Orifice Weld Neck Flanges

Orifice Weld Neck Flanges are used instead of the standard pipe flanges when orifice plate or flow nozzle is used.

Orifice Weld Neck Flanges

The basic purpose for this is to measuring the flow rate of either gases or liquids in the respective pipeline. These flanges are used in various industrial applications and are available in various sizes and materials.

Standards, Dimensions & Weight

Weld Neck Orifice Flanges are butt-welded into the pipeline. The inside diameter (bore diameter) of the pipe should be specified when ordering. Weldneck orifice flanges are available in ANSI classes 300, 600, 900, 1500 and 2500.

They are not available in ANSI 150 sizes because the thickness of ANSI 150 flanges are not enough to allow for drilling pressure taps.

  • 300# Slip-On Orifice Flange
  • 300# Weld Neck Orifice Flange
  • 600# Weld Neck Orifice (raised face and RTJ ring type joint) Flange
  • 900# Weld Neck Orifice (raised face and RTJ ring type joint) Flange
  • 1500# Weld Neck Orifice (raised face and RTJ ring type joint) Flange
  • 2500# Weld Neck Orifice (raised face and RTJ ring type joint) Flange

ASME B1.20.1 covers dimensions and gaging of NPT pipe threads for general purpose applications.

Type: Orifice Weld Neck Flange

Materials: Carbon Steel, Alloy Steel, Stainless Steel

  • ASTM A105
  • A350 LF1, LF2 CL1/CL2, LF3 CL1/CL2
  • A516.60
  • A694 (F42, F46, F48, F50, F52, F56, F60, F65, F70)
  • A182 F304/304L, F316/316L, F316H, F310, F321
  • A182 F11, F22

Welding neck and slip-on Orifice Flanges in class 300 only are conform to ANSI B16.36. Other types and pressure classes are available and sizes larger than 24" will conform to MSS SP-44. Unions are furnished with gaskets, carbon steel jack screws, pipe plugs for the tapped openings, and bolting per ANSI B16.5.

Tolerances and ratings follow ANSI B16.5 except for the following:
Tolerance for the tap-hole-to-face dimensions
  • ± 0.02" for flanges < 4" nominal size
  • ± 0.03" for flanges ≥ 4" nominal size
Tolerance for welding neck flange bores
  • ± 0.5% of nominal size

They are made in pressure classes 300 through 2500 lb.; in carbon steel, stainless steel and alloy materials; and raised face or ring joint.


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