For professionals in the steel pipe industry, these two American dimensional standards are frequently encountered in customer orders. Their specific dimensions (identified using DN, NPS, and SCHEDULE designations) are shown in the chart below. So, what are the differences between them?

1. Scope of Application

Based on their names alone — ASME B36.10M (Seamless and Welded Wrought Steel Pipe) and ASME B36.19M (Stainless Steel Pipe) — it is easy to see that ASME B36.10M applies to alloy pipes, carbon steel pipes, and stainless steel pipes, whereas ASME B36.19M applies only to stainless steel pipes.

2. Schedule Designation Differences

From the chart, the ASME B36.19M schedules — SCH5S, SCH10S, SCH40S, SCH80S — all carry an “S” suffix after the number. This “S” stands for stainless steel. By contrast, ASME B36.10M schedules — SCH10, SCH20, SCH30, SCH40, SCH80, SCH100, SCH120, SCH140, SCH160 — do not carry an “S” suffix.

3. Wall Thickness Differences at the Same Schedule Number

For the same schedule number — for example, SCH40S vs. SCH40 — the wall thicknesses are identical for smaller pipe diameters. However, for larger pipe diameters, the wall thickness of the schedule without the “S” suffix becomes greater. The same applies to SCH80S vs. SCH80. Pay close attention to this distinction.

4. Range of Dimensions

The dimensional range covered by ASME B36.19M is limited to what is shown in the chart, while ASME B36.10M covers a broader range — including additional dimensions defined by specific wall thicknesses. For everyday reference purposes such as checking specific outer diameters and wall thicknesses, the chart below is sufficient.