Seamless Stainless Steel Pipe

What is Seamless stainless steel pipe?

Seamless stainless pipe starts as a round billet that is heated and pierced or extruded into a hollow, then cold-drawn or cold-pilgered to size, solution-annealed, pickled and tested — there is no longitudinal weld, so there is no heat-affected zone, no bead and no joint factor: the code allows the full wall in the pressure calculation (E = 1.0) where welded pipe without full radiography gets 0.85. That is why seamless is specified for high pressure (sch 80, 160, XXS), for boiler and superheater tubes, heat-exchanger and condenser tubes (A213 / EN 10216-5 with tight wall tolerance), hydraulic and instrumentation lines (small-bore, 6–50 mm, often bright annealed and eddy-current tested), and for any service where a weld defect would be unacceptable — refinery, petrochemical, fertiliser, power, LNG and pharmaceutical projects. Grades are the same austenitics as welded pipe: 304L (1.4307) and 316L (1.4404) for most work, 321 (1.4541) and 347 for 400–800 °C, 310S for furnaces and duplex 2205 for chlorides. Dimensions follow ASME B36.19M (NPS ½–12, schedules 5S–160) or metric OD × wall (EN 10216-5, 6–323.9 mm); ends plain, bevelled or threaded. Seamless costs 30–60 % more than welded pipe of the same size and is usually made to order beyond the common ½"–4" sch 10S/40S range, which stock partners hold. Where the specification allows welded pipe (A312 welded, EN 10217-7) it is the cheaper and often more uniform choice; we supply both and say which is which on the certificate.

Weight table — round stainless tube by OD and wall (kg/m and per 6 m)

Metric OD × wall weights; for NPS × schedule sizes use ASME B36.19M (e.g. 2" sch 40S = 60.3 × 3.91 mm, 5.44 kg/m).

Grades, standards and tolerances

Seamless vs welded stainless pipe

Schedule and pressure guide

Lengths and stock

½"–4" in sch 10S and 40S, 304L and 316L, are held by our stock partners for despatch within 1–2 weeks; sch 80, 160, larger sizes, 321 / 347 / 310S / duplex and heat-exchanger tube are mill orders of 4–8 weeks. Random lengths 5–7 m or fixed 6 m; ends plain or bevelled 30°.

Cutting, bevelling and welding

Cold-saw or band-saw cutting, machine bevelling to 30–37.5° for butt welds; TIG root with argon purge and matching filler (ER308L / ER316L / ER347 for 321), then pickle; no preheat, interpass ≤ 150 °C. Bending of small-bore tube on mandrel benders; thick-wall pipe by induction. Hydraulic and instrumentation tube is supplied bright-annealed for compression fittings (Swagelok-type) and must not be scratched.

Where it is used

• High-pressure process, hydraulic and steam lines
• Boiler, superheater and heat-exchanger tubes
• Refinery, petrochemical and fertiliser plant piping
• Instrumentation and impulse lines (small-bore)
• LNG, cryogenic and offshore piping
• Pharmaceutical and food high-purity lines (bright annealed)

Seamless vs welded — when to pay for it

If the code, the pressure or the temperature calls for it, seamless is not negotiable; for process water, ducting, food lines and structures the welded 304 pipe and 316L pipe are cheaper and more uniform in wall. Carbon-steel seamless for the same duties is the seamless pipe page.

Price

Seamless stainless pipe is priced per metre or per ton by grade, size and schedule — 30–60 % above welded — and follows nickel; the bands below are indicative FOB Istanbul for the common sch 10S–40S range in 304L and 316L. Heavy schedules, special grades and A213 tubes are quoted per item.

Bands from our weekly export list (September 2026), FOB Istanbul, full-container quantities, excluding freight and certificates. Firm price per project on RFQ within one working day.

Export and packing

Seamless pipe is shipped in strapped bundles with plastic end caps, PE-wrapped against sea air, on timber bearers, tagged with heat, size, schedule and grade; small-bore instrumentation tube in wooden boxes. A 20' takes 15–20 t, a 40' HC 22–25 t of 6 m pipe. HS 7304.41 / 7304.49.

Certificates

Each heat ships with EN 10204 3.1 (chemistry, tensile, hardness, flattening / flaring, hydrostatic, eddy-current or UT) to A312 / A213 / EN 10216-5; 3.2 witnessing by Lloyd's, BV or TÜV, PED 2014/68/EU material certification, IGC (ASTM A262 E) and NACE MR0175 compliance are arranged at order.

How to order

Specify grade, NPS × schedule or OD × wall, standard (A312 / A213 / EN 10216-5), length and end finish, quantity in metres, certificate (3.1 / 3.2, PED, NACE MR0175 if sour service) and test requirements (hydro, ET/UT, IGC).

Standards

• ASTM A312 / A312M — seamless and welded austenitic pipe
• ASTM A213 — seamless boiler and heat-exchanger tubes
• EN 10216-5 — seamless stainless tubes for pressure purposes
• ASME B36.19M; EN 10204 3.1 / 3.2; PED

Grades

Grade data sheets (chemistry, mechanicals, equivalents) are on our reference site: 1.4404 · 1.4307 · 1.4541