This standard is issued under the fixed designation A 557/A 557M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon ( ュ) indicates an editorial change since the last revision or reapproval.

1.Scope

1.1 This specification covers minimum-wall-thickness, electric-resistance-welded, carbon steel tubes inclusion those bent, if specified, into the from of U-tubes for application in tubular feedwater heaters.

1.2 the tubing sizes covered shall be 5/8 to 1 1/4-in. [15.9 to 31.8-mm] outside diameter, inclusive, with minimum wall thicknesses equal to or greater than 0.045 in. [1.1 mm].

1.3 optional supplementary requirements are provided, and hen desired, shall be stated in the order.

1.4 The values stared in either inch-pound units or SI units are to be regarded separately as the standard. within the text, the SI units are shown in brackets. The values sated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.