UNS S31803 pipe is the original 22Cr duplex designation. Molybdenum is at 2.5 to 3.5%, and the specified minimum tensile strength is 620 MPa, which suits produced water and gathering lines.
View UNS S31803 PipeDuplex Steel Pipes Manufacturer in India
MLTI Private Limited (Moonlight Tube Industries) is a duplex steel pipes manufacturer, supplier and exporter based in Gujarat, established in 2008, and rated at near 8,000 MT a year. A duplex stainless steel pipe carries a two-phase microstructure of near-equal ferrite and austenite. Production runs to ASTM A790 / ASME SA-790, the specification for seamless and welded ferritic-austenitic stainless steel pipe. We manufacture two grades, UNS S31803 and UNS S32205, both of which SA-790 lists as 22Cr duplex grades with their own chemical and tensile limits.
Chromium runs 21.0 to 23.0% in S31803 and 22.0 to 23.0% in S32205, pairing with molybdenum of 2.5 to 3.5% and 3.0 to 3.5% respectively to resist chloride pitting, while nitrogen from 0.08 to 0.20% in S31803 and 0.14 to 0.20% in S32205 stabilises the austenite. SA-790 sets a 450 MPa minimum yield with 25% elongation, roughly twice the yield of standard austenitic pipe. Duplex pipe sizes span 1/8 inch to 10 inches NB across five schedules. We supply duplex seamless pipe pierced from solid billets for high-pressure service and duplex welded pipe roll-formed from strip and resistance-welded, with square and rectangular sections rolled to order. Offshore platforms, desalination plants and paper mills mainly use this grade range. PMI, tensile and hardness testing runs in-house, and every despatch carries EN 10204 3.1 certification. Our company holds ISO 14001 and 45001 certifications, BIS, EIL, IBR and PED approvals.
Specifications of Duplex Steel Pipes
The applicable standards and the full pipe duplex specification envelope are represented in the table given below.
| Parameter | Value |
|---|---|
| Applicable standards | ASTM A790: Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe / ASME SA-790 ASTM A999: General Requirements for Alloy and Stainless Steel Pipe / ASME SA-999 |
| Grades | S31803, S32205 |
| Dimensional standard | ASME B36.19M for SCH 5S, 10S, 40S and 80S; SCH 20S, and SCH 5S at 1/8, 1/4 and 3/8 inch NB, supplied to MLTI works dimensions |
| Nominal bore | 1/8 inch NB (6 mm) to 10 inch NB (250 mm) |
| Outside diameter | 10.3 mm to 273.1 mm |
| Schedule | SCH 5S, SCH 10S, SCH 20S, SCH 40S, SCH 80S |
| Wall thickness | 1.24 mm to 12.70 mm |
| Production process | Seamless, welded (ERW) |
| Section profile | Round, square, rectangular |
| Supply condition | Solution annealed at 1020 to 1100°C, rapidly cooled in air or water |
| Length | Up to 24 ft; random lengths in the 15 to 24 ft range, or cut to the ordered length |
| End type | Plain; bevelled on request |
Duplex Pipe Grades
Both duplex stainless steel pipe grades we roll are 22Cr duplex, yet SA-790 assigns each its own chemical limits and tensile minimum.
Grade 2205 is the common name listed against S32205 in SA-790, which records it as a widely used common name rather than a trademark. Nitrogen starts at 0.14% and the specified minimum tensile strength is 655 MPa, so weld-intensive fabrication work prefers this grade.
View UNS S32205 PipeDuplex Pipe Forms and Types
Duplex SS pipes leave the plant in two production processes and three section profiles; each duplex pipe material variant is specified at order.
01
Seamless Duplex Steel Pipe
Duplex seamless pipe starts as a pierced hollow that is elongated, sized and solution annealed. The wall carries no weld line, so subsea spools and high-cycle pressure service are ordered on this route.
02
Welded / ERW Duplex Steel Pipe
SA-790 requires welded duplex pipe seams to be closed automatically without filler metal, a condition our high-productivity electric resistance welding (ERW) route satisfies. This ERW method provides high-strength welds below seamless prices at equal bore.
03
Duplex Round Pipe
Round section is the only profile with ASME B36.19M dimensions, so nominal bore and schedule terminology belong to it. The size chart further down applies to round duplex pipe, which process piping consumes almost entirely.
04
Duplex Square Pipe
Square duplex pipe is rolled to an agreed side dimension and wall, since no schedule system covers box sections. Structural supports in chloride-heavy plant zones specify it over coated carbon steel.
05
Duplex Rectangular Pipe
A rectangular section carries different stiffness across its two axes. Width, depth and wall are fixed in order, and walkways or skid frames loaded in one plane use that geometry.
Duplex Pipe Size
Available duplex pipe sizes with wall thickness per schedule appear in the duplex pipe schedule chart given in the table below.
| NB (mm) | NB (inch) | OD (mm) | SCH 5S (mm) | SCH 10S (mm) | SCH 20S (mm) | SCH 40S (mm) | SCH 80S (mm) |
|---|---|---|---|---|---|---|---|
| 6 | 1/8 | 10.3 | 1.24 | 1.24 | 1.50 | 1.73 | 2.41 |
| 8 | 1/4 | 13.7 | 1.24 | 1.65 | 2.00 | 2.24 | 3.02 |
| 10 | 3/8 | 17.1 | 1.24 | 1.65 | 2.00 | 2.31 | 3.20 |
| 15 | 1/2 | 21.34 | 1.65 | 2.11 | 2.30 | 2.77 | 3.75 |
| 20 | 3/4 | 26.7 | 1.65 | 2.11 | 2.55 | 2.87 | 3.91 |
| 25 | 1 | 33.4 | 1.65 | 2.77 | 3.00 | 3.38 | 4.55 |
| 32 | 1 1/4 | 42.2 | 1.65 | 2.77 | 3.00 | 3.56 | 4.85 |
| 40 | 1 1/2 | 48.3 | 1.65 | 2.77 | 3.00 | 3.68 | 5.08 |
| 50 | 2 | 60.3 | 1.65 | 2.77 | 3.00 | 3.91 | 5.54 |
| 65 | 2 1/2 | 73.0 | 2.11 | 3.05 | 4.00 | 5.16 | 7.01 |
| 80 | 3 | 88.9 | 2.11 | 3.05 | 4.00 | 5.49 | 7.62 |
| 100 | 4 | 114.3 | 2.11 | 3.05 | 4.50 | 6.02 | 8.56 |
| 125 | 5 | 141.3 | 2.77 | 3.40 | 5.00 | 6.55 | 9.53 |
| 150 | 6 | 168.3 | 2.77 | 3.40 | 6.35 | 7.11 | 10.97 |
| 200 | 8 | 219.1 | 2.77 | 3.76 | 6.35 | 8.18 | 12.70 |
| 250 | 10 | 273.1 | 3.40 | 4.19 | 6.35 | 9.27 | 12.70 |
Weight Chart of Duplex Steel Pipes
Nominal mass in kg/m for every entry in the duplex stainless steel pipe schedule chart above is provided in the table below.
| NB (mm) | NB (inch) | OD (mm) | SCH 5S (kg/m) | SCH 10S (kg/m) | SCH 20S (kg/m) | SCH 40S (kg/m) | SCH 80S (kg/m) |
|---|---|---|---|---|---|---|---|
| 6 | 1/8 | 10.3 | 0.28 | 0.28 | 0.33 | 0.37 | 0.47 |
| 8 | 1/4 | 13.7 | 0.39 | 0.49 | 0.58 | 0.63 | 0.80 |
| 10 | 3/8 | 17.1 | 0.49 | 0.63 | 0.74 | 0.85 | 1.10 |
| 15 | 1/2 | 21.34 | 0.80 | 1.00 | 1.08 | 1.27 | 1.62 |
| 20 | 3/4 | 26.7 | 1.03 | 1.28 | 1.52 | 1.68 | 2.20 |
| 25 | 1 | 33.4 | 1.30 | 2.09 | 1.94 | 2.50 | 3.24 |
| 32 | 1 1/4 | 42.2 | 1.65 | 2.70 | 2.90 | 3.38 | 4.47 |
| 40 | 1 1/2 | 48.3 | 1.91 | 3.11 | 3.35 | 4.05 | 5.41 |
| 50 | 2 | 60.3 | 2.40 | 3.93 | 4.24 | 5.44 | 7.48 |
| 65 | 2 1/2 | 73.0 | 3.69 | 5.26 | 6.81 | 8.63 | 11.40 |
| 80 | 3 | 88.9 | 4.51 | 6.45 | 8.37 | 11.30 | 15.20 |
| 100 | 4 | 114.3 | 5.84 | 8.36 | 12.18 | 16.07 | 22.30 |
| 125 | 5 | 141.3 | 9.47 | 11.57 | 16.81 | 21.80 | 31.97 |
| 150 | 6 | 168.3 | 11.32 | 13.84 | 25.36 | 28.30 | 42.70 |
| 200 | 8 | 219.1 | 14.79 | 19.96 | 33.31 | 42.60 | 64.60 |
| 250 | 10 | 273.1 | 22.63 | 27.78 | 41.77 | 60.50 | 96.00 |
Duplex Pipe Industrial Application
Duplex stainless steel applications concentrate where chlorides, pressure and structural load act together. Five industries generate most enquiries.
Offshore Oil and Gas
Gathering headers, produced water injection lines and topside process pipework specify duplex because chloride stress corrosion cracking eliminates standard austenitic pipe. High performance at 450 MPa yield reduces deck weight.
Chemical and Petrochemical Processing
Acid coolers, organic chloride streams and chlor-alkali transfer lines run in duplex steel pipe. Molybdenum protects the passive film against pitting, while the ferrite fraction carries the load without an extra wall.
Desalination and Seawater Systems
Reverse osmosis feed headers, brine recirculation loops and marine intakes operate in ambient seawater and brackish water. Duplex 2205 (UNS S32205) reaches a pitting resistance equivalent of at least 34 at its specified minimum composition, which covers the duty, and membrane pressures sit within the yield margin.
Pulp and Paper
Chlorine dioxide stage piping, washer circuits and liquor lines combine warm acidity with chlorides. Duplex withstands that service at lower alloy cost than superaustenitic material, so mills fit it during rebuilds.
Power Generation
Flue gas desulphurisation recirculation piping and coastal cooling circuits run duplex stainless pipe in chloride-bearing water at moderate temperature. Thinner walls on large spray headers cut both mass and installed cost.
Shipping and Packaging
Pipes are packed securely for export and delivered with the required markings and documents. We supply ready stock across India and export to Brazil, Turkey, and Vietnam on FOB or CFR terms.
- Pipes are batched by grade and schedule, strapped into bundles and cased in timber for export.
- Bore ends receive plastic caps; bevelled ends receive protective rings.
- Documents include the EN 10204 3.1 certificate and packing list.
- Exports move on FOB or CFR terms to Brazil, Turkey, and Vietnam.
Why Choose MLTI Private Limited?
Buyers return to Moonlight Tubes for certified material, approved grades and stock that ships on schedule. Every order is backed by documented quality, a wide size range and delivery commitments we hold to.
Quality Certification
01
IBR & EIL Approved
02
Why
Choose Us
03
Wide Range of Grades & Sizes
04
Timely Global Delivery
Duplex Steel Pipes FAQs
A duplex stainless steel pipe holds ferrite and austenite in near-equal proportions. The meaning of the duplex pipe comes from that dual phase: ferrite supplies strength, austenite supplies toughness. Site paperwork shortens the name to DSS pipes.
The duplex pipe ASTM code is A790, adopted by ASME as SA-790. With filler metal deposited in the seam.
The duplex pipe material code on most drawings is the UNS number: S31803 or S32205, both Werkstoff 1.4462. Super duplex codes as UNS S32750 or S32760.
Our duplex pipe sizes run from 1/8 inch to 10 inch NB in SCH 5S, 10S, 20S, 40S and 80S, with walls from 1.24 mm to 12.70 mm and lengths up to 24 ft.
Duplex 2205 pipe should be specified where chlorides drive the corrosion mechanism. In the duplex stainless steel vs 316 comparison, yield stands at 450 MPa against 170 MPa for 316L, so the duplex wall runs thinner at equal pressure. Grade 316 stays correct for reducing acids and service beyond 300°C.
The difference between duplex pipe and super duplex pipe is the alloy level. A super duplex pipe holds about 25% chromium with more molybdenum and nitrogen, pushing its pitting resistance equivalent past 40. Our supplied range covers the 22Cr grades UNS S31803 and UNS S32205.
A duplex pipe welding procedure controls heat input within a defined window. Cooling too quickly leaves excess ferrite; cooling too slowly precipitates intermetallic phases, so anyone learning how to weld duplex pipe starts with arc energy limits.