ASTM A790 UNS S31803 Duplex Welded Pipe For Water Treatment
UNS Grade: S32750
Manufacturing Process: Electric Fusion Welded (EFW)
Size Range: 8" NB – 48" NB (up to 120" available upon request)
Outside Diameter: 219.1 – 609.6 mm (up to 3048 mm)
Wall Thickness: Sch 10 – Sch 160 / XXS (6 – 60 mm)
Length: Fixed lengths, multiple lengths, or cut-to-size (up to 12 m)
Pipe Ends: Plain end, beveled, threaded, or in accordance with ASME B16.25 standards
Are you upgrading or designing a water treatment piping system but struggling with frequent pinhole leaks, biofouling-induced crevice corrosion, and premature replacement of 316L stainless steel pipes in brackish water, chloride-rich, or seawater pipelines?
In applications such as municipal wastewater reuse, brackish water reverse osmosis (RO), seawater desalination intake, and brine transportation, chloride concentrations can exceed the practical corrosion resistance limits of conventional austenitic stainless steels. ASTM A790 UNS S31803 Duplex Stainless Steel Longitudinally Welded Pipe is designed to support long-term reliability in demanding water treatment applications.
UNS S31803 duplex stainless steel typically has a Pitting Resistance Equivalent Number (PREN) of approximately 32–36, higher than the typical range of around 24–28 for TP316L. It offers improved resistance to pitting corrosion, crevice corrosion, and chloride-induced stress corrosion cracking under suitable service conditions. These properties make it a potential solution for water treatment systems exposed to warm water, residual chlorine, and biofilms associated with microbiologically influenced corrosion (MIC), which can contribute to piping failures.
We supply ASTM A790 UNS S31803 duplex stainless steel pipes manufactured using an automated longitudinal welding process without filler metal, subject to the agreed manufacturing specification. The pipes undergo solution annealing to help establish the required duplex microstructure and maintain the specified mechanical properties and corrosion resistance. Available sizes cover NPS 2 to NPS 20, with wall thicknesses including SCH 10, SCH 40, SCH 80, and customized heavy-wall options, subject to availability and applicable dimensions. End preparation options include plain ends, deburred ends, and beveled ends for welding. Fixed-length cutting and customized marking according to project drawings can also be arranged.
ASTM A790 UNS S31803 welded pipe has a specified minimum yield strength of approximately 450 MPa, around 1.8 times the typical minimum value of 316L stainless steel pipe under common product specifications. This higher strength may allow engineers to consider thinner pipe walls, reducing piping weight, installation labor, and overall capital expenditure, subject to pressure design calculations and applicable codes. The final wall thickness and pressure rating must be verified for the specific reverse osmosis (RO) system, including high-pressure feedwater, permeate, and concentrate lines.
ASTM A790 Duplex Pipe Specification
| Item | Detail |
| Standard | ASTM A790 / A790M, ASME SA-790 |
| UNS Designation | S31803 |
| Common Name | Duplex 2205 / 2205 |
| Process | Welded (ERW / EFW) |
| OD Range (Welded) | 10.3 – 1219 mm (3/8" – 48") |
| Wall Thickness | 1.24 – 59.5 mm |
| Schedules | 5S, 10S, 40S/STD, 80S/XS, 160, XXS |
| Length | Single random (6 m), double random (12 m), or cut-to-length |
| Ends | Plain, beveled, threaded, or per ASME B16.25 |
| NDE | Hydrostatic test, RT / UT / MT / PT on weld seam |
| Certifications | EN 10204 3.1 / 3.2, NACE MR0175, ISO 9001, PED |
Chemical Composition (wt. %)
| Element | C | Mn | P | S | Si | Cr | Ni | Mo | N | Cu | Fe |
| Max / Range | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 21.0 – 23.0 | 4.5 – 6.5 | 2.5 – 3.5 | 0.08 – 0.20 | 0.50 | Bal. |
PREN (Pitting Resistance Equivalent Number): Cr + 3.3Mo + 16N ≈ 35 – 38 (typical ~36)
Mechanical Properties (Solution Annealed)
| Property | Value |
| Tensile Strength (min) | 620 MPa (90 ksi) |
| Yield Strength, 0.2% offset (min) | 450 MPa (65 ksi) |
| Elongation in 50 mm (min) | 25 % |
| Hardness (max) | 290 HBW / 30 HRC |
| Annealing Range | 1020 – 1100 °C |
ASTM A790 Dimensional Tolerances (Welded Pipe)
OD Tolerance
| Specified OD (mm) | OD Tolerance (mm) |
| < 12.7 | ±0.13 |
| 12.7 – 48.3 | +0.40 / −0.80 |
| > 48.3 – 114.3 | +0.80 / −0.80 |
| > 114.3 – 219.1 | +1.60 / −0.80 |
| > 219.1 – 457.0 | +2.40 / −0.80 |
| > 457.0 – 609.6 | +3.20 / −0.80 |
| > 609.6 – 1219.2 | +4.80 / −0.80 |
Wall Thickness Tolerance (Welded)
| Specified OD (mm) | Wall Tolerance |
| ≤ 114.3 | +15% / −12.5% |
| > 114.3 – 457.0 | +15% / −12.5% |
| > 457.0 – 609.6 | +17.5% / −10% |
| > 609.6 | By agreement |
Minimum Wall Thickness
| Condition | Requirement |
| General (any point) | ≥ 87.5% of specified (max 12.5% under) |
| At weld seam (EFW) | ≥ specified wall (weld reinforcement permitted) |
| Weld seam crown | Max 3 mm above base surface |
Length Tolerance (Definite Cut Length)
| Specified Length | Tolerance |
| Up to 6 m | +15 mm / −0 |
| 6 – 12 m | +15 mm / −0 |
| > 12 m | By agreement |
If you're planning a project or selection, let me know:
• What specific type of water (seawater, brackish, chemical-heavy wastewater) are you moving?
• What pressure or schedule size (e.g., SCH 40, SCH 80) do you require?
HS Code for ASTM A790 UNS S31803 Duplex Welded Pipe
The HS code depends on the outside diameter (OD) of the welded pipe:
| HS Code | Description | Applicable When |
| 7306.40 | Other tubes, pipes and hollow profiles, welded, of circular cross-section, of stainless steel | OD ≤ 406.4 mm (≤ 16") |
| 7305.31 | Line pipe of a kind used for oil or gas pipelines, longitudinally welded | OD > 406.4 mm (> 16") |
ASTM A790 UNS S31803 Duplex Welded Pipe Price List
|
Product Description |
Standard / Grade |
Indicative Price (USD/kg) |
Price (USD/MT) |
|---|---|---|---|
|
Standard welded pipe |
ASTM A790 UNS S31803 |
$4.20–6.00 |
$4,200–6,000 |
|
Small-diameter welded pipe |
ASTM A790 UNS S31803 |
$4.50–7.00 |
$4,500–7,000 |
|
Large-diameter welded pipe |
ASTM A790 UNS S31803 |
$4.00–6.50 |
$4,000–6,500 |
|
Heavy-wall welded pipe |
ASTM A790 UNS S31803 |
$4.80–7.50 |
$4,800–7,500 |
|
Project-specific welded pipe |
ASTM A790 UNS S31803 / 2205 |
By quotation |
By quotation |
GNEE can quote ASTM A790 UNS S31803 duplex welded pipes according to your required dimensions, testing plan and delivery destination. Submit your size list and quantity to receive a project-specific price, lead time and certificate options.
Inspection and Testing
Every batch of welded pipes undergoes the mandatory testing procedures required by the ASTM A790 standard. These include: chemical composition analysis of both the molten steel and the finished product; tensile and hardness testing; flattening tests to verify the ductility of the weld seam; 100% eddy-current non-destructive testing; and hydrostatic testing of every individual pipe. A material test certificate compliant with the EN 10204 3.1 standard is provided, and third-party witnessed inspections-conducted by organizations such as SGS, BV, or TÜV-are also supported.
Wooden crate packaging
Regarding delivery arrangements: Products with standard stock specifications can be dispatched within 12–20 business days. For shipment, the pipes are wrapped in anti-rust film and secured within heat-treated wooden crates, which also contain desiccant. This ensures that the pipes-including their weld seams-remain protected from damage or contamination caused by moisture during long-distance ocean transport to water conservancy project sites.
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