ASTM A312 TP317/317L Stainless Steel Seamless Tube for Boiler and Heat Exchanger

The stainless steel 317L U Tube is a special type of tube manufactured particularly for heat exchangers. The tubes are made in U shape and are used in repeating rows in the heat exchanger applications. The material has nickel, chromium, carbon, manganese, phosphorus, silicon, sulfur and molybdenum in its composition. It has an excellent corrosion resistance compared to other stainless steels, alloy 317L is non-magnetic in the annealed condition. It cannot be hardened by heat treatment.

Stainless steel TP317L is a low carbon version of TP317 stainless steel. It has the same high strength and corrosion resistance as 317 steel but can produce stronger welds due to the low carbon content.

Chemical Composition of ASTM A213 TP317L Stainless Steel Tubes

Physical Properties (Room Temperature) of ASTM A213 TP317L Stainless Steel Tubes

When procuring A213 TP317L U-Bend tubes, an expert would specify more than just the material:

1. Final Heat Treatment Condition: "Shall be solution annealed after bending."

2. Descaling/Pickling: "Shall be pickled after final heat treatment to a clean, passivated surface."

3. Bend Tolerances: Explicitly call out allowable ovality and wall thinning (e.g., "per TEMA R/C standards").

4. NDT Requirements: Specify any testing required on the bent section (e.g., "Eddy Current Testing on the entire U-bend").

The Criticality of the U-Bend Manufacturing Process

• 1. Bend Thinning and Ovality: During bending, the outer wall of the bend thins, and the tube cross-section can become slightly oval. For a high-integrity application, the bend is meticulously controlled to stay within the strict ovality and wall-thinning tolerances specified in standards like ASME TEMA (Tubular Exchanger Manufacturers Association). Excessive thinning is a direct reduction in pressure-retaining capability.

  2. Residual Stresses: The cold-working process of bending induces significant residual stresses in the bend. For standard applications, this might be acceptable. However, in corrosive environments (especially with chlorides), these stresses can dramatically accelerate Stress Corrosion Cracking (SCC).

  3. The Absolute Necessity of Solution Annealing & Pickling: Because of point #2, A213 TP317L U-bend tubes must be solution annealed after bending. This heat treatment (heating to around 1900-2050°F / 1040-1120°C and rapidly quenching) dissolves carbides and, most importantly, relieves the harmful residual stresses from bending. Following annealing, the tubes are pickled to remove the scale (oxide layer) formed during heating and to restore the passive corrosion-resistant film on the surface. A U-bend that has not been properly annealed is a ticking time bomb in a chloride environment.

Applications
1. Flue gas desulfurization scrubber systems
2. Chemical and petro-chemical processing equipment
3. Pulp and paper plants
4. Food processing equipment
5. Textile equipment
6. Boiler Tube
7. Heat Exchanger Tube