ASTM A105 Weld Neck Flange Pressure Rating and Dimensions
ASTM A105 WN (Weld Neck) flanges are forged carbon steel flanges designed for high-pressure and high-temperature piping systems. Manufactured in accordance with ASTM A105 material specifications and commonly produced to ASME B16.5 or ASME B16.47 standards, they are available in sizes from NPS 1/2" to 60" with pressure classes ranging from Class 150 to Class 2500. Their tapered hub design provides excellent strength, fatigue resistance, and leak-tight performance, making them widely used in oil and gas, petrochemical, power generation, and industrial process pipelines. This guide covers ASTM A105 WN flange dimensions, pressure ratings, specifications, and selection guidelines to help you choose the right flange for your application.
What Is an ASTM A105 WN Flange?
An ASTM A105 WN flange (Weld Neck Flange) is a forged carbon steel flange designed for high-pressure and high-temperature piping systems. It features a long tapered hub that is butt-welded to the pipe, providing excellent strength, reliable sealing, and smooth flow. Manufactured to the ASTM A105 standard, it is widely used in oil and gas, petrochemical, power generation, and industrial piping where durability and safety are essential.
ASTM A105 WN Flange Dimensions
Dimensioning System: ASME B16.5 vs B16.47
The dimensions of A105 WN flanges are based on two sets of standards: ASME B16.5 (small diameter) and ASME B16.47 (large diameter):
ASME B16.5: NPS ½″ – 24″ (≈ DN15–DN600), Class 150–2500
ASME B16.47: NPS 26″ – 60″ (≈ DN650–DN1500), divided into Series A (general purpose, large bolt holes, fewer bolt holes) and Series B (compact, small bolt holes, more bolt holes), Class 75/150/300/400/600/900
Below is a typical dimension (RF raised face) for B16.5 Class 150 WN flanges, consistent with the NPS Class... The higher the class, the larger the flange outer diameter, thickness, and bolt specifications will be—this is the most confusing point for beginners: don't just remember the NPS, you must also consider the Class.
ASME B16.5 Class 150 WN Common Dimensions (Excerpt)
|
Size
|
Outside
|
Bore
|
Thickness
|
Total
|
Neck
|
Hub
|
|
Holes
|
Raised Face
|
|
|
Diam.
|
Diam.
|
Thickness
|
Base
|
Thickness
|
Thickness
|
Diam.
|
Radius
|
Diam.
|
No.
|
P.C.D
|
Outside
|
Thickness
|
Net
|
|
|
|
|
Diam.
|
Diam.
|
Weight
|
|
mm
|
inch
|
D
|
B1*
|
t
|
T1
|
X
|
t2
|
t1
|
A
|
R
|
h
|
n
|
K
|
G
|
f
|
kg
|
|
15
|
1/2
|
88.9
|
15.75
|
11.18
|
47.75
|
30.23
|
29.21
|
7.37
|
21.34
|
3.05
|
15.75
|
4
|
60.45
|
35.05
|
1.52
|
0.49
|
|
20
|
3/4
|
98.55
|
20.83
|
12.7
|
52.32
|
38.1
|
31.75
|
7.87
|
26.67
|
3.05
|
15.75
|
4
|
69.85
|
42.93
|
1.52
|
0.72
|
|
25
|
1
|
107.95
|
26.67
|
14.22
|
55.63
|
49.28
|
33.02
|
8.38
|
33.53
|
3.05
|
15.75
|
4
|
79.25
|
50.8
|
1.52
|
1.03
|
|
32
|
1 1/4
|
117.35
|
35.05
|
15.75
|
57.15
|
58.67
|
33.02
|
8.38
|
42.16
|
4.83
|
15.75
|
4
|
88.9
|
63.5
|
1.52
|
1.34
|
|
40
|
1 1/2
|
127
|
40.89
|
17.53
|
61.98
|
65.02
|
35.56
|
8.89
|
48.26
|
6.35
|
15.75
|
4
|
98.55
|
73.15
|
1.52
|
1.74
|
|
50
|
2
|
152.4
|
52.58
|
19.05
|
63.5
|
77.72
|
35.56
|
8.89
|
60.45
|
7.87
|
19.05
|
4
|
120.65
|
91.95
|
1.52
|
2.6
|
|
65
|
2 1/2
|
177.8
|
62.74
|
22.35
|
69.85
|
90.42
|
38.1
|
9.4
|
73.15
|
7.87
|
19.05
|
4
|
139.7
|
104.65
|
1.52
|
4.17
|
|
80
|
3
|
190.5
|
77.93
|
23.88
|
69.85
|
107.95
|
36.83
|
9.14
|
88.9
|
9.65
|
19.05
|
4
|
152.4
|
127
|
1.52
|
4.99
|
|
90
|
3 1/2
|
215.9
|
90.17
|
23.88
|
71.37
|
122.17
|
38.1
|
9.4
|
101.6
|
9.65
|
19.05
|
8
|
177.8
|
139.7
|
1.52
|
6.18
|
|
100
|
4
|
228.6
|
102.26
|
23.88
|
76.2
|
134.87
|
41.91
|
10.41
|
114.3
|
11.18
|
19.05
|
8
|
190.5
|
157.23
|
1.52
|
6.98
|
|
125
|
5
|
254
|
128.19
|
23.88
|
88.9
|
163.58
|
52.07
|
12.95
|
141.22
|
11.18
|
22.35
|
8
|
215.9
|
185.67
|
1.52
|
8.72
|
|
150
|
6
|
279.4
|
154.05
|
25.4
|
88.9
|
192.02
|
50.8
|
12.7
|
168.4
|
12.7
|
22.35
|
8
|
241.3
|
215.9
|
1.52
|
10.74
|
|
200
|
8
|
342.9
|
202.72
|
28.45
|
101.6
|
246.13
|
58.42
|
14.73
|
219.2
|
12.7
|
22.35
|
8
|
298.45
|
269.75
|
1.52
|
17.68
|
|
250
|
10
|
406.4
|
254.51
|
30.23
|
101.6
|
304.8
|
57.15
|
14.22
|
273.05
|
12.7
|
25.4
|
12
|
361.95
|
323.85
|
1.52
|
24.25
|
|
300
|
12
|
482.6
|
304.8
|
31.75
|
114.3
|
365.25
|
66.04
|
16.51
|
323.85
|
12.7
|
25.4
|
12
|
431.8
|
381
|
1.52
|
36.93
|
|
350
|
14
|
533.4
|
336.55
|
35.05
|
127
|
400.05
|
73.66
|
18.29
|
355.6
|
12.7
|
28.45
|
12
|
476.25
|
412.75
|
1.52
|
48.88
|
|
400
|
16
|
596.9
|
387.35
|
36.58
|
127
|
457.2
|
72.39
|
18.03
|
406.4
|
12.7
|
28.45
|
16
|
539.75
|
469.9
|
1.52
|
60.47
|
|
450
|
18
|
635
|
438.15
|
39.62
|
139.7
|
504.95
|
80.01
|
20.07
|
457.2
|
12.7
|
31.75
|
16
|
577.85
|
533.4
|
1.52
|
68.37
|
|
500
|
20
|
698.5
|
488.95
|
42.93
|
144.53
|
558.8
|
81.28
|
20.32
|
508
|
12.7
|
31.75
|
20
|
635
|
584.2
|
1.52
|
84.6
|
|
600
|
24
|
812.8
|
590.55
|
47.75
|
152.4
|
663.45
|
83.82
|
20.83
|
609.6
|
12.7
|
35.05
|
20
|
749.3
|
692.15
|
1.52
|
115.33
|
Common sealing surface types include RF (raised face), FF (full flat face), and RTJ (ring connection). High-pressure (≥ Class 600) large-diameter pipes are generally equipped with RTJ.For standard dimensional data, refer to our ASME B16.5 Class 150 Weld Neck Flange Dimensions Chart.
ASTM A105 WN Flange PressureTemperature Rating Test
|
ASTM A105 Carbon Steel Weld Neck Flanges
|
Pressure And Temperature Ratings
|
|
TEMP°C
|
Class 150 As Per ASME B16.5
|
Class 300 As Per ASME B16.5
|
Class 400 As Per ASME B16.5
|
Class 600 As Per ASME B16.5
|
Class 900 As Per ASME B16.5
|
Class 1500 As Per ASME B16.5
|
Class 2500 As Per ASME B16.5
|
|
-20 to 100
|
275
|
720
|
960
|
1440
|
2160
|
3600
|
6000
|
|
200
|
230
|
600
|
800
|
1200
|
1800
|
3000
|
5000
|
|
300
|
205
|
540
|
720
|
1080
|
1620
|
2700
|
4500
|
|
400
|
190
|
495
|
660
|
995
|
1490
|
2485
|
4140
|
|
500
|
170
|
465
|
620
|
930
|
1395
|
2330
|
3880
|
|
600
|
140
|
435
|
580
|
875
|
1310
|
2185
|
3640
|
|
650
|
125
|
430
|
575
|
860
|
1290
|
2150
|
3580
|
|
700
|
110
|
425
|
565
|
850
|
1275
|
2125
|
3540
|
|
750
|
95
|
415
|
555
|
830
|
1245
|
2075
|
3460
|
|
800
|
80
|
405
|
540
|
805
|
1210
|
2015
|
3360
|
|
850
|
65
|
395
|
530
|
790
|
1190
|
1980
|
3300
|
|
900
|
50
|
390
|
520
|
780
|
1165
|
1945
|
3240
|
|
950
|
35
|
380
|
510
|
765
|
1145
|
1910
|
3180
|
|
1000
|
20
|
320
|
430
|
640
|
965
|
1605
|
2675
|
|
1050
|
20
|
310
|
410
|
615
|
925
|
1545
|
2570
|
|
1100
|
20
|
255
|
345
|
515
|
770
|
1285
|
2145
|
|
1150
|
20
|
200
|
265
|
400
|
595
|
995
|
1655
|
|
1200
|
20
|
155
|
205
|
310
|
465
|
770
|
1285
|
|
1250
|
20
|
115
|
150
|
225
|
340
|
565
|
945
|
|
1300
|
20
|
85
|
115
|
170
|
255
|
430
|
715
|
|
1350
|
20
|
60
|
80
|
125
|
185
|
310
|
515
|
|
1400
|
20
|
50
|
65
|
95
|
145
|
240
|
400
|
|
1450
|
15
|
35
|
45
|
70
|
105
|
170
|
285
|
|
1500
|
10
|
25
|
35
|
55
|
80
|
135
|
230
|
Advantages of ASTM A105 WN Flanges
Excellent sealing performance – The tapered neck and butt-weld connection provide a secure, leak-resistant seal.
High strength – Forged carbon steel construction delivers outstanding performance under high pressure and elevated temperatures.
Improved durability – The weld neck design reduces stress concentration and enhances fatigue resistance.
Easy maintenance – The flange allows convenient inspection, installation, and replacement.
Wide application range – Available in various sizes and pressure classes for demanding industrial piping systems.
ASTM A105 WN Flange vs Slip-On Flange
|
Feature
|
WN Flange
|
Slip-On Flange
|
|
Strength
|
Excellent
|
Good
|
|
Pressure
|
High
|
Medium
|
|
Fatigue Resistance
|
Excellent
|
Moderate
|
|
Welding
|
Butt Weld
|
Fillet Weld
|
|
Cost
|
Higher
|
Lower
|
|
Best Application
|
Critical pipelines
|
General service
|
How to Choose the Right ASTM A105 WN Flange？
Before purchasing, consider the following factors:
Nominal pipe size (NPS)
Pressure class
Facing type (RF, RTJ, FF)
Pipe schedule
Operating temperature
Corrosion environment
Applicable standards
Inspection requirements
Selecting the correct flange improves system reliability while reducing maintenance costs.
Advantages of ASTM A105 WN Flanges
Excellent sealing performance – The tapered neck and butt-weld connection provide a secure, leak-resistant seal.
High strength – Forged carbon steel construction delivers outstanding performance under high pressure and elevated temperatures.
Improved durability – The weld neck design reduces stress concentration and enhances fatigue resistance.
Easy maintenance – The flange allows convenient inspection, installation, and replacement.
Wide application range – Available in various sizes and pressure classes for demanding industrial piping systems.
ASTM A105 carbon steel weld neck flanges feature a tapered hub that strengthens the pipe-to-flange connection and minimizes stress concentration. Combined with strict manufacturing standards and multiple pressure ratings, they provide reliable performance for high-pressure, high-temperature, and critical sealing applications in oil and gas, petrochemical, power generation, and industrial pipelines.
Conclusion
ASTM A105 WN flanges combine forged carbon steel strength with the superior structural design of a weld neck connection, making them one of the most reliable flange types for high-pressure piping systems. Available in multiple sizes and pressure classes under ASME B16.5 and ASME B16.47 standards, they deliver excellent sealing performance, fatigue resistance, and long-term durability. By understanding their dimensions, pressure ratings, and material properties, engineers and buyers can select the most suitable flange for safe, efficient, and cost-effective pipeline operation.
FAQ
What standard covers ASTM A105 WN flange dimensions?
Dimensions generally comply with ASME B16.5 for sizes up to 24 inches and ASME B16.47 for larger diameters.
What is the maximum operating temperature?
ASTM A105 commonly serves piping systems up to approximately 425°C (800°F), depending on design conditions and ASME pressure-temperature ratings.
Why choose a weld neck flange instead of a slip-on flange?
A weld neck flange offers higher strength, better fatigue resistance, and improved sealing performance, making it ideal for critical piping systems under high pressure or cyclic loading.
Read more
ASTM A105 vs. ASME SA105
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