A. Dimensional Standards available for pipe fittings
B. Classification of pipe fittings based on end connections
1. Socket weld/ Screwed end pipe fittings
2. Butt weld end pipe fittings
3. Flanged end pipe fittings
The components used in piping system post details about the various components. These are used changing a direction, joining different sizes of pipes, taking a branch-off, etc. are generally referred to as Pipe Fittings.
Different Dimensional Standards available for pipe fittings
ASME B 16.1-Cast Iron Pipe Flanges and Flanged Fittings
ASME B 16.3-Malleable-Iron Threaded fittings
ASME B 16.4-Grey Iron Threaded fittings
ASME B 16.5-Pipe Flanges and Flanged fittings
ASME B 16.9-Factory-Made Wrought steel Butt welding
ASME B 16.11-Forged Fitting, Socket welding and Threaded
ASME B 16.28-Wrought Steel Butt welding Short Radius Elbows and Returns
ASME B 16.42-Ductile Iron Pipe Flanges and Flanged Fittings
ASME B 16.49-Buttwelding Induction Bends for Transportation and Distribution System
BS 1640-Buttweld Fittings
BS 3799-Socket weld and Screwed end fittings
Pipe fittings classification based on the end connections
1. Socket weld/ Screwed end fittings:
Dimensional standard-AME B 16.11/BS 3799 Sizes –upto 4” NPS only.
These fittings are designated by pressure class which represents the maximum cold non-shock working pressure and the thickness corresponding to that class.
The pressure classes used to designate these fitting are:
2000 # Class: Applicable for Screwed fittings only, Thickness-SCH 80 or XS
3000 # Class: Socket weld fittings, Thickness-SCH 80 or XS & Screwed fittings, Thickness-SCH 160
6000 # Class: Socket weld fittings, Thickness-SCH 160 & Screwed fittings, Thickness-SCH XXS
9000 # Class: Applicable for Socket weld fittings only, Thickness-SCH X XS
The screwed ends for fitting are generally with Taper threads. These threads can be Nominal Pipe threads (NPT) or British Screwed Pipe Threads (BSPT).
The socket weld/screwed fittings are generally forged.
The different grades of material used for these fittings are:
ASTM A105-Forged Carbon Steel
ASTM A181-Forged Carbon Steel for General purposes
ASTM A182-Forged Alloy Steel and Stainless Steel
ASTM A234-Wrought Carbon Steel and Alloy Steel pipe fittings for moderate and elevated temperatures
ASTM A350-Forged Alloy Steel for Low temperature Services
2. Butt weld end fittings:
Dimensional standard-AME B 16.9/ AME B 16.28/BS 1640
These are fittings are with Butt welded ends.
They are available in both seamless and welded type. They are usually with the same thickness as pipe.
The different grades of material used for these fittings are:
ASTM A234- Carbon Steel Fittings for Moderate & High temperature Services.
ASTM A403- Austenitic Stainless Steel Pipe Fittings.
ASTM A420- Carbon Steel & Alloy Steel Pipe Fittings for Low temperature Services.
3. Flanged end fittings:
Dimensional standard-AME B 16.5/BS 1650
These kind of fitting have both ends Flanged and are used in places where welding is not allowed.
They are cast fittings.
The different grades of material used for these fittings are:
ASTM A216- Carbon Steel Casting.
ASTM A403- Stainless Steel Casting.
ASTM A420- Alloy Steel Casting.
Related useful sources: