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Tutorial 3 — Supports & Restraints in Practice

Model: a 24 m straight DN150 header between two anchors, operating at 150 °C. We'll support it properly and watch friction and lift-off behave.

Setup: New project; DN150 SCH 40 section; carbon steel; T_max 150 °C; pressure 1.5 MPa. Route: anchor node at origin (Manual Node + Full Anchor), then one sequential segment dX 24, and anchor the far node too.

1. A row of resting supports in one action​

  1. Assign → Generate Supports Along a Straight Run.
  2. In the restraint editor above it, configure the support template: type Directional Support, Z = POS (one-way — the pipe may lift), μ = 0.3.
  3. Start Node = the origin anchor node, Direction = along the 24 m element, Spacing 4 m, Max Count blank, first support at start node unticked (the anchor is there).
  4. Generate Supports → 5 supports at 4, 8, 12, 16, 20 m; the pipe is split automatically.

Run OPE: the header slides through the supports; open Reactions — each support's Fx is its friction drag (≈ μ × its vertical load), and the anchors take the balance.

2. A guide, done in LOCAL coordinates​

  1. Click the support node at 12 m → Inspector → set X = FREE, Y = FIXED, Z = POS with Coordinate System = GLOBAL — that's a guide on an X-run. On a skewed run you'd instead pick LOCAL and fix Transverse.

3. Gaps and one-way behaviour​

  1. On the same guide give Gap Y = 3 mm. Re-run OPE: the guide only engages if lateral movement exceeds 3 mm — check the Displacements tab. Gapped/one-way states are solved iteratively; the mesh shows which engaged.

4. A variable spring hanger, auto-sized​

  1. Change the support at 8 m to type Variable Spring Hanger, leave Auto-size stiffness ticked.
  2. Settings → Auto-Size Spring Hangers. The two-pass MSS SP-58 sizing writes the spring rate and preload (hot load) into the hanger — open its editor to see the numbers, and check the spring row in Reactions after re-running.

5. A dynamic snubber​

  1. Add a node restraint of type Dynamic Snubber, axis X, near mid-span. Static cases ignore it; configure a seismic g-factor (Settings → Seismic, GENERIC, 0.3g, direction X) and run OCC-SEIS — the snubber now locks and picks up load (Reactions tab).

6. Imposed displacements (nozzle growth)​

  1. Edit the far anchor: enter Imposed Y = 10 mm — the connected vessel grows 10 mm laterally when hot. Re-run OPE and EXP; the line now bends to follow the nozzle. This is how equipment movements are modelled.

7. Lift-off check​

  1. Exaggerate: set T_max to 250 °C and re-run OPE. Some supports may unload to zero (lifted off — one-way behaviour). Reactions showing Fz = 0 at a rest = the pipe is airborne there. This is why rests should be one-way (POS), not FIXED.

Reference: Restraints & Supports documents every field.