YUHONG GROUP has recently completed the production and delivery of a batch of ASME SA179 U-bend tubes. The products have passed on-site full-process supervision by a third-party inspection agency and have been officially shipped and delivered to the client. These U-bend tubes will be used in a critical heat exchanger equipment re-manufacturing project for petrochemical plant facilities.

This batch of delivered ASME SA179 U-bend tubes conforms to the ASME SA179 / SA-179M standard, with product type being seamless cold-drawn low-carbon steel U-bend tubes. U-tube heat exchangers are a type of shell-and-tube heat exchanger in which the tubes are formed into U-shapes with only one tube sheet. The tube bundle can expand and contract freely, making it suitable for high-temperature, high-pressure, and large-temperature-differential operating conditions. The ASME SA179 standard specifies the technical requirements for seamless cold-drawn low-carbon steel tubes used in heat exchangers, condensers, and similar heat transfer equipment, with minimum tensile strength of 325 MPa, minimum yield strength of 180 MPa, minimum elongation of 35%, and maximum hardness of 72 HRB.

In addition to meeting the ASME SA179 standard's requirements for C (0.06%–0.18%), Mn (0.27%–0.63%), P (≤0.035%), and S (≤0.035%), all chemical composition analysis samples were witnessed and sampled on-site by a third-party inspection agency, with all test results meeting the requirements.

To address the technical challenges of U-bend tube bend sections, the following specialized inspections were performed:

• 100% Dye Penetrant Testing (DPT): Witnessed on-site by a third-party inspection agency, performed on each tube
• Destructive Testing: Cut at the midpoint of the innermost minimum bend radius to measure actual wall thickness reduction, with the maximum reduction rate far below the client's allowable upper limit

The ASME SA179 standard specifies that the minimum wall thickness at the bend section of U-bend tubes shall be 0.75 to 0.9 times the nominal wall thickness (depending on the ratio of bend radius to tube diameter), and ovality shall be controlled within 5% to 12%.

The production of this ASME SA179 U-bend tube batch involved the following key process control points:

• Manufacturing Process: Seamless process + cold-drawn forming, with heat treatment at 650°C or above after the final cold-drawing pas.
• Post-Bend Treatment: All U-bend sections underwent stress-relief heat treatment after bending to eliminate cold-work residual stresses
• Non-Destructive Testing: Each tube was subjected to hydrostatic testing or eddy current testing (subject to buyer's approval)
• Dimensional Accuracy: Outside diameter, wall thickness, bend radius, straight-leg length, and tube end offset were all executed in accordance with ASME SA179 and A450/A450M general requirements

The successful delivery of this ASME SA179 U-bend tube batch demonstrates YUHONG GROUP's technical capabilities and quality control standards in the high-standard heat exchanger tube manufacturing field, and provides reliable component assurance for the client's plant resumption and project restart.