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Tutorial 9 — Spring Hangers, Sized Automatically (Pro)

Where a pipe must move vertically (thermal growth near equipment) but still needs weight support, a rigid rest either lifts off or fights the movement. A variable spring hanger carries the weight while allowing travel. Sizing one by hand means catalogue tables; PipeFEA does it from the analysis.

Model: anchor → dX 6 → elbow → dZ 3 riser → elbow → dX 6 → anchor. DN150 SCH 40, 250 °C, 4 MPa. The horizontal runs each get a mid-span Variable Spring Hanger restraint (Restraints tab → type Variable Spring Hanger — leave stiffness/preload at defaults for now).

1. Auto-size​

  1. Settings → Auto-Size Spring Hangers.
  2. The sizer runs the weight (cold) and operating (hot) states, computes each hanger's required cold load and vertical travel, and picks a spring from the built-in catalogue: a size and series whose working range covers both positions with load variation ≤ 25 % (the usual variable-spring criterion).
  3. The result dialog lists, per hanger: hot load, cold load, travel, selected spring size/series, spring rate, and the variation percentage. Springs that can't meet 25 % are flagged — that location wants a constant-support hanger or a design change.

2. Apply and re-run​

  1. Accept the sizing — the hanger restraints are updated with the catalogue spring rate and preload.
  2. Run All Cases. Check:
    • Reactions at the hangers: hot-case load ≈ the sized hot load.
    • Sustained stress near the equipment anchor dropped compared to a rigid-rest design (try it: swap a hanger for a rest and compare — that's the whole point of springs).
    • Displacements: the riser grows freely; nothing binds.

3. Read the report​

The PDF gains a spring hanger schedule — the table a supplier quotes from: tag/node, hot & cold loads, travel, spring size, rate, variation. Hand it straight to procurement.

Manual override​

Each spring restraint's stiffness and preload stay editable in the Restraints tab afterwards — if the project standardises on a specific vendor series, type the vendor's rate in and re-run; the analysis uses exactly what you enter.

When a spring isn't the answer​

  • Travel near zero → a plain rest is cheaper; the sizer will show trivial travel.
  • Variation > 25 % even for the largest springs → constant-support territory (model as a vertical force equal to the hot load, or a very soft spring with preload).
  • Upward travel (pipe lifts hot) → check the sign of travel in the dialog; springs handle it, rests don't.