pre-Tension Force

The right pre-tension force is essential for ensuring the gasket functions properly. When installing the gasket, consider the following.

Understand Operating Conditions: Before setting the pre-tension force, understand the valve’s working pressure, temperature, and media properties to ensure that the selected gasket material and pre-tension force are suitable.
Set Appropriate Pre-Tension Force: The pre-tension force should be sufficient to prevent leakage during the pressure test, but it should be kept as low as possible to extend the gasket's lifespan.
Leave Some Play: After tightening the gasket, ensure the valve connections have some pre-tension clearance to accommodate any potential leakage from the gasket, preventing significant leakage issues.

Handling High and Low Temperatures

Valves may operate in environments with varying temperatures, requiring special attention to the gasket and bolts’ reactions.

High Temperature Conditions: At high temperatures, bolts may experience creep, leading to gasket leakage. In such cases, thermal tightening is necessary to compensate for the stress relaxation in the bolts and deformation of the gasket.
Low Temperature Conditions: In low temperatures, bolts may shrink. Cold loosening treatments should be applied to prevent bolts from being over-tightened, which could cause gasket seal failure.

Installation of Special Sealing Gaskets

Different sealing methods require specific installation techniques. Common special sealing gaskets include:

Liquid Sealing Gaskets: When using liquid sealing gaskets, the sealing surfaces should be cleaned or treated. For flat sealing surfaces, they may need to be ground to ensure a tight fit. Apply adhesive evenly and remove any air pockets. The adhesive layer thickness should generally be between 0.1 and 0.2mm.
Thread Sealing: For threaded valve connections, when using PTFE (Teflon) sealing tape, the tape should be thinned and applied evenly over the threads, ensuring it covers the threads and forms a wedge shape to avoid leakage.

Post-Installation Inspection and Adjustment

After installing the gasket, a thorough inspection should be conducted to ensure sealing and connection reliability.

Check Gasket Sealing: Confirm that the gasket is tightly in contact with the sealing surface, with no loose or leaking spots.
Adjust Pre-Tension Force: Based on the pressure test, adjust the pre-tension force to ensure the valve remains sealed and can withstand the operating pressure.

Conclusion

Installing valve sealing gaskets is not a complex task, but every detail must be handled with care to ensure proper sealing and the long-term stable operation of the valve. Correct installation not only improves the valve's lifespan but also reduces maintenance costs and minimizes leakage risks. Operators should keep these key points in mind, carefully checking each step to ensure the valve operates safely and reliably.