Seawater does not negotiate, so the tube has to. Metinox Overseas is a super duplex steel tubes manufacturer and supplier in Mumbai, covering both A789 grades, UNS S32750 (2507) and S32760, in straight lengths and U-bends for condenser and exchanger duty, with export lanes running to the USA, the Middle East and Africa under 3.1 certification. A pitting resistance number above 40 is the entry ticket to seawater service, and both grades on this page hold it with strength to spare. The tube family tree starts one level up at Stainless Steel Tubes.
How this page relates to its neighbours: single-grade depth for 2507, sizes, tolerances and datasheet detail, lives on our Super Duplex UNS S32750 Tubes page, the grade child of this family. And the bolted connections that match these tube bundles are on Duplex & Super Duplex Steel Flanges, one consolidation when ordered together.
Super Duplex Steel Tubes Products
Table of content
- What Makes a Duplex Super
- S32750 vs S32760: The Two Grades
- Super Duplex Tube Chemistry & Strength
- Seawater & Desalination: Where This Tube Earns Its Price
- Super Duplex U-Bends & Condenser Supply
- The ~300°C Ceiling and the ASTM A923 Test
- SD Tube Testing, Certification & Export to USA, Middle East & Africa
- Explore Related Ranges
- Super Duplex Steel Tubes: Frequently Asked Questions
What Makes a Duplex Super
Take the 2205 chemistry from Duplex Steel Pipes and raise every corrosion lever: chromium toward 25 percent, molybdenum toward 4, nitrogen toward 0.3. The pitting resistance equivalent climbs past 40, which is the working threshold where chloride-saturated water stops winning, and yield strength rises to 550 MPa on the way. Super duplex is not a different idea from duplex; it is the same idea taken to where seawater lives.
S32750 vs S32760: The Two Grades
| S32750 (2507) | S32760 | |
|---|---|---|
| The recipe | 25Cr-7Ni-4Mo-N | 25Cr-7Ni-3.5Mo-N plus deliberate copper and tungsten |
| PREN | ≥ 40 | ≥ 40 (specified as a minimum in the grade) |
| Character | The volume super duplex, widest availability | The specification grade, written into many offshore and seawater specs by name |
| When to order | Default choice unless the spec names otherwise | When the project spec says S32760, order S32760; equivalence arguments lose |
Performance overlaps heavily and both grades hold the seawater threshold. The practical difference is specification politics: match the paper, and where the paper is silent, 2507 availability usually decides it.
Seawater & Desalination: Where This Tube Earns Its Price
Once-through seawater cooling, desalination heat recovery, offshore process coolers, brine circuits: this is the duty list, and it is why the Middle East is this family's busiest lane and African coastal power is its fastest-growing one. In that water, 316L pits within seasons and even 2205 duplex is a calculated risk at temperature; super duplex is the grade written for the service rather than stretched to it. When a retube enquiry says seawater, this page is where the quote starts, and we will say so plainly if a cheaper family genuinely covers the actual chloride load.
Super Duplex U-Bends & Condenser Supply
Bundles ship retube-ready: straight lengths cut to set, U-bends formed to drawing with radii from 1.5 times OD, matched sets crated per bundle, and heat treatment after bending handled per specification, which matters more in super duplex than in any austenitic grade because the phase balance is the product. Send the tube sheet drawing and the reply comes back row by row.
The ~300°C Ceiling and the ASTM A923 Test
Two truths keep super duplex honest. First, the same embrittlement chemistry that caps duplex caps this family too; plan around 300°C sustained and design codes will agree. Second, everything the grade promises depends on the mill's solution anneal actually dissolving the intermetallic phases, and ASTM A923 is the test that proves it did. On seawater duty we recommend ordering A923 testing rather than assuming it; the certificate line costs little against a condenser full of tubes.
SD Tube Testing, Certification & Export to USA, Middle East & Africa
Tubes are hydrostatically or eddy current tested per A789 with flattening, flaring and hardness per the standard, A923 and PMI on request, and every order ships with an EN 10204 3.1 MTC, 3.2 via BV, SGS or TUV at order stage. Metinox Overseas is ISO 9001 and PED certified, approved to SABIC, ADNOC, KNPC, EIL, IOCL and BPCL standards; see Quality Policy. Consolidations run from Mumbai to the USA, the Middle East and Africa, crated and end-capped per Packing and Dispatch. Ex-stock sizes dispatch in 7 to 14 working days; made-to-order sizes and U-bend sets take 4 to 6 weeks.
Explore Related Ranges
- Super Duplex UNS S32750 Tubes – the grade child, with single-grade depth and datasheet detail
- Duplex & Super Duplex Steel Flanges – A182 F53/F55 bolted connections for the same circuits
- Duplex Steel Pipes – the 2205 step below, and its economics argument
- Stainless Steel Tubes – the tube hub, one level up, with the full chloride ladder
Super Duplex Steel Tubes: Frequently Asked Questions
Chemistry details and specification politics. S32760 adds deliberate copper and tungsten to the 25Cr-7Ni recipe and is written into many offshore and seawater specs by name; S32750, the 2507 grade, is the volume super duplex with the widest availability. Both hold PREN at or above 40 and 550 MPa yield. Match whatever the project paper names; where it is silent, 2507 usually wins on availability.
Chloride arithmetic. Seawater pits 316L within seasons, and 2205 at around PREN 35 is a calculated risk once temperature rises. The working threshold for open seawater is PREN 40, which is precisely what the super duplex grades are built to clear with margin. The premium is the price of tubes that outlive the water.
Product form. A789 covers duplex and super duplex tube, OD-and-wall sized for exchangers and condensers; A790 covers the matching pipe, NB-and-schedule sized for process lines. Same alloy families, two different products, and the letter on the PO decides which arrives.
Plan around 300 degrees C sustained, the same embrittlement ceiling as duplex. Super duplex buys corrosion resistance and strength, not heat resistance; hotter duty belongs to austenitic or alloy families. Its territory is aggressive water at modest temperature, which is exactly what condensers are.
Yes, and the Middle East desalination corridor is this family's busiest lane for us, with African coastal power close behind. Retube sets ship crated per bundle from Mumbai with the 3.1 documentation, and A923 results where ordered, travelling with the cargo.
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