The ASME B16.5 weld neck flange conforming to ASME B16.5 is a typical integral-type flange. It is cast or forged integrally with the tapered neck which is butt welded to the pipe. This design provides a smooth transition with little stress concentration since the high-stress concentration at the base of the weld neck flange. There are no gaps or recesses that could lead to crevice corrosion. The tapered neck is also known as “nozzle neck”, or more commonly as “high hub”.

What is ASME B16.5 Standard?

ASME B16.5 Standard covers pressure-temperature ratings,materials,dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Included are:

Flange with rating class designations 150#,300#,400#,600#,900#,and 1500#in sizes NPS % through NPS 24. Flanges with rating class designation 2500 in sizes NPS % through NPS 12.

Weld Neck Flange

What is ASME B16.5 Weld Neck Flange?

ASME B16.5 weld neck flange, is a kind of flange that can relocate stress to the pipes, ensuring a decrease in high-stress concentration at the bottom of the weld neck flange. There are two welding neck flanges designs the first type is used with wipes while the second, longer type cannot be used with pipes but with a process plant. The flange comprises of a round fitting that extends beyond the rim of the circumference.

There are many pressure levels for ASME B16.5 weld neck flanges, and the common pressure levels include 150#, 300#, 600#, 900#, 1500#, 2500#.

Class 150 lb Weld Neck Flange Dimensions & Weight 

NPS	A	B	C	D	E	F	G	H	I	J	W
	inch	inch	inch	inch	inch	inch	inch	No. of Holes	inch	inch	kg/pc
	mm	mm	mm	mm	mm	mm	mm		mm	mm
1/2	3.500	0.620	0.440	1.880	0.840	1.190	1.380	4	0.620	2.380	0.48
	88.90	15.70	11.20	47.80	21.30	30.20	35.00		15.70	60.45
3/4	3.880	0.820	0.500	2.060	1.050	1.500	1.690	4	0.620	2.750	0.71
	98.60	20.80	12.70	52.30	26.70	38.10	42.90		15.70	69.85
1	4.250	1.050	0.560	2.190	1.320	1.940	2.000	4	0.620	3.120	1.01
	108.0	26.70	14.20	55.60	33.50	49.30	50.80		15.70	79.25
1-1/4	4.620	1.380	0.620	2.250	1.660	2.310	2.550	4	0.620	3.500	1.33
	117.3	35.10	15.70	57.15	42.20	58.70	63.50		15.70	88.90
1-1/2	5.000	1.610	0.690	2.440	1.900	2.560	2.880	4	0.620	3.880	1.72
	127.0	40.90	17.50	62.00	48.30	65.00	73.15		15.70	98.60
2	6.000	2.070	0.750	2.500	2.380	3.060	3.620	4	0.750	4.750	2.58
	152.4	52.60	19.10	63.50	60.45	77.70	91.90		19.10	120.7
2-1/2	7.000	2.470	0.880	2.750	2.880	3.560	4.120	4	0.750	5.500	4.11
	177.8	62.70	22.40	69.85	73.15	90.40	104.6		19.10	139.7
3	7.500	3.070	0.940	2.750	3.500	4.250	5.000	4	0.750	6.000	4.92
	190.5	78.00	23.90	69.85	88.90	108.0	127.0		19.10	152.4
3-1/2	8.500	3.550	0.940	2.810	4.000	4.810	5.500	8	0.750	7.000	6.08
	215.9	90.20	23.90	71.40	101.6	122.2	139.7		19.10	177.8
4	9.000	4.030	0.940	3.000	4.500	5.310	6.190	8	0.750	7.500	6.84
	228.6	102.4	23.90	76.20	114.3	134.9	157.2		19.10	190.5
5	10.00	5.050	0.940	3.500	5.560	6.440	7.310	8	0.880	8.500	8.56
	254.0	128.3	23.90	88.90	141.2	163.6	185.7		22.40	215.9
6	11.00	6.070	1.000	3.500	6.630	7.560	8.500	8	0.880	9.500	10.6
	279.4	154.2	25.4	88.90	168.4	192.0	215.9		22.40	241.3
8	13.50	7.980	1.120	4.000	8.630	9.690	10.62	8	0.880	11.75	17.6
	342.9	202.7	28.40	101.6	219.2	246.1	269.7		22.40	298.5
10	16.00	10.02	1.190	4.000	10.75	12.00	12.75	12	1.000	14.25	24.0
	406.4	254.5	30.20	101.6	273.0	304.8	323.8		25.40	362.0
12	19.00	12.00	1.250	4.500	12.75	14.38	15.00	12	1.000	17.00	36.5
	482.6	304.8	31.75	114.3	323.8	365.3	381.0		25.40	431.8
14	21.00		1.380	5.000	14.00	15.75	16.25	12	1.120	18.75	48.4
	533.4		35.10	127.0	355.6	400.1	412.7		28.40	476.3
16	23.50		1.440	5.000	16.00	18.00	18.50	16	1.120	21.25	60.6
	596.9		36.60	127.0	406.4	475.2	469.9		28.40	539.8
18	25.00		1.560	5.500	18.00	19.88	21.00	16	1.250	22.75	68.3
	635.0		39.60	139.7	457.2	505.0	533.4		31.75	577.9
20	27.50		1.690	5.690	20.00	22.00	23.00	20	1.250	25.00	84.5
	698.5		42.90	144.5	508.0	558.8	584.2		31.75	635
24	32.00		1.880	6.000	24.00	26.12	27.25	20	1.380	29.50	115
	812.8		47.80	152.4	609.6	663.4	692.1		35.10	749.3

The material grades of ASME B16.5 weld neck flanges are divided into carbon steel, alloy steel, stainless steel, and duplex stainless steel.

Carcon Steel: ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel: ASTM A182 F5 / F9 / F11 / F12 / F22 / F91 / F92

Stainless Steel: A182 F304/304L/304H – F316/316L – F317 – F310S – F321 – F347 – F904L

Duplex Stainless Steel: A182 F51/53/55/60