This specification covers standard requirements for welded ferritic stainless steel feedforward heater tubes including those bent, if specified, into the form of U-tubes for application in tubular feed-water heaters. All finished straight tubing or straight tubing ready for U-bending shall be furnished in the solution-annealed condition. The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, aluminum, copper, nitrogen, titanium, and columbium. The material shall also conform to tensile properties such as tensile strength, yield strength, and elongation. The steel shall meet the specified values for Brinell and Rockwell hardness. The steel shall undergo mechanical tests such as tension test, hardness test, reverse flattening test, flange test, pressure test, hydrostatic test, and air underwater test. Corrosion resisting properties of the sample tube shall also be determined.

1.1 This specification covers seamless and welded ferritic stainless steel feedwater heater tubes including those bent, if specified, into the form of U-tubes for application in tubular feedwater heaters.

1.2 The tubing sizes covered shall be ⁵/₈ to 1 in. [15.9 to 25.4 mm] inclusive outside diameter, and average or minimum wall thicknesses of 0.028 in. [0.7 mm] and heavier.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.