Use ASME B16.47 for large-diameter steel flange RFQs from NPS 26 to NPS 60
BLD Forge Direct
ASME B16.47 Series A vs Series B Large-Diameter Flanges
ASME B16.47 flange RFQs must state more than NPS and Class. For NPS 26 to NPS 60 large-diameter steel flanges, Series A and Series B have different legacy bases, bolt patterns, weight and mating assumptions, so procurement teams should confirm the series, flange type, facing, material, inspection documents and existing-system dimensions before comparing offers.
Summary
ASME B16.47 flange RFQs must state more than NPS and Class. For NPS 26 to NPS 60 large-diameter steel flanges, Series A and Series B have different legacy bases, bolt patterns, weight and mating assumptions, so procurement teams should confirm the series, flange type, facing, material, inspection documents and existing-system dimensions before comparing offers.
State Series A or Series B; do not rely on ANSI flange, large flange or Class wording alone
Confirm whether the project follows MSS SP-44 continuity, API 605 replacement history or an owner drawing
Send dimensional report, MTC 3.1, NDT, PMI, bolting and packing requirements before price comparison
Engineering Selection Notes
Large-diameter flanges are expensive to remake, difficult to ship and highly sensitive to matching details at the bolted joint. In ASME B16.47 work, the buyer is not only selecting a pressure class; the buyer is selecting a dimensional family. Series A and Series B can both be valid B16.47 routes, but the bolt circle, hole count, outside diameter, thickness and mating assumptions are not interchangeable.
The practical tradeoff is weight and external-load margin versus compactness and replacement continuity. Series A is the MSS SP-44-derived route and is commonly selected when the line, nozzle or project specification expects heavier construction, larger bolts or RTJ face coverage. Series B is API 605-derived, more bolt-dense and lighter in many same-size comparisons, so it can be useful for existing API 605 systems, replacement work and lower external-load assumptions when the engineering specification permits it.
For procurement, the safest rule is to quote from the project specification or from measured existing dimensions, not from a short material list. A request such as 30 inch Class 300 flange A105 RF is incomplete for B16.47 because it omits the series, flange type, facing details, bore or schedule, material condition, inspection basis and whether the mating equipment is already Series A or Series B. Those missing fields create avoidable requotes and, worse, non-mating parts at site.
Source Basis
The tables below use public standard-scope notes and buyer document rules, not copied proprietary dimension tables.
- ASME B16.47 2025 large-diameter flange scope - Used for B16.47 scope statements: NPS 26 through NPS 60, Class 75 through 900, pressure-temperature ratings, materials, dimensions, tolerances, marking and testing.
- ASME B16.5 2025 scope - Used for the B16.5 boundary at NPS 1/2 through NPS 24 and the Class 2500 through NPS 12 note.
- ANSI note on ANSI/MSS SP-44-2026 - Used for current MSS SP-44 pipeline flange scope, NPS 12 through NPS 60, Class 150 through 900 and forged-steel / plate blind-flange notes.
- Texas Flange ASME B16.47 Series A vs Series B - Used for practical Series A / Series B differences: MSS SP-44 vs API 605 basis, larger or smaller bolting pattern, RTJ and Class 75 notes, and non-interchangeability.
- Coastal Flange Series A vs Series B comparison - Used as a second manufacturer source for thicker / heavier Series A attributes, more smaller Series B bolting and non-compatible bolting.
- ASME PCC-1 2022 bolted flange joint assembly scope - Used for bolted flange joint assembly and leak-tightness context when large flanges include gasket, bolting and assembly procedures.
- ISO 9712:2021 NDT personnel scope - Used for NDT method and personnel-qualification context for UT, MT, PT, RT, VT and related industrial NDT requirements.
- EN 10204 Type 3.1 explanation - Used for the practical Type 3.1 explanation: actual test results from the supplied lot and endorsement by the manufacturer's independent representative.
ASME B16.47 Scope and Adjacent Standard Check
| Route | Verified public scope used in this guide | RFQ implication | Procurement warning |
|---|---|---|---|
| ASME B16.5 | Pipe flanges and flanged fittings NPS 1/2 through NPS 24; Class 150, 300, 400, 600, 900 and 1500 through NPS 24; Class 2500 through NPS 12 | Use B16.5 for normal ASME flange RFQs up to NPS 24, then move to B16.47 or project drawing review above that range | Do not price NPS 26 and larger from a B16.5 table extension |
| ASME B16.47 | Large-diameter steel flanges NPS 26 through NPS 60 with Class 75, 150, 300, 400, 600 and 900; includes pressure-temperature ratings, materials, dimensions, tolerances, marking and testing | State ASME B16.47 plus Series A or Series B, flange type, Class, facing, material and document scope | Do not write only ANSI flange or large flange; the series controls mating dimensions |
| ANSI/MSS SP-44-2026 | Steel pipeline flanges NPS 12 through NPS 60 with Class 150, 300, 400, 600 and 900; welding neck flanges are forged steel, while blind flanges can be forged steel or steel plate | Use when the pipeline specification calls MSS SP-44 or the project needs MSS continuity; confirm whether B16.47 Series A wording is accepted | Do not assume every B16.47 RFQ can be converted to MSS SP-44 certificate wording without buyer approval |
| Owner drawing / non-standard large flange | B16.47 public guidance and manufacturer references identify weld neck and blind flanges as the core B16.47 shapes | For slip-on, custom nozzle, vessel, modified bore or non-standard drilling above NPS 24, attach the drawing and revision | Do not force a custom large flange into B16.47 only because the size is above NPS 24 |
Series A vs Series B Buyer Comparison
| Decision point | Series A | Series B | RFQ action |
|---|---|---|---|
| Legacy basis | Derived from MSS SP-44 dimensional practice | Derived from API 605 dimensional practice | State the series exactly; legacy wording should be converted only when the project permits it |
| Geometry and weight | Generally larger outside diameter, larger bolt circle, thicker / heavier construction in same-size comparisons | Generally smaller outside diameter, smaller bolt circle and lighter / thinner construction in same-size comparisons | Ask for dimension report against the exact B16.47 series, not just NPS and Class |
| Bolting pattern | Typically fewer, larger bolts | Typically more, smaller bolts | Never mix Series A and Series B mating flanges in the same bolted joint |
| Facing and class notes | Industry references note RTJ coverage in Series A for large-diameter severe-service work | Industry references note Class 75 availability and no B16.47 RTJ coverage for Series B | State RF, FF, RTJ and ring details before quotation; do not add RTJ after price comparison |
| Common procurement use | New construction, MSS SP-44 continuity, higher external-loading assumptions or owner specs that call Series A | Replacement or retrofit on existing API 605 / Series B systems, lower-weight requirements or owner specs that call Series B | For brownfield replacement, measure existing OD, bolt circle, hole count and hole diameter before ordering |
B16.47 RFQ Field Checklist
| RFQ field | Minimum data to send | Why it matters | Evidence to request |
|---|---|---|---|
| Size and rating | NPS 26 to NPS 60 plus Class 75, 150, 300, 400, 600 or 900 | Sets the B16.47 table family and pressure-temperature check basis | Quotation line item and dimensional report |
| Series | Series A or Series B, or exact legacy MSS SP-44 / API 605 requirement | Controls OD, bolt circle, bolting and mating compatibility | Series-stated drawing or supplier dimension sheet |
| Flange type | Weld neck, blind or drawing-controlled special flange | B16.47 core supply is not a blanket route for every large flange shape | Drawing revision, flange type and machining scope |
| Facing and gasket | RF, FF, RTJ, ring number, surface finish and gasket note where specified | Changes machining, inspection and bolted-joint compatibility | Face / groove dimensional report and gasket or ring reference |
| Material and product form | ASTM / ASME grade, forged / cast / plate allowance for blinds, heat treatment and impact note | Controls MTC, forging route, plate acceptance and service-temperature review | MTC 3.1, heat treatment record and impact / hardness results where required |
| Inspection and handover | Dimensional report, PMI, UT, MT, PT, third-party inspection, packing and marking language | Late inspection additions change lead time and make offers non-comparable | ITP, NDT reports, marking photos and export packing list |
Inspection and Document Controls for Large-Diameter Flanges
| Control | Large-diameter reason | What to check | RFQ note |
|---|---|---|---|
| Dimensional report | A small error in bolt circle, hole count, thickness or face detail can prevent field fit-up | OD, bolt circle, hole count, hole diameter, thickness, bore / schedule, face and RTJ groove where applicable | Require dimensions against ASME B16.47 Series A or Series B, not only against B16.47 |
| MTC 3.1 | Large forged or blind flanges need traceable material evidence before shipment release | Heat number, material grade, chemistry, mechanical test results, heat treatment and authorized inspection signature | State EN 10204 3.1 or project certificate wording in the first RFQ |
| NDT | Heavy forgings, high-pressure flanges, RTJ grooves and project-critical joints often require documented checks | UT, MT, PT, RT, VT or project methods with qualified personnel and acceptance criteria | Specify method, procedure, level, report language and witness hold point early |
| Bolting and gasket review | Large joints are sensitive to gasket seating, bolt loading and assembly practice | Bolt grade, washer / nut scope, gasket type, RTJ ring number and any ASME PCC-1 assembly expectation | Separate flange supply from bolt / gasket / assembly scope so price and responsibility are clear |
| Marking and export packing | Large flanges are often shipped in mixed batches and may be handled at several ports or laydown yards | Size, Class, Series, material, heat number, item number, face, packing mark and document language | Match marking, MTC, dimensional report and packing list line by line |
Practical Checklist
Use this list before sending drawings or line items for quotation review.
Governing route: ASME B16.47-2025, MSS SP-44-2026, legacy API 605 wording or owner drawing
Size and class: NPS 26 to NPS 60 plus Class 75, 150, 300, 400, 600 or 900
Series: Series A or Series B, confirmed against mating equipment or existing flange measurements
Flange type: weld neck, blind or drawing-controlled special flange; attach drawing for non-standard large flanges
Facing: RF, FF, RTJ or drawing-controlled face, including ring groove / ring number / surface finish notes
Material: exact ASTM / ASME or project grade, heat treatment condition, impact temperature and substitution policy
Inspection: MTC 3.1, dimensional report, PMI, UT, MT, PT, hardness, third-party witness or ITP requirement
Logistics: quantity, weight handling constraints, packing, marking language, destination and required delivery window
Common RFQ Mistakes
These points often cause repeated clarification, price revisions or document mismatch.
- Ordering a large ASME flange by NPS and Class without saying Series A or Series B
- Assuming Series A and Series B bolt together because both are ASME B16.47
- Using MSS SP-44 or API 605 legacy wording without confirming the accepted B16.47 series in the current project specification
- Adding RTJ facing after quotation even though the selected series and class must support the ring groove requirement
- Requesting a large slip-on or special nozzle flange as B16.47 without attaching a drawing and owner approval basis
- For brownfield replacement, trusting worn flange markings instead of measuring OD, bolt circle, hole count and hole diameter
- Comparing a forged blind quote with a plate blind quote when the project has not approved plate material
- Leaving NDT, PMI, dimensional report, MTC 3.1 or third-party hold points until the pre-shipment stage
FAQ
Short answers for buyers preparing this RFQ topic.
Is ASME B16.47 the same as ASME B16.5?
No. ASME B16.5 covers pipe flanges and flanged fittings through NPS 24, while ASME B16.47 covers large-diameter steel flanges from NPS 26 through NPS 60. The RFQ should use the correct standard boundary.
Are B16.47 Series A and Series B interchangeable?
No. Series A and Series B use different dimensional and bolting patterns, so they should not be mixed in the same bolted joint. Match the project specification or the existing mating flange dimensions.
Which B16.47 series is heavier?
Industry manufacturer references generally describe Series A as the heavier route with larger outside diameter, larger bolt circle and fewer larger bolts. Series B is generally lighter and uses more smaller bolts.
What should a B16.47 RFQ include?
Include NPS, Class, Series A or B, flange type, facing, material grade, bore or schedule, quantity, MTC 3.1, dimensional report, NDT or PMI requirements, packing and destination.
PDF Datasheets for RFQ Review
Use these direct PDF links with the article before sending line items. The PDFs are generated from published product-page RFQ scope tables and do not invent standard dimensions.
ASME B16.5 Flanges RFQ Datasheet
Use this PDF for ASME flange RFQs where NPS, Class, facing, material and inspection scope need to be aligned before quotation.
High Pressure Flanges RFQ Datasheet
Use this PDF when Class 600, 900, 1500, 2500 or RTJ / NDT requirements must be reviewed with the B16.47 article.
Send your RFQ or drawing directly to BLD Forge Direct.
Email quote@bldforgedirect.com with standard, drawing, material, quantity and inspection requirements.