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Learn Stress Analysis, Step by Step
Piping & Pipeline.
From data collection to final report: courses and calculators for piping and pipeline engineers using CAESAR II and AutoPIPE.
259+ ASME materials · engineering calculators · 35+ years of piping & pipeline experience
Created by a Principal Piping & Pipeline Stress Engineer · Author of Piping and Pipeline Engineering: Fundamental & Practical Guides
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Practical, step-by-step workflows from industry experience. Tap a guide to open it.
- Codes and standards: the project-mandated edition of ASME B31.3 or B31.1.
- The piping stress analysis specification, the most important project document.
- Piping material spec, class index and pipe support specification.
- Piping GA or 3D model, equipment GA and data sheets, and nozzle allowable loads.
Pro tip: The most common junior mistake is starting CAESAR II without all the data, then stopping again and again to chase what is missing.
- A stress sketch is not an isometric: major components, support locations and dimensions only.
- Calculate equipment nozzle initial movements and relief valve reaction force before finishing it.
- Add line data: size, wall thickness, material, design and operating temperature and pressure, insulation and allowable stresses.
- Number nodes from the anchor point and create CNodes at flanges and valves.
Pro tip: Always create CNodes at flanges. Without them you cannot check flange leakage from your output.
- Check units first, then enter geometry node by node.
- Pipe, temperature, pressure, material, fluid and insulation data are entered once and carry forward until changed.
- The first point is always an anchor.
- Enter initial equipment movements as displacements.
Pro tip: Never put an anchor and a displacement on the same node, as it over-specifies the boundary. Use a CNode for the displacement instead.
- Three main load types: sustained (weight and pressure), thermal expansion, and occasional (wind, seismic, slug, relief valve).
- Stress categories: operating (OPE), sustained (SUS), expansion (EXP) and occasional (OCC).
- Load case sets differ for liquid lines, gas and steam lines, spring-supported lines and pump piping.
- Always follow the project specification, as load cases vary by project.
Pro tip: For gas and steam lines, use WNC (weight without contents) rather than W in the operating case.
- Always run Error Checking before the Batch Run.
- Warnings do not stop the analysis, but investigate every one. Fatal errors must be fixed.
- Typical culprits: a temperature entered as zero, missing rigid element weights, and branch connections with SIF = 1.0.
Pro tip: If you can explain why a warning is acceptable, it is fine. If you cannot explain it, fix it.
- Code stress ratios below 1.0 for every load case.
- Support loads that are reasonable: not excessive and not zero.
- Equipment nozzle loads against vendor allowables, API 610 or API 560.
- Pipe movement and clashes.
- Flange leakage at every flange CNode.
- Lift-off at every support.
- Spring hangers and expansion joints selected from the manufacturer catalogue.
Pro tip: Many juniors check only code stress and forget lift-off. A lifted support does nothing, and its neighbours take the extra load.
- Report order: cover, critical line list, stress check list, marked-up stress sketch, software output, reference documents and manual calculations.
- Send support loads to civil and structural, nozzle loads to equipment, and the marked-up sketch to piping design.
- If a nozzle still exceeds its allowable after all options, document it and send it to the equipment group for vendor approval.
Pro tip: Send the marked-up stress sketch to piping design immediately. Do not wait for the full report.
These steps cover plant piping (ASME B31.3 / B31.1). For onshore pipelines (B31.4 / B31.8), see the pipeline engineering course. To go deeper on piping, take the Static Piping Stress Analysis & CAESAR II course.
- Read the contract scope, the client specifications and the governing codes.
- Note the design life and any line classes or approved vendor lists the client already mandates.
- Find out which standards govern when the client and project documents disagree.
Pro tip: Ask early whether the client has standard line classes. It can save you weeks.
- From Process: design basis, PFDs, draft P&IDs and the draft line list.
- From Materials and Corrosion: the draft corrosion loops or the Materials Selection Report, even if preliminary.
- Meet both engineers and ask what is firm, what may still change, and when each document will be issued.
Pro tip: Do not wait for every document. Start with what you have and track what is missing.
- Group the lines into services: hydrocarbon, sour, utility, water, chemical and so on.
- For each service note the rough pressure, temperature and contaminants.
- Check start-up, shutdown, cleaning and upset cases as well as normal operation.
Pro tip: Most late material changes come from non-normal cases, not from normal operation.
- Use the client's standard line classes or your company template as the starting point.
- Map each service to an existing class, and add a new class only when none fits.
- Keep the number of classes and materials as small as the project allows.
Pro tip: Fewer materials mean simpler procurement, fewer spares and fewer mistakes on site.
- Issue the first revision with conservative assumptions where data is missing.
- Tag each open item as a HOLD with its source, for example "pending Materials Selection Report".
- Do not commit long-lead or special-material items until the HOLDs are closed.
Pro tip: Starting with assumptions is fine. Not tracking them is the real risk.
- For each open item record the assumed value, who owns it, the impact if it is wrong, and a due date.
- Review the register every week and chase the owners.
- Close each item formally and update the PMS revision.
Pro tip: A named owner and a date turn "waiting for data" into a clear request.
- Process: line list, upset cases and minimum temperatures.
- Materials and Corrosion: selection report, corrosion allowance and special requirements.
- Stress: design conditions and flange ratings.
- Layout, Inspection and Procurement: branch tables, monitoring points, availability and lead times.
Pro tip: Make sure all disciplines use the same service names and conditions. Mismatches are the most common source of rework.
- Check that the PMS matches the line list, the P&IDs and the Materials Selection Report.
- Close or formally accept every HOLD before the MTO and purchase requisitions are issued.
- Hold a cross-discipline review, then issue the PMS for design.
Pro tip: A change before purchase costs an email. After purchase it costs money and schedule.
This guide is general guidance. Final material selection remains the responsibility of the Materials and Corrosion discipline and the project specifications.
Steps of Pipeline Stress Analysis
The onshore pipeline workflow (B31.4 / B31.8), from design basis to final report.
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