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| Brand Name: | YUHONG |
| Model Number: | ASTM A403 WP317 Stainless Steel Return Bend |
| MOQ: | 1PC |
| Payment Terms: | L/C,T/T |
ASTM A403 WP317 / UNS S31700 / 1.4449 Stainless Steel Return Bend Buttweld 180 Degree Elbow
A return bend is essentially a 180-degree elbow. It is used to reverse the direction of a pipe run, creating a "U" shape.
Center-to-Center (C-C): This is the critical dimension. It measures the distance between the two legs of the return bend (the center of one outlet to the center of the other). Standard sizes are usually based on the pipe size.
Why use a Return Bend?
Heat Exchangers: The most common application. Hairpin tubes (U-tubes) allow for thermal expansion without putting stress on the tube sheet.
Space Saving: In compact skid-mounted piping, it allows you to run two parallel pipes connected at the end without needing two 90° elbows and a short piece of pipe (though a return bend does introduce slightly more pressure drop than two long-radius 90s).
Coils: Used in steam coils or heating coils inside tanks.
Equivalent Grades of ASTM A403 WP317 Stainless Steel Return Bend Buttweld Pipe Fittings
| STANDARD | WERKSTOFF NR. | UNS | JIS | EN |
| SS 317 | 1.4449 | S31700 | SUS 317 | – |
Chemical Composition % of ASTM A403 WP317 Stainless Steel Return Bend Buttweld Pipe Fittings
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | Fe |
| SS 317 | 0.08 max | 2.0 max | 1.0 max | 0.045 max | 0.030 max | 18.00 – 20.00 | 3.00 – 4.00 | 11.00 – 15.00 | 57.845 min |
Mechanical Properties of ASTM A403 WP317 Stainless Steel Return Bend Buttweld Pipe Fittings
| Grade | Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
| 317/317L | 7.9 g/cm3 | 1400 °C (2550 °F) | Psi – 75000 , MPa – 515 | Psi – 30000 , MPa – 205 | 35 % |
Manufacturing Process (ASTM A403)
Fittings under A403 can be made in several ways, but for a Return Bend, the method is crucial because of the tight 180° bend.
Seamless vs. Welded: WP317 fittings can be made from seamless pipe (preferred for high pressure) or welded pipe (which is then cold-formed).
Hot or Cold Forming: The pipe is bent around a former. Due to the high molybdenum content (which makes the steel work-hardening), forming requires significant force.
Solution Annealing (Heat Treatment): This is mandatory for A403 WP317. After the bending process, the fitting must be solution annealed. This involves heating it to between 1900°F and 2100°F (1040°C - 1150°C) and then rapidly quenching (water cooling). This process:
Dissolves any carbides that may have precipitated.
Relieves internal stresses from forming.
Restores the maximum corrosion resistance.
Pickling & Passivation: After heat treatment, the fittings usually undergo pickling (to remove the oxide scale/heat tint) and passivation (to restore the protective chromium oxide layer).
Application
Because of the enhanced molybdenum content of WP317 (compared to 304/316), these return bends are used in more aggressive environments.
Chemical Processing: Handling hot sulfuric, sulfurous, or phosphoric acids.
Pulp & Paper: Specifically in the "bleach plant" and digesters where chlorine and chlorine dioxide are present (highly corrosive).
Flue Gas Desulfurization (FGD): In power plants, scrubbers handling sulfur-laden gases require high molybdenum stainless steels.
Petrochemical: In heat exchangers where the cooling medium is seawater or brackish water (high chloride content).
