ASME B16.5
Pipe flanges and flanged fittings, NPS ½ through NPS 24
The dimensional standard for pipe flanges and flanged fittings from NPS ½ to NPS 24, in pressure Classes 150, 300, 400, 600, 900, 1500 and 2500. It sets outside diameter, thickness, bolt circle, bolt holes, facings and pressure-temperature ratings by material group.
- Dimensional standards
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is ASME B16.5?
ASME B16.5 is the dimensional and pressure-rating standard for pipe flanges and flanged fittings from NPS ½ to NPS 24 in Classes 150, 300, 400, 600, 900, 1500 and 2500 (Class 2500 up to NPS 12). It sets dimensions, tolerances, facings, bolting and pressure-temperature ratings for each material group. The flange material comes from a separate specification such as ASTM A182, ASTM A105 or ASTM B564. Larger sizes are in ASME B16.47.
ASME B16.5 at a glance
| Sizes | NPS ½ – 24 |
|---|---|
| Classes | 150, 300, 400, 600, 900, 1500, 2500 |
| Flange types | Weld neck, slip-on, blind, socket weld, threaded, lap joint |
| Facings | Raised face, flat face, ring-type joint, tongue & groove, male & female |
| Pressure ratings | Pressure-temperature tables by material group (Table 1A lists the materials) |
| Material | Not set by B16.5 — named separately |
ASME B16.5 material groups for common flange materials
The class number is not a pressure: the allowable pressure depends on the material group and temperature.
| Material | Specification & grade | Group |
|---|---|---|
| Carbon steel | A105 | 1.1 |
| Low-temperature carbon steel | A350 LF2 | 1.1 |
| 304 | A182 F304 | 2.1 |
| 316L / 304L | A182 F316L / F304L | 2.3 |
| 321 | A182 F321 | 2.4 |
| 347 | A182 F347 | 2.5 |
| Duplex 2205 | A182 F51 | 2.8 |
| Monel 400 | B564 N04400 | 3.4 |
| Alloy 825 / 625 / C276 | B564 | 3.8 |
ASME B16.5 vs B16.47 vs EN 1092-1
| Standard | Sizes | Rating system |
|---|---|---|
| ASME B16.5 | NPS ½ – 24 | Class 150 – 2500 |
| ASME B16.47 | NPS 26 – 60 (Series A and B) | Class 75 – 900 |
| EN 1092-1 | DN 10 – 4000 | PN 2.5 – PN 400 |
How to write ASME B16.5 on a purchase order
Name the product, size, material specification and grade, the dimensional standard and the certificate. An example line:
Illustrative only — sizes, tests, inspection level and any project values come from your purchase specification.
ASME B16.5 edition and verification status
Which edition we have confirmed, and what is still being checked before any numerical requirement is published here.
| Current edition | Not yet confirmed against the publisher listing |
|---|---|
| Full-text verification | In progress — numerical requirements are not published on this page |
| Edition on your order | The edition named in your purchase order or design code governs — confirm it with your enquiry |
What to know before ordering to ASME B16.5
The points that decide whether material to ASME B16.5 is accepted at inspection.
- Material comes from a separate standard (A182, A105, B564); B16.5 sets size, class and rating.
- Facings include raised face, flat face and ring-type joint.
- Above NPS 24, flanges move to ASME B16.47.
Products made to ASME B16.5
How ASME B16.5 fits into an order
A purchase order line is only complete when it names the material standard, the dimensional standard and the inspection document. Miss one and the mill, the inspector and the buyer can each read the order differently.
ASME B16.5 — questions buyers ask
What is ASME B16.5?
ASME B16.5 is the dimensional and pressure-rating standard for pipe flanges and flanged fittings from NPS ½ to NPS 24 in Classes 150, 300, 400, 600, 900, 1500 and 2500 (Class 2500 up to NPS 12). It sets dimensions, tolerances, facings, bolting and pressure-temperature ratings for each material group. The flange material comes from a separate specification such as ASTM A182, ASTM A105 or ASTM B564. Larger sizes are in ASME B16.47.
What size range does ASME B16.5 cover?
NPS ½ through NPS 24. Flanges NPS 26 to 60 are covered by ASME B16.47 Series A or Series B.
Is a Class 150 flange rated for 150 psi?
No. The class is a rating designation. For example, a Class 150 flange in group 1.1 (A105) is rated about 19.6 bar at −29 to 38 °C in current editions, falling as temperature rises; other material groups have different values. Read the B16.5 table for your material and temperature.
Does ASME B16.5 specify the flange material?
No. It lists acceptable materials and rates them by group, but the order must name the material specification (e.g. A182 F316L, A105, B564 N08825).
What raised-face height does B16.5 use?
1.6 mm (1/16") for Class 150 and 300; 6.4 mm (1/4") for Class 400 and higher.
Does ASME B16.5 specify the material?
No. ASME B16.5 sets dimensions and pressure-temperature ratings; the material comes from a separate specification such as ASTM A182, A105 or B564 for flanges, or A403 and B366 for fittings. A complete order names both.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026