PASS/START-PROF® piping complexity is determined by the degree of freedom, calculated as:
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 - the number of fixed anchors;
cc - the number of closed circuits;
ss - the number of sliding supports;
g - the number of guiding supports;
ha - the number of moment free anchors;
t – the number of T-shaped joints;
s - the number of soil springs modeling soil;
rh - the number of hangers;
sh - the number of variable spring supports and variable spring hangers;
cf - the number of constant spring supports;
re - the number of rotational expansion joints;
ae - the number of axial expansion joints;
le - the number of lateral expansion joints;
ns - the number of links in custom restraints;
ea – the number of fixed anchors at pipe ends;
fe – the number of non-restrained (free) ends;
rl - the number of restraints removed by custom expansion joints.
When rigid rod hanger displacement is considered, m=3. Otherwise, m=1.
START-PROF analyzes pipelines with the 32000 degree of freedom: N ≤ 32000
The number of nodes is limited to:
NN < 32000 – 2 ∙(ej + v + ia + fe + ea) - (an + cc - 1) - b - t - s,
where
NN - overall node number;
ej - the number of axial expansion joints where internal pressure thrust force is considered;
ia - the number of intermediate fixed anchors;
b - the number of bends and elbows;
v - the number of valves.
the number of supports modeling soil, is determined by pipeline run length, structure and diameter.