Connection Performance Requirements for Flanged Fittings Under AWWA C 110
Nov. 12, 2025
1. Sealing Performance Requirements
Sealing performance is a core indicator of flange connections. The AWWA C 110 standard requires that fittings shall be free of leakage and sweating under rated working pressure.
· Hydrostatic sealing test: The test pressure is 1.5 times the nominal pressure, and the pressure holding time is not less than 30 minutes. During the test, there shall be no visible leakage at the flange sealing face, the joint between the fitting body and the flange, and the pressure drop shall not exceed 5% of the test pressure.
· Vacuum sealing test: For fittings used under negative pressure conditions, a vacuum test with a vacuum degree of not less than 0.08MPa shall be conducted, with a pressure holding time of 20 minutes. No air infiltration is considered qualified.
2. Pressure-Bearing Performance Requirements
Flanged fittings shall have sufficient pressure-bearing strength to withstand the working pressure and instantaneous pressure impact of the pipeline system.
· Hydrostatic strength test: The test pressure is 2.0 times the nominal pressure, and the pressure holding time is not less than 15 minutes. The fitting body, flange neck, and welds shall not show damage such as cracking or plastic deformation, and the pressure drop shall be controlled within the allowable range.
· Fatigue strength requirement: For fittings that frequently experience pressure fluctuations, a 1000-cycle pressure test (pressure range from 0 to nominal pressure) shall be conducted. After the test, there must be no leakage or structural damage to ensure reliability during long-term use.
3. Connection Stiffness Requirements
Flange connection components must possess adequate stiffness to prevent loosening due to pipeline vibration and temperature fluctuations during long-term operation. The standard stipulates that, under rated working pressure, the axial displacement of the flange connection should not exceed 0.2 mm, while the radial displacement should not exceed 0.1 mm. The stability of the connection after bolt tightening is verified through a torque test. The tightening torque for the bolts must adhere to the values specified in the standard, and there should be no warping or deformation of the flange sealing surface after tightening.
4. Conclusion
The AWWA C110 standard outlines clear and stringent requirements for the connection performance of flanged fittings. This standard serves as an essential technical foundation for ensuring the safe and stable operation of pipeline systems. By specifying strict connection performance criteria, it guarantees the system's tightness, pressure-bearing capacity, and stiffness.
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