What is Pipe Schedule?
As the main function of the pipes is to carry fluid under pressure therefore their internal diameter is their critical dimension. This critical dimension is referred to as the nominal bore (NB). Obviously, for pipes containing pressurised fluids the wall thickness, and by implication the pipe’s strength, is important. Wall thickness is expressed in “schedules“, referred to as pipe schedules. The pipe schedule is abbreviated as SCH. For a given size and schedule the thickness of the pipe is fixed and defined in the applicable ASME standard. Other than the pipe schedule, pipe thickness can also be specified in mm orinches to the value corresponding to that specified in the ASME standard.
What Standards Govern Pipe Sizes?
In the oil and gas and related downstream industries the most common standards are
– ASME/ANSI B 36.10 Welded and Seamless Wrought Steel Pipe, and
– ASME/ANSI B36.19 Stainless Steel Pipe
Does Pipe Schedule Change with Pipe Size?
For all pipe sizes the outside diameter remains relatively constant. Therefore any variation schedule i.e. wall thickness, affects only the inside diameter. As the schedule number increases, the wall thickness increases, and the actual bore is reduced.
STD is identical to SCH 40 for NPS 1/8 to NPS 10, inclusive. XS is identical to SCH 80 for NPS 1/8 to NPS 8, inclusive. XXS wall is thicker than SCH 160 from NPS 1/8″ to NPS 6″ inclusive, and SCH 160 is thicker than XXS wall for NPS 8″ and larger.
Pipe Schedule Charts
The wall thickness associated with a particular schedule depends on the pipe size as can be seen from the charts below for some of the more common sized carbon steel pipes encountered.
Stainless steel pipe is most often available in standard weight sizes (noted by the “S” designation, for example “NPS SCH 10S”). However stainless steel pipe can also be available in other schedules.
Abbreviations used: NPS– Nominal Pipe Size, NB – Nominal bore, STD – Standard, XS – Extra Strong, XXS – Double Extra Strong.
NPS | N.B. | O.D. | 10 | 20 | 30 | STD | 40 | 60 | XS | 80 | 100 | 120 | 140 | 160 | XXS |
1/8 | 6 | 10.3 | 1.24 | – | 1.45 | 1.73 | 1.73 | – | 2.41 | 2.41 | – | – | – | – | – |
1/4 | 8 | 13.7 | 1.65 | – | 1.85 | 2.24 | 2.24 | – | 3.02 | 3.02 | – | – | – | – | – |
3/8 | 10 | 17.1 | 1.65 | – | 1.85 | 2.31 | 2.31 | – | 3.2 | 3.2 | – | – | – | – | – |
1/2 | 15 | 21.34 | 2.11 | – | 2.41 | 2.77 | 2.77 | – | 3.73 | 3.73 | – | – | – | 4.77 | 7.47 |
3/4 | 20 | 26.67 | 2.11 | – | 2.41 | 2.87 | 2.87 | – | 3.91 | 3.91 | – | – | – | 5.56 | 7.82 |
1 | 25 | 33.4 | 2.77 | – | 2.90 | 3.38 | 3.38 | – | 4.55 | 4.55 | – | – | – | 6.35 | 9.09 |
1.1/4 | 32 | 42.16 | 2.77 | – | 2.97 | 3.56 | 3.56 | – | 4.85 | 4.85 | – | – | – | 6.35 | 9.7 |
1.1/2 | 40 | 48.26 | 2.77 | – | 3.18 | 3.68 | 3.68 | – | 5.08 | 5.08 | – | – | – | 7.14 | 10.16 |
2 | 50 | 60.32 | 2.77 | – | 3.18 | 3.91 | 3.91 | – | 5.54 | 5.54 | – | – | – | 8.74 | 11.07 |
2.1/2 | 65 | 73.02 | 3.05 | – | 4.78 | 5.16 | 5.16 | – | 7.01 | 7.01 | – | – | – | 9.52 | 14.02 |
3 | 80 | 88.9 | 3.05 | – | 4.78 | 5.49 | 5.49 | – | 7.62 | 7.62 | – | – | – | 11.12 | 15.24 |
3.1/2 | 90 | 101.6 | 3.05 | – | 4.78 | 5.74 | 5.74 | – | 8.08 | 8.08 | – | – | – | – | 16.15 |
4 | 100 | 114.3 | 3.05 | – | 4.78 | 6.02 | 6.02 | – | 8.56 | 8.56 | – | 11.12 | – | 13.49 | 17.12 |
Source: piping-engineering.com
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