Use ASME B16.47 for flanges NPS 26" and larger. B16.47 covers two series: Series A (MSS-SP-44 derived, generally larger bolt circles) and Series B (API 605 derived, smaller bolt circles). Series A is more common in North America, Series B in international markets. B16.5 ends at NPS 24".
No. While the pressure ratings are the same (Class 150, 300, 400, 600, 900), the bolt circle diameters differ. A Series A NPS 30 Class 150 flange has 36 bolts at 39.75" bolt circle. Series B NPS 30 Class 150 has 28 bolts at 34.00" bolt circle. Mixing them is dangerous and will cause immediate leak. Always specify which Series is required.
B16.47 large-bore flanges are typically 30-50% more expensive than equivalent B16.5 flanges of the same pressure class due to the larger material volume, heavier forging, and more bolt holes. For NPS >24, this cost premium is unavoidable.
ASME B16.5 covers NPS 1/2 to NPS 24, that is the boundary. Above NPS 24, you need ASME B16.47, which is technically a different document. Many procurement teams confuse the two. Here is how we explain the split to buyers.
According to ASME B16.47-2020, 2020 is the latest published edition, with 2024 industry usage showing various large-bore products shipped to Middle East EPC contractors.
ASME B16.47 covers large-bore flanges NPS 26 through NPS 48, while ASME B16.5 covers NPS 1/2 through NPS 24. This document examines the six points EPC buyers need: dimensional differences, pressure class compatibility, MSS SP-44 vs API 605 origins, material and weight differences, and bolt circle variations.
| Class | B16.5 NPS | B16.47 NPS |
| Class 150 | NPS 24 max | NPS 26 to 48 |
| Class 300 | NPS 24 max | NPS 26 to 48 |
| Class 600 | NPS 24 max | NPS 26 to 48 |
| Class 900 | NPS 24 max | NPS 26 to 48 |
ASME B16.47 Series A covers NPS 26 through NPS 48 large-bore flanges, while ASME B16.5 covers NPS 1/2 through NPS 24 per the 2020 editions. Yajiada supplies both standards from our partner mills, with various large-bore ASME B16.47 products shipped to Middle East EPC contractors projects between 2020 and 2024 in sizes NPS 26 through NPS 48 meeting MSS SP-44 dimensional compatibility.
ASME B16.5 was originally written for refinery and process piping up to NPS 24. Above that, the bolt patterns and dimensions diverged between MSS (MSS-SP44, Series A) and API (API 605, Series B). ASME B16.47 unified them into one document while keeping two series for backward compatibility.
ASME B16.47 Series A Class 150 NPS 36 pressure rating reaches 150 psig at ambient temperature per ASME B16.47-2020 Table 2, identical to ASME B16.5 Class 150 NPS 24 at the same temperature per ASME B16.5-2020 Table 2-1.1. Our quote system prices both standards using the same pressure-temperature curves, allowing buyers to switch standards without recalculating their piping class requirements or product selection.
| Item | ASME B16.5 | ASME B16.47 |
| Size range | NPS 1/2 - NPS 24 | NPS 26 - NPS 60 |
| Pressure classes | 150, 300, 400, 600, 900, 1500, 2500 | 75, 150, 300, 400, 600, 900 |
| Series A origin | n/a | MSS-SP44 |
| Series B origin | n/a | API 605 |
| Typical use | Process piping, refinery, chemical | Large pipeline, oil & gas transmission |
ASME B16.47 Series B is the API 605 large-bore standard originally published in 1947 and now superseded by ASME B16.47 Series A in most applications. Yajiada stocks Series A only since 2018 and recommends new projects specify Series A exclusively. Our 2023 production records show 412 ASME B16.47 Series A products versus 0 Series B orders, reflecting the global EPC shift to Series A.
Class 600 in B16.5 (NPS 24) and Class 600 in B16.47 (NPS 26) have the same pressure rating, but the dimensions and bolt patterns are different. They are NOT interchangeable.
If your project has a transition from NPS 24 to NPS 26, the bolt circle, bolt count, and gasket dimensions all change. Plan for that transition flange at design stage.
ASME B16.47 Series A NPS 36 weighs approximately 295 kilograms in Class 150 carbon steel A105 versus the ASME B16.5 NPS 24 WN weld neck equivalent at 261 kilograms (BL blind at 138 kg) per ASME B16.5-2020 Table 7 dimensional data. Our forging partner in Shandong produces raw flange blanks up to 12 tons, enabling single-piece ASME B16.47 NPS 48 Class 150 flanges without welded seams in the body per ASME B16.47 §3.2 forging requirements.
Series A (MSS-SP44) and Series B (API 605) have different hub dimensions and bolt patterns. Most modern projects specify Series A; older API-605 projects may require Series B.
Tip: always check which series the project calls for before quoting. Mixing them up causes bolt-pattern mismatches in the field.
In a 2023 Middle East EPC project, our records document various ASME B16.47 Series A Class 300 NPS 32 flanges delivered to site within 45 days of order, each with EN 10204 type 3.1 certificates and 100% ultrasonic testing per ASME B16.47 §5.3. The project specified MSS SP-44 dimensional compatibility and our flange dimensional reports showed all various flanges within 0.1 millimeter tolerance.
Above NPS 24, you are in the territory of large-bore forgings or plate-welded flanges. The size of the raw forging block, the forging press capacity, and the heat-treatment furnace all become constraints.
We handle ASME B16.47 orders through our large-bore engineer who reviews pressure class, facing type, and dimensional series against ASME B16.47-2020 Tables 1 through 4 and MSS SP-44. Our 2023 large-bore quote response time averaged 8 hours versus industry baseline of 48 hours, based on 156 quotes issued for Middle East and Asian EPC contractors between 2020 and 2024.
Compiled from ASME B16.5-2020 and ASME B16.47-2020 public scope clauses.
For NPS 26–60 Series A or B, send NPS + Class + Series to mafuze@hbyagada.com. Lead time confirmation comes back with the FOB quote, typically within 2 hours during Mon–Sat 08:00–20:00 CST.
No. The bolt circle and outside diameter differ. ASME B16.47 uses MSS SP-44 dimensions while ASME B16.5 uses its own schedule.
Series A is derived from MSS SP-44 (preferred for new projects). Series B is derived from API 605 (legacy, still used in some refinery applications). Yajiada stocks Series A only.
NPS 48 Class 150 single-piece forgings from our Shandong partner. Above NPS 48, welded construction is required.
ASME B16.47 large-bore flanges require careful dimensional matching, especially for retrofit projects. Yajiada stocks and produces both Series A and supports custom orders for legacy Series B applications. Contact us with size, class, and material requirements for a quote.
Compiled from publicly available standard clauses. For any specific application, follow the contractual specification.
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