Duplex Stainless Steel Tube
Duplex and super duplex seamless tube and pipe to ASTM A789 and A790
What Duplex Stainless Steel Tube Is
Duplex stainless combines austenite and ferrite in roughly equal parts, which roughly doubles the yield strength of 316L while raising resistance to chloride stress corrosion cracking.
For a heat exchanger designer that usually means thinner walls carrying the same pressure, and a tube that survives brackish or chloride bearing cooling water.
Grades run from lean duplex S32101 and S32304 up to super duplex S32750 and S32760 and hyper duplex S32707.
Why Engineers Specify It
Chloride stress corrosion resistance
The duplex structure resists the cracking mechanism that limits 304 and 316L in chloride service.
Higher strength than austenitic grades
Design stress allows a thinner wall for the same pressure, which also improves heat transfer.
Grades across the PREN range
Lean S32101 and S32304 through S32205 to super duplex S32750 and S32760 and hyper duplex S32707.
Large pipe sizes
Pipe to NPS 10" (273.05 mm) for process lines feeding the same plant as the tube bundles.
Where It Is Used
- Heaters
- Heat exchangers
- Condensers
- Instrumentation
- Process pipe lines
Buyers Who Come to Us for This Tube
Seawater and brackish water cooled plant
Condensers and coolers where chloride cracking is the design risk.
Desalination contractors
Duty that defeats standard austenitic tube.
Chemical plant EPCs
Lines needing both corrosion resistance and strength.
What Goes Wrong Without It
Chloride stress corrosion cracking in 316L
Duplex grades resist the mechanism that cracks austenitic tube in warm chloride service.
Wall thickness driven by strength, not corrosion
Duplex yield strength lets the wall come down and the heat transfer come up.
Pitting in aggressive cooling water
Super duplex S32750 and S32760 raise pitting resistance through higher chromium, molybdenum and nitrogen.
Duplex Stainless Steel Tube Dimensions
These are the ranges our production lines run. Sizes outside them are quoted case by case rather than assumed.
| Item | Specification |
|---|---|
| Tube outside diameter | 1/2" - 3" (12 mm - 76.2 mm) |
| Tube wall thickness | 0.02" - 0.5" (0.5 mm - 12.0 mm) |
| Tube length | up to 105 ft (32 m) |
| Pipe size | NPS 1/2" - 10" (21.34 mm - 273.05 mm) |
| Pipe wall thickness | Sch10 - Sch80 (2.11 mm - 12.7 mm) |
| Pipe length | up to 98 ft (30 m) |
Materials
| Component | Materials available |
|---|---|
| Lean duplex | UNS S32101, UNS S32304 (1.4362) |
| Standard duplex | UNS S31803 and UNS S32205 (1.4462) |
| Super duplex | UNS S32750 (1.4410), UNS S32760 (1.4501), UNS S32550 (1.4507), UNS S31260 |
| Hyper duplex | UNS S32707 |
Specifications We Produce To
| Standard | Scope |
|---|---|
| ASTM/ASME A/SA789 | Seamless and welded ferritic/austenitic stainless steel tubing for general service |
| ASTM/ASME A/SA790 | Seamless and welded ferritic/austenitic stainless steel pipe |
How It Is Made
Duplex Stainless Steel Tube on the Shop Floor
Inspection and Certification
Every tube passes eddy current and hydrostatic testing, with tensile, flattening, flaring, hardness and chemical analysis carried out on our own equipment. Fin pitch, fin height and finned length are verified as dimensional items in their own right.
The company holds ISO 9001:2015, CE certificate, Production licence for pressure pipe.
What Can Be Changed
- Base tube material and wall thickness within the range above
- Fin material, fin pitch and fin height to the bundle design
- Finned length and bare end length for the tubesheet joint
- Marking, packing and certificate scope for the destination market
Compared With the Alternatives
Against austenitic 316L, duplex offers about twice the yield strength and far better chloride cracking resistance at similar cost per kilogram. Against nickel alloys, duplex is markedly cheaper but is limited in reducing acid service and at high temperature, where nickel grades take over.
Use Guide
- Give the chloride content and the operating temperature - both are needed to choose between lean, standard and super duplex.
- Duplex requires controlled heat input in fabrication; confirm your welding procedure before finalising wall thickness.
- Ask for the intergranular corrosion and ferrite content tests with the order if your specification requires them.
Duplex Stainless Steel Tube FAQ
Which duplex grades do you supply?
S32101, S32304, S31803, S32205, S32550, S31260, S32750, S32760 and S32707.
What standards apply?
ASTM/ASME A/SA789 for tubing and A/SA790 for pipe.
What is the largest duplex pipe size you make?
NPS 10", which is 273.05 mm outside diameter.
Is duplex better than 316L for seawater cooling?
For chloride stress corrosion cracking resistance and strength, yes. Grade selection still depends on chloride level, temperature and velocity.
Often Compared With
Stainless Steel Tube
Austenitic and super austenitic seamless tube and pipe to ASTM A213, A269 and A312
Tube outside diameter: 1/2" - 3" (12 mm - 76.2 mm) · Tube wall thickness: 0.02" - 0.5" (0.5 mm - 12.0 mm)
Nickel / Nickel Alloy Tube
Monel, Inconel, Incoloy and Hastelloy grade seamless tube for the hardest corrosion duty
Tube outside diameter: 1/2" - 3" (12 mm - 76.2 mm) · Tube wall thickness: 0.02" - 0.5" (0.5 mm - 12.0 mm)
Tubesheet
Drilled tube plate up to 5000 mm diameter and 750 mm thick
Maximum outside diameter: 5000 mm · Maximum thickness: 750 mmIndustries using this tube
Related reading
Quote Duplex Stainless Steel Tube From Your Drawing
Send base tube size, wall thickness, fin geometry, material and length. You get a quotation against the drawing, not a catalogue page.
[email protected] · Tel 0086 512 58392615 · Monday to Saturday, 08:30 - 17:30 China Standard Time (GMT+8)