Construction Procedure and Characteristics of Corrosion Protection for Large-Diameter Flanges
Large-diameter flanges are a type of flange widely used in various industries, including machinery, chemical, wind power, sewage treatment, and more. They have received praise and favor from users. Large-diameter flanges have extensive applications, and their production processes can be categorized as rolling and forging. Super-large flanges can only be rolled and are made from carbon steel, stainless steel, and alloy steel. Different flange components exhibit different performance characteristics tailored for various occasions and spaces, resulting in different effects.
Principles and Requirements for Assembling Large-Diameter Flanges
For paired flange assembly, the bolt holes for mounting the flange should align with the corresponding bolt holes of the fixed flange and be parallel to the fixed flange. Deviations should not exceed 1.5‰ of the flange's outer diameter, and no more than 2mm.
Use a 90-degree square to check and correct the flange's position from the left and right directions, and perform spot welding on the flange after points three and four to secure it in place.
When selecting matching flanges for equipment or valve components, ensure that the flanges on the original equipment or valve components match the connection size of the flanges used in the pipeline.
When assembling slip-on flanges, insert the pipe end into the thickness of 2/3 of the flange's inner diameter, then perform spot welding between the flange and the pipeline. If it's a horizontal pipeline, welding should be done from above. Use a 90-degree square to inspect and correct the flange's position from different directions to ensure that the sealing surface is perpendicular to the pipeline's centerline, then perform spot welding below the weld.
Clean the flange surface, especially the sealing surface, before assembling the flanges.
Corrosion Protection Construction Procedure and Characteristics for Large-Diameter Flanges
Fill the gap between large-diameter flanges with a corrosion-inhibiting sealing compound. Paste (transparent) tape around the outer edge of the flange to prevent the outer edge from getting dirty when injecting the corrosion-inhibiting sealing compound. Seal and fill the gaps between flanges with a corrosion-inhibiting sealing compound to ensure a proper fill.
After filling the gaps with the corrosion-inhibiting compound, use an oil putty knife to smooth the surface in a circumferential direction, making the gap and flange edge on the same plane. Remove the tape on both sides.
If using flange anti-corrosion paste, cut it into narrow strips with a knife according to the width of the gap, then fill the gap directly by hand, pressing down as you go.
Gap and surface treatment for large-diameter flanges. Use a brush to remove floating rust and corrosion on the flange gaps and bolts. Clean the flange gaps with compressed air. If using chemical rust removers, assess whether the chemical rust removers will affect the flange seal. If uncertain, it is recommended not to use chemical methods. Wipe the flange surface with sandpaper or cotton yarn to meet the ST2 standard requirements.
Wrap external protective tape (choose as needed). Select the appropriate color of external protective tape based on the location. Choose the tape width as 50 mm or 100 mm based on the width of the flange. Wrap one round of external protective tape over the anti-corrosion tape, leaving 2-3mm wide anti-corrosion tape on both sides during wrapping.
Wrap the anti-corrosion tape. If the flange width is 50-100 mm, use a 50 mm × 5 m anti-corrosion tape. If the flange width is greater than 100 mm, use a 100 mm × 10 m anti-corrosion tape. Wrap the entire round of anti-corrosion tape around, ensuring there is no axial displacement exceeding the gap between the flanges and having a 100 mm overlap at the end. If the width of the anti-corrosion tape is less than the width of the flange and it is necessary to prevent corrosion of the flange, you can wrap it on both sides until the outer edge of the flange is covered by the anti-corrosion tape.
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