Flange Standards: ANSI/ASME B16.5 Pipe Flanges and Flanged Fittings (covering pressure ratings Class 150 to Class 2500); ASME B16.47 Large Diameter Steel Flanges (Class 75 to Class 900).
Material Standards: Carbon steel (ASTM A105/A516), stainless steel (ASTM A182 F304/F316), alloy steel (ASTM A350 LF2), etc., meeting requirements for different media corrosiveness and temperature conditions.
I. Standards & Specification Parameters
1. Executive Standards
●Flange Standards: ANSI/ASME B16.5 Pipe Flanges and Flanged Fittings (covering pressure ratings Class 150 to Class 2500); ASME B16.47 Large Diameter Steel Flanges (Class 75 to Class 900).
●Material Standards: Carbon steel (ASTM A105/A516), stainless steel (ASTM A182 F304/F316), alloy steel (ASTM A350 LF2), etc., meeting requirements for different media corrosiveness and temperature conditions.
2. Key Parameters
●Pressure Rating: Class 150 (PN2.0MPa), Class 300 (PN5.0MPa), Class 600 (PN11.0MPa), etc., corresponding to different thicknesses and sealing face designs.
●Nominal Pipe Size (NPS): 1/2" (15mm) to 60" (1500mm), compatible with outer diameters of seamless or welded pipes (e.g., NPS 2" corresponds to pipe outer diameter 60.3mm).
●Sealing Face Type: Common types include Flat Face (FF) and Raised Face (RF); Male-Female Face (MFM) or Tongue-Groove Face (TG) are available for Class 600 and above to enhance high-pressure sealing performance.
●Flange Thickness: Increases with pressure rating. For example, NPS 4" Class 150 flange has a thickness of 12.7mm, while NPS 4" Class 300 flange has a thickness of 19.1mm.
II. Material Selection & Application Scenarios
1. Materials & Properties
●Carbon Steel (ASTM A105): Low cost, high strength, suitable for ambient temperature, low-pressure, non-corrosive media (e.g., tap water, natural gas). Temperature range: -29℃ to 427℃.
●Stainless Steel (ASTM A182 F304): Contains Cr-Ni alloy, resistant to acid and alkali corrosion (pH 2-12), applicable to chemical solutions and seawater treatment systems. Maximum temperature resistance: 870℃.
●Alloy Steel (ASTM A350 LF2): Excellent low-temperature toughness (impact energy ≥27J at -46℃), used in low-temperature pipelines (e.g., LNG, liquid nitrogen) or high-temperature high-pressure steam systems (e.g., NPS 10" Class 900 flange).
2. Application Scenarios
●Carbon Steel Flanges: Urban water supply and drainage, heating pipelines, etc.
●Stainless Steel Flanges: Atmospheric and vacuum distillation units in refineries, reactor feed pipelines, etc.
●Alloy Steel Flanges: Circulating water systems in thermal power plants, etc.
III. Manufacturing Process & Quality Control
1. Production Process
●Raw Material Inspection: Spectral analysis to verify material composition (e.g., Cr content ≥18% for 304 stainless steel); ultrasonic testing (UT) to eliminate internal cracks.
●Forming: Carbon steel flanges adopt open die forging (NPS ≤12") or steel plate cutting and welding (NPS ≥14") to ensure no folding defects in the flange neck.
●Machining: CNC lathe processing of sealing faces (flatness ≤0.05mm/m) and bolt holes (positional tolerance ±0.3mm); threaded holes comply with ASME B1.1 Unified National Coarse (UNC) thread standard.
●Heat Treatment: Carbon steel flanges undergo normalization (holding at 890-920℃ followed by air cooling) to eliminate welding stress; stainless steel flanges undergo solution annealing (water quenching at 1050℃) to enhance corrosion resistance.
2. Quality Standards
●Non-Destructive Testing (NDT): 100% magnetic particle testing (MT) for flange neck welds; ultrasonic testing (UT) required for high-pressure flanges (Class 1500).
●Dimensional Inspection: Flange outer diameter deviation ±1.6mm; bolt circle diameter (BCD) tolerance ≤±0.76mm (for NPS 10" and above).
●Pressure Testing: Sampling hydrostatic test before delivery (1.5 times design pressure, 30-minute pressure holding with no leakage) or helium mass spectrometry leak detection (for vacuum system flanges).
IV. Comparison Between Slip-On Flange (SO) and Weld Neck Flange (WN)
Index | Slip-On Flange (SO) | Weld Neck Flange (WN) |
Welding Difficulty | Low (outer fillet weld) | High (full penetration groove weld, X-ray inspection required) |
Applicable Pressure | ≤Class 600（PN11MPa） | ≥Class 300（up to Class 2500） |
Cost | Low (less material, simple processing) | High (long neck structure, high welding cost) |
Sealing Performance | Medium (relies on gasket compression) | High (flange neck fused with pipe, no dead ends) |
Typical Scenarios | Low-pressure water systems, compressed air pipelines | High-pressure steam pipelines, main oil and gas transmission pipelines |
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