What Is ASME B36.19?

Quick Answer

ASME B36.19M is the dimensional standard for welded and seamless austenitic stainless steel pipe. It defines four schedule designations (5S, 10S, 40S, 80S) and shares the same OD values as ASME B36.10 but has different wall thicknesses for certain NPS/schedule combinations. The “S” suffix distinguishes stainless steel schedules from carbon steel schedules.

The standard applies to austenitic stainless steel pipe covered by specifications such as ASTM A312, ASTM A358, and ASTM A409. It covers pipe from NPS 1/8 through NPS 30.

Key Dimensional Data

NPS	DN	OD (mm)	SCH 5S WT (mm)	SCH 10S WT (mm)	SCH 40S WT (mm)	SCH 80S WT (mm)
1/2	15	21.3	1.65	2.11	2.77	3.73
1	25	33.4	1.65	2.77	3.38	4.55
2	50	60.3	1.65	2.77	3.91	5.54
3	80	88.9	1.65	2.77	5.49	7.62
4	100	114.3	1.65	2.77	6.02	8.56
6	150	168.3	1.65	2.77	7.11	10.97
8	200	219.1	1.65	2.77	8.18	12.70
10	250	273.1	1.65	3.40	9.27	12.70
12	300	323.9	1.65	3.96	9.53	12.70
14	350	355.6	1.65	3.96	9.53	12.70
16	400	406.4	1.65	3.96	9.53	12.70
24	600	610.0	1.65	3.96	9.53	17.48

SCH 40S vs SCH 40 Differences

For NPS 1/8 through NPS 10, SCH 40S and SCH 40 are identical. The difference appears above NPS 10:

NPS	SCH 40 WT (B36.10)	SCH 40S WT (B36.19)	Difference
10	9.27 mm	9.27 mm	None
12	10.31 mm	9.53 mm	0.78 mm thinner
14	11.13 mm	9.53 mm	1.60 mm thinner
16	12.70 mm	9.53 mm	3.17 mm thinner
18	14.27 mm	9.53 mm	4.74 mm thinner
24	17.48 mm	9.53 mm	7.95 mm thinner

Above NPS 10, SCH 40S defaults to the STD wall thickness of 9.53 mm, while SCH 40 per B36.10 continues to increase. This makes a significant difference in pressure rating and weight calculations.

Why Stainless Pipe Uses “S” Schedules

Austenitic stainless steels have higher allowable stresses and better corrosion resistance than carbon steel. For the same pressure rating, a thinner wall is acceptable. The “S” schedules reflect this by providing only four designations rather than the full range of schedules in B36.10.

For higher pressure stainless applications requiring heavier walls, engineers can specify carbon steel schedule numbers (SCH 80, 120, 160) for stainless pipe. The pipe will be manufactured to the B36.10 wall thickness but in stainless material per ASTM A312.

Pro Tip

When ordering stainless pipe, explicitly state “SCH 10S” or “SCH 40S” with the “S” suffix. If you specify “SCH 10” without the “S” for stainless pipe above NPS 10, the supplier may furnish the heavier carbon steel wall thickness per B36.10 instead of the lighter B36.19 wall. This increases material cost and weight unnecessarily.

Applications by Schedule

Schedule	Typical Application
5S	Low-pressure utility, architectural, food/pharma
10S	Low to moderate pressure, standard process piping
40S	General-purpose process piping, refinery service
80S	High-pressure stainless piping, socket weld small bore

For complete dimensional tables covering both ASME B36.10 and B36.19, refer to the pipe size charts.

Read the full guide to pipe types