Technical guide3 min read
What is the difference between stainless steel pipe and tube?
Pipe is sized by nominal bore and schedule; tube by actual outside diameter and wall thickness. Why the difference matters when you order.
Short answer: pipe is made to carry fluid and is specified by nominal bore and schedule, which together fix the wall thickness. Tube is specified by its actual outside diameter and wall thickness, and is used for heat exchangers, instrumentation, structural and decorative work. If you have an outside diameter and a wall thickness in millimetres, you are probably buying tube.
| Pipe | Tube | |
|---|---|---|
| Sized by | Nominal bore (NPS or DN) and schedule | Actual outside diameter and wall thickness |
| Typical use | Conveying fluid, structural lines | Heat exchangers, instrumentation, structural and decorative work |
| Sections | Round | Round, and square or rectangular in welded tube |
| Tolerances | Set by the pipe standard | Usually tighter, set by the tube standard |
| Commonly specified to | ASTM A312 / ASME SA-312 | ASTM A213 / SA-213, ASTM A269 |
Scroll the table horizontally to see all columns.
Common ordering mistakes
- Ordering by nominal size when the drawing gives an actual outside diameter, which are not the same number for small sizes.
- Not stating seamless or welded, which changes price, availability and sometimes acceptance.
- Leaving out the product standard, which fixes the tolerances and the tests.
Grades covered
Products covered
Specifying for a live project?
Send the service conditions and we will tell you what we would specify, and what we hold.