ASME B36.19-2022 is the current edition of the dimensional standard for welded and seamless wrought stainless steel pipe. Published by ASME as a companion to B36.10, it defines four schedule designations — 5S, 10S, 40S, and 80S — covering NPS 1/8 (DN 6) through NPS 30 (DN 750). The "S" suffix distinguishes these as stainless steel schedules. While stainless pipe can also be manufactured to B36.10 schedule dimensions, B36.19 schedules are specifically optimized for the corrosion resistance and strength characteristics of austenitic, ferritic, and duplex stainless steels.

The fundamental difference from B36.10 is practical: because stainless steel resists corrosion, you generally do not need the same corrosion allowance as carbon steel. This means stainless pipe often runs at thinner walls for the same design pressure. Schedule 10S, in particular, is widely used in process plants for stainless steel piping because it provides sufficient pressure capacity without the weight and cost penalty of thicker schedules.

NPS to Outside Diameter Quick Reference

The outside diameters in B36.19 are identical to those in B36.10 — both standards use the same OD per NPS. As with carbon steel, NPS 1/8 through NPS 12 have ODs that do not equal the nominal size, while NPS 14 and above match.

Complete Stainless Steel Pipe Schedule Table – NPS 1/2 through NPS 12

For the sizes most commonly ordered — NPS 1/2 through NPS 12 — all four B36.19 schedules are available. Schedule 5S and 10S dominate stainless process piping because of their thinner walls. Schedule 40S matches Sch 40 from B36.10 through NPS 10, and Schedule 80S matches Sch 80 through NPS 8. Wall thickness and weight are given in metric units.

Stainless Steel Pipe – NPS 14 through NPS 30

For large diameter stainless pipe, the schedule availability narrows. B36.19 defines 5S and 10S across the entire range to NPS 30. Schedule 40S and 80S extend only to NPS 24 in the standard, and for NPS 22 and NPS 30 only 5S and 10S are defined. These large-bore stainless pipes are commonly used in seawater intake lines, chemical process headers, and desalination plant piping.

Common Stainless Steel Grades for ASME B36.19 Pipe

ASME B36.19 specifies dimensions only — material chemistry and mechanical properties are governed by the applicable ASTM standard. The table below lists the stainless steel grades most frequently specified with B36.19 dimensions. Each grade brings a specific corrosion resistance and temperature capability to the table.

ASME B36.10 vs ASME B36.19 – Key Differences at a Glance

Engineers frequently ask whether to order stainless pipe to B36.10 or B36.19. The choice matters for procurement because the supplier may default to one or the other depending on the schedule called out. The table below highlights where the two standards diverge.

Frequently Asked Questions

Why use Schedule 10S for stainless steel instead of Schedule 40S?

Schedule 10S is the most commonly specified stainless schedule in process plants for a practical reason: stainless steel's higher corrosion resistance means you do not need the extra wall thickness as a corrosion allowance. A Sch 10S pipe handles the same design pressure as Sch 40S for most medium-pressure process services (Class 150 and Class 300 flanged systems), and it costs significantly less — both in material cost and in welding time due to thinner walls requiring less filler metal and heat input.

Can I substitute B36.10 Sch 40 pipe for B36.19 Sch 40S?

For NPS 1/8 through NPS 10, they are dimensionally identical — same OD and same wall thickness. The only difference is the standard that governs. However, for NPS 12 and above, B36.10 Sch 40 is thicker than B36.19 Sch 40S. A substitution in the larger sizes would result in a heavier, more expensive pipe with a smaller inside diameter — potentially affecting flow calculations. Always verify the dimensional requirements against your piping specification before substituting.

What is the tolerance on wall thickness for B36.19 pipe?

ASME B36.19 itself does not define tolerances — these come from the applicable ASTM material standard. For ASTM A312 (the most common stainless pipe specification), the wall thickness tolerance is typically ±12.5% of nominal for seamless pipe, and can be tighter for welded pipe depending on the manufacturer's capability. Always reference the mill test certificate (MTC) for the actual measured wall thickness of the heat you receive.

Does Schedule 5S have any pressure rating at all?

Yes — but it is limited. Schedule 5S stainless pipe is typically used for gravity flow, low-pressure vent lines, and exhaust ducting rather than pressurized services. A quick calculation: at NPS 4 (OD 114.3 mm, wall 2.11 mm), an ASTM A312 TP316 Sch 5S pipe has an allowable working pressure of roughly 8 bar at ambient temperature per ASME B31.3. For anything carrying process pressure, Sch 10S or heavier is the safer default.