Manufacturing process
Produced by extrusion or rotary piercing of hot stainless billet, followed by pilger cold-rolling and / or cold-drawing to final dimensions. Solution-annealed and pickled to restore austenitic structure and remove scale.
Cross-section · Circular Hollow Section
Seamless Pipe
Stainless Steel Pipes & Tubes · Pressure & process seamless pipe
Stainless Steel Seamless Pipes
Seamless stainless pipes for pressure & process service
Seamless stainless pipes are extruded or pierced from solid billet without longitudinal weld, delivering homogeneous wall structure and superior pressure / temperature performance. The default choice for process, instrumentation, oil & gas, refinery, pharmaceutical and high-pressure stainless service.
No longitudinal weld
Pressure & high-temperature rated
Austenitic & duplex range
PMI & hydrostatic test reports
Standards
ASTM A312, A213, A269, A790 (duplex)
Grades
TP 304 / 304L / 316 / 316L / 321 / 347 / S31803 / S32750
OD range
6 – 660 mm
Wall thickness
Sch 5S – Sch 160
Finish
Pickled / polished
Lengths
6 m random / 12 m fixed
Quick reference
Stainless Steel Seamless Pipes: the essentials.
A concise, citation-ready summary for engineers, architects, AI assistants and procurement teams.
- Seamless stainless pipes have no longitudinal weld, produced from a solid billet by hot extrusion and cold pilger / draw, then solution-annealed and pickled.
- Standards: ASTM A312 (austenitic), ASTM A790 (duplex), EN 10216-5 (pressure service), JIS G3459.
- Common grades: 304L (1.4307), 316L (1.4404), 321 (1.4541), duplex 2205 (1.4462), super-duplex 2507 (1.4410).
- Dimensions per ASME B36.19M, Sch 5S / 10S / 40S / 80S in NPS ½" to 24".
- Specified for pressure piping, chemical, refinery, sour-service and hygienic systems where weld integrity cannot be compromised.
Service & inspection
Hydrostatic tested per ASTM A312, eddy-current or ultrasonic NDT, PMI verification, EN 10204 3.1 / 3.2 MTC. Suitable for class 150 – 2500 pressure service depending on grade and dimension.
Specifications
Stainless Steel Seamless Pipes: full technical data.
| Property | Value |
|---|---|
| Standards | ASTM A312 (general), A213 (boiler), A269 (general low-pressure), A790 (duplex) |
| Grades | TP 304 / 304L / 316 / 316L / 321 / 347, UNS S31803 (2205), S32750 (2507) |
| Outside diameter | 6 – 660 mm (1/8" – 26") |
| Wall thickness | Sch 5S, 10S, 40S, 80S, 160 / XS, XXS |
| Tolerance | ASTM A999 / EN ISO 1127 |
| Standard lengths | 6 m random, 12 m fixed (cut-to-length on request) |
| Testing | Hydrostatic, eddy current / ultrasonic, PMI |
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Applications
Where stainless steel seamless pipes are specified.
Oil & gas process lines
Refinery & petrochemical
Pharmaceutical & food-grade
Boiler & heat exchanger tubes
Instrumentation lines
High-pressure utilities
Marine & offshore systems
Engineering guide
Understanding stainless steel seamless pipes.
How seamless stainless pipe is made
Production begins with a solid round billet of the specified stainless grade. The billet is heated to ~1200 °C and pierced by a rotary mandrel to form a hollow shell, then progressively elongated and reduced through a hot extrusion press or a Mannesmann-Pilger mill. Final sizing is performed cold on a pilger or draw bench to deliver tight OD and wall tolerances. The pipe is then solution-annealed (typically 1050 – 1100 °C, water-quenched) to restore austenitic microstructure, pickled in HNO₃/HF to remove scale and passivated for corrosion performance.
Pipe schedules: what Sch 10S, 40S and 80S really mean
Schedule is a dimensionless number defining wall thickness at each Nominal Pipe Size (NPS) per ASME B36.19M. Sch 10S is light wall, preferred for hygienic, architectural and low-pressure service. Sch 40S is the general-purpose process pipe and the default when no schedule is stated. Sch 80S is heavy wall for higher-pressure service, sour duty and Class 300+ flanged systems. Stainless ‘S’ schedules are thinner than carbon-steel equivalents because stainless does not require a corrosion allowance.
Selecting the right grade for piping service
304L is appropriate for utility water, condensate and clean indoor service. 316L is the default for chemical process piping, marine, food CIP/SIP and any chloride exposure. 321 (titanium-stabilised) is used where service exceeds 425 °C to avoid sensitisation. Duplex 2205 is selected for weight-critical higher-pressure service and seawater duty; super-duplex 2507 for splash-zone and aggressive chloride / sour systems qualified to NACE MR0175.
Dimensional data
Stainless seamless pipe: ASME B36.19M (OD × wall in mm)
| NPS / DN | OD (mm) | Sch 10S (mm) | Sch 40S (mm) | Sch 80S (mm) |
|---|---|---|---|---|
| 1" / DN 25 | 33.4 | 2.77 | 3.38 | 4.55 |
| 1½" / DN 40 | 48.3 | 2.77 | 3.68 | 5.08 |
| 2" / DN 50 | 60.3 | 2.77 | 3.91 | 5.54 |
| 3" / DN 80 | 88.9 | 3.05 | 5.49 | 7.62 |
| 4" / DN 100 | 114.3 | 3.05 | 6.02 | 8.56 |
| 6" / DN 150 | 168.3 | 3.4 | 7.11 | 10.97 |
| 8" / DN 200 | 219.1 | 3.76 | 8.18 | 12.7 |
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Wall thickness data per ASME B36.19M / B36.10M; full schedule range available on request.
Comparison
Seamless vs Welded Stainless Pipe
| Property | Seamless (A312) | Welded (A312 EFW / ERW) |
|---|---|---|
| Production | Hot extruded from billet | Plate / coil rolled & longitudinally welded |
| Weld seam | None | Longitudinal HF or laser weld |
| Pressure rating | Highest | Slightly reduced (weld joint factor) |
| Wall thickness range | Up to Sch 160 / XXS | Typically up to Sch 40S / 80S |
| Concentricity | ± 12.5 % | Better (rolled from flat) |
| Cost | Higher (~1.4 – 1.8×) | Lower |
| Typical use | High pressure, sour, critical | General process, utility, architectural |
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International standards
Stainless Steel Seamless Pipes across global standards.
| Region | Standard | Designation | Notes |
|---|---|---|---|
| USA | ASTM A312 / A312M | Seamless & welded austenitic pipe | TP304L, TP316L, TP321, TP347 |
| USA | ASTM A790 / A928 | Seamless & welded ferritic-austenitic (duplex) | S31803, S32205, S32750 |
| Europe | EN 10216-5 | Seamless pressure pipe, stainless | 1.4404, 1.4541, 1.4571, 1.4462 |
| Dimensions | ASME B36.19M / B36.10M | Stainless pipe dimensions | Sch 5S / 10S / 40S / 80S / 160 |
| Japan | JIS G3459 | Stainless pipes for piping | SUS304TP, SUS316TP |
| Sour service | NACE MR0175 / ISO 15156 | H₂S service qualification | 316L (limited), 22Cr / 25Cr duplex |
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How to specify
Specifying stainless steel seamless pipes for your project.
A step-by-step engineering workflow used by architects, consultants and procurement teams to specify the correct grade, finish and standard.
- Step 01
Confirm design code
Identify the governing code, ASME B31.1 (power), B31.3 (process), B31.4/B31.8 (pipelines), and the design pressure, temperature and fluid category.
- Step 02
Pick the grade
Match grade to service: 304L general, 316L process/marine, 321 high-temp, duplex 2205 for chloride, super-duplex for severe sour or splash-zone (NACE MR0175 qualified).
- Step 03
Select schedule
Use Sch 40S as the starting point. Downgrade to Sch 10S only for low-pressure architectural or hygienic service; upgrade to Sch 80S / 160 for high pressure or sour duty.
- Step 04
Specify end finish
Plain ends (PE), bevelled ends (BE, 30° / 37.5°) for butt welding, or threaded (NPT / BSPT) for utility piping.
- Step 05
Call up testing
Hydrostatic test, NDT (RT or UT for critical), PMI verification, EN 10204 3.1 (or 3.2 for pressure / sour service) MTC, IGC test per ASTM A262 Practice E if specified.
- Step 06
Confirm packaging & marking
Bundled with plastic end caps and PVC film for premium service; heat number, grade, size, schedule, standard and mill stencilled on each length.
Related guides & products
Continue exploring stainless steel.
Welded Stainless Pipes
ASTM A312 EFW / ERW pipes for general process service.
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304 vs 316 Stainless Steel: full comparison
Chemistry, PREN, corrosion behaviour and selection rules for the two most-specified austenitic grades.
Stainless Steel Finishes: 2B, BA, No.4, HL, Mirror
Mill, brushed, hairline, mirror and PVD finishes, what to specify for architecture and hygiene.
Pipe Schedule Guide: Sch 10S, 40S, 80S
ASME B36.19M stainless pipe wall thicknesses with selection guidance.
FAQ
Stainless Steel Seamless Pipes: answered.
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