Why look at the report closely
The report is the record that the riser can safely take the movements of the building. The builder, the consultant and the gas company may all rely on it, so it should be clear enough for a reader to follow how the result was reached.
Design basis and inputs
It should state the pipe size, material and wall thickness, the operating pressure, the installation and design temperatures, the building height and floor levels, and the sway and seismic data used, with their source and version. The PNGRB guidelines use 20 °C at installation and 65 °C as the design temperature.
Load cases
The report should list each load case and combination that was checked: pressure, self-weight, settlement, thermal expansion, sway in each direction and seismic effect. The PNGRB guidelines name five combinations for buildings over 40 metres.
Results
Look for the pipe stresses compared with the allowable limits, the forces and moments at each support, and the movement at each level. Results should be shown for the worst case, with a clear pass or fail.
Supports and flexibility
The report should say where the anchors, guides, loops or bellows go and how the pipe is held at each floor, with a drawing the installer can follow.
Sway table cross-check
The floor-by-floor sway table from the structural designer should be compared with the displacements used in the model, so the pipe analysis and the building data agree.
Questions to ask before you accept it
Is the building data the latest version? Do the load cases match the guidelines and the gas company's requirements? Are all results within limits? Does the support layout match what the installer will build? If the building design changes, who updates the analysis?
If you need a stress analysis report for a high-rise riser, send us the building data and we will outline what we need. See our PNG riser stress analysis service.