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Restraints & Supports

Restraints live on nodes. Set them while routing, in the node Inspector (click the node in 3D), in Manual Node mode, or via the tools in the Assign tab. The same restraint editor appears everywhere.

Restraint types​

Full Anchor (Fixed)​

Locks all six degrees of freedom. Use at equipment nozzles, line terminations and boundary tie-ins. Supports imposed displacements/rotations (mm / rad) — model equipment nozzle growth by entering the hot movement of the connection.

Directional Support / Limit Stop​

The general-purpose support. Each of the six directions (X, Y, Z, RX, RY, RZ) is set independently:

StateMeaning
FREENo restraint in this direction
FIXEDRigid both ways (guide, line stop)
POS / NEGOne-way: resists motion in one direction only — the pipe can lift off. A resting shoe is Z: POS-style one-way support
DOUBLETwo-way limit stop with a gap each side
  • Gaps (mm) — clearance before a one-way/double direction engages. The solver iterates the contact state (engaged/lifted) automatically.
  • Friction μ — Coulomb friction on the sliding plane, computed from the actual normal force each iteration using an elastic stick-slip model (see the Technical Reference). Steel-on-steel is typically 0.3.
  • Imposed displacements — settlement or forced movement at the support.
  • Coordinate System — GLOBAL (X/Y/Z) or LOCAL (Axial / Vertical / Transverse relative to the pipe direction) — use LOCAL for guides on skewed runs.

Variable Spring Hanger​

Vertical (and optionally lateral) spring rates in N/mm plus a Preload (the hot load). With Auto-size stiffness ticked, the spring sizing tool fills these for you.

Dynamic Snubber​

Free during static cases (weight, thermal — the pipe moves through it), rigid along its axis during occasional (wind/seismic) and modal analysis. Choose the acting axis.

Placing supports mid-pipe​

Assign → Insert Support Along Element: pick the element (or click it in 3D), enter the axial distance from its start node, configure the restraint, and Slice Pipe & Insert Support — the pipe is split at that point and the support applied. A preview marker shows the position in 3D as you type.

Generate supports along a straight run​

Assign → Generate Supports Along a Straight Run places a whole row of identical supports in one action:

  1. Configure the support in the restraint editor above (type, directions, friction…).
  2. Pick the Start Node and the Direction (which connected element to walk along).
  3. Set the Spacing and optionally a Max Count (blank = to the end of the run) and whether to place the first support at the start node.
  4. Generate Supports.

The generator walks the collinear run, splitting pipe wherever a support lands mid-element (all element properties carry over), skips nodes that already have restraints, skips points that fall inside valves/flanges/rigid elements, and stops at bends/tees or direction changes. The whole operation is one undo step.

Auto-sizing spring hangers​

Settings → Auto-Size Spring Hangers runs the two-pass MSS SP-58 procedure: a rigid-weight pass finds each spring's hot load, a free-thermal pass finds its vertical travel, and the tool writes the resulting spring rate and preload back into every spring restraint that has Auto-size stiffness ticked. Review the values in each spring's editor afterwards.

Modelling guidance​

  • Resting supports: Z: POS one-way + friction — lets the pipe lift off and drag realistically.
  • Guides: lateral direction FIXED (use LOCAL coords on skewed runs), vertical FREE or one-way as built.
  • Line stops: axial FIXED (LOCAL X).
  • A model must restrain all six rigid-body motions overall or the solver rejects it — one anchor anywhere usually suffices; Check Model counts your restraints for you.
  • Every support's reported reaction includes its friction force, so support loads can be taken straight from the Reactions table for support design.