PipingToolset for Claude — B31 Piping Skills for Claude Code and Cowork
Version 0.5.1 · released · Apache-2.0 · free · Content last reviewed · page regenerated 2026-10-27 at build.
B31 calcs you can reproduce and defend in review, with Claude. Claude does the interview. A script does the math. You read the table. Seven piping engineering skills from the people who build the free calculators on this site, written and maintained by a practicing, licensed piping engineer.
What a run looks like
You type (Cowork form; in Claude Code prefix /piping-toolset:pressure-design):
Use the pressure design skill. B31.3-2022, normal fluid service. NPS 6 seamless pipe, OD 6.625 in, design 750 psig at 600 F, corrosion allowance 0.0625 in, 12.5% mill tolerance. My allowable S at 600 F is 17900 psi from my copy, E = 1.0, W = 1.0, Y = 0.4. What minimum thickness do I need and does 0.280 in nominal wall work?
The skill writes the inputs to a job file, runs pressure_design.py, and reports from the script output:
| Quantity | Value | Basis |
|---|---|---|
| Pressure design thickness t | 0.1365 in | B31.3-2022 ¶304.1.2 Eq. (3a): PD / 2(SEW + PY) |
| Minimum required tm | 0.1990 in | t + c, c = 0.0625 in |
| Nominal wall to order | 0.2274 in | tm / (1 − 0.125), 12.5 % mill tolerance |
| Allowable pressure at 0.280 in nominal | 1,008 psig | Same equation solved for P on 0.280 × 0.875 − c |
Verdict: PASS 0.280 in nominal works, with 0.053 in of wall and about 34 % of pressure margin. S, E, W and Y are echoed as user-supplied. The calc sheet names the edition, the equation, every input and anything you left to be ASSUMED, then lists what a reviewer would flag: the Table A-1 line behind S, the Table A-1A line behind E, the Table 304.1.1 row behind Y, the purchase spec behind the mill tolerance.
What it does
PipingToolset for Claude is a plugin: seven skills, each a set of written instructions Claude follows plus a standard-library Python script that performs the calculation. Claude asks for the code basis and the inputs, writes a small specification file, runs the script by path, and reads the result back to you. The same engine behind the free calculators on this site produces the numbers.
| Skill | What it does | What you get |
|---|---|---|
| Pressure design | Code-basis interview, then wall thickness, allowable pressure, branch reinforcement, bends, miters and leak-test pressure to B31.3 / B31.1 | A calc sheet with the edition, the equation, every input and the ASSUMED flags |
| Stress screening | Sustained, occasional and expansion hand checks; the f factor by edition; which document supplies the SIFs; the formal-analysis exemption; support spans and spring variability | A reviewer's hand check of what CAESAR II or AutoPIPE applied |
| Load case builder | Complete B31.1 / B31.3 static load case sets for CAESAR II and AutoPIPE: HGR, HYD, OPE, SUS, EXP, OCC and envelopes, generated symbolically so references never go stale | The load case table, a QC gate and a report extraction matrix |
| Pipe support | Support assemblies (arm, column, welds, bolts, base plate, anchors, pier) checked against CAESAR II restraint loads: ASCE 7-22 combinations, AISC 360-22, ACI 318-19 Chapter 17, AWS D1.1 detailing. The PiperSTR engine from this site | A PE-style review, ranked code-passing alternatives and an engineer-ready calc report (calc.md, result.json) |
| Iso to PCF | PDF stress isometrics to a clean CAESAR II PCF: Claude transcribes the drawing, a script builds the geometry in exact fractions, a validator catches orphan nodes, zero-length elements and off-line supports before import | line.pcf and a report text file; live CAESAR II import confirmed |
| Nozzle load | Piping forces and moments on equipment nozzles, checked the way the vendor will: API 610 Table 5 and Annex F for pumps, the API 617 / 611 / 612 and NEMA SM-23 combined form for compressors and turbines, API 660 / 661 / 560 per-component and header-sum checks, API 650 Annex P ordinates, and the PVP2011-57100 method for a vessel with no API allowable. The PiperNOZ engine from this site | Ratios and the governing component from a script run; you read every table row |
| Bolted flange | Piping loads on a bolted flanged joint in a fixed order: the pressure-equivalent screen against the B16.5 rating you read, then the BPVC Section VIII Division 2 Part 4.16 analysis for integral and loose flanges with rigidity. The PiperFLG engine from this site | The screen verdict, then bolt area, hub, radial and tangential stresses and rigidity |
How it works
Three rules hold in every skill:
- Claude never does the arithmetic. Every number a skill states comes from a script run on inputs you supplied. If you see a number and no script ran, treat the answer as untrusted and ask again.
- Claude never recalls a code table value. Allowable stresses, moduli, SIFs, spans, ASCE 7 coefficients, anchor bond values, flange ratings, gasket factors: the skill names the table, row and edition and asks you to read it from your own copy. Asking for "just the number" is a pinned test, and the answer is no.
- The edition is an input, never a silent default. Where a rule changed between editions (for example the f-factor form before and after B31.3-2022, or Appendix D giving way to B31J from B31.3-2020), the skill asks which one governs your project.
What it will not do
- It will not give you a tabulated code value. Not an allowable stress, not a quality factor, not a Y coefficient, not an SIF, not a support span, not a catalog bond strength, not a B16.5 rating, not a gasket factor, not an API nozzle allowable. You read those from the document you are licensed to use; the plugin contains none of them.
- It will not replace a flexibility analysis. Stress screening is a hand check of what the program applied. CAESAR II and AutoPIPE remain the analysis tools; the load case builder and iso-to-PCF skills exist to feed them.
- It will not pick your code or edition for you. Basis items you do not answer are marked ASSUMED on the calc sheet, never silently filled in.
- It will not compute in the model's head. A skill that cannot run its script stops and says so instead of estimating.
- It will not seal anything. Results are engineering aids. The engineer of record verifies them before issue, and you remain responsible for the result.
- It will not reproduce code text. Paragraph numbers and equation references are cited; the wording of the standard is not included.
- It will not touch your Piping Toolset account. The plugin is free and separate from the site's paid tiers. Installing it unlocks nothing on the site, and a subscription changes nothing in the plugin.
Where your data goes
Short answer: nothing you enter reaches PipingToolset or Flexible Piping Solutions. The plugin makes no network calls, carries no telemetry, needs no API key and no account with us. The only contact with our infrastructure is the download, and that is served by GitHub.
| What | Claude Code | Claude Cowork |
|---|---|---|
| Your prompt and the files you attach | Go to Anthropic to be processed by Claude, under the terms and data-handling settings of your Anthropic account or your employer's plan. We do not see them. | |
| The calculation scripts | Run on your own machine, with your own Python 3.9+ | Run inside the Cowork session's sandbox, which provides Python |
Input files the skill writes (job.json, spec.json) | Your current working directory | The chat's working folder |
| Output files (calc reports, result JSON, PCF) | Your current working directory | The chat's working folder |
| Anything sent to pipingtoolset.com | Nothing. No usage pings, no crash reports, no copies of inputs or results. | |
| Update checks | None. You update by installing the next release; see the recall note below. | |
Install
In Claude Cowork
- Download
piping-toolset.pluginfrom the latest GitHub Release. - Drag the file into a Cowork chat. A preview card appears; press Accept.
- Start a fresh chat. The seven skills appear in the skills menu under PipingToolset.
Or, in the app's plugin settings, add the marketplace pipingtoolset/pipingtoolset-claude.
In Claude Code
/plugin marketplace add pipingtoolset/pipingtoolset-claude /plugin install piping-toolset@pipingtoolset
Then call a skill by its slash name: /piping-toolset:pressure-design, /piping-toolset:stress-screening, /piping-toolset:load-case-builder, /piping-toolset:pipe-support, /piping-toolset:iso-to-pcf, /piping-toolset:nozzle-load, /piping-toolset:bolted-flange. In Cowork there is no slash prefix; name the skill in plain words ("use the pipe support skill to check PS-201"). Naming it matters, because other installed skills on the same topics would otherwise compete.
In other assistants
The skills are plain Agent Skills, so the same repository installs into assistants that read that format: npx skills add pipingtoolset/pipingtoolset-claude for Cursor, GitHub Copilot, OpenAI Codex, Gemini CLI and others, or codex plugin marketplace add pipingtoolset/pipingtoolset-claude in Codex. The plugin is built and tested in Claude Code and Claude Cowork; elsewhere the host must be able to run the bundled Python scripts, or the skill stops at the interview.
Requirements
Python 3.9 or newer wherever the skills run: your own machine for Claude Code; Cowork's sandbox provides it. There is nothing else to install.
Try it in twenty seconds
Paste the worked example at the top of this page. Then ask for what it will not give you:
Use the pressure design skill. What's the allowable stress for A106 Grade B at 650 F under B31.3? Just give me the number.
Expected: no number. It names B31.3 Table A-1 (A-1C in the 2024 edition), the material row and the two temperature columns, and offers to interpolate once you have read both values. Twelve more prompts with pass criteria are in the repository's test prompt set.
How it is verified
- One engine. Every script that computes a code equation reproduces the locked fixture cases of this site's calculation engine, value for value. A red parity test blocks a release. The fixtures and the method are described on the validation page and listed on the coverage page.
- Golden outputs. The load case generator's tables and the PCF builder's output are locked byte for byte for the worked examples. A change to case order, combination strings or QC text is a deliberate, reviewed golden update.
- Content guard. An automated test fails the build if any skill text or script embeds a tabulated code value or third-party proprietary material.
- Recall channel. An installed copy keeps any defect it shipped with until you update it. A release labelled UNCONSERVATIVE-FIX in the changelog and on GitHub Releases corrects a result that could have been less conservative than the code requires, and names the skill, the affected inputs and the fix. Update when you see one.
Questions
Do I still need my own copy of the code?
Yes. The skills cite paragraphs and equations and ask you to read table values from your licensed copy. They are a way to apply the code correctly and traceably, not a substitute for having it.
Which codes and editions?
ASME B31.3 and B31.1 for pressure design, screening and load cases, with the edition as an explicit input wherever a rule differs between editions. Pipe support checks use ASCE 7-22, AISC 360-22, ACI 318-19 Chapter 17 and AWS D1.1. Nozzle loads follow API 610, 617 / 611 / 612, NEMA SM-23, API 660 / 661 / 560, API 650 Annex P and ASME PVP2011-57100. Flange checks follow ASME B16.5 and BPVC Section VIII Division 2 Part 4.16. The iso-to-PCF skill targets the CAESAR II PCF import.
Does it work in the claude.ai chat?
The skills need a host that can run the bundled Python scripts. Claude Code and Claude Cowork can; the plain claude.ai chat cannot run them, so the skill would stop at the interview. Use Cowork in the Claude desktop app.
How much does it cost?
Nothing. The plugin is free and open source under the Apache License 2.0. You pay only for your own Anthropic plan.
How do I report a wrong result?
Open an issue in the GitHub repository with the prompt, the script command that ran and the line you dispute, or write to support@pipingtoolset.com. A confirmed unconservative result ships as an UNCONSERVATIVE-FIX release.
The plugin is an engineering aid. Results must be independently verified and reviewed by a qualified, licensed engineer before any design, fabrication or operation decision. Claude is a product of Anthropic, PBC; this plugin is not affiliated with or endorsed by Anthropic.