ASME SA-557-SA-557M:2021 pdf free download – SPECIFICA TION FOR ELECTRIC-RESISTA NCE- WELDED CARBON STEEL FEEDWATER HEATER TUBES
1.1 This specification covers minimum-wall-thickness, electric-resistance-welded, carbon steel tubes including those bent, if specified, into the form of U-tubes for applica- tion in tubular feedwater heaters.
1.2 The tubing sizes covered shall be发to 1% in. [15.9 to 31.8 mm] outside diameter, inclusive, and wall thicknesses equal to or greater than 0.045 in. [1.1 mm]
1.3 Optional supplementary requirements are provided and, when desired, shall be stated in the order.
1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated 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.
5.2.2 If cold drawn, tubes shall be heated after the final cold-working operation to a temperature of at least 1200°F [640°C] to ensure ductility satisfactory for rolling into tube sheets and to meet the specified mechanical prop- erties.
5.2.3 If heat treatment of the U-bends is specified, such heat treatment shall consist of heating the stressed portion within a range from 1100 to 1200°F [590 to 640°C].
6. Surface Condition
6.1 Finished tubes shall be free of scale but may have a superficial oxide film on the surfaces. A light-oxide scale on the outside and inside surfaces of U-bend shall be allowed for tubes which have been heat treated for relief of stress.
6.2 Finished tubes shall be coated on both outside and inside diameter with a thin paraffin oil to prevent corrosion in transit. Other types of coatings may be applied as mutu- ally agreed upon and specified in the order. 7. Chemical Composition
7.1 The steel shall conform to one of the requirements as to chemical composition as prescribed in Table 1. 7.2 For all tubes, the steel shall be fully killed.
7.3 When a grade is ordered under this specification, supplying an alloy grade that specifically requires the addi- tion of any element other than those listed for the ordered grade in Table 1 is not permitted.
10.1 Permissible variations from the specified outside diameter shall be in accordance with the applicable portions of Specification A 450/A 450M. The height of fash on the inside of hot- rolled tubes shall be as specified in Specifica- tion A 450/A 450M. Cold-drawn tubes shall have no dimensional indication of welding flash. Tolerances for diameter and wall thickness do not apply to the bent portion of U-tubes. At the bent portion of a U-tube, forR = 2 x D, neither the major nor minor diameter of the tube shall deviate from nominal by more than 10%.
10.2 Permissible variations from the specified mini- mum wall thickness shall not exceed + 18% – 0 for the straight tubing. The wall thickness of the U-tube in the bent section shall be not less than the value determined by