A model is the centreline of the line with everything attached to it: sizes, materials, components, supports and loads. SWBPIPE fills in nothing. A value the solve needs and does not have stops it, with a message naming what is missing.

1.Units and geometry.

Every quantity is entered with its unit and converted to SI for the solve. The model is a table with one row per node; the drawing is made from the rows. Put nodes at every change of direction, at every support, component and branch, at every change of size, material or temperature, and wherever you want a result. Long straight runs need no intermediate nodes for accuracy, because the beam element is exact under end loads and consistent span loads, but intermediate nodes give intermediate results.

2.Pipe sizes.

Each pipe carries its nominal outside diameter and wall, directly or from a section you define once. For weight, give the densities of the pipe, its contents and its insulation, and the insulation thickness. Corrosion and other allowances reduce the section for stress only.

3.Materials.

A material needs its elastic modulus, shear modulus and mean expansion coefficient. Enter them at the temperatures you need; each load case takes the values at one of them, or interpolates between two, and never extrapolates. For the code range, the modulus is the reference (installed) value (Part II D).

Model each support as it is built, not as it is drawn on the isometric. A shoe on a steel beam is a rest, with friction, and probably a guide if it has lugs. A rod hanger holds only in tension. A trunnion resting on a beam is a stub from the centreline to the support point, with the rest at its end.

A model needs enough restraint to hold it against rigid-body movement in every direction. If it does not have it, the program stops and names the directions that are still free.

Build the basic loads first, then the cases a code check needs from them. For a line with one operating condition:

With several operating conditions, each has its own OPE case, and the expansion range is taken between the extreme states. Part II C and D explain why.

SWBPIPE ships with no code tables. Flexibility factors, SIFs, component dimensions and allowables belong to the codes and catalogues you work to, and you enter them from those sources: for the B31 codes, ASME B31J for SIFs and flexibility factors, and your owner’s and manufacturers’ data for components and hangers. The classical forms of Part II E are a check on what you enter.

The program uses k in the bend stiffness and shows your SIFs against the recovered moments. It does not classify stresses or compare them with allowables; that check is made in the program you validate in (Part V).

Your material, section, component and hanger data can be kept in private libraries, and your projects in a local store. All of it stays on your machine.

Check the model before reading its results. A few quick runs catch most mistakes.

• Movements first. Look at the largest displacement and rotation in every case. Metres of movement or whole radians of rotation mean a mechanism or a unit error, not a result (Status).
• Weight balance. In the weight case with every rest acting, the vertical support loads add up to the total weight entered.
• Free growth. Hold the line at one anchor only and apply the thermal case. Every node should move by αΔT times its distance from the anchor, with no forces anywhere.
• Order of magnitude. Compare the thermal load on a leg with the guided-cantilever estimate of Part II A. A result ten times larger or smaller needs explaining.
• Support states. In each case with nonlinear supports, read which rests have lifted off, which gaps have closed and which shoes slide, and ask whether that is what the line would do.
• The validating program. The final check is the model in the program you validate in, compared result by result (Part V C).