scope:

General

This Standard covers threaded malleable iron unions, Classes 150, 250, and 300. It also contains provisions for using steel for NPS ¹⁄₈ unions. This Standard includes

(a) design

(b) pressure-temperature ratings

(c) size

(d) marking

(e) materials

(f) joints and seats

(g) threads

(h) hydrostatic strength

(i) tensile strength

(j) air pressure test

(k) sampling

(l) coatings

(m) dimensions

Mandatory Appendix I provides tables in U.S. Customary units.

References

Standards and specifications adopted by reference in this Standard are shown in Mandatory Appendix II, which is part of this Standard. It is not considered practical to identify the specific edition of each referenced standard and specification in the text, when referenced. Instead, the specific editions of the referenced standards and specifications are listed in Mandatory Appendix II.

Quality Systems

Nonmandatory requirements relating to the fitting manufacturer's quality system programs are described in Nonmandatory Appendix A.

Relevant Units

This Standard states values in both SI (metric) and U.S. Customary units. These systems of units are to be regarded separately.Within the text, the U.S. Customary units are shown in parentheses or in separate tables. The values stated in each table 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 may constitute nonconformance with the Standard.

Service Conditions

Criteria for selection of materials suitable for particular fluid service are not within the scope of this Standard.

Convention

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 rounded as defined in ASTM E 29. This requires that an observed or calculated value shall be rounded off to the nearest unit in the last right-hand digit used for expressing the limit. Decimal values and tolerance do not imply a particular method of measurement.

Denotation

Pressure Rating Designation. Class, followed by a dimensionless number, is the designation for pressure-temperature ratings.

Size. NPS, followed by a dimensionless number, is the designation for nominal fitting size. NPS is related to the reference nominal diameter, DN, used in international standards.