Everyone who has looked at a pipe spool knows the feeling of being uncertain. It’s when the flange seems to be in good shape and the markings on the hub are all correct, but then something doesn’t feel right about the bolts. That moment of hesitation is exactly why knowing about proper pipe flange dimensions is needed. ASME B16.5 and ASME B16.47 are the two specifications that govern nearly all steel flanges used in industrial piping systems in the USA. Knowing which one is applicable and what the actual values are helps avoid problems on-site.
USA Piping Solution has put together this guide, in which both specifications are explained in simple language, along with a pipe flange dimensions chart, so that the reader doesn’t have to go through different pages for every bolt diameter.
Need to confirm a flange dimension before you order? Request a quote from our team with your size, class and standard and we will verify it for you.
What Is ASME B16.5
ASME B16.5, sometimes written as ASME B 16.5 or ANSI B16.5 depending on which era of the standard someone learned it under, covers pipe flanges and flanged fittings from NPS 1/2 through NPS 24. It sets the pressure temperature ratings, materials, dimensions, tolerances, marking and testing requirements for flanges made from forged or cast materials, with blind flanges and some reducing flanges also permitted in plate material. ASME B16.5 flange dimensions span seven pressure classes: 150, 300, 400, 600, 900, 1500, and 2500, with class 2500 limited to sizes NPS 1/2 through NPS 12. The standard covers threaded, slip on, lap joint, blind, and weld neck flange types, which is a wider variety of flange types than its large diameter counterpart offers.
What Is ASME B16.47
ASME B16.47 continues where B16.5 ends, addressing large-scale steel pipe flanges starting from NPS 26 up to NPS 60. It has a restricted range since it only talks about weld neck flanges manufactured from forged or cast materials and blind flanges that can be made from cast, forged or plate materials. This is also an important point as ASME B16.47 does not cover any slip-on, threaded, or socket-weld flanges. Such types of flanges are still manufactured above the NPS 24 size, but they are made based on standard industry dimensions that are not provided in ASME publications and can differ from manufacturer to manufacturer, so it is crucial to check the compatibility of the bolt patterns before purchasing a slip-on or threaded flange of a larger diameter.
ASME B16.47 Series A vs. Series B
ASME B16.47 splits into two series, and mixing them up is one of the more common mistakes on a large diameter flange order. Series A, based on the former MSS SP 44 standard, is the thicker, heavier design with a larger bolt circle diameter, typically specified for higher stress service such as offshore platforms, transmission pipelines and heavy process plants. Series B, based on the former API 605 standard, is lighter with a smaller bolt circle diameter, generally suited to pipeline repairs, retrofits and lower stress, cost sensitive projects. Both series span multiple pressure classes rather than a single class each, Series A covering 150 through 900 and Series B covering 75 through 900, and the two series are not interchangeable since their bolt circle diameters do not match.
ASME B16.5 vs. ASME B16.47 Series A vs. Series B Comparison Table
Feature | ASME B16.5 | B16.47 Series A | B16.47 Series B |
|---|---|---|---|
Size Range | NPS 1/2 to 24 | NPS 26 to 60 | NPS 26 to 60 |
Pressure Classes | 150 to 2500 | 150 to 900 | 75 to 900 |
Flange Types Covered | Threaded, slip on, lap joint, blind, weld neck | Blind, weld neck | Blind, weld neck |
Relative Thickness | Standard | Heavier | Lighter |
Typical Application | General process piping | Offshore, high stress | Pipeline repair, retrofit |
ASME B16.5 Class 150 Flange Dimensions Chart
NPS | Outside Diameter (OD) | Bolt Circle Diameter (BCD) | Bolt Hole Diameter | Flange Thickness |
|---|---|---|---|---|
1/2 | 3.50 | 2.38 | 0.62 | 0.44 |
3/4 | 3.88 | 2.75 | 0.62 | 0.50 |
1 | 4.25 | 3.13 | 0.62 | 0.56 |
1-1/4 | 4.63 | 3.50 | 0.62 | 0.62 |
1-1/2 | 5.00 | 3.88 | 0.62 | 0.69 |
2 | 6.00 | 4.75 | 0.75 | 0.75 |
2-1/2 | 7.00 | 5.50 | 0.75 | 0.88 |
3 | 7.50 | 6.00 | 0.75 | 0.94 |
4 | 9.00 | 7.50 | 0.75 | 0.94 |
5 | 10.00 | 8.50 | 0.88 | 0.94 |
6 | 11.00 | 9.50 | 0.88 | 1.00 |
8 | 13.50 | 11.75 | 0.88 | 1.12 |
10 | 16.00 | 14.25 | 1.00 | 1.19 |
12 | 19.00 | 17.00 | 1.00 | 1.31 |
14 | 21.00 | 18.75 | 1.13 | 1.38 |
16 | 23.50 | 21.25 | 1.13 | 1.44 |
18 | 25.00 | 22.75 | 1.25 | 1.56 |
20 | 27.50 | 25.00 | 1.25 | 1.69 |
24 | 32.00 | 29.50 | 1.38 | 1.81 |
ASME B16.47 Flange Dimensions Chart, Series A and Series B
Large diameter flanges under ASME B16.47 follow a similar layout to the B16.5 chart above, but Series A and Series B diverge on bolt circle diameter and thickness at the same nominal size.
NPS | ASME B16.47 Series A | ASME B16.47 Series B |
|---|---|---|
26 | 31.75 | 28.50 |
28 | 34.00 | 30.50 |
30 | 36.00 | 32.50 |
32 | 38.50 | 34.50 |
34 | 40.50 | 36.50 |
36 | 42.75 | 38.50 |
42 | 49.50 | 44.50 |
48 | 56.00 | 50.75 |
54 | 62.75 | 56.75 |
60 | 69.25 | 63.00 |
BS 10 Table D Flange Dimensions
Not every project in the world specifies ASME. BS 10 is a British flange standard that still shows up regularly on projects tied to Australian, New Zealand, and some Commonwealth market specifications, and Table D is one of its more commonly referenced pressure and dimension series within that standard. BS 10 Table D flange dimensions are not directly interchangeable with ASME B16.5 dimensions, since the bolt circle diameters, bolt hole patterns, and overall outside diameters follow a different design lineage entirely. If a project specification calls out BS 10 Table D, do not substitute an ASME B16.5 flange of a similar nominal size without confirming the bolt pattern matches, since a mismatch here will not be caught until the flanges are actually being bolted together on site.
Flange PCD Chart: Why Bolt Circle Diameter Is the Dimension That Matters Most
PCD stands for pitch circle diameter, also called bolt circle diameter, and it is arguably the single most important number on any flange PCD chart. Two flanges can look almost identical in outside diameter and still fail to bolt together if their PCD does not match exactly, since the bolt holes simply will not line up. This is exactly why mixing standards, or mixing Series A and Series B within ASME B16.47, causes real problems on site rather than just paperwork headaches. Whenever you are matching an existing flange in the field, measuring PCD accurately, center to center between two bolt holes on opposite sides of the flange for even bolt counts, is the fastest way to confirm which standard and class you are actually looking at.
Materials and Face Types
Flange dimensions charts are typically published independent of material grade, but material selection still affects which pressure class a given flange can safely carry at a given temperature.
- ASTM A105: standard carbon steel forging grade for general service flanges
- ASTM A182 Gr. F304 / F316: stainless steel grades for corrosive or sanitary service
- ASTM A182 low alloy grades (F5, F9, F11, F22, F91): used where elevated temperature service requires added chromium and molybdenum
- Raised face: the most common face type under ASME B16.5, with a raised ring around the bore
- Flat face: used where the mating equipment, such as a cast iron valve or pump, cannot tolerate a raised face
- Ring type joint: used in high-pressure and high-temperature service, with a metal ring gasket seated in a machined groove
Ordering flanges for a new project? Contact us with your standard, class, and size list and we will confirm dimensions before you finalize the order.
FAQs
What is the difference between ASME B16.5 and ASME B16.47?
ASME B16.5 covers pipe flanges and flanged fittings from NPS 1/2 through 24 across seven pressure classes and several flange types. ASME B16.47 covers large diameter flanges from NPS 26 through 60, limited to weld neck and blind flange types only.
What sizes does ASME B16.47 cover?
ASME B16.47 covers flange sizes from NPS 26 through NPS 60, picking up immediately where ASME B16.5 leaves off at NPS 24.
What is the difference between B16.47 Series A and Series B?
Series A is thicker and heavier, with a larger bolt circle diameter and is generally used for higher-stress applications. Series B is lighter with a smaller bolt circle diameter, generally used for pipeline repairs and lower-stress or cost-sensitive projects. The two series are not interchangeable.
What is a flange PCD chart?
A flange PCD chart lists the pitch circle diameter, also called bolt circle diameter, for each flange size and class. PCD is the single dimension that must match exactly between two mating flanges for the bolt holes to align.
Is BS 10 Table D the same as ASME B16.5?
No. BS 10 Table D is a separate British flange standard with its own bolt circle diameters and bolt hole patterns. It is not directly interchangeable with ASME B16.5, so bolt patterns should always be confirmed before substituting one for the other.
Are slip-on and threaded flanges covered by ASME B16.47?
No. ASME B16.47 covers only weld neck and blind flanges. Slip-on, threaded, and socket-weld flanges above NPS 24 are manufactured to industry standard dimensions that vary by manufacturer rather than a single ASME chart.
Request Flanges from USA Piping Solution
USA Piping Solution can help you source or verify flanges built to ASME B16.5 and ASME B16.47 dimensions across the classes and materials covered in this guide. Contact us with your size, class, and standard, or browse our full product range for related piping components.
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