FOREWORD
In 1921, the American Engineering Standards Committee, later the American Standards
Association (ASA), organized Sectional Committee B16 to unify and further develop national
standards for pipe flanges and fittings (and later, for valves, gaskets, and valve actuators). Cosponsors
of the B16 Committee were The American Society of Mechanical Engineers (ASME), the
Heating and Piping Contractors National Association [now the Mechanical Contractors
Association of America (MCAA)], and the Manufacturers Standardization Society of the Valve
and Fittings Industry (MSS). Cosponsors were later designated as cosecretariat organizations.
Standardization ofwelding fittingswas initiated in 1937 by a subgroup (designated Subgroup 6)
of Subcommittee 3. After consideration of several drafts, a standard was approved by the
Committee, cosponsors, and ASA, and published with the designation ASA B16.9-1940.
Revisions were made in 1950 and 1955 to add sizes up to NPS 24 and to complete coverage
of fittings in some sizes. These revisions were approved and published as ASA B16.9-1951 and
ASA B16.9-1958. With the subgroup now designated Subcommittee 6 (later Subcommittee F),
further revisions were begun to clarify the intent of the standard, to add angularity tolerances,
and to include fittings of different types (long radius reducing elbows and crosses) and smaller
sizes (NPS 14 and NPS 1㈠). This revision was published as ASA B16.9-1964 after ASA approval.
After reorganization of ASA, first as the United States of America Standards Institute (USASI),
then as the American National Standards Institute (ANSI), with the Sectional Committee being
redesignated as an American National Standards Committee, another revision increasing the size
range to NPS 48 and revising the text for clarity was approved and published as ANSI B16.9-1971.
In 1975, Subcommittee F began a major revision to bring the standard up to date with current
practice and usage. Common fractions were expressed as decimals (but without intending higher
precision) and metric dimensional equivalents were added. Provisions for step-wise change of
radius for NPS 34 long radius elbows and 180-deg returns were introduced. Following Standards
Committee, cosecretariat, and ANSI approval, the revision was published as ANSI B16.9-1978.
It was updated by a corrective addendum, B16.9a-1981, issued in February 1982.
In 1982, American National Standards Committee B16 was reorganized as an ASME Committee
operating under procedures accredited by ANSI. In ASME/ANSI B16.9-1986, the text was revised
and inch dimensions were established as the standard.
In 1991, the Subcommittee reviewed the document and made a number of revisions that were
included in ASME B16.9-1993. Dimensions for short pattern lap joints were also added.
In ASME B16.9-2001, short radius elbows and returns were added, which included all dimensions
and tolerances of ASME B16.28-1994. Metric units were provided as an independent but
parallel alternative standard to U.S. Customary units, and a Quality System Program appendix
was added.
In 2003, the Subcommittee reviewed the document and made a number of revisions. The scope
of the standard was changed to permit fabricated lap joint stub ends employing circumferential
or intersection welds.
In 2006, the Subcommittee reviewed the document and made a number of additions and
revisions. Segmental elbow requirements were added as were 3D elbow dimensions. Reference
documents were updated.
In 2012, the Subcommittee reviewed the document and made numerous revisions to the design
proof test in section 9 and updated the references in Mandatory Appendix II.
This Standard was approved as an American National Standard on November 16, 2012.