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Buttweld Fittings General

Buttweld Fittings General

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Buttweld Fittings General


A pipe fitting is defined as a part used in a piping system, for changing direction, branching or for change of pipe diameter, and which is mechanically joined to the system. There are many different types of fittings and they are the same in all sizes and schedules as the pipe.

Fittings are divided into three groups:
  • Buttweld (BW) fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43.
  • Socket Weld (SW) fittings Class 3000, 6000, 9000 are defined in the ASME B16.11 standards.
  • Threaded (THD) fittings Class 2000, 3000, 6000 are defined in the ASME B16.11 standards.
Image of most used buttweld fittings.

Applications of Buttweld Fittings
A piping system using buttweld fittings has many inherent advantages over other forms.
  • Welding a fitting to the pipe means it is permanently leakproof
  • The continuous metal structure formed between pipe and fitting adds strength to the system
  • Smooth inner surface and gradual directional changes reduce pressure losses and turbulenceand minimize the action of corrosion and erosion
  • A welded system utilizes a minimum of space