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What are elbows

What are elbows?

Table of Contents

Pipe elbows are pipe fittings used to change the direction of pipes in a piping systemAccording to the angle, there are three most commonly used 45° elbow90° elbow and 180° elbow, according to engineering needs, but also includes other abnormal angle elbow, such as 60° elbow. The bending radius is less than or equal to 1.5 times the diameter of the elbow and greater than 1.5 times the diameter of the elbow. Elbow materials are cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics. Connection with the pipe are: direct welding (the most common way) flange connection, hot fusion connection, fusion welding connection, threaded connection and socket connection. According to the production process can be divided into: welding elbow, stamping elbow, push elbow, casting elbow, butt welding elbow.

asme b16 9 astm a403 wp316l smls 90 degree lr elbow 2 sch80s - What are elbows

Use of elbow

Connect two pipes with the same or different nominal diameters to make the pipe turn 90°, 45°, 180° and various degrees.

Because the elbow has good comprehensive performance, it is widely used in chemical engineering, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire protection, electric power, aerospace, shipbuilding and other basic projects.

  • Wall thickness: SCH5 to SCH160
  • Size range: 1/2 to 56 inches (DN 15 to DN 1,400mm)
  • Degree: 22.5 Deg, 45 Deg, 90 Deg, 180 Deg
  • Manufacturing standards: ANSI, ISO, JIS and DIN
  • Process: butt welding, seamless
  • Type: Long radius, Short radius, Large size
  • Pressure: class 3000, 6000 and 9000

Types of pipe elbow

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 pipe fitting is called a reducing elbow or reducer elbow.

 short radius 90degree - What are elbows
Short radius elbows
 long radius 90degree 1.5d - What are elbows
Long radius elbows
 stailness elbow - What are elbows
Stainless pipe elbows
larg diameter elbow - What are elbows
Big diameter elbows

The degree types of short radius pipe elbows as below:

An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 180° or 90° angle, though 45° elbows are also made. The ends may be machined for butt welding (SW) or socketed welding (SW) etc.

Most elbows are available in short radius or long radius variants. When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow.

Elbows are categorized based on various design features as below:

  • Long Radius (LR) Elbow is also called LR elbow – means the 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 return bend allows complete reversal of flow.
  • Short Radius (SR) Elbow is also called SR elbow, – means the radius is 1.0 times the pipe diameter
    • Short radiu 45°Elbow: Short radius 45° elbow changes the direction by 45 degrees.
    • Short radius 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.
    • Short radius 180° Elbow: Short Radius 180° return bend allows complete reversal of flow.

Elbows are categorized based on various design features as below:

  • Long Radius (LR) Elbows – radius is 1.5 times the pipe diameter
  • Short Radius (SR) Elbows – radius is 1.0 times the pipe diameter
  • 90 Degree Elbow – where change in direction required is 90°
  • 45 Degree Elbow – where change in direction required is 45°

A 90 degree elbow is also called a “90 bend” or “90 ell”. It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe. It used to change the direction in piping and is also sometimes called a “quarter bend”. A 90 degree elbow attaches readily to plastic, copper, cast iron, steel and lead. It can also attach to rubber with stainless steel clamps. It is available in many materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains. These elbows can be made from tough nylon material or NPT thread.

Types of 90° elbows

90° elbows are manufactured as SR (Short Radius) elbows and LR (Long Radius) elbows: 
SR (Short Radius) Elbows:
These elbows have a Center-to-Face dimension of 1.0 X diameter. They are typically used in tight areas where clearance is the main issue.
LR (Long Radius) Elbows:
These elbows have a Center-to-Face dimension of 1.5 X diameter. They are the most common type of elbow and used when space is available and flow is more critical.

What is a 90 degree long radius elbow?

The 90 degree Long Radius Elbow manufactured using superior grade raw materials. The 90 degree Long Radius Elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

We have adopted advanced production equipment to make our 90 degree Short Radius Elbow(1D D711.2~D1219.2), which can not only improve product quality, but also save raw materials.

How to calculation weight of 90 degree long radius elbow?

Weight formula = 0.0387 * S( D – S ) * 1.5D/1000

  • W = Weight (kg/piece).
  • S = Thickness Schedule.
  • D = Nominal Diameter.

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

90 deg long redius dimen - What are elbows

ASME B16.9 90°Short Radius Elbow Dimensional Tolerance

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

42.2

48

25

95

39

48.3

57

29

114

47

2

60.3

76

35

152

63

73

95

44

190

79

3

88.9

114

51

229

95

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 90° Long Radius Elbow Dimensional Tolerance

DIMENSIONAL TOLERANCES – ELBOWS
For all fittings Elbows 90/45 deg 180° Returns
Nominal Pipe Size (NPS) Outside Ø 
at Bevel
Inside Ø 
at End
Wall Thickness 
t / t1
Center to End Dim. A-B-C-M Center to Center Dim.
O
Back to Face Dim.
K
Align- ment of Ends
U
1/2 a 2 1/2 1 0,8 Not 2 7 7 1
3 a 3 1/2 1 1,6 less 2 7 7 1
4 +2 -1 1,6 than 2 7 7 1
5 a 6 +3 -1 1,6 87,50% 2 7 7 1
8 2 1,6 of nominal 2 7 7 1
10 +4 -3 3,2 thickness 2 7 7 2
12 a 18 +4 -3 3,2 3 10 7 2
20 a 24 +6 -5 4,8 3 10 7 2
26 a 30 +7 -5 4,8 3 ….. ….. …..
32 a 48 +7 -5 4,8 5 ….. ….. …..

What is a 90 degree short radius elbow?

The 90 degree short radius elbow manufactured using superior grade raw materials. The 90 degree short radius elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

ASME B16.9 90 degree Short Radius Elbow Dimensional Tolerance

90 deg short redius dimen - What are elbows

NPS O.D.
D
Center-to-End
A
1 33.4 25
42.2 32
48.3 38
2 60.3 51
73 64
3 88.9 76
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

Nominal Pipe Size 1/2 to 2½ 3 to  4 5 to 8 10 to 18 20 to 24 26 to 30 32 to 48
Outside Diameter
at Bevel (D)
+ 1.6
– 0.8
1.6 1.6 + 2.4
– 1.6
+ 4
– 3.2
+ 6.4
– 4.8
+ 6.4
– 4.8
+ 6.4
– 4.8
Inside Diameter at End 0.8 1.6 1.6 1.6 3.2 4.8 + 6.4
– 4.8
+ 6.4
– 4.8
Center-to-End (A) 2 2 2 2 2 2 3 5
Wall Thickness (t) Not less than 87.5% of Nominal Wall Thickness

What is a 45° elbow?

45° Pipe Elbow is also known as 45 “ells”. The 45° pipe elbow is used to connect tubes at a 45° pipe angle. As the name suggests, this is a pipe fitting device which is bent in such a way to produce 45° change in the direction of flow of the fluid/gas in the pipe.
Like a 90° elbow, the 45° pipe elbow also attaches readily to pipes of various materials like plastic, copper, cast iron, steel, lead, rubber etc. They are typically made as LR (Long Radius) elbows. These types of elbows are available in various sizes (in mm or inches). They are available with different male to female BSP thread connections. Providing a wide choice of colors, these 45° elbows can be manufactured to meet different specifications, in terms of size and diameter.

45 degree long radius elbow

The 45 degree long radius elbow manufactured using superior grade raw materials.

Butt weld 45 degree LOng Radius Elbow are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

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

45 deg long redius dimen - What are elbows

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

42.2

48

25

95

39

48.3

57

29

114

47

2

60.3

76

35

152

63

73

95

44

190

79

3

88.9

114

51

229

95

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° Long Radius Elbow Dimensional Tolerance

DIMENSIONAL TOLERANCES – ELBOWS
For all fittings Elbows 90/45 deg 180° Returns
Nominal Pipe Size (NPS) Outside Ø 
at Bevel
Inside Ø 
at End
Wall Thickness 
t / t1
Center to End Dim. A-B-C-M Center to Center Dim.
O
Back to Face Dim.
K
Align- ment of Ends
U
1/2 a 2 1/2 1 0,8 Not 2 7 7 1
3 a 3 1/2 1 1,6 less 2 7 7 1
4 +2 -1 1,6 than 2 7 7 1
5 a 6 +3 -1 1,6 87,50% 2 7 7 1
8 2 1,6 of nominal 2 7 7 1
10 +4 -3 3,2 tickness 2 7 7 2
12 a 18 +4 -3 3,2   3 10 7 2
20 a 24 +6 -5 4,8   3 10 7 2
26 a 30 +7 -5 4,8   3 ….. ….. …..
32 a 48 +7 -5 4,8   5 ….. ….. …..

The 180 degree Short radius Elbow manufactured using superior grade raw materials. The 180 degree Short radius Elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

45 degree SR elbow

The 45 degree short radius elbow manufactured using superior grade raw materials. Butt weld 45 degree short radius elbow are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

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

45 deg short redius dimen - What are elbows

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

DIMENSIONAL TOLERANCES – ELBOWS
For all fittings Elbows 90/45 deg 180° Returns
Nominal Pipe Size (NPS) Outside Ø 
at Bevel
Inside Ø 
at End
Wall Thickness 
t / t1
Center to End Dim. A-B-C-M Center to Center Dim.
O
Back to Face Dim.
K
Align- ment of Ends
U
1/2 a 2 1/2 1 0,8 Not 2 7 7 1
3 a 3 1/2 1 1,6 less 2 7 7 1
4 +2 -1 1,6 than 2 7 7 1
5 a 6 +3 -1 1,6 87,50% 2 7 7 1
8 2 1,6 of nominal 2 7 7 1
10 +4 -3 3,2 tickness 2 7 7 2
12 a 18 +4 -3 3,2   3 10 7 2
20 a 24 +6 -5 4,8 3 10 7 2
26 a 30 +7 -5 4,8 3 ….. ….. …..
32 a 48 +7 -5 4,8   5 ….. ….. …..

What is a 180 degree short radius elbow?

The 180 degree short radius elbow manufactured using superior grade raw materials. The 180 degree short radius elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

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

180 deg short redius dimen - What are elbows

ASME B16.9 180 degree Short radius Elbow Dimensional Tolerance

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
42.2 95 70 64 52
48.3 114 83 76 62
2 60.3 152 106 102 81
73 190 132 127 100
3 88.9 229 159 152 121
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

For all fittings 180° Returns
Nominal Pipe Size (NPS) Outside Ø 
at Bevel
Inside Ø
at End
Wall Thickness 
t / t1
Center to Center Dim.
O
Back to Face Dim.
K
Align- ment of Ends
U
1/2 a 2 1/2 1 0,8 Not 7 7 1
3 a 3 1/2 1 1,6 less 7 7 1
4 +2 -1 1,6 than 7 7 1
5 a 6 +3 -1 1,6 87,50% 7 7 1
8 2 1,6 of nominal 7 7 1
10 +4 -3 3,2 thickness 7 7 2
12 a 18 +4 -3 3,2 10 7 2
20 a 24 +6 -5 4,8 10 7 2
26 a 30 +7 -5 4,8 ….. ….. …..
32 a 48 +7 -5 4,8 ….. ….. …..

What is a 180 degree long eadius elbow?

The 180 degree long radius elbow manufactured using superior grade raw materials.

The 180 degree long radius elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & ship builders.

We have adopted advanced production equipment to make our 180 degree Long Radius Elbow(1D D711.2~D1219.2), which can not only improve product quality, but also save raw materials.

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

180 deg long redius dimen - What are elbows

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
42.2 95 70
48.3 114 83
2 60.3 152 106
73 190 132
3 88.9 229 159
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

For all fittings 180° Returns
Nominal Pipe Size (NPS) Outside Ø 
at Bevel
Inside Ø
at End
Wall Thickness 
t / t1
Center to Center Dim.
O
Back to Face Dim.
K
Align- ment of Ends
U
1/2 a 2 1/2 1 0,8 Not 7 7 1
3 a 3 1/2 1 1,6 less 7 7 1
4 +2 -1 1,6 than 7 7 1
5 a 6 +3 -1 1,6 87,50% 7 7 1
8 2 1,6 of nominal 7 7 1
10 +4 -3 3,2 thickness 7 7 2
12 a 18 +4 -3 3,2 10 7 2
20 a 24 +6 -5 4,8 10 7 2
26 a 30 +7 -5 4,8 ….. ….. …..
32 a 48 +7 -5 4,8 ….. ….. …..

Most elbows are available in short radius or long radius variants.

SHORT RADIUS ELBOWS

The short radius elbows have a center-to-end distance equal to the Nominal Pipe Size (NPS) in inches, while the long radius is 1.5 times the NPS in inches. Short elbows are widely available, and are typically used in pressurized systems.

LONG RADIUS ELBOWS

Long elbows are typically used in low-pressure gravity-fed systems and other applications where low turbulence and minimum deposition of entrained solids are of concern.

What are forged pipe elbows?

Forged elbows are typically used to change the direction in the pipe and thus the direction of media flow. Forged socket weld fittings are limited to smaller pipe diameters (up to NPS 4, but usually NPS 2 or less) and are available in 3000, 6000 and 9000 pressure classes corresponding to Schedule 40, 80 and 160 pipes. Socket fittings are welded in place by fillet welds, which makes them weaker than butt-weld fittings, but still superior to threaded fittings for high-end projects.

  • Pressure: 2000LBS, 3000LBS, 6000LBS, 9000LBS.
  • Size: from 1/8″ to 4″.
  • Material: ASTM A105, F304, F316, F304L, F316L, A182 F11/F22/F91.
  • Connection ends: socket weld and threaded.

Threaded Pipe Fitting SS304 Precision Cast Fittings

Threaded Pipe Fitting SS304 with 90 degrees Elbow, Class 150lb, Male and Female Thread.

Size: 1/2 to 4 inch

threaded pipe fitting - What are elbows

304 90 degrees elbow, class 150lb, with male and female thread

Materials: SS304 and SS316

Manufacturing standards: ANSI, JIS, and DIN

Our prefessional foundry can do sand casting,lost wax casting and die casting.

forged elbows - What are elbows

The material as bellowing: 
Gray Iron, Ductile Iron, Steel, Stainless Steel, Malleable Iron and Alloy.
The products is widely used in automobile , machinery, pipe fittings, pump parts, valve part and other industry.

We are a group company consisting of:

  • 4. Sand Casting Plants (mainly produce Cast Iron and Ductile Iron Products).
  • 2. Resin Sand Casting Plants (mainly produce Cast Steel&Cast Iron Products).
  • 3. Investment Casting Plants (mainly produce Stainless Steel and Carbon Steel products.
Butt welded Elbows:
  • Pipe is connected to butt welded elbow as shown in Fig.4 by having a butt-welding joint.
  • Butt welded fittings are supplied with bevel ends suitable for welding to pipe. It is important to indicate the connected pipe thickness /schedule while ordering. All edge preparations for butt welding should conform to ASME B16.25.
  • Dimensions of butt welded elbows are as per ASME B16.9. This standard is applicable for carbon steel & alloy steel butt weld fittings of NPS 1/2” through 48”.
untitled 1 - What are elbows
Fig.4: A typical Butt-Welded Elbow
  • Dimensions of stainless steel butt welded fittings are as per MSS-SP-43. Physical dimensions for fittings are identical under ASME B16.9 and MSS-SP-43. It is implied that the scope of ASME B16.9 deals primarily with the wall thicknesses which are common to carbon and low alloy steel piping, whereas MSS-SP-43 deals specifically with schedule 5S & 10S in stainless steel piping.
  • Dimensions for short radius elbows are as per ASME B16.28 in case of carbon steel & low alloy steel and MSS-SP-59 for stainless steel.
  • Butt welded fittings are usually used for sizes 2” above. However, for smaller sizes up to 1-1/2” on critical lines where use of socket welded joints is prohibited, pipe bends are normally used. These bends are usually of 5D radius and made at site by cold bending of pipe. Alternatively, butt welded elbows can be used in lieu of pipe bends but usually smaller dia lines are field routed and it is not possible to have the requirement known at initial stage of the project for procurement purpose. So pipe bends are preferred. However, pipe bends do occupy more space and particularly in pharmaceutical plants where major portion of piping is of small dia. and layout is congested, butt welded elbows are preferred.
  • Butt welded joints can be radiographed and hence preferred for all critical services.
  • Material standards as applicable to butt welded fittings are as follows:
ASTM A234:

This specification covers wrought carbon steel & alloy steel fittings of seamless and welded construction. Unless seamless or welded construction is specified in order, either may be furnished at the option of the supplier. All welded construction fittings as per this standard are supplied with 100% radiography. Under ASTM A234, several grades are available depending upon chemical composition. Selection would depend upon pipe material connected to these pipe fittings.
Some of the grades available under this specification and corresponding connected pipe material specification are listed below:
untitled2 1 - What are elbows
ASTM A403:
This specification covers two general classes, WP & CR, of wrought austenitic stainless steel fittings of seamless and welded construction.
Class WP fittings are manufactured to the requirements of ASME B16.9 & ASME B16.28 and are subdivided into three subclasses as follows:
  • WP – SManufactured from seamless product by a seamless method of manufacture.
  • WP – W These fittings contain welds and all welds made by the fitting manufacturer including starting pipe weld if the pipe was welded with the addition of filler material are radiographed. However no radiography is done for the starting pipe weld if the pipe was welded without the addition of filler material.
  • WP-WX These fittings contain welds and all welds whether made by the fitting manufacturer or by the starting material manufacturer are radiographed.
  • Class CR fittings are manufactured to the requirements of MSS-SP-43 and do not require non-destructive examination.
Under ASTM A403 several grades are available depending upon chemical composition. Selection would depend upon pipe material connected to these fittings. Some of the grades available under this specification and corresponding connected pipe material specification are listed below:
untitled3 1 - What are elbows
ASTM A420:
  • This specification covers wrought carbon steel and alloy steel fittings of seamless & welded construction intended for use at low temperatures. It covers four grades WPL6, WPL9, WPL3 & WPL8 depending upon chemical composition. Fittings WPL6 are impact tested at temp – 50° C, WPL9 at -75° C, WPL3 at -100° C and WPL8 at -195° C temperature.
  • The allowable pressure ratings for fittings may be calculated as for straight seamless pipe in accordance with the rules established in the applicable section of ASME B31.3.
  • The pipe wall thickness and material type shall be that with which the fittings have been ordered to be used, their identity on the fittings is in lieu of pressure rating markings.

Manufacturing process of the pipe elbow

Mandrel method (Hot Forming)

  • One of the most common Pipe Fittings Manufacturing Process for manufacturing Elbows Or Pipe Bends from the pipe is mandrel method which is kind of hot forming methods.
  • In this method, the pipe is cut in pieces and push with the help of hydraulic ram. It is pushed over a die called “mandrel” which allows the pipe to expand and bend simultaneously.
  • This method can be used to manufacture a wide range of the diameter of elbows or pipe bends.

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  • ELBOWS Or Pipe Bends Mandrel method.

Extrusion Method

In cold Extrusion method, a pipe with the same diameter as finished product is pushed through a die and formed into its desired shape. Usually applied to stainless steel small to medium sizes elbows or pipe bends.

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Extrusion Method

UO Method

UO method is used to manufacture medium size of the elbow, tee, and reducers. The plate is cut out into a specially designed shape, it is formed first into a U-shape using a die and then into an O-shape or tubular form using another die, that is why this method is known as UO method. Once the pipe fittings formed in tumbler shaped it is welded from inside and outside of the closing seam. A cut plate is 1st from in U shape and then in O shape.

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UO Method

Hot Forming Method

In a hot forming die bending method, a pipe is heated to forming temperature & formed in the die with the specific shape, this process may be repeated as needed to obtain the required shape, size and wall thickness. Usually applied to thick-wall items that cannot be bent on a mandrel die.

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Hot Forming method for Elbow Manufacturing

Materials of elbows

  • Carbon steel: ASTM/ASME A234 WPB-WPC
  • Alloy steel: –WP 22-WP 5-WP 91-WP 911
    • ASTM A335 P22
    • ASME SA335 P91 elbow
    • ASTM A234 WP 11
  • Low temperature steel: ASTM/ASME A402 WPL3-WPL6
  • High performance steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
  • Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
    • ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
    • ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H

Standards of elbows

  • GB/T12459-2005 GB/T13401-2005 GB/T10752-2005 SH/T3408-1996 SH/T3409-1996
  • SY/T0609-2006 SY/T0518-2002 SY/T0510-1998
  • DL/T695-1999 GD2000 GD87-1101
  • HG/T21635-1987 HG/T21631-1990
  • ASME B16.9-2007 ASME B16.25-2007
  • MSS SP 75-2008 MSS SP 43-2008
  • CSA Z245.11-05-2005
  • EN10253-1-1999 EN10253-2-2007 EN10253-3-2008 EN10253-4-2008
  • DIN2605-1-1992 DIN2605-2-1995
  • BS1640-1-1962 BS1640-2-1962 BS1640-3-1968 BS1640-4-1968 BS1965-1-1963
  • AFNOR NF A 49-289-1990 AFNOR NF A 49-170-1-1999 AFNOR NF A 49-170-2-2009 AFNOR NF A 49-170-3-2009
  • AFNOR NF A 49-170-4-2009 ISO3419-1981 ISO5251-1981
  • JIS B2311-2009 JIS B2312-2009 JIS B2313-2009
  • ASME B16.9 Butt weld 45 degree Long Radius Elbow Dimensions

Applications of pipe elbows

Various applications of pipe elbows are as follows:

  • They are manufactured to be used in flow lines for gases, fluids in industrial processes, medical, construction and many other specialized applications.
  • The elbows are constructed of heavy materials for rigid applications like extreme high/low temperature resistance etc.
  • The elbows are specifically designed for use on process and control systems, instrumentation, and equipment used in chemical, petroleum, fluid power, electronic and pulp and paper plants. 

How to check the quality of elbow?

Whether the quality of elbow meets the requirements of technical standards is directly related to the quality of construction project and the operation safety of equipment. The construction site is the final acceptance and use link. Therefore, it is very necessary to adopt a scientific and feasible elbow detection method in the field.

Inspection of elbow

The elbow shall be subject to chemical composition analysis, mechanical property test and appearance and dimension inspection before delivery. For some elbow fittings with special requirements, low-temperature toughness impact testing, nondestructive testing, magnetic particle testing, etc. are also required. In order to avoid unnecessary rework or hidden danger to the operation of the device due to unqualified elbow quality, resulting in waste of human and material resources, loss of construction quality and extension of project construction period, the construction unit shall conduct on-site inspection before using elbow and other pipe fittings. This paper focuses on the detection method of elbow on the construction site.

Check of elbow

First, check the material grade of elbow, product code of elbow, standard number of elbow, standard size and wall thickness grade of elbow, and professionals use testing equipment to test and analyze the material of elbow. Generally, the chemical composition of the elbow shall be the same or similar to that of the welded pipe section, and shall be of the same steel grade, and the physical properties will not change or produce cracks and other defects due to reheating.

Appearance inspection of elbow

The inner and outer surfaces of the elbow shall be smooth and regular, and shall be free of defects such as crack, delamination, stutter, thinning, depression, sharp scratch, notch, folding, etc.

Geometric dimension inspection of elbow

The geometric dimension inspection is the work carried out by the pipeline installer after checking the elbow identification and elbow materials, and the appearance of the elbow has been visually inspected. It is the continuation of the appearance inspection. Since most construction sites do not have professional testing equipment, installation workers can only use ordinary tools such as level ruler, angle ruler, ruler, caliper, powder line and thickness gauge to carry out a series of inspections on bending, flatness, ovality, end groove, port perpendicularity, bending radius and thinning rate, so as to check whether the pipe fittings meet the requirements of the document and determine the blanking size of the pipe section, And eliminate the defects found, which requires pipeline installers to have high operation skills. Select flat ground or steel plate and place the elbow horizontally. Check repeatedly with a level ruler, adjust the height of different parts of the elbow, and plug gaskets under it until the middle and both ends of the elbow are horizontal. Use a square, level and steel ruler to find out the top, middle and bottom four bisection points of the two ends of the elbow, and connect the corresponding points respectively to obtain the inner arc, outer arc and two middle arcs. As shown in Figure 1.

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Figure.1

  • (1) Ovality detection: ovality, also known as out of roundness, is usually the diameter measurement of the same section in the vertical and horizontal directions. If the diameter is large, the measurement points must be added. During the measurement, the values of the two ends and the middle three sections shall be recorded respectively, and the two values of the same section shall be subtracted to ovality.
  • (2) Detection of bending radius: take the outer arc point and inner arc point at both ends of the elbow as the reference point, lead two chalk lines to intersect at a point, and measure the distance between the point and the inner arc with a ruler or tape. The distance value plus the bending radius of the elbow ½ The outer diameter is the bending radius of the elbow. According to the specification, the bending radius measured at both ends of the elbow shall be equal, but the value may be different due to machining deviation. If any, the two halves of the elbow shall be calculated separately to ensure the accurate blanking of the pipe section. If there is a steel plate, you can also draw the standard inner arc of the elbow on the steel plate with a scribe gauge, and place the elbow on the steel plate so that the inner arc of the elbow coincides with the projection of the scribed arc, so that the required value can be measured on the steel plate. The measured values of the above two detection methods are easy to deviate due to the roundness of the elbow port, so the influence of ovality on the measurement should be considered in advance.
  • (3) Detection of thinning rate: elbow thinning is generally local thinning, which mostly occurs at the outer arc. At present, the detection method of thinning rate is relatively simple. Use a portable thickness gauge to measure the wall thickness of the elbow at multiple points, and the thinning rate can be obtained by comparing the measured value with the standard value. There is little research on the detection method of elbow local thinning in the industry, and the current detection method is the same The possibility of missing inspection cannot be completely avoided. If the wall thickness difference between the elbow and the pipe section exceeds 2mm, the inner wall shall be thinned at 15 °.
  • (4) Detection of bending degree: the detection method is basically similar to the detection method of bending radius. Use two long steel ruler or powder line to lead out and intersect at one point based on the inner and outer arc of the end face, and measure the bending degree with an angle ruler or protractor.
  • (5) Detection of port perpendicularity: it is best to detect the perpendicularity on the steel plate. If there is no suitable steel plate due to conditions, you can use a ruler or find a straight pipe section flat on the top of the elbow as the reference line. One end of the square rests against the reference line and the other end is close to the elbow port for perpendicularity detection.
  • (6) Groove and flatness detection: most seamless elbows are connected by welding. In order to ensure the welding quality, there are machine-made grooves at both ends, and the angle and the thickness of the blunt edge are strictly regulated, which can be measured with caliper. When checking the groove, the flatness of the surfaces at both ends must also be checked, and the flatness can be determined by clinging a flat wooden board or steel plate to the end face and checking the gap Whether the flatness deviation exceeds the standard.

What is the difference between an elbow and a bend?

Elbows and bends are fittings used to change the direction of pipes. These two kinds of pipe fittings have been widely used in buildings. However, in practical use, the performance of elbow and elbow is different. Let’s take a look at the difference between elbow and elbow.

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Elbow is a kind of pipe fitting, an ordinary pipe fitting, which is usually manufactured according to specific needs. The length is much longer than the elbow. Although they are all fittings that change the direction of the pipe, there are still many differences between them. The most basic difference between bend and elbow is that elbow is relatively short compared with elbow. R = 1 to 2 times is the elbow, and the larger multiple is called the bend.

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1. Different manufacturing processes
The essential difference between bend and elbow is mainly the difference between “head” and “pipe”. In addition, there are great differences in the production process. During the manufacture of elbows, pipes can be used for cold bending. Then bend it directly with a pipe bender. Elbows can be manufactured at one time without secondary corrosion protection, but they need to be customized by the manufacturer, which requires corrosion resistance and long service life.
2. Different prices
The price of elbow is lower than that of bend, but it is easy to be damaged without anti-corrosion protection. However, due to its low price, elbow has been widely used in some projects with low requirements.
3. Different bending radii
The bending radius of bend is usually larger than that of elbow; The mechanical strength per unit area of elbow is usually greater than that of elbow. In use, you can choose according to your needs. For example, to deal with the scour of pipeline fluid at the corner, thick wall elbow can be selected to achieve the purpose of erosion resistance; Large radius bend can also be used to reduce (disperse) scouring force.
4. Different scope of application
In a good construction enterprise environment, elbows and bends can be used. If we only consider the product cost, we choose cold bend. After all, the quality of hot bends is good, but the cost is high. In the process of building development, due to the convenience of engineering construction technology, elbow is more suitable for use in relatively narrow places. The specific construction working environment of the problem needs to be fully considered. Although they can also be used in narrow environments. However, some troubles are often encountered in practical use.
In fact, from the point of view of producing parts. The elbow is short. In the actual construction process, if you need to change the direction, you can choose which pipe fitting to use according to the specific construction conditions.
The above is the difference between elbow and elbow. We hope that through these contents, we can better understand elbows and bends for you. During the construction process, you can also make reasonable choices based on the analysis of the actual development of the company. Elbow and bend are two different pipe components, so they can better complete the construction and improve the construction quality.

Source: China Pipe Elbows Manufacturer – Yaang Pipe Industry Co., Limited (www.epowermetals.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]

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