Asme B16 B-Norm Flange Dimensions Table
CONTENTS
Our Products
Asme B16 B-Norm Flange Dimensions Table (Class 150 – 900)
These Asme B16 B-Norm Flange Dimensions cover Class 150, 300, 600 and 900 in nominal sizes DN 15 to DN 250 — the figures needed to confirm that a valve flange mates with the counter-flange on the line.
Connection dimensions of ASME B16 B-Norm flanges in Class 150, 300, 600 and 900 for nominal sizes DN 15 to DN 250.All dimensions in millimetres. ØD flange outside diameter · ØF raised face diameter · f raised face height · b flange thickness · Øk bolt circle diameter · Øl bolt hole diameter · n number of bolts.
| DN | CLASS 150 | CLASS 300 | CLASS 600 | CLASS 900 | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ØD | ØF | f | b | Øk | Øl | n | ØD | ØF | f | b | Øk | Øl | n | ØD | ØF | f | b | Øk | Øl | n | ØD | ØF | f | b | Øk | Øl | n | |
| 15 | 88,9 | 35,1 | 1,6 | 11,2 | 60,5 | 15,7 | 4 | 95,3 | 35,1 | 1,6 | 14,2 | 66,5 | 15,7 | 4 | 95,3 | 35,1 | 6,4 | 14,2 | 66,5 | 15,7 | 4 | 120,7 | 35,1 | 6,4 | 22,4 | 82,6 | 22,4 | 4 |
| 20 | 98,6 | 42,9 | 1,6 | 12,7 | 69,9 | 15,7 | 4 | 117,3 | 42,9 | 1,6 | 15,7 | 82,6 | 19,1 | 4 | 117,3 | 42,9 | 6,4 | 15,7 | 82,6 | 19,1 | 4 | 130,0 | 42,9 | 6,4 | 25,4 | 88,9 | 22,4 | 4 |
| 25 | 108,0 | 50,8 | 1,6 | 14,2 | 79,2 | 15,7 | 4 | 124,0 | 50,8 | 1,6 | 17,5 | 88,9 | 19,1 | 4 | 124,0 | 50,8 | 6,4 | 17,5 | 88,9 | 19,1 | 4 | 149,4 | 50,8 | 6,4 | 28,4 | 101,6 | 25,4 | 4 |
| 32 | 117,3 | 12,7 | 1,6 | 15,7 | 88,9 | 15,7 | 4 | 133,4 | 63,5 | 1,6 | 19,1 | 98,6 | 19,1 | 4 | 133,4 | 63,5 | 6,4 | 20,6 | 98,6 | 19,1 | 4 | 158,8 | 63,5 | 6,4 | 28,4 | 111,3 | 25,4 | 4 |
| 40 | 127,0 | 73,2 | 1,6 | 17,5 | 98,6 | 15,7 | 4 | 155,4 | 73,2 | 1,6 | 20,6 | 114,3 | 22,4 | 4 | 155,4 | 73,2 | 6,4 | 22,4 | 114,3 | 22,4 | 4 | 177,8 | 73,2 | 6,4 | 31,8 | 124,0 | 28,4 | 4 |
| 50 | 152,4 | 91,9 | 1,6 | 19,1 | 120,7 | 19,1 | 4 | 165,1 | 91,9 | 1,6 | 22,4 | 127,0 | 19,1 | 8 | 165,1 | 91,9 | 6,4 | 25,4 | 127,0 | 19,1 | 8 | 215,9 | 91,9 | 6,4 | 38,1 | 165,1 | 25,4 | 8 |
| 65 | 177,8 | 104,6 | 1,6 | 22,4 | 139,7 | 19,1 | 4 | 190,5 | 104,6 | 1,6 | 25,4 | 149,4 | 22,4 | 8 | 190,5 | 104,6 | 6,4 | 28,4 | 149,4 | 22,4 | 8 | 244,3 | 104,6 | 6,4 | 41,1 | 190,5 | 28,4 | 8 |
| 80 | 190,5 | 127,0 | 1,6 | 23,9 | 152,4 | 19,1 | 4 | 209,6 | 127,0 | 1,6 | 28,4 | 168,1 | 22,4 | 8 | 209,6 | 127,0 | 6,4 | 31,8 | 168,1 | 22,4 | 8 | 241,3 | 127,0 | 6,4 | 38,1 | 190,5 | 25,4 | 8 |
| 100 | 228,6 | 157,2 | 1,6 | 23,9 | 190,5 | 19,1 | 8 | 254,0 | 157,2 | 1,6 | 31,8 | 200,2 | 22,4 | 8 | 273,1 | 157,2 | 6,4 | 38,1 | 215,9 | 25,4 | 8 | 292,1 | 157,2 | 6,4 | 44,5 | 235,0 | 31,8 | 8 |
| 125 | 254,0 | 185,7 | 1,6 | 23,9 | 215,9 | 22,4 | 8 | 279,4 | 185,7 | 1,6 | 35,1 | 235,0 | 22,4 | 8 | 330,2 | 185,7 | 6,4 | 44,5 | 266,7 | 28,4 | 8 | 349,3 | 185,7 | 6,4 | 50,8 | 279,4 | 35,1 | 8 |
| 150 | 279,4 | 215,9 | 1,6 | 25,4 | 241,3 | 22,4 | 8 | 317,5 | 215,9 | 1,6 | 36,6 | 269,7 | 22,4 | 12 | 355,6 | 215,9 | 6,4 | 47,8 | 292,1 | 28,4 | 12 | 381,0 | 215,9 | 6,4 | 55,6 | 317,5 | 31,8 | 12 |
| 200 | 342,9 | 269,7 | 1,6 | 28,4 | 298,5 | 22,4 | 8 | 381,0 | 269,7 | 1,6 | 41,1 | 330,2 | 25,4 | 12 | 419,1 | 269,7 | 6,4 | 55,6 | 349,3 | 31,8 | 12 | 469,9 | 269,7 | 6,4 | 63,5 | 393,7 | 38,1 | 12 |
| 250 | 406,4 | 323,9 | 1,6 | 30,2 | 362,0 | 25,4 | 12 | 444,5 | 323,9 | 1,6 | 47,8 | 387,4 | 28,4 | 16 | 508,0 | 323,9 | 6,4 | 63,5 | 431,8 | 35,1 | 16 | 546,1 | 323,9 | 6,4 | 69,9 | 469,9 | 38,1 | 16 |
Where the Standard Starts and Stops
ASME B16.5 covers NPS 1/2 through NPS 24. Above that size the flange standard changes to B16.47, which is published in two series that are not interchangeable with each other, so a drawing that simply says ASME without a number is incomplete once the line passes NPS 24.
Within its range the standard fixes five figures, and the Asme B16 B-Norm Flange Dimensions on this page give all of them: outside diameter, flange thickness, bolt circle diameter, number and size of bolts, and raised face diameter. Those five decide whether two flanges meet.
The Class Is a Curve, Not a Pressure
Class 150 does not mean 150 psi. The Asme B16 B-Norm Flange Dimensions are dimensional data; the pressure a flange may carry comes from the separate pressure-temperature tables and depends on the body material group and the working temperature.
A carbon steel Class 150 flange is rated 285 psi cold and about 110 psi at 371 °C. Take the Asme B16 B-Norm Flange Dimensions to confirm the fit and the pressure-temperature table to confirm the duty; the psi to kg/cm² conversion puts that rating into kg/cm² if the paperwork is metric.
Raised Face Height Changes With Class
The raised face is 1.6 mm high for Class 150 and Class 300, and 6.4 mm for Class 400 and above. That step matters twice: it changes the stud length, and it changes whether the flange thickness quoted in a set of Asme B16 B-Norm Flange Dimensions includes the face or not.
When comparing two datasheets, check which convention each one uses before concluding that the flanges differ. A 1.6 mm discrepancy in a thickness column is almost always the raised face rather than a real difference in the Asme B16 B-Norm Flange Dimensions.
RF, FF and RTJ
Raised face is the default. Flat face is used against cast iron bodies, where a raised face would bend a brittle flange. Ring type joint replaces both on high-pressure and high-temperature service, and it needs a machined groove rather than a flat seating surface.
An RTJ flange and an RF flange of the same class share bolt circle and hole pattern in the Asme B16 B-Norm Flange Dimensions, but they cannot be bolted to each other and sealed: one has a groove and the other does not. Ring numbers are quoted as R-xx and are tied to the size and class, so the ring has to be ordered with the flange.
NPS Is Not a Millimetre Dimension
NPS 4 is not 100 mm of anything. It is a designation, and the actual outside diameter of the pipe is 114.3 mm. The Asme B16 B-Norm Flange Dimensions are published in inches and converted to millimetres for convenience, which is why the metric columns carry awkward decimals.
When converting by hand, use the exact factor rather than a rounded one: the inch to mm metric conversion table keeps the Asme B16 B-Norm Flange Dimensions consistent with the DIN figures they will be compared against.
What Changes Between Class 150 and Class 300
Everything grows. At NPS 4 the Class 150 flange carries eight 5/8 inch bolts on a 190.5 mm bolt circle, while the Class 300 flange at the same size carries eight 3/4 inch bolts on a 200 mm circle. Same bolt count, larger circle, larger bolts.
That is the trap in a like-for-like replacement. The bolt count agreeing is not evidence that two flanges match, and reading the whole row of the Asme B16 B-Norm Flange Dimensions is the only way to be sure.
Bolt Holes Straddle the Centreline
As in the metric standards, the holes are set to straddle the principal centrelines rather than sit on them, so an even-hole flange has no bolt at top dead centre. Drains, vents and level connections stay clear as a result.
The consequence for valves is the rotation increment. With eight holes a body can only be turned in 45 degree steps, so a lever or a gearbox that has to clear a wall or a platform must be planned against the hole count in the Asme B16 B-Norm Flange Dimensions.
Bolting Is Part of the Specification
Studs are normally ASTM A193 Grade B7 with A194 Grade 2H nuts for carbon and low alloy service, in inch threads. The Asme B16 B-Norm Flange Dimensions give the bolt size and the hole size, and these are not the same number: the hole is drilled larger to give clearance.
Stud length follows from two flange thicknesses, the gasket, two washers and two nuts. Tighten in a star pattern in at least three passes, and re-check after the line reaches temperature. A joint made from correct parts still leaks if it is pulled up unevenly.
Gaskets Follow the Class
Spiral wound gaskets are made to ASME B16.20 and are sized by class as well as by nominal size, so a Class 300 gasket does not fit a Class 150 flange even at the same NPS. Non-metallic gaskets follow B16.21.
Take the gasket dimensions from the gasket standard rather than assuming them from the Asme B16 B-Norm Flange Dimensions. The raised face diameter is the figure that matters for a ring gasket, not the flange outside diameter.
Weld Neck Flanges Need a Schedule
The AAsme B16 B-Norm Flange Dimensions are identical for weld neck, slip-on, socket weld, threaded, lap joint and blind flanges of the same size and class. What differs is the pipe-side connection.
For a weld neck the bore has to match the pipe schedule, so an order that states size and class but omits the schedule cannot be filled correctly. A Schedule 40 and a Schedule 80 weld neck share their Asme B16 B-Norm Flange Dimensions and have different bores.
Identifying an Installed Flange
Measure the outside diameter, count the bolts, measure one bolt hole, and measure the bolt circle across two opposite holes. Four figures together identify a row in the Asme B16 B-Norm Flange Dimensions with certainty; one figure on its own does not.
Check the marking as well. B16.5 flanges are marked with the standard, the class, the material and the size, and where a marking survives it settles the question faster than any measurement of the Asme B16 B-Norm Flange Dimensions.
Related Tables
The metric half of the question is next door. The DIN flange dimensions table gives the same five figures for the PN series, and the ANSI Class to DIN PN conversion pairs the ratings. Read together with the Asme B16 B-Norm Flange Dimensions Table above, they answer the two questions that decide a substitution: is the rating adequate, and will the flanges actually bolt together.
Asme B16 B-Norm Flange Dimensions Table, DN 15 to DN 250.
Reference: ASME Codes and Standards — the B16 series of flange standards
