Stainless Steel U Shape Pipe – Cold-Bent U-Shaped Steel Pipe for Heat Exchangers

Material Overview

Stainless Steel U Shape Pipes (U-bent tubes) are fabricated by cold bending seamless or welded stainless steel heat exchanger tubes into precise U or multi-U geometries, followed by stress-relief or solution annealing where required. They are designed for shell-and-tube heat exchangers, condensers, boilers, and feedwater heaters operating under high temperature and pressure, and are commonly produced in austenitic grades such as TP304/304L, TP316/316L, and TP321 to standards like ASTM A213 or related specifications.

Specifications

Base material

• Austenitic stainless steels: ASTM A213 TP304, TP304L, TP316, TP316L, TP321

• Other options on request: higher-alloy stainless steels, duplex stainless steels, nickel alloys

Dimensional range (typical capability)

• Outside diameter (OD): approx. 12.7–38.1 mm (½"–1½"), larger sizes on request

• Wall thickness (WT): approx. 0.70–4.0 mm

• Bending radius (CLR):

  • Minimum: typically ≥1.5 × OD

  • Maximum: up to about 1500–1700 mm depending on OD and grade

• Straight leg length: up to about 12,000 mm

• Maximum developed length per U-tube: up to about 27,000–30,000 mm

Manufacturing route

• Mother tube: seamless or welded stainless steel heat exchanger tubes

• Bending: cold bending to specified radius and leg length (commonly in line with TEMA / DIN 28179 practice)

• Heat treatment:

  • Solution annealing or stress-relief after bending for austenitic stainless grades when required by code or client

• Finishing: pickled, bright annealed, or mechanically polished OD as specified

• Ends: plain, beveled, or prepared for tube-to-tubesheet welding

Main Features

• Excellent corrosion resistance in water, steam, many chemicals, and refinery/petrochemical media, especially in TP316/316L and TP321.

• High temperature capability for boiler and heat-exchanger duty, with stable mechanical properties at elevated service temperatures.

• Compact bundle layout thanks to U-shape design, reducing exchanger length and allowing for thermal expansion without expansion joints.

• Tight bending control (radius, wall thinning, ovality) to maintain pressure integrity and flow performance at the bend.

• Fully traceable production with pressure testing and non-destructive examination according to international standards.

Our Advantages

1. “How do you control wall thinning and ovality at the U-bend?”

Wall thinning and cross-section distortion are the main engineering concerns in cold-bent tubes, because the outer wall of the bend tends to thin while the inner wall thickens and the section becomes slightly oval.

• We design bending procedures to keep wall thinning at the bend within a controlled low percentage of the original wall and ovality within tight limits of the OD, in line with common heat-exchanger specifications for U-bent tubes.

• Bend tooling, mandrels, and lubrication are selected to suit OD/WT and grade, reducing local strain and preventing flattening.

• Each batch is checked dimensionally at the bend (OD, WT, ovality) so that tubes will fit tube-sheet holes and meet process pressure requirements.

2. “Is the tube properly heat-treated after cold bending?”

Cold bending introduces residual stresses and can reduce corrosion resistance if high strains are left in the material.

• For austenitic stainless steel U-tubes we apply solution annealing or stress-relief heat treatment after bending whenever required by customer or code.

• Heat treatment is performed in controlled furnaces or by electric resistance methods, as commonly used by major U-tube manufacturers.

• Mechanical and corrosion properties after bending are thereby restored to the levels specified in the base tube standards (for example ASTM A213).

3. “Which standards and grades can you meet?”

End users typically require compatibility with well-known tube standards and exchanger design codes. We can supply U-bent tubes based on:

• ASTM / ASME

  • ASTM A213 / ASME SA213 for seamless austenitic stainless heat-exchanger tubes (TP304/304L, TP316/316L, TP321, TP347H, etc.)

  • ASTM A249 / ASME SA249 for welded austenitic boiler and heat-exchanger tubes where welded mother tubes are specified

  • ASTM A688 / ASTM A803 for feedwater-heater type U-bent tubes based on welded or seamless austenitic stainless steel

• EN / DIN

  • EN 10216-5 for seamless stainless tubes for pressure and corrosion-resisting purposes

  • EN 10217-7 for welded stainless pressure tubes where applicable

  • DIN 28179 / DIN 28180 for U-bend geometry and dimensional tolerances in tubular heat exchangers

• GOST

  • GOST 9941 stainless steel tubes for corrosion-resistant service, including heat-exchanger applications

• JIS

  • JIS G3463 stainless steel tubes for boiler and heat exchanger

• GB (China)

  • GB/T 13296 seamless stainless steel tubes for boiler and heat exchanger

  • GB/T 14976 seamless stainless steel pipes for fluid transport, when specified for process piping service

This allows U-shape pipes to be supplied to match most international projects and code requirements.

4. “What about inspection, testing and documentation?”

• Tubes are subjected to hydrostatic or non-destructive electric tests (eddy-current, ultrasonic) on each piece, as permitted in the applicable tube standards.

• Additional tests such as intergranular corrosion testing, PMI, and hardness checks can be provided for critical services.

• Mill test certificates (for example EN 10204 3.1) are supplied, covering heat number, grade, dimensions, NDT, and heat treatment status.

5. “Which material do you recommend for my service?”

• For general water, steam, and many low-chloride media, TP304/TP304L is typically sufficient.

• For chloride-bearing or mildly aggressive chemicals, TP316/TP316L is usually the safer choice thanks to its molybdenum content and improved pitting resistance.

• For higher-temperature service with frequent thermal cycling, TP321 (Ti-stabilized) or TP347H are often preferred.

Chemical Composition

Mechanical Properties

Execution Standard

ASTM / ASME

• ASTM A213 / ASME SA213 – seamless ferritic and austenitic alloy steel tubes for boilers, superheaters, and heat exchangers

• ASTM A249 / ASME SA249 – welded austenitic boiler, superheater, heat-exchanger, and condenser tubes

• ASTM A688 / ASTM A803 – austenitic and ferritic stainless feedwater-heater and U-bend tubes

EN / DIN

• EN 10216-5 – seamless stainless steel tubes for pressure purposes

• EN 10217-7 – welded stainless steel tubes for pressure purposes

• DIN 28179 / DIN 28180 – tubes and U-bends for tubular heat exchangers; dimensions, materials, and bending tolerances

GOST

• GOST 9941 – stainless steel tubes of corrosion-resistant steels, widely used in CIS markets for heat-exchanger and process equipment

JIS

• JIS G3463 – stainless steel tubes for boiler and heat exchanger

GB (China)

• GB/T 13296 – seamless stainless steel tubes for boiler and heat exchanger

• GB/T 14976 – seamless stainless steel pipes for fluid transport

Application Fields

General Application Areas

Thanks to their high corrosion resistance, temperature capability, and compact geometry, stainless steel U Shape Pipes are widely used in:

• Shell-and-tube heat exchangers

• Condensers and feedwater heaters

• Waste heat boilers and fired heaters

• Power plant and renewable energy heat-recovery units

• Nuclear and petrochemical process equipment

Q: Are you trading company or manufacturer ?

A: manufacturer,also can do trading.

Q: How long is your delivery time?

A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock,

it is according to quantity.

Q: Do you provide samples? is it free or extra ?

A: Yes, we could offer the sample for free charge but need pay the cost of freight.

Q: What is your terms of payment ?

A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.

If you have another question, pls feel free to contact with me.