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ASME B16.9 Specification for Butt Welded Fittings

ASME B16.9 specification is designed for butt welded fittings applied in industrial construction pipelines. Including elbow, tee, cross, cap, reducer, and etc.

Standard Scope

The standard includes specifications of NPS 1/2 to NPS 48 (DN15-DN1200) factory-made wrought butt welded pipe fittings overall dimensions, tolerances ratings, test methods and markings.

Special Fittings

Special fittings here refers to special sizes, forms and tolerances that agreed between buyer and manufacturer.

Fabricated Fittings

Fabricated laterals and other fittings by circumferential or intersection welds are considered pipe fabrication could not apply this standard.


Units under ASME B16.9 shall be stated in both SI (Metric) and U.S. Customary units. Designation for size is NPS.

Reference Standards

It is not considered practical to identify the specific edition of each standard and specification in the individual references. A product made comply with a prior edition of referenced standards and in all other respects conforming to this standard will be considered complied.

  • ASME B16.5: Pipe Flanges and Flanged Fittings: NPS 1∕2 Through NPS 24 Metric/Inch Standard
  • ASME B16.25: For Buttwelding Ends
  • ASME B31: Code for Pressure Piping
  • ASME B31.3: Process Piping
  • ASME B36.10M, Welded and Seamless Wrought Steel Pipe
  • ASME B36.19M, Stainless Steel Pipe
  • ASME Boiler and Pressure Vessel Code
  • ASTM A234/A234M-17, Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service
  • ASTM A403/A403M-16, Specification for Wrought Austenitic Stainless Steel Piping Fittings
  • ASTM A420/A420M-16, Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for LowTemperature Service
  • ASTM A815/A815M-14e1, Specification for Wrought Ferritic, Ferritic/Austenitic and Martensitic Stainless Steel Piping Fittings
  • ASTM A960/A960M-16a, Specification for Common Requirements for Wrought Steel Piping Fittings
  • ASTM E29-13, Practice for Using Significant Digits in Test Data to Determine Conformance With Specifications
  • ASTM B361-16, ASTM B363-14, ASTM B366/B366M-17: For other material metals. (Aluminum, Titanium, Nickel, and alloy).
  • ISO 6708:1995, Pipework components — Definition and selection of DN (nominal size)
  • ISO 9000:2015, ISO 9004:2009​.

Codes and Regulations

A fittings sued under ASME Boiler and Pressure Vessel Code (BPVC), the ASME code for pressure piping, or a governmental regulation is subject to any limitation of that code or regulation. It includes any maximum temperature limitation or rule governing the use of material at low temperature.

Welding Requirements

ASME 16.9 didn't specify the welding specifications, so it is outside this scope.

Pressure Ratings Designation

Standardized designations for flanges as per ASME B16.5 referenced in this standard are Class 150, 300, 600, 900, 1500 and 2500.


Fittings under ASME B16.9 are expressed in NPS. It is related to reference nominal diameter, DN, used in international standards. Typically as below:










1 1/4


1 1/2




2 1/2





For NPS > 4, the equivalent is DN = 25 X NPS.


Standard marking

Each pipe fitting marks permanently , indicating the following content:
The name or trademark of the manufacturer
Material identification mark (ASTM or ASME level symbol)
Wall thickness serial number or nominal wall thickness
Specifications – Engineering pipe diameter (NPS) related to end connection should be used
Compliance – standard and special pipe fittings


When the specifications of the pipe fitting are all not allowed to mark, the identification mark may be omitted in the reverse order.

The depth of steel stamp

When using the steel stamp, it should not too deep or too sharp cause cracking or to reduce the wall thickness to less than the minimum allowance of wall thickness.

Compliance - Standard Fittings and Special Fittings

Standard Fittings: Means the fittings manufactured comply with this standard, including all dimensional requirement, is certified by a prefix "WP" in the material grade designation.

Special fittings: The fittings manufactured with this standard, except that dimensional requirements are as agreed between the purchaser and manufacturer, is certified by a supplementary suffix to the material grade designation marking as follows:

  • “S58” of ASTM A960 applies for fittings of ASTM A234, A403 and A420.
  • “S8”  of fittings in ASTM A815.
  • “SPLD” of fittings comply with ASTM B361, B363, and B366.

Material Types Referred

Wrought fittings covered by this Standard shall be in accordance with ASTM A234, ASTM A403, ASTM A420, ASTM A815, ASTM B361, ASTM B363, ASTM B366, or the corresponding specification listed in ASME BPVC, Section II. The term “wrought” denotes fittings made of pipe, tubing, plate, or forgings.

ASME B16.9 Steel Pipe Fittings Dimensions

This Standard provides for a fixed position for the welding ends with reference to either the centerline of the fittings or the overall dimensions. Dimensional requirements for these fittings are in below links.

ASME B16.9 Steel Pipe Fittings Dimensions

Surface Contours

Where adjacent openings in fittings are not in parallel planes, they shall be joined by a circular arc or radius on the external surfaces. The arc or radius may be terminated in tangents. 

End Preparation

Unless otherwise specified, the details of the welding end preparation shall be in accordance with Table 8-1. Transitions from the welding bevel to the outside surface of the fitting and from the root face to the inside surface of the fitting lying within the maximum envelope shown in Figure 8-1 are at the manufacturer’s option, except as covered in Note (5) of Figure 8-1 or unless otherwise specifically ordered.

Production Tests

Hydrostatic testing of wrought fittings is not required by this Standard. All fittings shall be capable of withstanding, without leakage or impairment of serviceability, a hydrostatic test pressure required by the applicable piping code for seamless pipe of material equivalent to the fitting material, and of the size and wall thickness the fitting marking identifies.


Tolerances for fittings are shown in Table 11-1 and apply to the nominal dimensions given for each of type fittings. Where given for the fittings, the minimum and maximum dimensions are based on these tolerances. The listings with decimals do not imply precision measurement, such as use of vernier, micrometer, or electronic readout equipment.

Supply Range for Butt Weld Pipes Fittings Refer ASME B16.9

Standard: ASTM A234, MSS SP-75, ASTM A403, ASTM A420
Types: Elbow, Tee Equal and Reducing, Cap, Concentric/Eccentric Reducer
Size Range: 1/2”, 1”, 2”, 3”, 4”, 6”, 8”, 10”, 12”, 16”, 20” to 48”.
Thickness: SCH 10, SCH 40, SCH 80
Surface Coatings: Black Painted, Varnished, Epoxy Coated, Galvanized

Steel Pipe Tee

Steel Pipe Elbow

Steel Pipe Cap

Butt Weld Pipe Fittings

Socket Weld Pipe Fittings