ASTM A688 TP304 Stainless Steel Seamless U-bend Tube

If you are seeking reliable ASTM A688 TP304 stainless steel seamless U-bent tubes, we can provide you with U-bent tubes manufactured in strict compliance with the ASTM A688 standard and subjected to rigorous testing. These tubes are specifically designed to address common issues encountered in heat exchange equipment, such as inconsistent bend quality, residual stress cracking, premature corrosion, and leakage.

Our ASME SA688 TP304 stainless steel seamless U-bent tubes-specifically designed for use in feedwater heaters-are high-performance heat exchange tubing materials. They contain 18.0–20.0% chromium, 8.0–10.5% nickel, and ≤0.08% carbon; they possess a minimum yield strength of 205 MPa and a tensile strength ranging from 515 to 790 MPa.

ASME SA688 TP304 tubing features a seamless structure and a U-bent geometry (with a bend radius typically ranging from 1.5 to 3.0 times the tube's outer diameter), while adhering to strict dimensional tolerance standards (outer diameter tolerance of ±0.05 mm and wall thickness tolerance of ±0.03 mm). These characteristics ensure reliable performance in feedwater heater systems operating at maximum temperatures of up to 300°C and maximum pressures of up to 10 MPa. These tubes are widely utilized in power plants, petrochemical facilities, and industrial heating equipment-specifically in feedwater heaters, condensers, heat exchangers, and various thermal systems.

Heat treatment shall be applied to the U-bend area plus approximately 6 in. [150 mm] of each leg beyond the tangent point of the U-bend after bending, if specified.

Straight length: max 30000 mm

Leg length: 12000 mm, points of tangency of the bend to the leg end

Bending radius: max 1500 mm

Manufacturing method: cold drawing, cold worked

Straight length equal to 2 x leg length + 3.1416 x R

ASTM A688 / A688M standard covers seamless and welded austenitic stainless steel feedwater heater tubes intended for use in tubular feedwater heaters, including U-bent tubes. The scope of this standard encompasses tubes with an outer diameter ranging from 5/8 inch to 1 inch [15.9 to 25.4 mm] (inclusive), as well as tubes with an average or minimum wall thickness of 0.028 inch [0.7 mm] or greater.

Chemical Composition

Mechanical Properties

Physical Properties

We offer ASTM A688 tp304 seamless and welded U bend stainless steel tube for feedwater heaters, Austenitic stainless steel and Ferritic stainless steels, surface condition in annealing and pickling, or bright annealed finishing, used in heat exchanger, boiler, condenser, heat transfer system.

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High-Pressure Heater Project Supply

During the recent supply of ASTM A688 TP304 stainless steel seamless U-tubes for a high-pressure heater project commissioned by a major power utility group, we addressed the client's primary concerns-specifically, the risks of Stress Corrosion Cracking (SCC) at the bends and potential pressure-bearing hazards resulting from excessive wall thinning during bending. To mitigate these risks, we implemented a rigorous localized induction heating stress relief process. Furthermore, we subjected all U-bend sections to a 100% Ball Pass Test and precise in-line ultrasonic wall thickness measurement, thereby ensuring that both internal bore clearance and wall thinning rates significantly exceeded standard requirements. 

ASTM A688 U Bend Stainless Steel Tube Manufacturer

As a professional manufacturer certified under ISO 9001, PED (2014/68/EU), and ASME, GNEE possesses a robust annual production capacity of 3,500 tons of high-standard ASTM A688 TP304 seamless U-tubes. Our facility is equipped with 12 high-precision, fully automated cold-drawing and CNC bending production lines, ensuring that the wall thickness reduction rate in the bent sections is consistently maintained within 5%. 

high quality packaging

Regarding delivery assurance, we employ a rigorous packaging protocol utilizing fully enclosed, heavy-duty, fumigation-free wooden crates suitable for maritime transport. We utilize layered PE foam padding for separation and custom-designed positioning brackets to securely anchor each tube bundle, thereby completely eliminating the risk of mechanical damage or geometric deformation during long-distance transit. This packaging is accompanied by comprehensive inspection data fully compliant with the EN 10204 3.1 standard.

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