Part V, Validation Elsewhere — SWBPIPE, the open manual

Part V · Validation ElsewhereV–1

Part V

Validation Elsewhere

A. Design here, validate there

SWBPIPE is for working a design out: routing, supporting, trying alternatives, learning why the line behaves as it does. It does not judge compliance with any code and does not vouch for its results. When a design is settled and needs validation, it goes to the program your industry already accepts, where the code check is made under your engineer’s judgement.

One seat of that program can validate the work of many people designing in SWBPIPE. The first export is a model batch file (.mbf). Other formats will follow.

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B. The export today

The .mbf export is under construction. Today it writes the skeleton of the model: nodes with their coordinates, the pipes joining them, and anchors and guides. It carries no sizes, materials, fittings, temperatures or loads. Each export comes with a map from SWBPIPE’s names to the file’s numbers, and a list of what it left out or approximated.

Not yet exported	What to do in the receiving program
Pipe sizes and material properties	Enter them.
Bends, tees, valves, flanges and reducers	Listed as omitted; add them.
Rests, springs, hangers, stops and gaps	Written as guides and listed as approximated. A rest or spring written as a guide changes the mechanics completely: delete each one and model the real support.
Temperatures, pressures, weights, forces and load cases	None are written. Enter the operating conditions and build the load cases there.

Today

Coordinates entered in US units are written with a millimetre label (Status). Until the file carries the whole model, treat it as a start for the model in the receiving program, and check it there row by row.

1.Other exports.

The program can also write a piping component file (PCF) with the straight runs, a native model package, the results as CSV or JSON, the centreline geometry for viewing, and a package of loads and movements for a local model of one detail.

2.How the export will be checked.

A check of each export format is planned. It compares three versions of the same model: the problem as defined, a model of it built by hand in the receiving program, and the model the export produces. Each feature will be recorded as carried exactly, approximated, not carried, or not yet tested. A file that opens in the receiving program will not count as a faithful export until the model inside it has been shown to be the one intended. Nothing in this check has been run yet (Part VI).

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C. What changes when you validate

The same line, modelled carefully in two programs, gives nearly the same movements and loads, but not identical ones. The differences come from choices each program makes, and knowing them in advance saves hours of reconciliation. Compare the two models before comparing their results: geometry, sizes, materials, support types and directions, and load cases, row by row.

Subject	What to expect
Shear deformation	Commercial programs include it; SWBPIPE does not. Short, heavy legs are stiffer here, so their loads are higher.
Bends	The validating program takes k and the SIFs from the code you select. Enter the same values here, or expect differences at every elbow. Today SWBPIPE solves drawn bends as chords (Status).
Pressure	Programs differ on pressure elongation (the Bourdon effect) and on the longitudinal pressure formula. Today SWBPIPE’s pressure results are wrong (Status).
Modulus	The code range uses the installed modulus, and hot reactions are scaled from it. Solve the thermal case here at the same modulus before comparing.
Springs and hangers	The validating program designs hangers, selects them from catalogues and applies their preload. Compare only after entering the same rate and cold load, and note that SWBPIPE does not yet apply the preload (Status).
Friction and nonlinear supports	Friction results depend on the solution path and on how each program treats the sustained case. Compare runs without friction first.
Code stresses	The validating program computes the sustained stress, the displacement stress range and the occasional stresses, and compares them with allowables. SWBPIPE computes none of them.

1.A reconciliation order.

Weight only, with every support rigid: support loads should agree closely.
Thermal only, without friction and with nonlinear supports held in one state: movements and anchor loads should agree within the effect of shear deformation and bend modelling.
Then add pressure, springs, friction and the nonlinear supports one at a time, and explain each change in the difference before adding the next.

Where the two programs still disagree, the model in the validating program is the design basis, under your engineer’s judgement.