Flange connections are commonly used in industrial assemblies, often employed for connecting pipes, pressure vessels, and other heavy-duty workloads. And they are typically installed at nodes in a pipeline, where they bear higher pressure compared to other parts of the pipe.

Therefore, specific techniques and steps need to be taken during flange installation or connection. So, how exactly are flanges installed and connected? Let's find out!

5 Secrets of Flange Connections

1. Gasket Installation >> 

After installing two bolts, a seal is inserted between the two flange surfaces, followed by the installation of a third bolt positioned approximately 120 degrees from the other two. This effectively reduces the gap between the two flanges and helps prevent potential leaks.

2. Gradual Tightening and Aligning of the Gasket >>

The flange has a gasket placed between its surfaces, and the nuts are hand-tightened until they contact the supporting surface. After aligning the gasket, the installed bolts are slightly tightened. It is essential to carry out this step; otherwise, the flange gasket will not fit properly, leading to possible pipe leakage.

3. Installation of the Remaining Bolts and Gradual Tightening >> 

Hand-tighten the nuts until they contact the supporting surface, and then symmetrically and evenly tighten the bolts with a torque wrench. The tightening process can be divided into several steps: 25%, 50%, 75%, and finally 100% of the torque value. Avoid attempting to torque them all the way to 100% in one go, as this could potentially damage the flange's structure.

4. Check Flange Parallelism (at 50% torque) >>

Use calipers or a dial gauge to measure the flange parallelism, ensuring it meets the required specifications. Afterward, continue tightening the bolts until they reach 100% torque to complete the fastening. At this point, each bolt should be further tightened clockwise until they all reach the final specified torque value. Finally, check the flange's parallelism; if it doesn't meet the requirements, further adjustments are necessary.

5. Nut Locking >>

Tap the locking gasket or other nuts to prevent loosening.

Bonus: Precautions for Flange Connection/Installation

1. Flange Cover

The sealing surface must be cleaned and free from radial scratches, severe corrosion, and excessive deformation. (Avoid using a screwdriver to clean the flange cover.)

2. Flange Installation Quality Check

Check parallelism, concentricity, clearance, flatness, and hole alignment. If any of the above checks do not meet the requirements, adjustments can be made through grinding, turning, and thermal correction. If necessary, flanges and pipes should be replaced.

3. Tools

Electric torque wrench, hydraulic torque wrench, bolt extender.

4. Others

Gasket cutting tool, slide bar, flange separator, etc.
The above provides some tips and insights into flange connection. I hope this article is helpful to you.

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