Overview
A flange size chart is useful only when it identifies the dimensional standard, edition, nominal size, rating, flange type, and facing. There is no single universal chart for every flange. The same nominal pipe size can have different outside diameters, thicknesses, bolt patterns, bores, and facing dimensions under different standards and ratings.
Why It Matters for Pipe Components
Engineers use charts to select components, prepare drawings, check supplier data, and inspect delivered goods. Buyers use them to compare quotations. A chart without its source and scope can create an expensive mismatch.
The chart should support, not replace, the governing standard. Controlled standard data is especially important for bolt-circle dimensions, hole sizes, flange thickness, hub geometry, RTJ grooves, and pressure-temperature ratings.
Methods, Parameters, or Process
Choose the chart in this sequence.
| Step | Question to answer |
|---|---|
| 1 | Which dimensional standard does the project require? |
| 2 | Which edition is contractually applicable? |
| 3 | Is the size stated as NPS, DN, or another system? |
| 4 | Is the rating ASME class, PN, or project-specific? |
| 5 | What flange type is required? |
| 6 | What facing is required? |
| 7 | Does the bore match the pipe wall or schedule? |
| 8 | Are tolerances and notes included with the table? |
ASME B16.5 applies within NPS 1/2 through NPS 24. ASME B16.47 addresses large-diameter steel flanges from NPS 26 through NPS 60. Other systems, including EN and project standards, use their own designations and tables.
A useful internal chart should show at least outside diameter, flange thickness, bolt-circle diameter, number and diameter of bolt holes, facing data, bore, hub dimensions where applicable, and units. Keep inch and metric tables clearly separated.
Verification note: numerical dimensions are intentionally not reproduced here. They must be checked against the licensed standard edition required by the project.
Supplier and Inspection Checklist
- Confirm the chart title includes standard, edition, rating, and flange type.
- Check whether dimensions are nominal, minimum, maximum, or reference values.
- Read all table notes and tolerances.
- Confirm units before copying data.
- Match the bore to the pipe wall.
- Use separate checks for facing, gasket, and bolting.
- Record the source document on inspection reports.
- Prevent uncontrolled spreadsheet copies from becoming the master chart.
Application to Pipe Fittings, Valves, and Flanges
Flange charts support pipe spools, valve connections, equipment nozzles, spectacle blinds, orifice assemblies, and replacement parts. They also help estimate weights and packaging, but final weights should come from approved drawings or supplier data.
For multi-standard projects, keep separate chart libraries. A DN value and an NPS value may be treated as nominal equivalents in some contexts, but their components are not automatically interchangeable.
FAQ
Why do two charts show different dimensions for the same size?
They may use different standards, ratings, flange types, editions, or units. Check the chart scope before deciding that one is wrong.
Can a Class 150 chart be used for Class 300?
No. Rating classes can have different thicknesses, drilling, and facing details.
Does the chart determine the material?
No. Dimensional and material specifications are separate parts of the purchase designation.
Should a supplier provide a drawing even for a standard flange?
A supplier drawing is useful for confirmation, especially for bore, facing, large diameters, special machining, and inspection planning.
Next Steps
Build the inquiry from the standard and line class first, then attach the correct controlled chart or drawing. Ask the supplier to list every deviation rather than silently substituting a similar flange.
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