Pipe Spacing
Center-to-center spacing between two parallel lines on a pipe rack, looked up from bare and insulated line-spacing tables for NPS 1"–24".
When to use this calculator
Use when laying out a pipe rack or a sleeper way and you need the horizontal center-to-center distance between two adjacent lines. Pick the size and type of each pipe and the tool selects the right reference table — both bare, one bare and one insulated, or both insulated — then returns the tabulated spacing in mm and inches. It is a layout and plot-plan tool, used at the stage where you are fixing rack width and line order rather than analysing any single line.
Required inputs
- Pipe 1 — nominal size (1", 1½", 2", 3", 4", 6", 8", 10", 12", 14", 16", 18", 20", 24")
- Pipe 1 — bare or insulated
- Pipe 2 — nominal size
- Pipe 2 — bare or insulated
Expected outputs
- Center-to-center spacing in mm and inches
- Which reference table was applied (T1, T2, or T3)
- DN of each line, recorded for the layout note
Formula overview
Nominal sizes in inches, spacing returned in mm with an inch conversion. Insulation thickness is already built into the T2 and T3 values (roughly 40 mm at 1"–1½" rising to 75 mm at 10" and above).
Table lookup, not a formula. The pipe-type pair selects the table:
both bare → T1 Both Bare
one bare, one insulated → T2 Bare & Insulated
both insulated → T3 Both Insulated
The pair of nominal sizes then indexes the center-to-center value.
Tables are symmetric, so the order of the two lines does not matter.Worked example
A 12" bare line next to a 6" bare line on the same rack level:
both bare → Table T1
pair 12" × 6" → 390 mm center to center (15.4 in)
Insulate both lines and the same pair moves to Table T3, where the
spacing opens up to leave room for the insulation and its cladding.Common mistakes
- Confusing this with support span. This tool gives the horizontal gap between two neighbouring lines; the maximum distance between supports along one line is a different calculation — use the Pipe Span tool on PipingCalcPro for that.
- Applying bare-pipe spacing to a line that will be insulated later. Steam tracing, personnel protection, and cold insulation all widen the required gap, so decide the insulation scope before fixing the rack width.
- Treating the table value as final clearance. It is a nominal line-to-line spacing — flange OD, valve handwheels and stem travel, flange bolt removal, and branch take-offs can all demand more, and are checked separately against the 3D model.
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