PASS/START-PROF® determines piping system complexity using the following degrees of freedom formula:
N=6 ∙ (an + cc - 1) + 3 ∙ (ss + g + ha + s + t) + m ∙ rh + sh + cf + 2 ∙ (re + le) + ae + (ns + rl) + 12 ∙ fe + 9 ∙ ea,
Where:
an - Number of fixed anchors;
cc - Number of closed loops;
ss - Number of sliding supports;
g - Number of guide supports;
ha - Number of moment-free anchors;
t – Number of tee connections;
s - Number of soil springs;
rh - Number of rod hangers;
sh - Number of variable spring supports and hangers;
cf - Number of constant spring supports;
re - Number of rotational expansion joints;
ae - Number of axial expansion joints;
le - Number of lateral expansion joints;
ns - Number of constraints in custom restraints;
ea – Number of terminal anchors;
fe – Number of free ends;
rl - Number of restraints released by custom expansion joints.
For rigid rod hangers with displacement consideration, m=3. Otherwise, m=1.
START-PROF supports systems with up to 32,000 degrees of freedom: N ≤ 32000
Maximum node count is limited by:
NN < 32000 – 2 ∙(ej + v + ia + fe + ea) - (an + cc - 1) - b - t - s,
Where:
NN - Total number of nodes;
ej - Number of axial expansion joints with pressure thrust;
ia - Number of intermediate anchors;
b - Number of bends and elbows;
v - Number of valves.
The quantity of soil springs depends on pipeline length, configuration, and diameter.