Lap Joint Flange Dimensions: ASME B16.5

Lap-joint connection comes in two separate parts, One Loose Lap flange, and another stub-end or backing Ring. A loose lap flange is very identical in look and dimension to a slip-on flange, but instead of welding it directly to the pipe, it should be slid on stub end fitting. Then stub end fitting will be butt-welded to the pipe, so the flange is free to rotate on the pipe co-axial axis.

ASME B16.5 is limited to flanges and flanged fittings made from cast or forged materials. B16.5 also includes requirements and recommendations regarding flange bolts, gaskets, and flanged joints. Careful application of these B16 Standards will help users to comply with applicable regulations within their jurisdictions while achieving the operational, cost, and safety benefits to be gained from the many industry best practices.

This page will cover key dimensions for ASME B16.5 Lap Joint Flanges From 1/2 NPS to 24 NPS with Pressure rating classes 150, 300, 400, 600, 900, 1500, & 2500.

Please click on blow link for more information about:

ASME B16.5 Dimensional Tolerances & Welding Bevel Standards
ASME B16.5 Bolt & Stud Dimensions
ASME B16.47 A/B Large Diameter Flange Dimension from 26 NPS to 60 NPS

Lap-joint Flange Dimension — Lap-Joint Flange CL150

Lap Joint Flange Class 150: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	3.50	0.44	0.12	1.19	4-0.62	2.38	0.88	0.62
2	¾	3.88	0.50	0.12	1.50	4-0.62	2.75	1.09	0.62
3	1	4.25	0.56	0.12	1.94	4-0.62	3.12	1.36	0.69
4	1¼	4.62	0.62	0.19	2.31	4-0.62	3.50	1.70	0.81
5	1½	5.00	0.69	0.25	2.56	4-0.62	3.88	1.95	0.88
6	2	6.00	0.75	0.31	3.06	4-0.75	4.75	2.44	1.00
7	2½	7.00	0.88	0.31	3.56	4-0.75	5.50	2.94	1.12
8	3	7.50	0.94	0.38	4.25	4-0.75	6.00	3.57	1.19
9	3½	8.50	0.94	0.38	4.81	8-0.75	7.00	4.07	1.25
10	4	9.00	0.94	0.44	5.31	8-0.75	7.50	4.57	1.31
11	5	10.00	0.94	0.44	6.44	8-0.88	8.50	5.66	1.44
12	6	11.00	1.00	0.50	7.56	8-0.88	9.50	6.72	1.56
13	8	13.50	1.12	0.50	9.69	8-0.88	11.75	8.72	1.75
14	10	16.00	1.19	0.50	12.00	12-1.00	14.25	10.88	1.94
15	12	19.00	1.25	0.50	14.38	12-1.00	17.00	12.88	2.19
16	14	21.00	1.38	0.50	15.75	12-1.12	18.75	14.14	3.12
17	16	23.50	1.44	0.50	18.00	16-1.12	21.25	16.16	3.44
18	18	25.00	1.56	0.50	19.88	16-1.25	22.75	18.18	3.81
19	20	27.50	1.69	0.50	22.00	20-1.25	25.00	20.20	4.06
20	22	29.50	1.81	0.50	24.25	20-1.38	27.25	22.22	4.25
21	24	32.00	1.88	0.50	26.12	20-1.38	29.50	24.25	4.38
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 300: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	3.75	0.56	0.12	1.50	4-0.63	2.62	0.90	0.88
2	¾	4.62	0.62	0.12	1.88	4-0.75	3.25	1.11	1.00
3	1	4.88	0.69	0.12	2.12	4-0.75	3.50	1.38	1.06
4	1¼	5.25	0.75	0.19	2.50	4-0.75	3.88	1.72	1.06
5	1½	6.12	0.81	0.25	2.75	4-0.88	4.50	1.97	1.19
6	2	6.50	0.88	0.31	3.31	8-0.75	5.00	2.46	1.31
7	2½	7.50	1.00	0.31	3.94	8-0.88	5.88	2.97	1.50
8	3	8.25	1.12	0.38	4.62	8-0.88	6.62	3.60	1.69
9	3½	9.00	1.19	0.38	5.25	8-0.88	7.25	4.10	1.75
10	4	10.00	1.25	0.44	5.75	8-0.88	7.88	4.60	1.88
11	5	11.00	1.38	0.44	7.00	8-0.88	9.25	5.69	2.00
12	6	12.50	1.44	0.50	8.12	12-0.88	10.62	6.75	2.06
13	8	15.00	1.62	0.50	10.25	12-1.00	13.00	8.75	2.44
14	10	17.50	1.88	0.50	12.62	16-1.12	15.25	10.92	3.75
15	12	20.50	2.00	0.50	14.75	16-1.25	17.75	12.92	4.00
16	14	23.00	2.12	0.50	16.75	20-1.25	20.25	14.18	4.38
17	16	25.50	2.25	0.50	19.00	20-1.38	22.50	16.19	4.75
18	18	28.00	2.38	0.50	21.00	24-1.38	24.75	18.20	5.12
19	20	30.50	2.50	0.50	23.12	24-1.38	27.00	20.25	5.50
20	22	33.00	2.63	0.50	25.25	24-1.63	29.25	22.25	5.75
21	24	36.00	2.75	0.50	27.62	24-1.63	32.00	24.25	6.00
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 400: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	3.75	0.56	0.12	1.50	4-0.63	2.62	0.90	0.88
2	¾	4.62	0.62	0.12	1.88	4-0.75	3.25	1.11	1.00
3	1	4.88	0.69	0.12	2.12	4- 75	3.50	1.38	1.06
4	1¼	5.25	0.81	0.19	2.50	4-0.75	3.88	1.72	1.12
5	1½	6.12	0.88	0.25	2.75	4-0.88	4.50	1.97	1.25
6	2	6.50	1.00	0.31	3.31	8-0.75	5.00	2.46	1.44
7	2½	7.50	1.12	0.31	3.94	8-0.88	5.88	2.97	1.62
8	3	8.25	1.25	0.38	4.62	8-0.88	6.62	3.60	1.81
9	3½	9.00	1.38	0.38	5.25	8-1.00	7.25	4.10	1.94
10	4	10.00	1.38	0.44	5.75	8-1.00	7.88	4.60	2.00
11	5	11.00	1.50	0.44	7.00	8-1.00	9.25	5.69	2.12
12	6	12.50	1.62	0.50	8.12	12-1.00	10.62	6.75	2.25
13	8	15.00	1.88	0.50	10.25	12-1.12	13.00	8.75	2.69
14	10	17.50	2.12	0.50	12.62	16-1.25	15.25	10.92	4.00
15	12	20.50	2.25	0.50	14.75	16-1.38	17.75	12.92	4.25
16	14	23.00	2.38	0.50	16.75	20-1.38	20.25	14.18	4.62
17	16	25.50	2.50	0.50	19.00	20-1.50	22.50	16.19	5.00
18	18	28.00	2.62	0.50	21.00	24-1.50	24.75	18.20	5.38
19	20	30.50	2.75	0.50	23.12	24-1.62	27.00	20.25	5.75
20	22	33.00	2.88	0.50	25.25	24-1.75	29.25	22.25	6.00
21	24	36.00	3.00	0.50	27.62	24-1.88	32.00	24.25	6.25
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 600: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	3.75	0.56	0.12	1.50	4-0.63	2.62	0.90	0.88
2	¾	4.62	0.62	0.12	1.88	4-0.75	3.25	1.11	1.00
3	1	4.88	0.69	0.12	2.12	4-0.75	3.50	1.38	1.06
4	1¼	5.25	0.81	0.19	2.50	4-0.75	3.88	1.72	1.12
5	1½	6.12	0.88	0.25	2.75	4-0.88	4.50	1.97	1.25
6	2	6.50	1.00	0.31	3.31	8-0.75	5.00	2.46	1.44
7	2½	7.50	1.12	0.31	3.94	8-0.88	5.88	2.97	1.62
8	3	8.25	1.25	0.38	4.62	8-0.88	6.62	3.60	1.81
9	3½	9.00	1.38	0.38	5.25	8-1.00	7.25	4.10	1.94
10	4	10.75	1.50	0.44	6.00	8-1.00	8.50	4.60	2.12
11	5	13.00	1.75	0.44	7.44	8-1.12	10.50	5.69	2.38
12	6	14.00	1.88	0.50	8.75	12-1.12	11.50	6.75	2.62
13	8	16.50	2.19	0.50	10.75	12-1.25	13.75	8.75	3.00
14	10	20.00	2.50	0.50	13.50	16-1.38	17.00	10.92	4.38
15	12	22.00	2.62	0.50	15.75	20-1.38	19.25	12.92	4.62
16	14	23.75	2.75	0.50	17.00	20-1.50	20.75	14.18	5.00
17	16	27.00	3.00	0.50	19.50	20-1.63	23.75	16.19	5.50
18	18	29.25	3.25	0.50	21.50	20-1.75	25.75	18.20	6.00
19	20	32.00	3.50	0.50	24.00	24-1.75	28.50	20.25	6.50
20	22	34.25	3.75	0.50	26.25	24-1.75	30.63	22.25	6.88
21	24	37.00	4.00	0.50	28.25	24-2.00	33.00	24.25	7.25
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 900: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	4.75	0.88	0.12	1.50	4-0.88	3.25	0.90	1.25
2	¾	5.12	1.00	0.12	1.75	4-0.88	3.50	1.11	1.38
3	1	5.88	1.12	0.12	2.06	4-1.00	4.00	1.38	1.62
4	1¼	6.25	1.12	0.19	2.50	4-1.00	4.38	1.72	1.62
5	1½	7.00	1.25	0.25	2.75	4-1.12	4.88	1.97	1.75
6	2	8.50	1.50	0.31	4.12	8-1.00	6.50	2.46	2.25
7	2½	9.62	1.62	0.31	4.88	8-1.12	7.50	2.97	2.50
8	3	9.50	1.50	0.38	5.00	8-1.00	7.50	3.60	2.12
9	4	11.50	1.75	0.44	6.25	8-1.25	9.25	4.60	2.75
10	5	13.75	2.00	0.44	7.50	8-1.38	11.00	5.69	3.12
11	6	15.00	2.19	0.50	9.25	12-1.25	12.50	6.75	3.38
12	8	18.50	2.50	0.50	11.75	12-1.50	15.50	8.75	4.50
13	10	21.50	2.75	0.50	14.50	16-1.50	18.50	10.92	5.00
14	12	24.00	3.12	0.50	16.50	20-1.50	21.00	12.92	5.62
15	14	25.25	3.38	0.50	17.75	20-1.63	22.00	14.18	6.12
16	16	27.75	3.50	0.50	20.00	20-1.75	24.25	16.19	6.50
17	18	31.00	4.00	0.50	22.25	20-2.00	27.00	18.20	7.50
18	20	33.75	4.25	0.50	24.50	20-2.13	29.50	20.25	8.25
19	24	41.00	5.50	0.50	29.50	20-2.63	35.50	24.25	10.50
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 1500: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	4.75	0.88	0.12	1.50	4-0.88	3.25	0.90	1.25
2	¾	5.12	1.00	0.12	1.75	4-0.88	3.50	1.11	1.38
3	1	5.88	1.12	0.12	2.06	4-1.00	4.00	1.38	1.62
4	1¼	6.25	1.12	0.19	2.50	4-1.00	4.38	1.72	1.62
5	1½	7.00	1.25	0.25	2.75	4-1.12	4.88	1.97	1.75
6	2	8.50	1.50	0.31	4.12	8-1.00	6.50	2.46	2.25
7	2½	9.62	1.62	0.31	4.88	8-1.12	7.50	2.97	2.50
8	3	10.50	1.88	0.38	5.25	8-1.25	8.00	3.60	2.88
9	4	12.25	2.12	0.44	6.38	8-1.38	9.50	4.60	3.56
10	5	14.75	2.88	0.44	7.75	8-1.63	11.50	5.69	4.12
11	6	15.50	3.25	0.50	9.00	12-1.50	12.50	6.75	4.69
12	8	19.00	3.62	0.50	11.50	12-1.75	15.50	8.75	5.62
13	10	23.00	4.25	0.50	14.50	12-2.00	19.00	10.92	7.00
14	12	26.50	4.88	0.50	17.75	16-2.12	22.50	12.92	8.62
15	14	29.50	5.25	0.50	19.50	16-2.38	25.00	14.18	9.50
16	16	32.50	5.75	0.50	21.75	16-2.63	27.75	16.19	10.25
17	18	36.00	6.38	0.50	23.50	16-2.88	30.50	18.20	10.88
18	20	38.75	7.00	0.50	25.25	16-3.12	32.75	20.25	11.50
19	24	46.00	8.00	0.50	30.00	16-3.63	39.00	24.25	13.00
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L

Lap Joint Flange Class 2500: ASME B16.5

wdt_ID	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L
1	½	5.25	1.19	0.12	1.69	4-0.88	3.50	0.90	1.56
2	¾	5.50	1.25	0.12	2.00	4-0.88	3.75	1.11	1.69
3	1	6.25	1.38	0.12	2.25	4-1.00	4.25	1.38	1.88
4	1¼	7.25	1.50	0.19	2.88	4-1.12	5.13	1.72	2.06
5	1½	8.00	1.75	0.25	3.12	4-1.25	5.75	1.97	2.38
6	2	9.25	2.00	0.31	3.75	8-1.12	6.75	2.46	2.75
7	2½	10.50	2.25	0.31	4.50	8-1.25	7.75	2.97	3.12
8	3	12.00	2.62	0.38	5.25	8-1.38	9.00	3.60	3.62
9	4	14.00	3.00	0.44	6.50	8-1.63	10.75	4.60	4.25
10	5	16.50	3.62	0.44	8.00	8-1.88	12.75	5.69	5.12
11	6	19.00	4.25	0.50	9.25	8-2.12	14.50	6.75	6.00
12	8	21.75	5.00	0.50	12.00	12-2.12	17.25	8.75	7.00
13	10	26.50	6.50	0.50	14.75	12-2.63	21.25	10.92	9.00
14	12	30.00	7.25	0.50	17.38	12-2.88	24.38	12.92	10.00
	Nom. Pipe Size	O	T	r	X	# - Bolt Hole	B.C.D	B	L