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A carbon steel weld neck flange is a forged flange identified by its long tapered hub, which is butt welded directly to the pipe end so the flange, the weld and the pipe wall form one continuous piece of steel. This is the flange type governed by ASME B16.5 and ASME B16.47, supplied in ASTM A105 forged grade and ASTM A694 high yield grades, across Class 150 through 2500 duty. Because the neck and the pipe are joined by a full penetration weld rather than a lighter fillet weld, a weld neck flange is the default choice for critical, high-pressure and high-temperature piping, and it is the only flange type most engineering specifications permit above Class 600. Solitaire Overseas manufactures carbon steel weld neck flanges with full mill test certification, and hydrostatic testing, ultrasonic testing or third party inspection can be arranged on request.
| Parameter | Specification |
|---|---|
Standard |
ASTM A105, ASTM A694, ASME B16.5, ASME B16.47 |
Size Range |
NPS 1/2 inch to 48 inch |
Pressure Class |
Class 150, 300, 600, 900, 1500, 2500 |
Facing |
Raised Face or Ring Type Joint |
Construction |
Forged, tapered hub, full penetration butt weld to pipe |
Testing |
Hydrostatic test, ultrasonic test, third party inspection on request |
Certification |
Mill Test Certificate EN 10204 3.1, 3.2 on request |
| Grade | C max | Mn | P max | S max | Si |
|---|---|---|---|---|---|
A105 |
0.35 |
0.60 to 1.05 |
0.035 |
0.040 |
0.10 to 0.35 |
| Grade | Tensile Strength min | Yield Strength min | Elongation min (%) |
|---|---|---|---|
A105 |
485 MPa (70 ksi) |
250 MPa (36 ksi) |
22 |
A694 F60 |
586 MPa (85 ksi) |
415 MPa (60 ksi) |
18 |
| Class | Approximate Rating at Ambient (psi) | Approximate Rating at Ambient (bar) |
|---|---|---|
150 |
285 |
20 |
300 |
740 |
51 |
600 |
1480 |
102 |
900 |
2220 |
153 |
1500 |
3705 |
255 |
2500 |
6170 |
425 |
| NPS | Outside Diameter (mm) | Bolt Circle (mm) | Number of Bolt Holes | Bolt Hole Diameter (mm) | Flange Thickness (mm) | Hub Length (mm) |
|---|---|---|---|---|---|---|
1/2 inch |
89 |
60 |
4 |
16 |
12 |
51 |
1 inch |
108 |
79 |
4 |
16 |
14 |
54 |
2 inch |
152 |
121 |
4 |
19 |
19 |
64 |
4 inch |
229 |
190 |
8 |
19 |
22 |
76 |
6 inch |
279 |
241 |
8 |
22 |
24 |
87 |
8 inch |
343 |
298 |
8 |
22 |
25 |
90 |
12 inch |
483 |
432 |
12 |
25 |
32 |
103 |
For sizes, classes or weights beyond this reference table, use our Flange Weight Calculator.
It is a forged flange with a long tapered hub that is butt welded directly to the pipe, so the flange, the weld and the pipe form one continuous piece of steel, built to ASME B16.5 and ASME B16.47.
The tapered hub spreads stress gradually across the transition from the flange to the pipe wall, instead of concentrating it at a sharp edge. This is what gives a weld neck flange its resistance to cracking under cyclic pressure, thermal expansion and vibration.
Solitaire Overseas supplies carbon steel weld neck flanges from Class 150 through Class 2500 per ASME B16.5 and ASME B16.47.
ASTM A105 is the standard grade. ASTM A694 is used for higher pressure duty needing greater yield strength. See our Carbon Steel High Pressure Flanges page for the full grade comparison.
Standard ASTM A105 weld neck flanges are rated for service up to about 800 degrees Fahrenheit (427 degrees Celsius). Higher temperature duty calls for an alloy steel grade rather than carbon steel.
Contact Solitaire Overseas for expert guidance and the right flange solution for your application.
Carbon Steel Flanges, Carbon Steel Pipe Flanges, Carbon Steel High Pressure Flanges, and Carbon Steel Forged Flanges.