Bolted Flange Analysis Online — Kellogg Peq Screen to Full ASME Appendix 2
Pick a class and size, let the tool fill the ASME B16.5 dimensions, gasket factors and a starting allowable set, and run three checks in one workspace: the Kellogg equivalent-pressure screen against the pressure–temperature rating, the full BPVC Section VIII Appendix 2 bolt-load, stress and rigidity design, and an EN 1591-1 load-balance screen — with a parametric 3D model of the exact flange being analysed. Pro Plus tier; the method write-up below is free to read.
Content last reviewed · page regenerated 2026-09-03 at build.
What it does
The workspace is built around not re-typing what the standard already fixed:
Auto-fill from B16.5
- Dimensions: facing and drilling for NPS 1/2 through 24 in all seven classes — 150, 300, 400, 600, 900, 1500, 2500 — plus hub geometry and B16.20 spiral-wound gasket sizes, embedded and locked by a transcription fixture. The standard's own exclusions are built in: Class 400 below NPS 4 uses Class 600 dimensions by direction of the standard, Class 900 at NPS 2-1/2 and below defers to Class 1500, Class 2500 stops at NPS 12, and NPS 26+ is B16.47 — out of scope, and the tool says so.
- Rating: the pressure–temperature rating for your material group, class and design temperature is derived from the embedded B16.5 rating tables — the 2025 current edition by default, with the retired 2017 edition selectable for a job whose code of record needs it — so the Kellogg screen has a real denominator instead of a typed one.
- Gasket factors: the Appendix 2 Table 2-5.1 gasket m and y library (Table 4.16.1 in the 2025 structure), every row cross-checked at test time against the VIII-2 dataset.
- Allowable stresses: a curated starting library — deliberately not Section II-D data — that the tool itself tells you to review against the job's own values before the calculation is issued. Everything auto-filled stays editable.
Three checks
- Kellogg equivalent pressure: Pe = P + 16|M|/(πG³) + 4F/(πG²) against the derived rating, with the moment taken as an absolute value and a warning when a compressive axial force is flattering the result.
- Full Appendix 2: bolt loads, shape and hub factors, operating and seating stresses, and both rigidity indices — the complete output set is itemized in the next section.
- EN 1591-1 screen: the load-balance check — gasket seating and operating bolt-load requirements against available bolt load and the gasket crush limit — flagging joints that need the full iterative EN 1591-1 run.
3D model and report
The model tab renders the flange being analysed — lathe-revolved body from the same B16.5 dimensions driving the calculation, bolt holes, optional studs, gasket ring, a section cut, and iso/front/plan presets. Add to report files the design basis, gasket, bolting, geometry, the Peq screen, Appendix 2 bolt loads and factors, both stress cases, the EN 1591-1 screen and a 3D snapshot into the Report Manager as one titleblocked package.
The Appendix 2 output, in full
The engine computes the complete Appendix 2 sequence for integral and loose attachments, not a shortcut through it:
- Hydrostatic end forces and gasket loads H, HP, HD, HT, HG with moment arms hD, hT, hG
- Bolt-load requirements Wm1 and Wm2, required and actual bolt areas Am and Ab, and the flange design bolt load W
- Shape factors K, T, Z, Y, U and — for integral flanges — the hub factors F, V, f, e, d and L, computed from the exact §2-7.6 series or the VIII-2-2025 Table 4.16.5 curve fits, selectable
- The bolt-spacing correction Bsc, applied to the stress moment and deliberately not to the rigidity moment
- Longitudinal hub, radial and tangential stresses SH, SR, ST with their averages, for the operating case and the gasket-seating case separately
- The rigidity index J for both cases per §2-14, and the §2-8(a) attached-pipe cap on the hub allowable — min(1.5Sf, 2.5Sn) — with a standing warning when Sn is not supplied to close it
Citations follow the 2025 edition structure: VIII-1 rewrote Appendix 2 to cross-reference VIII-2 Part 4.16 as the normative source, and the tool carries the mapping (Fig. 2-7.1 → Table 4.16.4, §2-14 → 4.16.10, Table 2-5.1 → 4.16.1) instead of citing paragraphs that no longer stand alone.
Verified against a commercial flange report
The anchor fixture is a Bentley AutoPIPE Advanced flange report — NPS 16 Class 150 weld-neck, SA-105 flange, SA-193 B7 bolting, spiral-wound gasket, 500 psi at 500°F. The engine reproduces the report's flange moment, longitudinal hub stress and both rigidity indices to the printed digit; the radial and tangential stresses agree within 0.7%, traced to AutoPIPE's own four-decimal rounding of intermediate factors. Two conventions that agreement required are documented in the source rather than left implicit: the hydrostatic end force uses π/4 exactly, not the code's literal 0.785 — matching AutoPIPE and CAESAR II — and Bsc scales the stress moment only. Six fixture cases lock the integral engine in CI, alongside the transcription fixtures on the B16.5 tables themselves; a change to any locked number turns the build red before it can deploy. External piping loads enter through the same Kellogg equivalent-pressure route in both the screen and the full design — the ring-bending alternative some programs add is deliberately not used, because it requires section properties that are not an ASME construction.
A typical run: class and size to issued check
- 1 — Pick the joint. NPS, class, material group, attachment type (integral or loose), design pressure and temperature. The dimensions, rating, and a starting gasket and allowable set fill in — everything editable.
- 2 — Screen it. Enter the flexibility analysis's moment and axial force; the Kellogg card returns Pe and utilization against the rating. A joint that passes here with margin often needs nothing more.
- 3 — Run Appendix 2. The full sequence — bolt loads through rigidity — for operating and seating, with every factor visible and every allowable editable. Supply Sn if the hub is welded to pipe, and the §2-8(a) cap closes.
- 4 — Screen the gasket, if the joint is EN-style. The EN 1591-1 card balances bolt load against seating, operating and crush limits.
- 5 — Check the model. The 3D tab is the flange the numbers describe — a wrong bore or bolt circle is visible before it is expensive.
- 6 — Capture. One click files the complete run, tables and 3D snapshot included, into the Report Manager; print to PDF or download HTML, and save the .pcp to reopen it with everything live.
What's free and what needs Pro Plus
The methods are public on this site regardless of tier: the Kellogg equivalent-pressure calculator page documents the screen with a fixture-verified worked example, the EN 1591-1 screening page does the same for the load-balance check, and the B16.5 flange rating lookup is a free calculator. PiperFLG is the Pro Plus workspace that connects them:
- Free — $0: the calculators and every method write-up, including this page.
- Pro — $2.99/month or $29/year: report capture, Report Manager, .pcp files, batch runs, cited factor pickers.
- Pro Plus — $7.99/month or $79/year: PiperFLG (this tool), PiperNOZ nozzle loading, PiperHGR spring sizing, and the UCS-66 MDMT tool. The monthly plan starts with 30 days free — card required, nothing charged until day 30, cancelling during the trial is immediate.
- Ultimate — $14.99/month or $149/year: adds PiperFEA, PiperSTR, the PiperISO premium exports, and the equipment nozzle-load presets.
The full matrix and billing FAQ are at /pricing/.
Demo video
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PiperFLG - ASME Flange Calculator - New 3D Analysis Features & Reference Data Tables (1:18) — The dedicated PiperFLG demo: the Kellogg equivalent-pressure screen auto-filled from the embedded B16.5 dimensional data, the full Appendix 2 bolt-load and stress design against allowables interpolated at design temperature, and the 3D model of the assembly. Watch on YouTube.
Open the tool
Open PiperFLG — it loads in this tab on a Pro Plus account. If you are evaluating first, read the equivalent-pressure method page and run its worked example by hand; the tool's job is to make the tenth flange of the week as careful as the first.
FAQ
How is the Appendix 2 engine verified?
Against a commercial stress program's own printed output. The anchor fixture is a Bentley AutoPIPE Advanced flange report — an NPS 16 Class 150 weld-neck joint, SA-105 flange, SA-193 B7 bolting, spiral-wound gasket, 500 psi at 500°F — and the engine reproduces the report's flange moment, longitudinal hub stress, and both rigidity indices to the printed digit, with the radial and tangential stresses inside 0.7 percent traced to AutoPIPE's own four-decimal rounding of intermediate factors. Two conventions that anchor required are documented in the source rather than left implicit: the hydrostatic end force uses π/4 exactly instead of the code's literal 0.785, matching what AutoPIPE and CAESAR II both do, and the bolt-spacing correction scales the stress moment but not the rigidity moment. Six fixture cases lock the engine in CI — the build goes red before a change to any of those numbers can deploy.
Where do the flange dimensions, gasket factors and allowable stresses come from?
Three different places, with three different confidence levels — and the tool says which is which. Dimensions come from embedded ASME B16.5-2017 tables: facing and drilling for all seven classes, hub geometry, and B16.20 spiral-wound gasket sizes, transcribed double-blind and locked by a twelve-case fixture — a gate added together with a five-cell Class 600 bolting correction, exactly the defect class it now blocks. Gasket m and y factors are the Appendix 2 Table 2-5.1 values (Table 4.16.1 in the 2025 structure), and every row is cross-checked at test time against the VIII-2 dataset so a wrong-line copy cannot recur — one did, on the metal-jacketed row, and was corrected in the published changelog. Allowable stresses are the one thing deliberately not embedded: a curated starting library the empty-state text tells you to review against the job's own Section II-D values, because the flange calc is only as good as the S you feed it.
Which flange types and sizes does it cover?
ASME B16.5 only: NPS 1/2 through 24, all seven pressure classes — 150, 300, 400, 600, 900, 1500 and 2500 — with the standard's own exclusions built in rather than silently interpolated: Class 400 below NPS 4 uses Class 600 dimensions by direction of the standard, Class 900 at NPS 2-1/2 and below defers to Class 1500, and Class 2500 stops at NPS 12. The Appendix 2 engine handles integral and loose attachments; the optional category is not implemented, and a loose flange without a hub reports its longitudinal-hub and radial stresses as zero with a warning, which is what the method defines for that construction. NPS 26 and larger is ASME B16.47 territory and deliberately out of scope — the tool tells you so instead of extrapolating. For a joint outside those bounds, the equivalent-pressure and EN 1591-1 screens still run, since their inputs are generic geometry.
How do external piping loads enter the flange check?
Through the Kellogg equivalent-pressure route, in both places it matters. The screening card converts the flexibility analysis's bending moment and axial force into Pe = P + 16M/(πG³) + 4F/(πG²) and compares it to the B16.5 pressure–temperature rating the tool derives for your material group and class. The full Appendix 2 run then folds the same equivalent pressure into the design pressure, so bolt loads and flange stresses see the external loads too. Two conventions are worth knowing: the moment enters as an absolute value, because direction does not relieve a bolted joint, and a compressive axial force triggers a warning telling you to screen the tensile case separately rather than banking the reduction. The alternative some programs offer — a ring-bending moment term added to the flange moment — is deliberately not used, and the source documents why: it needs section properties that are not an ASME construction.
What tier is PiperFLG on, and is there a trial?
Pro Plus — $7.99/month or $79/year — alongside PiperNOZ nozzle loading, PiperHGR spring sizing, and the UCS-66 MDMT tool, and the monthly plan starts with 30 days free: a card is required at checkout, nothing is charged until day 30, and cancelling during the trial is immediate and free. Before subscribing you can evaluate the methods at no cost, because the write-ups are public: the equivalent-pressure calculator page publishes the Kellogg method with a fixture-verified worked example, the EN 1591-1 screening page does the same for the load-balance check, and the B16.5 rating lookup is a free calculator. What the subscription adds is the workspace that connects them — dimensions and ratings auto-filled from the embedded B16.5 tables, the full Appendix 2 stress and rigidity run, the 3D model, and report capture into the Report Manager's titleblocked, print-ready package.