Specifications by material

Sizes and supply

U-tubes and bend radius

U-tubes let the tube bundle expand freely and need only one tube sheet. Each row of a U-tube bundle has a different bend radius, from the tightest inner row to the outer rows. The minimum practical bend radius depends on the tube diameter and wall thickness – tighter bends thin the outer wall and flatten the tube more. TEMA and the tube specifications set limits on wall thinning and ovality at the bend, and stainless U-bends are often solution annealed or stress relieved in the bend area after bending to restore corrosion resistance. Please send the bundle layout or a list of bend radii and leg lengths with the enquiry, so the bending can be confirmed with the mill.

Choosing the material

Carbon steel A179 tubes are used for oil coolers, reboilers and other non-corrosive duties. Stainless 304L and 316L tubes are used for chemical, food and pharmaceutical exchangers and for cooling water with low chlorides. Duplex and super duplex tubes are used for brackish and seawater cooling and chloride-bearing process streams. Titanium Grade 2 tubes are the standard for seawater-cooled condensers. Alloy steel T11 and T22 tubes are used for high-temperature refinery and power duties. Weight per metre can be estimated with our weight calculator.

Tube wall thickness is chosen for pressure, corrosion allowance and the expanding process used to fix tubes into the tube sheet. Thin walls improve heat transfer and reduce cost, but must still allow for erosion at the tube inlets, where turbulence is highest; tube-end inserts or ferrules are sometimes fitted for protection. Tubes ordered to minimum wall have no undertolerance, while average-wall tubes may be thinner than nominal by the tolerance in the specification, which should be considered in design.

Finned tubes, low-fin tubes and corrugated tubes increase the heat-transfer area and are available on enquiry in several materials. For feedwater heaters, A688 welded stainless U-tubes are standard because of their consistent wall thickness and close tolerances.

Ordering heat exchanger tubes

Please give the material and specification, seamless or welded, outside diameter, wall thickness (minimum or average), length or U-bend list, quantity, and any additional tests such as eddy-current, ultrasonic, intergranular corrosion or third-party inspection. Tubes are packed in wooden boxes with end caps, and U-tubes are packed by row with separators.

Related pipe and tube pages: stainless steel seamless pipes, stainless steel tubes, carbon steel seamless pipes, alloy steel pipes and tubes, duplex steel pipes and tubes and super duplex pipes and tubes. All materials are on the seamless pipes and tubes page.