Overview
ASME B16.47 flanges are large-diameter steel pipe flanges covered within the standard's stated NPS and pressure-class scope. A usable purchase description must identify the standard edition required by the contract, nominal pipe size, rating class, dimensional series where applicable, flange type, facing, material, and bore.
The standard currently covers NPS 26 through NPS 60 and includes Classes 75, 150, 300, 400, 600, and 900. These scope statements help identify the correct document, but they do not replace the project line class, piping design code, or approved flange datasheet.
Why It Matters for Pipe Components
Large-diameter flange errors are expensive because the components are heavy, machining time is significant, and field modification may not be acceptable. Two flanges can share the same NPS and class while using different dimensional series, drilling, thickness, hub geometry, or bore details.
The flange must also match the connected pipe, gasket, bolting, valve, equipment nozzle, or mating flange. A supplier should not infer Series A or Series B from an incomplete description. Where the standard provides more than one dimensional series, the series must be stated on the inquiry, drawing, and purchase order.
ASME B16.47 controls product requirements within its scope, including pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing. The project documents still determine whether the selected flange is suitable for the fluid, temperature, loads, corrosion allowance, fabrication route, and examination level.
Methods, Parameters, or Process
Use the following sequence when preparing an RFQ or checking a supplier drawing.
| Parameter | What the buyer should state | Why it matters |
|---|---|---|
| Standard edition | Contract-required edition of ASME B16.47 | Standards are revised and project editions may differ |
| Nominal size | NPS 26 through NPS 60 within the standard scope | Defines the applicable dimensional row |
| Rating class | 75, 150, 300, 400, 600, or 900 as required | Controls the rating and dimensional family |
| Dimensional series | Series A or Series B where applicable | Series are not automatically interchangeable |
| Flange type | Weld neck or blind within the required scope and design | Controls hub, bore, and closure geometry |
| Facing | RF, RTJ, or another facing allowed by the design | Must match the gasket and mating component |
| Material | Full material specification and grade | Material designation is separate from flange dimensions |
| Bore | Pipe schedule, actual wall thickness, or approved bore | Prevents an uncontrolled internal mismatch |
| Product form | Forged, cast, or permitted plate construction for a blind flange | Must remain within the standard and purchase specification |
| Documentation | MTR, dimensional report, NDE, heat treatment, and marking records as required | Supports traceability and release |
The ASME scope states that the standard is limited to flanges made from cast or forged materials, while blind flanges may also be made from plate materials. That scope statement does not mean every project permits every product form. The purchase specification may impose tighter restrictions.
For a weld neck flange, review the bore against the actual pipe wall and the approved weld transition. For a blind flange, review the full pressure load, flange thickness, handling method, and any special tapping. For both types, verify the outside diameter, bolt circle, hole quantity and diameter, flange thickness, facing geometry, and marking against a controlled copy of the required standard.
Verification required: numerical dimensions, pressure-temperature ratings, tolerances, and material-group rules must be checked against the licensed edition named by the contract.
Supplier and Inspection Checklist
- Confirm the standard edition, NPS, class, series, type, facing, and material.
- Check that the supplier drawing clearly states Series A or Series B where applicable.
- Match the weld neck bore to the specified pipe wall or approved transition.
- Verify raw-material heat numbers and finished-component traceability.
- Measure flange OD, thickness, bolt circle, bolt holes, facing, bore, hub, and overall height as applicable.
- Inspect the gasket seating area for dents, corrosion, coating, chatter, and unacceptable scratches.
- Review the required NDE, impact testing, PMI, hardness, and heat-treatment records.
- Confirm product form, especially when a blind flange is proposed from plate.
- Review marking, weight, lifting points, packing, and face protection before shipment.
Application to Pipe Fittings, Valves, and Flanges
ASME B16.47 flanges are used on large process lines, pipelines, water systems, storage terminals, power facilities, large valves, and equipment nozzles. They may connect fabricated pipe spools to valves, pumps, pressure equipment, or other flanged assemblies.
For valves and equipment, verify the exact mating standard and dimensional series. An imported valve described only as “Class 150” may not provide enough information to confirm compatibility. For fabricated fittings and spools, control flange orientation, bolt-hole position, weld shrinkage, and final face alignment.
When a project transitions between ASME B16.5 and ASME B16.47 size ranges, the line-class documents should clearly identify which standard applies to each nominal size.
FAQ
What size range does ASME B16.47 cover?
The current ASME scope covers large-diameter steel flanges from NPS 26 through NPS 60. The contract-required edition must still be confirmed before design or inspection.
What is the difference between Series A and Series B?
They are different dimensional series within ASME B16.47 where the standard provides alternatives. Dimensions, drilling, thickness, and mass can differ, so the series must be stated rather than assumed.
Can ASME B16.47 dimensions be replaced with ASME B16.5 dimensions?
No. ASME B16.5 and ASME B16.47 have different scopes. Use the standard assigned by the line class and nominal size.
Can a blind flange be made from plate?
The ASME B16.47 scope permits plate material for blind flanges, but the project specification, material requirements, and purchaser approval still control the proposed product form.
Does ASME B16.47 define the complete piping design?
No. It is a flange product standard. The piping design code, project specifications, loads, service conditions, gasket selection, and bolted-joint procedure remain separate requirements.
Next Steps
Issue the RFQ with the complete ASME B16.47 designation, including edition, NPS, class, series, type, facing, material, bore, quantity, examination level, and documentation. Require a supplier drawing before production and list every proposed deviation for written approval.
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