Long Radius Elbow VS Short Radius Elbow

Long Radius Elbow VS Short Radius Elbow

In a piping system, an pipe elbow is a pipe fitting that changes the direction of the pipe. According to the angle, there are three most commonly used 45° and 90°180°, and other abnormal angle elbows such as 60° are also included according to engineering needs. Elbows are made of cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics. The way to connect to the pipe is: direct welding (the most common way) flange connection, hot melt connection, fused connection, threaded connection and socket connection. According to the production process, it can be divided into: welding elbow, punching elbow, push elbow, casting elbow, butt weld elbow.

Elbows are available in two radius types, Short radius elbow (1D) and Long radius elbow (1.5D).

What is a long radius elbow	What is a short radius elbow
Types of elbows	Long Radius Elbow vs Short Radius Elbow
LR or SR elbow to use	How to purchase elbows

What is a long radius elbow?

The center line of one end to the opposite face. This is known as the “center to face” distance and is equivalent to the radius through which the elbow is bent.
The center to face distance for a “long” radius elbow, the LR radius elbows have a center to end distance that is 1.5 times the NPS in inches (R = 1.5D), if it is more than 1.5 times, it is a bend. D is the diameter of the elbow. Long radii are commonly used. Generally, the default is also a long radius. Where the pressure is high or the flow rate is high, a long radius is used. If the resistance of the solid conveying pipe is strict, a larger radius elbow is used.

What is a short radius elbow?

Short radius elbow’s radius is equal to the NPS in inches (R = 1.0D). Short radii are generally used in low pressure fluids or where the elbows are limited during installation. Long-radius elbows are preferred if there are no conditions or are not specified in the contract.

for example, we 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.

Types of elbows
Types of long radius (LR) elbows

Long radius elbows Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter

• L/R 45°Elbow – Long radius 45 degree elbow changes the direction by 45 degrees.
• L/R 90°Elbow – Long radius 90 degree elbow changes the direction by 90 degrees.
• L/R 180°Elbow – Long radius 180 degree elbow changes the direction by 180 degrees.

Dimensions of 45 degree LR elbow

Dimensions of 90 degree LR elbow

Dimensions of 180 degree LR elbow

Types of short radius (SR) elbows

Short radius elbows Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter

• S/R 45°Elbow – Short radius 45° elbow changes the direction by 45 degrees.
• S/R 90°Elbow – Short Radius 90° elbow is same as LR90 except for the measurement between end of elbow to center line is 1 x NPS.
• S/R 180°Elbow- Short Radius 180° return bend allows complete reversal of flow.

Dimensions of 45 degree SR elbow

Dimensions of 90 degree SR elbow

Dimensions of 180 degree SR elbow

ASME B16.9 Butt weld 45/90 degree Long Radius Elbow Dimensions

NPS	O.D. D	90 degrees Long Radius Center-to-End A	45 degrees Long Radius Center-to-End B	90 degrees 3D Center-to-End A	45 degrees 3D Center-to-End B
1/2	21.3	38	16	–	–
3/4	26.7	38	19	57	24
1	33.4	38	22	76	31
1¼	42.2	48	25	95	39
1½	48.3	57	29	114	47
2	60.3	76	35	152	63
2½	73	95	44	190	79
3	88.9	114	51	229	95
3½	101.6	133	57	267	111
4	114.3	152	64	305	127
5	141.3	190	79	381	157
6	168.3	229	95	457	189
8	219.1	305	127	610	252
10	273	381	159	762	316
12	323.8	457	190	914	378
14	355.6	533	222	1067	441
16	406.4	610	254	1219	505
18	457	686	286	1372	568
20	508	762	318	1524	632
22	559	838	343	1676	694
24	610	914	381	1829	757
26	660	991	406	1981	821
28	711	1067	438	2134	883
30	762	1143	470	2286	964
32	813	1219	502	2438	1010
34	864	1295	533	2591	1073
36	914	1372	565	2743	1135
38	965	1448	600	2896	1200
40	1016	1524	632	3048	1264
42	1067	1600	660	3200	1326
44	1118	1676	695	3353	1389
46	1168	1753	727	3505	1453
48	1219	1829	759	3658	1516

ASME B16.9 45°/90° Long Radius Elbow Dimensional Tolerance

ASME B16.9 Butt weld 180 degree Long Radius Elbow Dimensions

NPS	O.D. D	180° Long Radius
		Center to Center O	Back to Face K
1/2	21.3	76	48
3/4	26.7	76	51
1	33.4	76	56
1¼	42.2	95	70
1½	48.3	114	83
2	60.3	152	106
2½	73	190	132
3	88.9	229	159
3½	101.6	267	184
4	114.3	305	210
5	141.3	381	262
6	168.3	457	313
8	219.1	610	414
10	273	762	518
12	323.8	914	619
14	355.6	1067	711
16	406.4	1219	813
18	457	1372	914
20	508	1524	1016
22	559	1676	1118
24	610	1829	1219

ASME B16.9 180° Long Radius Elbow Dimensional Tolerance

ASME B16.9 Butt weld 45 degree Short Radius Elbow Dimensions

Nom.  Pipe  Size	Pipe  Sched.  or No.	Center-  to-end  Dimen.	Outside  Dia.	Inside  Dia.	Wall  Thick.	Approx.  Weight  (lb.)
		F	OD	ID	T
STANDARD WEIGHT
1/2	40	5/8	0.840	0.622	0.109	0.1
3/4	40	7/16	1.050	0.824	0.113	0.1
1	40	7/8	1.315	1.049	0.133	0.2
1 1/4	40	1	1.660	1.380	0.140	0.4
1 1/2	40	1 1/8	1.900	1.610	0.145	0.5
2	40	1 3/8	2.375	2.067	0.154	0.9
2 1/2	40	1 3/4	2.875	2.469	0.203	1.5
3	40	2	3.500	3.068	0.216	2.5
3 1/2	40	2 1/4	4.000	3.548	0.226	3.5
4	40	2 1/2	4.500	4.026	0.237	4.8
5	40	3 1/8	5.563	5.047	0.258	7.8
6	40	3 3/4	6.625	6.065	0.280	12
8	40	5	8.625	7.981	0.322	23
10	40	6 1/4	10.750	10.020	0.365	42
12	–	7 1/2	12.750	12.000	0.375	61
14	30	8 3/4	14.000	13.250	0.375	79
16	30	10	16.000	15.250	0.375	103
18	–	11 1/4	18.000	17.250	0.375	132
20	20	12 1/2	20.000	19.250	0.375	160
22	20	13 1/2	22.000	21.250	0.375	195
24	20	15	24.000	23.250	0.375	238
EXTRA STRONG
Nom.  Pipe  Size	Pipe  Sched.  or No.	Center-  to-end  Dimen.	Outside  Dia.	Inside  Dia.	Wall  Thick.	Approx.  Weight  (lb.)
		F	OD	ID	T
1/2	80	5/8	0.840	0.546	0.147	0.2
3/4	80	7/16	1.050	0.742	0.154	0.3
1	80	7/8	1.315	0.957	0.179	0.4
1 1/4	80	1	1.660	1.278	0.191	0.5
1 1/2	80	1 1/8	1.900	1.500	0.200	0.6
2	80	1 3/8	2.375	1.939	0.218	1.1
2 1/2	80	1 3/4	2.875	2.323	0.276	2.1
3	80	2	3.500	2.900	0.300	3.5
3 1/2	80	2 1/4	4.000	3.364	0.318	4.8
4	80	2 1/2	4.500	3.826	0.337	6.5
5	80	3 1/8	5.563	4.813	0.375	11
6	80	3 3/4	6.625	5.761	0.432	18
8	80	5	8.625	7.625	0.500	35
10	60	6 1/4	10.750	9.750	0.500	56
12	–	7 1/2	12.750	11.750	0.500	80
14	–	8 3/4	14.000	13.000	0.500	100
16	40	10	16.000	15.000	0.500	131
18	–	11 1/4	18.000	17.000	0.500	172
20	30	12 1/2	20.000	19.000	0.500	210
22	30	13 1/2	22.000	21.000	0.500	259
24	–	15	24.000	23.000	0.500	302

Ansi 16.9 tolerances – 45 Degree short radius elbow

ASME B16.9 90 degree Short Radius Elbow Dimensional

NPS	O.D. D	Center-to-End A
1	33.4	25
1¼	42.2	32
1½	48.3	38
2	60.3	51
2½	73	64
3	88.9	76
3½	101.6	89
4	114.3	102
5	141.3	127
6	168.3	152
8	219.1	203
10	273	254
12	323.8	305
14	355.6	356
16	406.4	406
18	457	457
20	508	508
22	559	559
24	610	610

ASME B16.9 90°Short Radius Elbow Dimensional Tolerance

ASME B16.9 Butt weld 180 degree Short radius Elbow Dimensions

NPS	O.D. D	180° Short radius		180° Short Radius
		Center to Center O	Back to Face K	Center to Center O	Back to Face K
1/2	21.3	76	48	–	–
3/4	26.7	76	51	–	–
1	33.4	76	56	51	41
1¼	42.2	95	70	64	52
1½	48.3	114	83	76	62
2	60.3	152	106	102	81
2½	73	190	132	127	100
3	88.9	229	159	152	121
3½	101.6	267	184	178	140
4	114.3	305	210	203	159
5	141.3	381	262	254	197
6	168.3	457	313	305	237
8	219.1	610	414	406	313
10	273	762	518	508	391
12	323.8	914	619	610	467
14	355.6	1067	711	711	533
16	406.4	1219	813	813	610
18	457	1372	914	914	686
20	508	1524	1016	1016	762
22	559	1676	1118	1118	838
24	610	1829	1219	1219	914

ASME B16.9 180° Short Radius Elbow Dimensional Tolerance

What is the difference between a long radius elbow and a short radius elbow?

The elbow is divided into its radius of curvature and can be divided into a long radius elbow and a short radius elbow. The long radius elbow refers to the outer diameter of the tube whose radius of curvature is equal to 1.5 times, that is, R = 1.5D. A short radius elbow means that its radius of curvature is equal to the outer diameter of the tube, ie R = D. Where D is the diameter of the elbow and R is the radius of curvature. Normal use of the length of the radius Sometimes to reduce the loss of resistance or elbow wear, the elbow with a larger bending radius will be used (in fact, it is not called elbow); when there is a limit on the installation position, a short radius elbow will be used.

For example:
ASME B16.9

• Short Radius Elbow = 1 x NPS
• Long Radius Elbow = 1.5 x NPS

Lets take an 18″-SCH XH seamless long radius elbow, Material: SA-234-WP11 a Design Temperature of 400°F, ASME Section VIII, Division I (Table IID) has an allowable stress of 16800 psi.
Using a B16.9 long radius elbow the allowable stress would be 16800psi. we recall there was a reduction in the allowable stress of (A) * 16800. What I am looking for is what the value of (A) is and the referenced code/paragraph.

1. There are two types of pipes in the process installation, namely the outer diameter and the nominal size of the pipe. D, DN, refers to the nominal size of the pipe. It does not represent the inner diameter of the pipe or the outer diameter of the pipe. It is a nominal size designed and used. The elbow is the elbow, and the manufacturing method is divided into the push elbow, the extrusion elbow and the welded miter elbow. The structure length is 1.0D, 1.5D, 2.0D. At present, there are two kinds of norms implemented in this area in China: metric and imperial. For example: 1.5D steel seamless elbow, DN100 outer diameter ¢108 and ¢114.3, actual structural length L152, DN200 outer diameter ¢219 and ¢216.3, actual structural length L302. In use, long radius elbow (R = 15DN): in general, should be preferred; short radius elbow (R = 1.0DN): mostly used in applications where size is limited. Its high working pressure should not exceed 0.8 times of the long radius elbow of the same specification.
2. Elbow (R = nDN): used to ease the scouring and kinetic energy of the media at the corner, available to R = 3DN, 6DN, 10DN, 20DN.
3. According to different manufacturing methods, it is divided into push elbow, extrusion elbow and welded miter elbow.
4. Pushing elbows and extrusion elbows: Commonly used for welding mitered elbows on medium and small-sized pipes with strict media conditions: It is often used on large-sized pipes with moderate media conditions, and the bending radius is not less than 1.5 times the nominal diameter. When the miter angle of the miter elbow is greater than 450, it should not be used on highly toxic, flammable medium pipes, or on pipes subjected to mechanical vibration, pressure pulsation and alternating load due to temperature changes.

LR or SR elbow to use?

1. The short radius elbow is used in tight areas, while the long radius is used under normal working conditions.
2. The long radius elbow is better than short radius elbow when it is scoured and worn.
3. The position of the two elbows should be determined according to the practical conditions, because the positions are necessary.

How to purchase elbows?

1. Detecting the back arc of the elbow: Seamless elbow detection of the thickness of the back arc is an important task. Many large pipe elbow manufacturers or strict engineering inspection of the back arc is a must. It is related to the safety and stability of the pipeline operation.
2. Everyone knows that both the pipeline and the seamless elbow are under pressure, that is, the pressure is very large when running. Under normal circumstances, the safety factor of the thickness of the seamless elbow designed and installed is about six times. For example, the 219*8 seamless elbow, the pipeline medium is ordinary water, the temperature is usually not higher than one hundred degrees Celsius, and the pressure required to blast such a seamless elbow is about 300 kg, that is, The pressure inside the pipeline needs to reach PN30, and the seamless elbow will be blasted, and the operating pressure of this elbow is probably about it. It is estimated that the maximum will not exceed PN6.4, which is generally around PN4.0, of course. With the corrosion of the pipeline, the seamless elbow will also be corroded to varying degrees. In order to ensure its safe operation, the necessity of overhaul is great.
3. The current process of making seamless elbows will lead to the phenomenon of back arc thinning. Under normal circumstances, the wall thickness of the mouth will be about two millimeters thinner than the back arc. The common thickness and pressure will not be thin even if the back arc is thinned. There are too many safety hazards, because the elbow has not been replaced until the elbow has a dangerous accident. But as a rigorous project, what is not the same, and the medium inside the pipeline is also responsible, not just water. There may be oil or other impurities, the temperature is high and the pressure is high, and the thickness of the back arc as the weak place determines the life of the seamless elbow. Therefore, the importance of detecting the back arc is naturally great. With a thickness gauge, read the thickness of a point at the elbow directly.
4. Detect the inner and outer diameters of the elbow: For example, the outer diameter dimension D of the elbow is detected: the data of the upper limit and the lower limit are referenced, and the actually measured outer diameter of the product is qualified between the upper and lower limits, and the unqualified product is outside the upper or lower limit range.
   Chart detection range: 90° elbow 1.5D outer diameter dimension D, height is H and outer arc size W
    
5. Detect the wall thickness of the elbow: use the thickness gauge to directly read the thickness of the thinnest part of the elbow.
6. Detect the center height of the elbow: first measure the length of the outer circle of the elbow. Using this length value /1.57, the value obtained by subtracting half of the diameter of the elbow is the center height of the elbow.
7. Detecting the weight of the elbow: The elbow is made of steel pipe. We only know the weight of the elbow when the elbow is cut, and the size of the elbow and the back arc of the elbow. The dimensions are basically the same. Let’s calculate the length of the back arc of the elbow: the diameter of the elbow is D, the radius of curvature is 1.5D, and the length of the back arc of the elbow is (1.5+0.5)*D*2*3.14/4 Simplification we can get, 1.5 times elbow back arc length L = D * 3.14. This is only an estimate. The value of the Chinese standard is slightly smaller than this value. After the length of the back arc is L, the weight of the steel pipe is calculated by the calculation formula of the steel pipe: (Da)*a*0.02466*L/1000, ( a is the wall thickness of the elbow), the unit of this weight is KG, so we can get the weight of the carbon steel elbow. If it is a stainless steel elbow, just replace 0.02466 with 0.02491. The calculated theoretical weight is then compared to the actual weight.
8. Radiographic inspection of elbows: Radiographic inspection detects volumetric defects of elbows, such as pores, slag inclusions, shrinkage cavities, and looseness.

Through a series of tests, you will be able to purchase good quality elbows.

Source: China Steel Elbows Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at [email protected]

Please notice that you might be interested in the other technical articles we’ve published:

• Difference Between A Pipe Elbow And A Pipe Bend
• What is a pipe elbow
• How to get high quality pipe elbow
• Use and maintenance of stainless steel elbows
• Seamless Steel Elbow VS Welded Steel Elbow
• Knowledge of Long Radius Elbow

References:

• www.yaang.com

How to calculate long radius elbow Center?

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
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.

What is Elbow Radius?

The elbow radius mean curvature radius. If the radius is the same as pipe diameter, it called short radius elbow, also called SR elbow, normally for low pressure and low speed pipelines.
If the radius is larger than pipe diameter, R ≥ 1.5 Diameter, then we call it a long radius elbow (LR Elbow), applied for high pressure and high flow rate pipelines.

What is Long radius 90 degree elbow?

90 degree LR elbow are installed between different lengths pipe or tubing. It helps to change direction at 90 degree, and is commonly used to connect hoses to pumps, deck drains and valve.

What is Short radius 90 degree elbow?

90 degree SR elbow is the same as the pipe elbow mentioned above, but the diameter is shorter. Therefore, this kind of steel elbow is often used when space is not enough.