Pipe Loop — Companion Article
1. What this tool does
Pipe Loop sizes a symmetrical U-loop from the same guided-cantilever length as Pipe Leg. The calculation runs in the browser. It does not call the Engineering API.
2. When to use it
Use it when a designer is sketching a loop that takes the growth of one run. The result is preliminary. It is not a flexibility analysis.
3. Inputs
Enter the run, the temperatures or the expansion, the outside diameter, E, and Sa.
4. How it works
The running tool is the calculation. The relations already written for version 1.0.0 are:
Δ = α × run length × temperature difference
L = sqrt(3 × E × D × Δ / Sa)
W + 2H = L
The source named on the page is the guided cantilever method, M.W. Kellogg, Design of Piping Systems. The page takes L as the straight developed length of the loop. The usual proportion is height twice the width, so W = L/5 and H = 2L/5. Two other rows keep that same developed length and only change the proportion. Those rows are layout options, not extra code requirements. Elbow arc length is not included.
Assumptions stated on the page: anchors at both ends of the run, guides so the growth goes into the loop, and no friction.
5. Understanding the result
Read the developed length W + 2H, then the three proportions: height twice the width, height equal to width, and width twice the height.
The two proportions other than height twice the width are layout options. They are not extra code requirements. Elbow arcs are not included.
6. Engineering considerations
No catalogue facts are read. Anchors, guides, and no friction are assumed. The page does not name a code edition. This article does not add one.
The developed-length form is the one the page says is published for thermal expansion loops.
7. Example
Same basis as the pipe-leg run on 3 October 2026: NPS 6 Sch 40 carbon steel, outside diameter 168.3 mm, operating 150°C, install 20°C (temperature difference 130°C), α 12.0×10⁻⁶ /°C, E 203000 MPa, Sa 207 MPa, run 30 m. The figures were hand-checked.
Developed length W + 2H = 4813.8 mm. Elbow arcs are not included.
- Height twice the width: W 962.761 mm, H 1925.52 mm.
- Height equal to width: 1604.6 mm each.
- Width twice the height: W 2406.9 mm, H 1203.45 mm.
8. Standards/references (licensed vs interim)
No catalogue facts are read. The method citation is M.W. Kellogg, Design of Piping Systems, as the page states. The developed-length form is the one the page says is published for thermal expansion loops. This article does not name a code edition. The page does not name one.
Interim pipe dimensions on this site follow ASME B36.10-2022 Table 2-1. This tool does not use that table.
9. Limitations/disclaimer
- The result is preliminary and needs engineering review. It is not a flexibility analysis.
- Elbow arc length is not included.
- The two proportions other than height twice the width are layout options. They are not extra code requirements.
- Anchors, guides, and no friction are assumed.
A member check is not an engineering fact.
10. Use the tool
Calculate now: Pipe Loop
Related tools
Pipe Leg, at /tools-training/pipe-leg/, is the guided-cantilever leg page. This page uses that same length for a symmetrical U-loop. It is a different page.