I. Installation Procedure
1. Pre-installation Preparation
Material inspection: Verify that the specifications and materials of the compression flange, sealing gasket, and bolts comply with the design requirements. Check whether the sealing surface of the flange is flat, without scratches or rust, and ensure that the gasket is undamaged and not aged.
Tool Preparation: Prepare a torque wrench, compression tools, level, square, wire brush, lubricant (such as molybdenum disulfide), etc.
Pipe straightening: Ensure that the axis of the pipe is aligned with the centerline of the flange. The deviation must comply with the standards (for DN ≤ 300, the axial deviation should be ≤ 1mm; for DN > 300, ≤ 2mm).
2. Alignment of Flange and Pipeline
Installation positioning: Place the flange vertically onto the end of the pipe. Use a level or angle gauge to check the perpendicularity of the flange sealing surface to the pipe axis (deviation ≤ 1°).
Spot welding fixation: Perform symmetrical spot welding at 2-3 locations to prevent welding deformation. The spot welding length should be approximately 2-3 times the wall thickness.
3. Welding and Sealing Surface Treatment
Symmetrical welding: Start from the free end of the flange and weld in segments in a symmetrical sequence (such as 12 o'clock → 6 o'clock → 3 o'clock → 9 o'clock) to reduce thermal deformation.
Weld inspection: After welding is completed, inspect the appearance of the weld (for no pores, cracks, or slag inclusions). If necessary, conduct non-destructive testing (such as X-ray or penetrant testing).
Clean the sealing surface: Use a wire brush, sandpaper or a special cleaner to remove oil stains, rust, and burrs from the sealing surface of the flange.
4. Gasket Installation
Gasket positioning: Place the gasket centrally on the sealing surface of the flange, avoiding any skewing or folding.
Special gasket treatment: For metal wound gaskets, ensure that the inner and outer rings are tightly in contact with the sealing surface of the flange without any warping; for rubber gaskets, check the uniformity of thickness to avoid using gaskets that are aged or cracked.
5. Bolt Installation and Tightening
Thread insertion: Insert the bolt vertically into the bolt hole of the flange, with the nut on the other side. Ensure that the threads are clean and undamaged.
Initial tightening: Use your hands or a wrench to symmetrically tighten the nuts, allowing the gasket to be slightly compressed, but do not exert excessive force.
Cross fastening:
Low-pressure connection: Tighten in 2-3 stages following the diagonal pattern, with the torque increasing by 30%-50% each time.
High-pressure connection: Use a hydraulic wrench and tighten in stages according to the torque values recommended by the manufacturer (e.g. 50% initially → 75% in the middle → 100% at the end).
Final inspection: Ensure that all bolt tightening torques are consistent, and the deviation of the flange surface parallelism is ≤ 0.5mm.
II. Maintenance Points
1. Daily inspection
Visual inspection: Regularly check for any leakage, corrosion, deformation or cracks at the flange connection area, whether the flange sealing surface is intact, and whether the bolts are loose or rusted.
Sealing performance inspection: Check the sealing areas for any leaks by visual inspection or using leak detection tools (such as soapy water).
2. Tightening and Adjustment
Re-tightening of bolts: Regularly re-tighten the connecting bolts according to the specified torque to prevent loosening and resulting leakage.
Parallelism correction: If it is found that the sealing surface of the flange is not parallel, the heat bending method (heating the pipe with an oxygen-acetylene flame and then bending it) or the mechanical correction method can be used to adjust.
3. Gasket Replacement
Replacement conditions: The gasket needs to be replaced when it becomes aged, damaged or when the medium parameters change.
Replacement steps:
Loosen the nut and separate the flange.
Remove the remaining old gaskets and clean the sealing surfaces.
Install the new gasket and make sure it 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 the flange connection parts in outdoor or humid environments.
Underground flange: If the flange needs to be buried, a inspection well must be set up and anti-corrosion measures (such as sacrificial anode protection) should be taken.
5. Lubrication and Maintenance
Lag bolt lubrication: Apply lubricant (such as molybdenum disulfide) to the threaded parts of the lag bolts to prevent rusting and seizing.
Lubrication of rotating components: Add lubricants to the rotating parts of equipment such as valves (such as valve stems and bearings) to ensure smooth operation.
III. Key Considerations
1. Material compatibility: The materials of the flange, gasket, and bolts should be compatible with the medium (for example, for highly corrosive media, stainless steel or Hastelloy alloy should be used).
2. Temperature influence: In high-temperature conditions, thermal expansion needs to be taken into account. Gaps should be reserved or spring washers can be used.
3. Avoid excessive tightening: Excessive torque may cause the gasket to collapse or the flange to deform. It is necessary to strictly follow the standards.
4. Regular maintenance: Conduct regular inspections of bolt looseness during operation. In high-temperature or vibration conditions, the inspection frequency should be shortened.
5. Handling of Special Circumstances:
Vacuum system: Special vacuum gaskets (such as graphite composite gaskets) must be used.
Low-temperature system: Avoid using rubber gaskets and instead use polytetrafluoroethylene or metal gaskets.
