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ANSI/ASME B16.5 Class 300
Weld Neck Flange Dimensions

Flange dimensions to the ANSI/ASME B16.5 Class 300 weld neck standard. Every size we list is one we manufacture and ship, with custom sizes and modifications available on request.

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ASME B16.47 Class 300, Class 300 Weld Neck Flange Dimensions

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B16.5 Class 300 Weld Neck Flange Dimensions

Select a material and flange type to view the ANSI/ASME B16.5 Class 300 weld neck flange dimensions, including outside diameter, bolt circle, number and size of bolt holes, and thickness.

Flange type

Weld Neck
ANSI/ASME B16.5 Class 300 weld neck flange dimensions, in inches.
Nominal Pipe SizeO.D. (O)Flange THK (tf)Length Thru Hub (Y)Hub Dia (X)Hub Top Dia (A)R.F. Dia (R)Bolt CircleNo. BoltsBolt Hole Dia
0.53.750.502.001.500.841.3752.6340.750
0.754.630.562.191.881.051.6883.2540.750
14.880.622.382.121.322.0003.5040.750
1.255.250.692.502.501.662.5003.8840.750
1.56.130.752.632.751.902.8754.5040.875
26.500.812.693.312.383.6255.0080.750
2.57.500.942.943.942.884.1255.8880.875
38.251.063.064.623.505.0006.6380.875
3.59.001.123.135.254.005.5007.2580.875
410.001.193.325.754.506.1887.8880.875
511.001.313.827.005.567.3139.2580.875
612.501.383.828.126.638.50010.63120.875
815.001.564.3210.258.6310.62513.00121.000
1017.501.814.5612.6210.7512.75015.25161.125
1220.501.945.0614.7512.7515.00017.75161.250
1423.002.065.5616.7514.0016.25020.25201.250
1625.502.195.6919.0016.0018.50022.50201.375
1828.002.316.1921.0018.0021.00024.75241.375
2030.502.446.3223.1220.0023.00027.00241.375
2436.002.696.5627.6224.0027.25032.00241.625
Notes: Weld neck dimensions (O.D., flange thickness, length through hub, and hub diameters) per ASME/ANSI B16.5 Table 11C, Class 300, U.S. customary units. Raised face diameter, bolt circle, and number and size of bolt holes are the Class 300 drilling shared across flange types. The same dimensions apply to carbon steel (ASTM A105) and stainless steel (ASTM A182, 304/304L or 316/316L). Minimum flange thickness does not include the raised face thickness. The hub diameter at the weld end equals the outside diameter of the matching pipe; the bore is specified by the purchaser to suit the pipe. ALL DIMENSIONS ARE IN INCHES UNLESS OTHERWISE STATED.

How to Read The Tables

asme b16 47 series a flange dimensions

Each table lists, per nominal size, dimensions such as outside diameter, flange thickness, bolt circle, number and size of bolt holes, bolt size, length through hub, and bore, depending on the flange type. Dimensions follow the governing ANSI/ASME and AWWA standards; where shown, weights vary by flange type and facing.

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FAQs

What is a weld neck flange?
A weld neck flange has a long tapered hub that is butt welded to the pipe, forming a smooth, gradual transition between the flange and the pipe. That hub reinforces the joint and reduces stress at the weld, which is why weld neck flanges are preferred for high pressure, high temperature, and cyclic or critical service. For a given size and class, the outside diameter, bolt circle, and drilling are the same as the other ANSI/ASME B16.5 flange types, so a weld neck bolts up to any matching Class 150 or Class 300 flange.

What sizes and pressure classes does ANSI/ASME B16.5 cover?
ANSI/ASME B16.5 covers flanges and flanged fittings from NPS ½ inch through 24 inch in seven pressure classes: 150, 300, 400, 600, 900, 1500, and 2500. The class sets the pressure and temperature rating, and each class has its own dimensions, bolt circle, and drilling. Larger sizes, 26 inch and up, fall under ANSI/ASME B16.47 instead.

What flange types are covered by ANSI/ASME B16.5?
ANSI/ASME B16.5 covers weld neck, slip-on, blind, threaded, socket weld, and lap joint flanges. For a given size and class, every type shares the same outside diameter, bolt circle, and drilling, so they bolt to the same mating flange. What changes between types is the hub and the bore.

What is the bolt circle (B.C.) on a flange?
The bolt circle, also called the bolt hole circle (B.H.C.) or bolt circle diameter, is the diameter of the imaginary circle that passes through the centers of all the bolt holes. It sets where the bolts sit and must match the mating flange exactly, even when two flanges share the same outside diameter. Every dimension table lists the bolt circle along with the number and size of the bolt holes.

Do flange dimensions change with the material or finish?
No. The dimensions (outside diameter, bolt circle, bore, thickness and drilling) are set by the governing standard, ANSI/ASME or AWWA, and stay the same whether the flange is carbon steel, stainless steel, galvanized, epoxy coated or painted. Material and finish affect corrosion resistance, pressure and temperature limits, and weight, but not the dimensional layout.

What is the difference between Class 150 and Class 300 flanges?
The class is a pressure and temperature rating. At a given temperature, a Class 300 flange is rated for higher pressure than a Class 150 flange. Class 300 is also physically heavier, with a larger bolt circle and more (and larger) bolts. Select the class that matches the maximum pressure and temperature of your piping system; the two classes are not interchangeable.