Pipe elbows size

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made.

The ends may be machined for butt welding, threaded (usually female), or socketed, etc. When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow.

Pressure: SCH5 to SCH160
Size range: 1/2 to 56 inches (DN 15 to DN 1,400mm), 22.5 Deg, 45 Deg, 90 Deg, 180 Deg
Manufacturing standards: ANSI, ISO, JIS and DIN
Process: butt welding, seamless, threaded , or socketed

Here below, for example, you will find the center to face distance of NPS 2 elbows (the A distance on the image)

•  90°-LR : = 1½ x 2(NPS) x 25.4 A=76.2 mm
•  180°-LR : = 2 times the 90° LR elbow A=152.4 mm
• 90°-SR : = 2(NPS) x 25.4 A=50.8 mm
• 180°-SR : = 2 times the 90° SR elbow A=101.6 mm

The center to face distance for a “long” radius elbow, abbreviated LR always is “1½ x Nominal Pipe Size (NPS) (1½D)”, while the center to face distance for a “short” radius elbow, abbreviated SR even is to nominal pipe size.

Pipe elbow size

Nominal pipe size		Outside Diameter at Bevel		Center to End			Center to Center		Back to Faces
				45° Elbows	90°Elbows		180°Return
				H	F		P		K
DN	INCH	Series A	Series B	LR	LR	SR	LR	SR	LR	SR
15		21.3	18	16	38	-	76	-	48	-
20		26.9	25	16	38	-	76	-	51	-
25	1	33.7	32	16	38	25	76	51	56	41
32		42.4	38	20	48	32	95	64	70	52
40		48.3	45	24	57	38	114	76	83	62
50	2	60.3	57	32	76	51	152	102	106	81
65		76.1(73)	76	40	95	64	191	127	132	100
80	3	88.9	89	47	114	76	229	152	159	121
90	31/2	101.6	-	55	133	89	267	178	184	140
100	4	114.3	108	63	152	102	305	203	210	159
125	5	139.7	133	79	190	127	381	254	262	197
150	6	168.3	159	95	229	152	457	305	313	237
200	8	219.1	219	126	305	203	610	406	414	313
250	10	273	273	158	381	254	762	508	518	391
300	12	323.9	325	189	457	305	914	610	619	467
350	14	355.6	377	221	533	356	1067	711	711	533
400	16	406.4	426	253	610	406	1219	813	813	610
450	18	457.2	478	284	686	457	1372	914	914	686
500	20	508	529	316	762	508	1524	1016	1016	762
550	22	559	-	347	838	559
600	24	610	630	379	914	610
650	26	660	-	410	991	660
700	28	711	720	442	1067	711
750	30	762	-	473	1143	762
800	32	813	820	505	1219	813
850	34	864	-	537	1295	864
900	36	914	920	568	1372	914
950	38	965	-	600	1448	965
1000	40	1016	1020	631	1524	1016
1050	42	1067	-	663	1600	1067
1100	44	1118	1120	694	1676	1118
1150	46	1168	-	726	1753	1168
1200	48	1220	1220	758	1829	1219

For standard degrees of pipe elbows such as 45° and 90°, elbow center to end dimensions are available in standard pipe charts. But many times, custom elbow angles are required at site which should be cut from standard 45° or 90° elbows.

Formula for calculating center to end distance of such elbows is as follows:

Elbow length in mm = Tan(Elbow Angle/2) X Elbow Radius in mm

Where:

For 90° Long Radius elbows, center to end dimension given in dimension tables of ASME B16.9 is same as radius of elbow. This is because Tan(90/2) i.e. Tan 45 is 1.

Normally custom elbow angles from 45 degree to 90 are cut from 90 degree standard elbow. But for custom elbow angles smaller than 45 degree, elbow is normally cut from existing standard 45 degree elbow. Center to end dimension given in dimension tables for 45 degree elbow must be divided by Tan(22.5) to get elbow radius for standard 45 degree elbow. Then we can use above formula to get elbow angle for custom degrees.

Same procedure applies to 3D elbows.

Example 1:

Calculate elbow center to end dimension for 4 inch nominal pipe diameter elbow at 60 degree angle, cut from 90 degree LR elbow.

From ASME B16.9, center to elbow dimension for 4 in elbow is 152 mm.

Length = Tan (60/2) X 152

Length = 0.57735027 X 152

Length = 87.757 i.e. 88 mm Approx.

Example 2:

Calculate elbow center to end dimension for 2 inch nominal pipe diameter elbow at 30 degree angle, cut from 45 degree LR elbow.

From ASME B16.9, center to elbow dimension for 2 inch 45 degree elbow is 35 mm.

Radius of elbow = 35/Tan(22.5)

Radius of elbow = 35/0.4142 = 84.5 mm

Length = 0.26795 X 84.5

Length = 22.64 i.e. 23 mm Approx.

The weakest point on an elbow is the inside radius. ASME B16.9 only standardizes the center to face dimensions and some squareness dimensional tolerances. The wall thickness at the weld line location even is standardized, but not through the rest of an elbow. The standard states that the minimum tolerance will be within 12.5% of the minimum ordered wall thickness of the pipe. A maximum tolerance is specified only at the ends of the fitting.

Many providers of buttweld elbows (and tees) provide one schedule greater thickness so that sufficient wall thickness, after forming, remains.

Theoretical weight of elbows

NPS	LR 90° ELBOWS				ELBOWS SR 90°
inches	Sch. 5S	Sch. 10S	Sch. 40S	Sch. 80S	Sch. 5S	Sch. 10S	Sch. 40S	Sch. 80S
1/2	0.05	0.06	0.08	0.1	0.03	0.04	0.05	0.07
3/4	0.06	0.07	0.09	0.11	0.04	0.05	0.06	0.07
1	0.09	0.15	0.18	0.2	0.06	0.1	0.12	0.13
1.25	0.13	0.2	0.25	0.35	0.09	0.13	0.17	0.12
1.5	0.18	0.3	0.4	0.5	0.12	0.2	0.27	0.33
2	0.3	0.5	0.7	0.9	0.2	0.33	0.47	0.6
2.5	0.6	0.85	1.35	1.8	0.4	0.6	0.9	1.2
3	0.9	1.3	2	2.9	0.6	0.9	1.35	1.9
4	1.4	2	4	5.9	0.9	1.35	2.65	3.9
5	2.9	3.6	6.5	9.7	1.95	2.4	4.35	6.5
6	4	5	10.5	16	2.7	3.35	7	10.5
8	7.4	10	21.5	33.5	4.9	6.7	14.5	22.5
10	13.6	16.8	38.5	52.5	9.1	11.2	25.6	35
12	23.4	27	59	79	15.6	18	39.5	53
14	29	35	70	94	19.3	23.5	47	63
16	41.3	47	95	125	27.5	31.5	63.5	84
18	51.8	59	120	158	34.5	39.5	80	105
20	73	85	146	194	49	57	98	129
24	122	140	210	282	82	94	140	188

Angularity tolerances of pipe elbow

ND	Max off angle	Max off plane
	Q	P
1/2 a 4	1	2
5 a 8	2	4
10 a 12	3	5
14 a 16	3	7
18 a 24	4	10
26 a 30	5	10
32 a 42	5	13
44 a 48	5	20