ASME B16.5 weld neck (WN) flange: dimensions and weight by class

Flange with a tapered hub butt welded to the pipe. The hub distributes the stresses, which is why it is the standard for high pressure, high temperature, thermal cycling and fatigue.

Technical review Oct 2026 · Source: ASME B16.5-2020

Weld neck in section. Butt weld (bevel) to the pipe; bore B follows the pipe schedule.

StandardASME B16.5-2020

Classes150, 300, 400, 600, 900, 1,500, 2,500

Range in class 150NPS ½ to 24

Unitsmm, kg; hole and bolt in inches

Dimensions by pressure class

Choose the class and click a row: the drawing changes to the scale and dimensions of that diameter.

Weld neck, class 150: dimensions in mm · raised face 1.6 mm · all types in class 150
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½"	15	89	9.7	30	21.3	46	15.7	60.5	4	⅝"	½"	0.5
¾"	20	99	11.2	38	26.7	51	20.8	69.8	4	⅝"	½"	0.7
1"	25	108	12.7	49	33.5	54	26.7	79.2	4	⅝"	½"	1.1
1¼"	32	117	14.2	59	42.2	56	35.1	88.9	4	⅝"	½"	1.4
1½"	40	127	15.9	65	48.3	60	40.9	98.6	4	⅝"	½"	1.8
2"	50	152	17.5	78	60.5	62	52.6	120.6	4	¾"	⅝"	2.7
2½"	65	178	20.6	90	73.2	68	62.7	139.7	4	¾"	⅝"	4.2
3"	80	190	22.4	108	88.9	68	78.0	152.4	4	¾"	⅝"	5.1
3½"	90	216	22.4	122	101.6	70	90.2	177.8	8	¾"	⅝"	6.3
4"	100	229	22.4	135	114.3	75	102.4	190.5	8	¾"	⅝"	7.2
5"	125	254	22.4	164	141.2	87	128.3	215.9	8	⅞"	¾"	9
6"	150	279	23.9	192	168.4	87	154.2	241.3	8	⅞"	¾"	11
8"	200	343	26.9	246	219.2	100	202.7	298.4	8	⅞"	¾"	18.2
10"	250	406	28.4	305	273.0	100	254.5	362.0	12	1"	⅞"	24.9
12"	300	483	30.2	365	323.8	113	304.8	431.8	12	1"	⅞"	38.4
14"	350	533	33.3	400	355.6	125	customer	476.2	12	1⅛"	1"	50.4
16"	400	597	35.1	457	406.4	125	customer	539.8	16	1⅛"	1"	62.8
18"	450	635	38.1	505	457.2	138	customer	577.8	16	1¼"	1⅛"	71.2
20"	500	698.5	41.1	559	508.0	143	customer	635.0	20	1¼"	1⅛"	85.8
22"	550	749	44.4	610	558.8	148	customer	692.2	20	1⅜"	1¼"	100.5
24"	600	813	46.0	663	609.6	151	customer	749.3	20	1⅜"	1¼"	119.4

Weld neck, class 300: dimensions in mm · raised face 1.6 mm · all types in class 300
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½"	15	95	12.7	38	21.3	51	15.7	66.5	4	⅝"	½"	0.8
¾"	20	117	14.2	48	26.7	56	20.8	82.6	4	¾"	⅝"	1.3
1"	25	124	15.7	54	33.5	60	26.7	88.9	4	¾"	⅝"	1.6
1¼"	32	133	17.5	64	42.2	64	35.1	98.6	4	¾"	⅝"	2.1
1½"	40	155	19.0	70	48.3	67	40.9	114.3	4	⅞"	¾"	3
2"	50	165	20.6	84	60.5	68	52.6	127.0	8	¾"	⅝"	3.5
2½"	65	190	23.9	100	73.2	75	62.7	149.4	8	⅞"	¾"	5.4
3"	80	210	26.9	117	88.9	78	78.0	168.1	8	⅞"	¾"	7.2
3½"	90	229	28.4	133	101.6	80	90.2	184.2	8	⅞"	¾"	9
4"	100	254	30.2	146	114.3	84	102.4	200.2	8	⅞"	¾"	11.6
5"	125	279	33.3	178	141.2	97	128.3	235.0	8	⅞"	¾"	15.6
6"	150	318	35.1	206	168.4	97	154.2	269.7	12	⅞"	¾"	20
8"	200	381	39.6	260	219.2	110	202.7	330.2	12	1"	⅞"	31
10"	250	444	46.0	321	273.0	116	254.5	387.4	16	1⅛"	1"	44.4
12"	300	521	49.3	375	323.8	129	304.8	450.8	16	1¼"	1⅛"	64.3
14"	350	584	52.3	425	355.6	141	customer	514.4	20	1¼"	1⅛"	89.1
16"	400	648	55.6	483	406.4	145	customer	571.5	20	1⅜"	1¼"	111.4
18"	450	711	58.7	533	457.2	157	customer	628.6	24	1⅜"	1¼"	136.3
20"	500	775	62.0	587	508.0	161	customer	685.8	24	1⅜"	1¼"	165.4
22"	550	838	65.0	641	558.8	164	customer	743.0	24	1⅝"	1½"	191.7
24"	600	914	68.3	702	609.6	167	customer	812.8	24	1⅝"	1½"	238.9

Up to NPS 3½, class 400 uses the same dimensions as class 600 (rows marked "= 600").

Weld neck, class 400: dimensions in mm · raised face 6.4 mm · all types in class 400
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½" = 600	15	95	14.2	38	21.3	52	customer	66.5	4	⅝"	½"	0.9
¾" = 600	20	117	15.7	48	26.7	57	customer	82.6	4	¾"	⅝"	1.5
1" = 600	25	124	17.5	54	33.5	62	customer	88.9	4	¾"	⅝"	1.8
1¼" = 600	32	133	20.6	64	42.2	67	customer	98.6	4	¾"	⅝"	2.5
1½" = 600	40	155	22.4	70	48.3	70	customer	114.3	4	⅞"	¾"	3.5
2" = 600	50	165	25.4	84	60.5	73	customer	127.0	8	¾"	⅝"	4.3
2½" = 600	65	190	28.4	100	73.2	79	customer	149.4	8	⅞"	¾"	6.3
3" = 600	80	210	31.8	117	88.9	83	customer	168.1	8	⅞"	¾"	8.5
3½" = 600	90	229	35.1	133	101.6	86	customer	184.2	8	1"	⅞"	10.7
4"	100	254	35.1	146	114.3	89	customer	200.2	8	1"	⅞"	13.3
5"	125	279	38.1	178	141.2	102	customer	235.0	8	1"	⅞"	17.5
6"	150	318	41.1	206	168.4	103	customer	269.7	12	1"	⅞"	22.9
8"	200	381	47.8	260	219.2	117	customer	330.2	12	1⅛"	1"	36.1
10"	250	444	53.8	321	273.0	124	customer	387.4	16	1¼"	1⅛"	50.4
12"	300	521	57.2	375	323.8	137	customer	450.8	16	1⅜"	1¼"	72.6
14"	350	584	60.5	425	355.6	149	customer	514.4	20	1⅜"	1¼"	99.7
16"	400	648	63.5	483	406.4	152	customer	571.5	20	1½"	1⅜"	123.4
18"	450	711	66.5	533	457.2	165	customer	628.6	24	1½"	1⅜"	150.5
20"	500	775	69.8	587	508.0	168	customer	685.8	24	1⅝"	1½"	179.1
22"	550	838	73.2	641	558.8	171	customer	743.0	24	1¾"	1⅝"	210.5
24"	600	914	76.2	702	609.6	175	customer	812.8	24	1⅞"	1¾"	258.2

Weld neck, class 600: dimensions in mm · raised face 6.4 mm · all types in class 600
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½"	15	95	14.2	38	21.3	52	customer	66.5	4	⅝"	½"	0.9
¾"	20	117	15.7	48	26.7	57	customer	82.6	4	¾"	⅝"	1.5
1"	25	124	17.5	54	33.5	62	customer	88.9	4	¾"	⅝"	1.8
1¼"	32	133	20.6	64	42.2	67	customer	98.6	4	¾"	⅝"	2.5
1½"	40	155	22.4	70	48.3	70	customer	114.3	4	⅞"	¾"	3.5
2"	50	165	25.4	84	60.5	73	customer	127.0	8	¾"	⅝"	4.3
2½"	65	190	28.4	100	73.2	79	customer	149.4	8	⅞"	¾"	6.3
3"	80	210	31.8	117	88.9	83	customer	168.1	8	⅞"	¾"	8.5
3½"	90	229	35.1	133	101.6	86	customer	184.2	8	1"	⅞"	10.7
4"	100	273	38.1	152	114.3	102	customer	215.9	8	1"	⅞"	17.3
5"	125	330	44.4	189	141.2	114	customer	266.7	8	1⅛"	1"	28.9
6"	150	356	47.8	222	168.4	117	customer	292.1	12	1⅛"	1"	34.6
8"	200	419	55.6	273	219.2	133	customer	349.2	12	1¼"	1⅛"	52.6
10"	250	508	63.5	343	273.0	152	customer	431.8	16	1⅜"	1¼"	86.3
12"	300	559	66.5	400	323.8	155	customer	489.0	20	1⅜"	1¼"	103.1
14"	350	603	69.8	432	355.6	165	customer	527.0	20	1½"	1⅜"	122.3
16"	400	686	76.2	495	406.4	178	customer	603.2	20	1⅝"	1½"	171.1
18"	450	743	82.6	546	457.2	184	customer	654.0	20	1¾"	1⅝"	204.6
20"	500	813	88.9	610	508.0	190	customer	723.9	24	1¾"	1⅝"	255.6
22"	550	870	95.2	663	558.8	197	customer	777.7	24	1⅞"	1¾"	298
24"	600	940	101.6	718	609.6	203	customer	838.2	24	2"	1⅞"	359.4

Up to NPS 2½, class 900 uses the same dimensions as class 1500 (rows marked "= 1500").

Weld neck, class 900: dimensions in mm · raised face 6.4 mm · all types in class 900
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½" = 1500	15	121	22.4	38	21.3	60	customer	82.6	4	⅞"	¾"	1.9
¾" = 1500	20	130	25.4	44	26.7	70	customer	88.9	4	⅞"	¾"	2.6
1" = 1500	25	149	28.4	52	33.5	73	customer	101.6	4	1"	⅞"	3.7
1¼" = 1500	32	159	28.4	64	42.2	73	customer	111.1	4	1"	⅞"	4.3
1½" = 1500	40	178	31.8	70	48.3	83	customer	124.0	4	1⅛"	1"	6
2" = 1500	50	216	38.1	105	60.5	102	customer	165.1	8	1"	⅞"	11
2½" = 1500	65	244	41.1	124	73.2	105	customer	190.5	8	1⅛"	1"	15.1
3"	80	241	38.1	127	88.9	102	customer	190.5	8	1"	⅞"	13.6
4"	100	292	44.5	159	114.3	114	customer	235.0	8	1¼"	1⅛"	22.4
5"	125	349	50.8	190	141.2	127	customer	279.4	8	1⅜"	1¼"	35.9
6"	150	381	55.6	235	168.4	140	customer	317.5	12	1¼"	1⅛"	47.4
8"	200	470	63.5	298	219.2	162	customer	393.7	12	1½"	1⅜"	80.8
10"	250	546	69.8	368	273.0	184	customer	469.9	16	1½"	1⅜"	119.3
12"	300	610	79.2	419	323.8	200	customer	533.4	20	1½"	1⅜"	158.3
14"	350	641	85.9	451	355.6	213	customer	558.8	20	1⅝"	1½"	181.1
16"	400	705	88.9	508	406.4	216	customer	616.0	20	1¾"	1⅝"	218.2
18"	450	787	101.6	565	457.2	229	customer	685.8	20	2"	1⅞"	294.2
20"	500	857	108.0	622	508.0	248	customer	749.3	20	2⅛"	2"	365.2
24"	600	1041	139.7	749	609.6	292	customer	901.7	20	2⅝"	2½"	668.9

Weld neck, class 1500: dimensions in mm · raised face 6.4 mm · all types in class 1500
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½"	15	121	22.4	38	21.3	60	customer	82.6	4	⅞"	¾"	1.9
¾"	20	130	25.4	44	26.7	70	customer	88.9	4	⅞"	¾"	2.6
1"	25	149	28.4	52	33.5	73	customer	101.6	4	1"	⅞"	3.7
1¼"	32	159	28.4	64	42.2	73	customer	111.1	4	1"	⅞"	4.3
1½"	40	178	31.8	70	48.3	83	customer	124.0	4	1⅛"	1"	6
2"	50	216	38.1	105	60.5	102	customer	165.1	8	1"	⅞"	11
2½"	65	244	41.1	124	73.2	105	customer	190.5	8	1⅛"	1"	15.1
3"	80	267	47.8	133	88.9	117	customer	203.2	8	1¼"	1⅛"	20
4"	100	311	53.8	162	114.3	124	customer	241.3	8	1⅜"	1¼"	29.7
5"	125	375	73.2	197	141.2	155	customer	292.1	8	1⅝"	1½"	56.8
6"	150	394	82.6	229	168.4	171	customer	317.5	12	1½"	1⅜"	67.7
8"	200	483	91.9	292	219.2	213	customer	393.7	12	1¾"	1⅝"	115.1
10"	250	584	108.0	368	273.0	254	customer	482.6	12	2"	1⅞"	199.8
12"	300	673	124.0	451	323.8	282	customer	571.5	16	2⅛"	2"	298.7
14"	350	749	133.4	495	355.6	298	customer	635.0	16	2⅜"	2¼"	392.9
16"	400	826	146.0	552	406.4	311	customer	704.8	16	2⅝"	2½"	500.6
18"	450	914	162.1	597	457.2	327	customer	774.7	16	2⅞"	2¾"	650.4
20"	500	984	177.8	641	508.0	356	customer	831.8	16	3⅛"	3"	794.4
24"	600	1168	203.2	762	609.6	406	customer	990.6	16	3⅝"	3½"	1261.8

Weld neck, class 2500: dimensions in mm · raised face 6.4 mm · all types in class 2500
NPS	DN	O	tf	X	Ah	Y	B	W	No. of holes	Hole Ø	Bolt Ø	Weight*
½"	15	133	30.2	43	21.3	73	customer	88.9	4	⅞"	¾"	3.1
¾"	20	140	31.8	51	26.7	79	customer	95.2	4	⅞"	¾"	3.8
1"	25	159	35.1	57	33.5	89	customer	108.0	4	1"	⅞"	5.3
1¼"	32	184	38.1	73	42.2	95	customer	130.0	4	1⅛"	1"	7.8
1½"	40	203	44.4	79	48.3	111	customer	146.0	4	1¼"	1⅛"	10.9
2"	50	235	50.8	95	60.5	127	customer	171.4	8	1⅛"	1"	16.2
2½"	65	267	57.2	114	73.2	143	customer	196.8	8	1¼"	1⅛"	23.8
3"	80	305	66.5	133	88.9	168	customer	228.6	8	1⅜"	1¼"	36
4"	100	356	76.2	165	114.3	190	customer	273.0	8	1⅝"	1½"	55.2
5"	125	419	91.9	203	141.2	229	customer	323.8	8	1⅞"	1¾"	92
6"	150	483	108.0	235	168.4	273	customer	368.3	8	2⅛"	2"	142.5
8"	200	552	127.0	305	219.2	318	customer	438.2	12	2⅛"	2"	213.5
10"	250	673	165.1	375	273.0	419	customer	539.8	12	2⅝"	2½"	406.7
12"	300	762	184.2	441	323.8	464	customer	619.3	12	2⅞"	2¾"	577.3

Scale drawing

Section drawing, proportional to the table dimensions (mm).

O = outside diameter · tf = thickness without raised face · X = hub diameter at base · Ah = diameter at bevel · Y = overall length without raised face · B = bore · W = bolt circle. * Weight estimated from geometry in carbon steel.

Frequently asked questions

What is the asme b16.5 weld neck (wn) flange: dimensions and weight by class used for?

Flange with a tapered hub butt welded to the pipe. The hub distributes the stresses, which is why it is the standard for high pressure, high temperature, thermal cycling and fatigue.

Do the dimensions include the raised face?

No. Since the 2017 edition, the thickness (tf) and length (Y) in ASME B16.5 are measured without the raised face. Add 1.6 mm for classes 150 and 300 and 6.4 mm from class 400 upward.

In which materials does Dustre supply it?

A105 and A350 LF2 carbon steel, F304L and F316L stainless, F51/F60 duplex, F53/F55 super duplex, F11, F22 and F91 Cr-Mo, nickel alloys and titanium, forged and machined with 3.1 certificate.

Weld neck in special alloysForged and machined at Dustre, in any class, with 3.1 certificate.

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