Seamless Pipe

Seamless pipe has no longitudinal weld seam, so there is no weld line to inspect or fail — which is why it is often specified for high-pressure, high-temperature, cyclic and sour service. It still has dimensional tolerances, possible eccentricity and manufacturing defects, so the choice depends on the specification, grade, dimensions, service and design code rather than a universal “seamless is always better” rule; for many services a qualified welded pipe is fully acceptable.

Only up to a point. STD and Sch 40 have the same wall up to NPS 10 and then diverge — at NPS 12, STD is 9.53 mm but Sch 40 is 10.31 mm. XS and Sch 80 have the same wall up to NPS 8 and then diverge — at NPS 10, XS is 12.70 mm but Sch 80 is 15.09 mm. Above those sizes STD stays at 9.53 mm and XS stays at 12.70 mm, so the correct wall must be taken from the right column.

Mostly, but not always. ASME B36.19M S-schedules (5S, 10S, 40S, 80S) coincide with many B36.10M walls, with specific exceptions — for example 10S differs at NPS 14–22, 40S at NPS 12, and 80S at NPS 10 and 12. S-schedule walls are therefore taken from B36.19M rather than assumed equal.

Theoretical plain-end mass is kg/m = π × ρ × 10⁻⁶ × t × (D − t), with outside diameter D and wall t in mm and density ρ in kg/m³. Our weight chart uses carbon steel (ρ = 7850). For stainless, duplex or nickel alloys the weight scales by the grade’s density ratio, so carbon-steel figures are not used directly. Actual weighed mass varies with tolerances and length.

Yes, by named grade and specification: Incoloy/Alloy 825 (N08825) to ASTM B423, Monel 400 (N04400) to B165, Alloy 625 (N06625) to B444, and named Hastelloy grades (for example C-276) to B622 where offered. “Inconel 825” is a naming error — 825 is an Incoloy/Alloy grade — and because a trademark like Hastelloy covers several alloys, the exact grade and UNS are always confirmed.

No. A schedule defines a nominal wall thickness, not an allowable working pressure, and a hydrostatic test pressure is not a working pressure either. Pressure suitability is a design-code calculation using the allowable stress at temperature, the minimum wall after tolerance, corrosion allowance and other factors, for the specific grade and service.

Provide the material standard and edition, grade and condition, seamless route, NPS or OD, wall or schedule, length, quantity, end preparation, finish/coating, design and service conditions (temperature, pressure, medium, corrosion allowance), required testing and documentation, and delivery location. Availability by grade and size is confirmed with the quotation.