What causes flange leakage andHow to prevent flange leaks in piping systems?

Common causes of flange leaks:

1. Misalignment: Misalignment refers to a situation where the pipe and flange are not aligned, but the two flanges are not concentric, preventing the bolts from freely entering the bolt holes. Some may choose to enlarge the holes or use smaller bolts, but this will reduce the clamping force of the flange.

2. Misalignment: Misalignment refers to a situation where the pipe and flange are not aligned, and the flange surfaces are not parallel or concentric. If the internal medium pressure exceeds the load pressure of the gasket, leakage will occur.

3. Corrosion: Long-term corrosion of the gasket by corrosive media can cause chemical changes in the gasket, making it soft and losing its clamping force.

4. Misalignment of bolt holes: Misalignment of bolt holes is relatively easy to understand. It refers to the situation where the pipe and flange are concentric, but the distance between the corresponding bolt holes on the two flanges is too large, causing stress on the bolts. Over time, this can cause the bolts to break, leading to seal failure.

How to prevent flange leaks in piping systems:

1. Confirm pipe size and wall thickness
Before selecting a flange, confirm the pipe’s nominal size (Le NPS) and wall thickness (wall thickness rating). The flange must be compatible with the pipe size.

2. Check the flange dimensions
Measure the flange dimensions, including the outer diameter (OD), inner diameter (ID), and thickness. Ensure these dimensions meet your application requirements and are compatible with the gaskets and bolts you will use.

3. Ensure proper alignment
When installing flanges on pipes, proper alignment is essential. For weld neck flanges, ensure the flange is centred on the pipe end. For slip-on flanges, slide them onto the pipe until they reach the desired position. For socket weld flanges, insert the pipe into the socket until it reaches the bottom.

4. Clean the pipe and flange
Thoroughly clean the pipe end and flange surface, removing any dirt, rust, scale, or burrs. Clean surfaces ensure better sealing performance and prevent gasket damage.

5. Use the correct gasket
Select a gasket compatible with the flange face type and the fluid, temperature, and pressure in the system. The gasket should have appropriate dimensions and material.

6. Apply sealant or tape (if required)
For threaded flanges, apply thread sealant or wrap tape around the male threads to ensure a tight seal. For other flange types, apply a layer of anti-seize compound to the bolt threads to prevent seizing and facilitate future disassembly.

7. Tighten the flange bolts
– Place the gasket on the raised surface of one of the flanges.
– Assemble the bolts, nuts, and gasket.
– Insert the bolts through the bolt holes in the flanges.
– Hand-tighten the nuts to pull the flanges together and compress the gasket.
– Use a torque wrench to tighten the bolts to the specified torque value, typically using a cross-tightening method to ensure even distribution of force on the gasket.

8. Inspect the connection
After the bolts are secured, inspect the flange and pipe connection for misalignment, damage, or missing components. Ensure the gasket is properly seated and the bolts are tightened to the correct torque.

9. Conduct a pressure test
After the flange is installed, perform a pressure test to verify there are no leaks at the connection. This involves pressurising the system to the specified test pressure and checking for leaks.

10. Regular maintenance
Regularly inspect and maintain flange connections to ensure they remain leak-free and function properly. This includes periodically retightening bolts and replacing worn gaskets.

By following these steps, you can ensure that flanges are properly installed and functioning correctly within the piping system. Adhering to industry standards and manufacturer guidelines during installation is critical for maintaining safety and system integrity.Translated with DeepL.com (free version)

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