Page 119 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

PIPING 2.69

TABLE 2.8 UNS Metal Family Designations

The first letter
(followed by
five digits) Alloy category (assigned to date)
Axxxxx Aluminum and its alloys
Cxxxxx Copper and its alloys
Exxxxx Rare-earth metals, and similar metals and alloys
Fxxxxx Cast irons
Gxxxxx AISI and SAE carbon and alloy steels
Hxxxxx AISI and SAE H-steels
Jxxxxx Cast steels (except tool steels)
Kxxxxx Miscellaneous steels and ferrous alloys
Lxxxxx Low-melting metals and their alloys
Mxxxxx Miscellaneous nonferrous metals and their alloys
Nxxxxx Nickel and its alloys
Pxxxxx Precious metals and their alloys
Rxxxxx Reactive and refractory metals and their alloys
Sxxxxx Heat- and corrosion-resistant steels (including stainless), valve steels, and
iron-based “superalloys”
Txxxxx Tool steels (wrought and cast)
Wxxxxx Welding filler metals
Zxxxxx Zinc and its alloys

a confusing array of names and numbers for metal and alloy designations had been devel-
oped independently over a 60-year period. Proprietary alloys were designated by trade
names and some were registered trademarks. Often, different companies manufactured the
same alloy under different trade names. Another factor is that the old numbering system
does not allow the use of computer databases requiring uniform designations. Although it
originated in the United States, the UNS is gaining national and worldwide acceptance. The
book, Metals and Alloys in the Unified Numbering System, ASTM DS56B, published by
ASTM, is now in its 5th edition.
The UNS is a simple alphanumeric system consisting of a letter prefix followed by five
digits. This requires only six spaces to identify any metal or alloy. The letter prefix is usu-
ally suggestive of the family of metals identified. The system establishes 17 categories or
families of metals. The categories are given in Table 2.8.
As an example, stainless steel ASTM type 304 is now S30400 and type 316 is S31600.
If 304L is required, it is called S30403.
The UNS designation is not a specification, and it does not establish a requirement for
form, condition, properties, or quality. These are all established by individual specification
literature such as ASTM alloy standards and those obtained from manufacturers.
There is no UNS for plastic pipe or related materials.

METRIC PIPE SIZES

The United States is the only major industrial country where inch sizes are commonly used.
This is commonly referred to as the inch/pound, or IP system. All U.S. government projects
are required to be in metric sizes, and many individual states are also requiring project
documents to use metric units. Metric units are referred to as SI units, or International
System of Units. Table 2.9 is compiled from several sources and presents the different

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