Piping, Tanks, and Industrial Systems
Codes and system boundaries
ASME B31.1 governs power piping, B31.3 process piping, CSA B51 boiler external piping, and CSA B149 fuel gas piping. The boundary between boiler and piping decides which code and which test applies, so locate it before you cut anything.
Offsets and take-outs
- 45° offset: travel = set × 1.414; cut length = travel − 2 × fitting take-out.
- Long-radius 90° elbows have a centre-to-face take-out of 1.5 × NPS; short radius is 1.0 × NPS.
- Rolling offset: travel = √(set² + roll²), then true offset = √(travel² + advance²).
- Add root gap and subtract backing ring thickness when calculating the cut.
Worked example: rolling offset
Set 300 mm, roll 400 mm, advance 600 mm. Travel = √(300² + 400²) = √250 000 = 500 mm. True offset = √(500² + 600²) = √610 000 = 781 mm. Subtract the two fitting take-outs from 781 mm for the pipe cut length. Using 500 mm - the flat travel only - leaves the spool roughly 280 mm short.
Supports, flanges and alignment
- Spring hangers are set to cold load and travel; shipping pins come out only when specified.
- Flange limits cover gap, offset and angularity; bolts are brought up in a star pattern, and the gasket is never used to pull a joint together.
- Cold spring, slope and drainage direction are recorded on the drawing and must survive installation.
Tanks
API 650 style work: shell courses erected with plumbness commonly limited to 1/200 of total height, shell-to-bottom welds sequenced to control distortion, and the wind girder installed before the shell is left free-standing.
Traps
- Mixing B31.1 and B31.3 acceptance and testing requirements.
- Forgetting fitting take-out, so the spool is long and the flanges will not close.
- Confirming the bolt-hole orientation on horizontal flanges before welding.
- Pulling a misaligned joint with bolts, which preloads the flange and gasket unevenly.