Short answer: Seamless pipe is made from a pierced billet and is preferred for thick walls, ultra-high pressures and the most conservative process codes. Welded pipe (ERW, EFW, welded and drawn) is produced from rolled strip and delivers superior concentricity, longer random lengths and lower cost in thin-to-medium walls. The right choice depends on the governing code, wall thickness, test regime and end connector configuration.
This guide is written for stainless steel buyers, sourcing teams, engineers and product manufacturers. The purpose is not to declare one universal winner, but to turn a broad material question into a specification that a mill or service center can quote, process and inspect consistently.
Quick Comparison
| Option | Key point | Typical use or decision |
|---|---|---|
| ERW welded pipe | Continuous longitudinal weld, efficient | Process piping, low-to-medium pressure, Sch 10S/40S |
| Welded & drawn (DOM) tube | Weld then cold-draw for tight tolerances | Instrumentation, hydraulic, precision mechanical |
| Seamless pipe | No longitudinal weld, thick wall available | High pressure, refinery, high-temperature headers |
| Hygienic / sanitary tube | Polished ID, clamp or orbital weld ends | Food, dairy, beverage, biopharma |
The table is a starting point. Actual performance depends on the governing standard, delivered condition, dimensions, surface finish, fabrication route and service environment. Commercial names should never replace a complete purchase specification.
What Buyers Should Evaluate
- State the exact dimensional standard: ASME B36.19M for Sch S piping, ASTM A269/A270 for tubing, ISO 1127 or DIN 11850 for sanitary.
- Define end preparation: plain end, beveled, grooved, clamp-ready, stub-end compatible.
- Require applicable NDT: hydrotest, eddy current, ultrasonic or radiography of welds.
For production orders, share the end use rather than requesting a grade or finish in isolation. A supplier can then review corrosion exposure, forming severity, welding, visual requirements and packing before material is cut. This early review is usually less expensive than correcting a rejected shipment or unstable production trial.
Common Purchasing Mistakes
- Ordering “304 pipe” without a schedule or tolerances, and receiving tubing that is too thin for the pressure class
- Mixing sanitary tube ends with standard ASME B16.5 flanges without adapter pieces
- Skipping weld-seam verification on welded pipe for regulated service
These mistakes are avoidable when drawings, approved samples, inspection methods and certificate requirements are agreed before production. For visual products, retain a signed master sample. For functional dimensions, define where and how measurements will be taken.
Recommended RFQ Wording
Include nominal size and schedule or OD × wall, material grade (UNS preferred), product form (seamless vs welded), dimensional standard, end finish, NDT tests, hydro test pressure and certificate type (EN 10204 3.1 or 3.2 if required).
Also include order quantity, acceptable quantity variation, destination, required delivery date and whether partial shipments are allowed. If a requirement is critical, make it measurable and place it on the purchase order rather than only in an email conversation.
How Still Steel Supports the Project
Still Steel supplies stainless steel coil, strip and sheet and provides slitting, cut-to-length, brushing, polishing and protective-film services. We can compare available mill material with your drawing, prepare trial quantities and preserve heat-number traceability through service-center processing.
Send the grade, dimensions, annual volume and application to vip@still-steel.com, or discuss the requirement on WhatsApp.
Frequently Asked Questions
Is seamless always better than welded?
Not for every project. ERW and welded-and-drawn tube are cost-effective and reliable when produced and tested to modern standards, while seamless excels at very high pressure, large wall thickness or critical service histories.
What does schedule number mean?
Schedule (Sch 5S, 10S, 40S, 80S, etc.) is a pipe wall-thickness series referenced to a nominal pipe size. Larger schedules mean thicker walls and higher pressure ratings at the same OD.
Can sanitary tube be used for process pressure piping?
Sanitary tube dimensions, weld ends and pressure ratings differ from ASME B36 piping. Confirm with the design code before mixing.
Technical References
Reference documents support general selection and fabrication principles. The final material decision must follow the applicable contract, standard, regulation and engineering review for the specific product.