Stainless Steel Weld Neck Flanges

Welding neck flange have two forms (shapes), one with reducing neck as we called reducing weld neck flange; One with a even diameter of typical long neck named as long neck weld flange.

Reducing Weld Neck Flange
As it's name it is like a combination of pipe reducer and flange, so it could be welded to a smaller pipe directly.

Long Weld Neck Flange
Simplified called as LWN flange, the neck part seems like a elongated pipe and connected to a flange. So in most cases it works as a nozzle for a column or a barrel.

You can choose for a normal thickness long welding neck flange or a heavy LWN flange that with bigger thickness and a differently shape.

Like other flanges it has Raised Face (RF) Type and Ring Type Joint (RTJ).

Raised face weld neck flange bottom side has a small portion surrounding the bore that protrudes from the face. Gasket seat will be placed in this raised area. Depending on the different pressure ratings, different height of raised face will be adopted. For example, 150# and 300# flange raised face height is 1/6'', above 300# the height will be above 1/4''. 

The ring-joint type of WN flange has a special made groove, here you can place a metal gasket seat to seal the connects. So this type of SW flange is used in high temperature and high pressure services.

Material Standards
ASTM A105/N For carbon steel weld neck flange
ASTM A182 F11, F22 for alloy steel
ASTM A182 F304 / F304L, F316 / F316L for stainless steel weld neck flange.
Manufacturing Standards
ASME B16.5
ASME B16.47
BS 3293
DIN 2630 PN 1 and PN 2.5, 2631 PN 6, 2632 PN 10, 2634 PN 16, 2634 PN 25, 2635 PN 40

Weld neck flange mainly used in medium, high pressure pipes connecting, most butt weld flange with neck also called nipple flange.

Therefore, the installation cost of the welding flange, labor costs and auxiliary materials costs are higher, because there is more than one process.

Weld neck flange dimensions are covered in ASME B16.5 – which covers Pipe Flanges and Flanged Fittings for size NPS ½” to 24” for above NPS 26” to 60” it should be as per ASME B16.47.

During a dimensional inspection of weld neck flange, you should check for

Outer & Inner Diameter of body
Bolt Circle & Bolt hole Diameter
the thickness of weld end
Length of the Hub and
Straightness and alignment of the bolt hole

Size in Inch	Size in mm	Outer Diameter	Flange Thickness	Hub OD	Weld Neck OD	Welding Neck Length	Bore	RF Diameter	RF Height	PCD	Weld Face
		A	B	C	D	E	F	G	H	I	J
1/2	15	90	9.6	30	21.3	46	Welding Neck bore is derived from the pipe schedule	34.9	2	60.3	1.6
3/4	20	100	11.2	38	26.7	51		42.9	2	69.9	1.6
1	25	110	12.7	49	33.4	54		50.8	2	79.4	1.6
1 1/4	32	115	14.3	59	42.2	56		63.5	2	88.9	1.6
1 1/2	40	125	15.9	65	48.3	60		73	2	98.4	1.6
2	50	150	17.5	78	60.3	62		92.1	2	120.7	1.6
2 1/2	65	180	20.7	90	73	68		104.8	2	139.7	1.6
3	80	190	22.3	108	88.9	68		127	2	152.4	1.6
3 1/2	90	215	22.3	122	101.6	70		139.7	2	177.8	1.6
4	100	230	22.3	135	114.3	75		157.2	2	190.5	1.6
5	125	255	22.3	164	141.3	87		185.7	2	215.9	1.6
6	150	280	23.9	192	168.3	87		215.9	2	241.3	1.6
8	200	345	27	246	219.1	100		269.9	2	298.5	1.6
10	250	405	28.6	305	273	100		323.8	2	362	1.6
12	300	485	30.2	365	323.8	113		381	2	431.8	1.6
14	350	535	33.4	400	355.6	125		412.8	2	476.3	1.6
16	400	595	35	457	406.4	125		469.9	2	539.8	1.6
18	450	635	38.1	505	457.2	138		533.4	2	577.9	1.6
20	500	700	41.3	559	508	143		584.2	2	635	1.6
24	600	815	46.1	663	610	151		692.2	2	749.3	1.6

Size in Inch	Size in mm	No of Bolts	Bolt Size UNC	Machine Bolt Length	RF Stud Length	Hole Size	ISO Stud Size	Weight in kg
1/2	15	4	1/2	50	55	5/8	M14	0.6
3/4	20	4	1/2	50	65	5/8	M14	0.9
1	25	4	1/2	55	65	5/8	M14	1.4
1 1/4	32	4	1/2	55	70	5/8	M14	1.4
1 1/2	40	4	1/2	65	70	5/8	M14	1.8
2	50	4	5/8	70	85	3/4	M16	2.7
2 1/2	65	4	5/8	75	90	3/4	M16	3.7
3	80	4	5/8	75	90	3/4	M16	4.6
3 1/2	90	8	5/8	75	90	3/4	M16	5.5
4	100	8	5/8	75	90	3/4	M16	6.8
5	125	8	3/4	85	95	7/8	M20	8.7
6	150	8	3/4	85	100	7/8	M20	10.9
8	200	8	3/4	90	110	7/8	M20	17.7
10	250	12	7/8	100	115	1	M24	24
12	300	12	7/8	100	120	1	M24	37
14	350	12	1	115	135	1 1/8	M27	50
16	400	16	1	115	135	1 1/8	M27	64
18	450	16	1 1/8	125	145	1 1/4	M30	68
20	500	20	1 1/8	140	160	1 1/4	M30	82
24	600	20	1 1/4	150	170	1 3/8	M33	118

Size in Inch	Size in mm	Outer Diameter	Flange Thickness	Hub OD	Weld Neck OD	Welding Neck Length	Bore	RF Diameter	RF Height	PCD	Weld Face
		A	B	C	D	E	F	G	H	I	J
1/2	15	95	12.7	38	21.3	51	Welding Neck bore is derived from the pipe schedule	34.9	2	66.7	1.6
3/4	20	115	14.3	48	26.7	56		42.9	2	82.6	1.6
1	25	125	15.9	54	33.4	60		50.8	2	88.9	1.6
1 1/4	32	135	17.5	64	42.2	64		63.5	2	98.4	1.6
1 1/2	40	155	19.1	70	48.3	67		73	2	114.3	1.6
2	50	165	20.7	84	60.3	68		92.1	2	127	1.6
2 1/2	65	190	23.9	100	73	75		104.8	2	149.2	1.6
3	80	210	27	117	88.9	78		127	2	168.3	1.6
3 1/2	90	230	28.6	133	101.6	79		139.7	2	184.2	1.6
4	100	255	30.2	146	114.3	84		157.2	2	200	1.6
5	125	280	33.4	178	141.3	97		185.7	2	235	1.6
6	150	320	35	206	168.3	97		215.9	2	269.9	1.6
8	200	380	39.7	260	219.1	110		269.9	2	330.2	1.6
10	250	445	46.1	321	273	116		323.8	2	387.4	1.6
12	300	520	49.3	375	323.8	129		381	2	450.8	1.6
14	350	585	52.4	425	355.6	141		412.8	2	514.4	1.6
16	400	650	55.6	483	406.4	144		469.9	2	571.5	1.6
18	450	710	58.8	533	457	157		533.4	2	628.6	1.6
20	500	775	62	587	508	160		584.2	2	685.8	1.6
24	600	915	68.3	702	610	167		692.2	2	812.8	1.6