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This Standard applies to new construction and covers
pressure–temperature ratings, dimensions, tolerances, materials,
nondestructive examination requirements, testing, and marking for
cast, forged, and fabricated flanged, threaded, and welding end and
wafer or flangeless valves of steel, nickel-base alloys, and other
alloys shown in Table 1. Wafer or flangeless valves, bolted or
through-bolt types, that are installed between flanges or against a
flange are treated as flanged-end valves. Alternative rules for NPS
2½ and smaller valves are given in Mandatory Appendix V.
Standards and Specifications. Standards and
specifications adopted by reference in this Standard and the names
and addresses of the sponsoring organizations are shown in
Mandatory Appendix VIII. It is not considered practical to refer to
a specific edition of each of the standards and specifications in
the individual clause references. Instead, the specific edition
references are included in Mandatory Appendix VIII. A product made
in conformance with a prior edition of reference standards and in
all other respects conforming to this Standard shall be considered
to be in conformance even though the edition reference may have
been changed in a subsequent revision of this Standard.
Time of Purchase, Manufacture, or
Installation.The pressure–temperature ratings included in
this Standard are applicable, upon publication, to all valves
covered within its scope that meet its requirements. For unused
valves, valves that have been maintained in inventory, the
manufacturer may certify conformance to this edition provided that
it can be demonstrated that all requirements of this edition have
been met. However, where such components were installed under the
pressure–temperature ratings of an earlier edition of ASME B16.34,
those ratings shall apply except as may be governed by an
applicable Code or regulation.
User Accountability. This Standard cites duties
and responsibilities that are to be assumed by the valve user in
the areas of, for example, application, installation, system
hydrostatic testing, operation, and material selection.
Quality Systems. Requirements relating to a
valve manufacturer 's Quality System Program are described in
Nonmandatory Appendix C.
Relevant Units. This Standard states valves in
both metric and U.S. Customary units. These systems of units are to
be regarded separately. The U.S. Customary units are shown in
parentheses or are listed in separate tables. The values stated in
each system are not exact equivalents; therefore it is required
that each system of units be used independently of the other.
Combining values from the two systems constitutes nonconformance
with the Standard.
Selection of Valve Types and Material Service
Criteria for selection of valve types and materials suitable for
particular fluid service are not within the scope of this
For the purpose of determining conformance with this Standard,
the convention for fixing significant digits where limits, maximum
and minimum values, are specified shall be ‘‘rounding off'' as
defined in ASTM Practice E 29. This requires that an observed or
calculated value shall be rounded off to the nearest unit in the
last righthand digit used for expressing the limit. Decimal values
and tolerances do not imply a particular method of measurement.
Pressure Rating Designation. Class, followed by a dimensionless
number, is the designation for pressure- temperature ratings.
Standardized designations are as follows:
Class 150 300 600 900 1500 2500 4500
Class 400, an infrequently used flanged-end valve designation,
is regarded as an intermediate class designation.
Size. NPS, followed by a dimensionless number,
is the designation for nominal valve size. NPS is related to the
reference nominal diameter, DN, used in international
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