1、 Installation process

1. Preparation before installation

Material inspection: Confirm that the specifications and materials of the clamping flange, sealing gasket, and bolt meet the design requirements. Check whether the flange sealing surface is flat, free of scratches or rust, and whether the gasket is damaged or aged.

● Tool preparation: Prepare torque wrenches, clamping tools, level gauges, angle gauges, wire brushes, lubricants (such as molybdenum disulfide), etc.

● Pipeline straightening: Ensure that the pipeline axis is consistent with the flange centerline, and the deviation must meet the standard (such as when DN ≤ 300, axial deviation ≤ 1mm; when DN>300, ≤ 2mm).

2. Flange and pipeline alignment

● Positioning installation: Insert the flange vertically into the end of the pipeline, and use a level or angle gauge to check the perpendicularity of the flange sealing surface to the pipeline axis (deviation ≤ 1 °).

● Spot welding fixation: Symmetrically spot weld 2-3 places to prevent welding deformation, and the spot welding length is about 2-3 times the wall thickness.

3. Welding and sealing surface treatment

Symmetrical welding: Starting from the free end of the flange, weld in sections in a symmetrical order (such as 12 o'clock → 6 o'clock → 3 o'clock → 9 o'clock) to reduce thermal deformation.

● Weld seam inspection: After welding is completed, inspect the appearance of the weld seam (without pores, cracks, slag inclusions), and perform non-destructive testing (such as X-ray, penetrant testing) if necessary.

● Cleaning the sealing surface: Use a wire brush, sandpaper, or specialized cleaning agent to remove oil stains, rust, and burrs from the flange sealing surface.

4. Gasket installation

● Gasket positioning: Place the gasket in the center on the flange sealing surface to avoid deviation or folding.

Special gasket treatment: The metal wrapped gasket needs to ensure that the inner and outer rings are in contact with the flange sealing surface without warping; The thickness uniformity of the rubber pad needs to be checked to avoid using aged or cracked gaskets.

5. Bolt installation and fastening

Bolt insertion: Insert the bolt vertically into the flange bolt hole, with the nut on the other side, ensuring that the thread is clean and undamaged.

● Initial tightening: Tighten the nut symmetrically by hand or wrench to compress the gasket initially, but without excessive force.

● Cross fastening:

Low voltage connection: Tighten gradually 2-3 times in diagonal order, increasing torque by 30% -50% each time.

High voltage connection: Use a hydraulic wrench to tighten in stages according to the manufacturer's recommended torque values (such as initial 50% → middle 75% → final 100%).

Final inspection: Confirm that all bolt tightening torques are consistent, and the parallelism deviation of the flange surface is ≤ 0.5mm.

2、 Maintenance points

1. Daily inspection

● Appearance inspection: Regularly check for leaks, corrosion, deformation, or cracks in the flange connection parts, whether the flange sealing surface is intact, and whether the bolts are loose or corroded.

Sealing performance inspection: Check for leaks in the sealing area by visual inspection or using leak detection tools (such as soapy water).

2. Tightening and adjustment

● Bolt tightening: Regularly tighten the connecting bolts to the specified torque to prevent loosening and leakage.

● Parallelism correction: If it is found that the flange sealing surface is not parallel, the hot bending method (heating the tube with an oxyacetylene flame and bending it) or mechanical correction method can be used to adjust it.

3. Gasket replacement

● Replacement conditions: The gasket needs to be replaced when it is aging, damaged, or when the medium parameters change.

● Replacement steps:

Loosen the nut and separate the flange.

Remove the old gasket residue and clean the sealing surface.

Install the new gasket and ensure its position is centered.

Re tighten the bolts according to the specified torque.

4. Anti corrosion treatment

Coating protection: Apply anti rust paint or anti-corrosion coating to flange connection parts in outdoor or humid environments.

Buried flange: If the flange must be buried underground, inspection wells should be set up and anti-corrosion measures should be taken (such as sacrificial anode protection).

5. Lubrication and maintenance

Bolt lubrication: Apply lubricant (such as molybdenum disulfide) to the threaded part of the bolt to prevent rusting and biting.

Lubrication of rotating parts: Add lubricant to the rotating parts of valves and other equipment (such as valve stems and bearings) to ensure flexible operation.

3、 Key precautions

1. Material matching: The flange, gasket, and bolt materials should be compatible with the medium (such as stainless steel or Hastelloy for highly corrosive media).

2. Temperature effect: Under high temperature conditions, thermal expansion should be considered, and gaps should be reserved or spring washers should be used.

3. Avoid excessive tightening: Excessive torque may cause gasket crushing or flange deformation, and strict adherence to standards is required.

4. Regular maintenance: Regularly check the loosening of bolts during operation, and shorten the inspection cycle under high temperature or vibration conditions.

5. Special working condition handling:

Vacuum system: Special vacuum gaskets (such as graphite composite gaskets) are required.

Low temperature system: Avoid using rubber pads and choose polytetrafluoroethylene or metal gaskets.