In heat exchanger projects, TP304L U-bend tubes often develop cracking in the bending area, assembly difficulties, and even reduced heat transfer efficiency after a period of operation. The root causes typically lie in insufficient stress relief after bending, wall thinning in the bend radius (R section), and inadequate control of geometric precision,all of which directly affect the long-term stability of the equipment.
The ASTM A213 TP304L seamless U-bend tubes we supply are specifically designed for high-standard heat exchange systems and offer significant advantages in bending quality control. All U-bend tubes undergo solution annealing after bending, typically at temperatures above 1040°C followed by rapid cooling. This process effectively eliminates residual stresses generated during bending, restores the material's corrosion resistance, and prevents stress corrosion cracking during service.
For the critical R section (bending zone), we apply high-precision bending processes, strictly controlling the wall thinning rate to ≤10% and ovality to within ≤8%. This ensures sufficient pressure-bearing capacity in the bend area and guarantees proper fit-up with tube sheets and support structures, avoiding issues such as tube interference or installation difficulties.
In terms of cleanliness and surface quality, all tubes undergo full-process cleaning and degreasing treatment. The الداخلية surface is free from oxide scale, oil, and contaminants, with uniform surface roughness, which helps reduce fluid resistance and scaling tendency-thereby improving heat transfer efficiency and extending service life. Meanwhile, the external surface is free from cracks, folds, and mechanical damage, fully meeting the stringent requirements of high-end equipment manufacturing.
Chemical Composition of ASTM A213 TP304L
| Grade | C | Mn | Si | P | S | Ni | Cr | |
| TP304 | Min | 8.0 | 18.0 | |||||
| Max | 0.08 | 2.0 | 1.0 | 0.045 | 0.03 | 11.0 | 20.0 |
Mechanical Properies of ASME SA213 TP304L
| Grade | Tensile Str Ksi(Mpa) | Yield Str Ksi(Mpa) | Elongation(%) | Hardness | |
| Rockwell (HRB) | Brinell(HBW) | ||||
| TP304L | ≥75(515) | ≥30(205) | ≥35 | ≤90 | ≤200 |
Wall Thickness Tolerance of ASME SA213
| Welded, Hot-Finished Tubes | Type | Wall Thickness Tolerance |
| OD Range | Average(-) | |
| 6~65mm(Incl.) | SMLS&WLD | (-12.5%,+20%) |
| >65mm | SMLS&WLD t/D≤5% | (-12.5%,+22.5%) |
| >65mm | SMLS&WLD t/D>5% | (-12.5%,+15%) |
Applications:
Petrochemical & Chemical: Used in refineries, chemical plants, and other facilities for heat transfer and cooling processes.
Power Generation: Employed in both conventional and nuclear power plants for condenser cooling and heat recovery systems.
HVAC: Utilized in air conditioning and refrigeration units for efficient heat exchange.
Food & Beverage/Pharmaceutical: Applied in processing equipment for tasks like pasteurization, sterilization, and cooling of products.
Application data from a chemical plant in Vietnam demonstrates that the use of GNEE's high-quality TP304L seamless U-tubes for heat exchangers boosts installation efficiency by over 20% and reduces the failure rate in the bent sections by more than 30%. Furthermore, the overall service life of the equipment is extended by approximately 20%, resulting in a significant reduction in maintenance costs and enhanced system operational reliability.
GNEE Stainless Steel is a specialized manufacturer of Stainless Steel U Bend Tube / Stainless Steel U bent Tubes for U Tube Heat Exchanger (U bent Stainless Steel Tube for U bent Tube Heat Exchanger). Our U Bend Tube Tube-bending production line, installed in 2008. Solution annealing after bending will be processed to lower the residual stress, and followed by Hydrostatic testing/Pneumatic test and Dye Penetrant testing if required.
Our Stainless Steel U bend Tube / U bent Stainless Steel tubes included ASTM A213 ASME SA213 TP304 TP304L TP304H TP316 TP316L TP316Ti TP317 TP317L TP317LMN TP321 TP321H TP347H TP309S TP310S TP310H 904L N08904 254SMo S31254, ASME SA789 S31803 S32205 S32750 S32304 S32760 S32101.
Fully compliant with ASTM A213/ASME SA213 standards, with options for mill test certificates (EN 10204 3.1) and third-party inspection reports to ensure traceability and adherence to international quality requirements.
To ensure 100% product reliability, every shipment undergoes Non-Destructive Testing (NDT), including Eddy Current Testing in accordance with ASTM E426 and Hydrostatic Testing. Additionally, we provide comprehensive quality traceability services through Mill Test Reports (MTRs) that comply with the EN 10204 3.1 standard.
PACKAGING
All tubing shall be packaged and blocked in such a manner as to prevent damage in ordinary handling and transportation. The boxes shall be constructed in such a manner that no nails, staples, screws, or similar fasteners are required to close and secure the box after the tubes have been placed in the box. The box shall be lined with plastic sheet or vapor barrier materials so as to prevent chloride contamination of the tube during handling, transportation, and storage.
