What are miter elbows?

What are miter elbows?

Miter elbows are not standard fittings they are fabricated from pipes. High skill pipe fitter is required to fabricate this type of elbows and Usually, they are preferred for size 10” & above because large size elbow is expensive. Use of miter elbow is restricted to the water line. Miter elbow can be fabricated in 2, 3, & 5 pieces.  Generally, fire water line, cooling water in old refinery & petrochemical plant you can see the use miter elbow. Nowadays the use of miter elbow is limited.

When setting out, first draw the theoretical cutting line, then determine the position of the cutting line of the highest and lowest point (after beveling) according to the wall thickness, connect the two points, then calculate the length of the prime line of each bisection point, and then cut the line on the coil pipe, and then the required angle can be guaranteed after the assembly. The material is generally carbon steel, stainless steel and alloy steel. In the daily construction, the miter elbow is much less than the elbow welded by the original pipe and the middle plate.

AWWA Recomends:

  • 22.5< to ≤ 45, use 3 pieces
  • 45 < to ≤ 67.5, use 4 pieces
  • 67.5 < to ≤ 90, use 5 pieces
  • A)  The larger the O.D. of the fitting, the more competitive a mitered fitting will be.  Because of the ultimate use, most fittings 54″ and larger can be fabricated and will provide that competitive edge.
  • B)  AWWA C208-96 elbows are made from miter cut pieces of pipe.  The mitered pieces that make up the elbow are called gores.  In a 5-piece elbow, there are two end gores and three middle gores.  The dimensions of the end and middle gores are determined based upon formulas provided by AWWA on page 7 of C208-96.
  • C)  AWWA C208-96 recommends 2 and a half X diameter as an optimum radius, (centerline radius), for mitered elbows with 1 X diameter as the minimum.  Due to industry standards for elbows of other specifications, (e.g. A234 WPB), we set the normal radius at 1 and a half X diameter.
  • D)  However, other standards set the “center-to-face,” or the line originating 90 degrees from the plane of the face of one end of the elbow to the center line of the other end as equal to the center-line radius.  AWWA C208-96 DOES NOT FOLLOW THIS PRACTICE!  In the AWWA spec, the “radius” is a calculation based upon the formulas mentioned above.  The AWWA spec states the radius of a 60″ elbow is 90″.  The “center-to-face” is 92.065″.

Miter Elbow Weight

  • Weight = 2*R*n*tan(alfa/(2*n))*W, where
  • R = bend radius at end (=circumscribed)
  • n = number of miter joints
  • alfa = bend angle (total)
  • W = Unit weight of pipe (kg/m or lb/ft)

Steps to calculate miter elbow weight

  • Calculate the total length of the bend using the formula, l=r x theta, where r=radius of the center line of the bend and theta = bend angle in radians.
  • Unit weight of the pipe/ metre can be obtained from the pipe manufacturer end or from the relevant codes and standard governing the material and process of manufature of the pipe piece used for fabricating the pipe bend. for example: in case the pipe piece grade is API 5L, then refer API 5L for unit weight per meter, or you can refer ASTM A53 code for ASTM pipes and so on.
  • And then multiply the unit weight per meter calculated in step 2 to the length of the pipe piece calculated in step 1.

Formula of Miter Elbow

miter fabrication formula - What are miter elbows?

In above pic, dotted lines shows where the pipe should be cut. Each dotted cut line has a vertical reference line marked at following distances from pipe end.

  • L2 : Distance of first and last reference line from pipe ends.
  • L1 : Distance between reference lines.
  • Cut Back : Offset distance of cut lines from reference lines at the top and bottom of pipe.

Given a formula to make 90 degree elbow of 10″ size with elbow center radius same as standard elbow i.e. 381 mm.

Miter Elbow Input values:

  • D = 90 mm : Required Miter Elbow Degree
  • N = 4 : Number of cuts
  • E = 381 mm : Standard Miter Elbow Radius
  • POD = 273 mm : Pipe Outside Diameter

formula - What are miter elbows?

Mitered Elbow Dimensions

90 Degree Mitered Elbow Dimensions

FOUR WELD 90° LONG RADIUS MITER ELBOW

90 deg mitered elbow - What are miter elbows?

NOM.
DIA
A Min. R
Radius
S
Inches
M
30 42w” 45″ 17p”
32 44s” 48″ 18s”
34 47r” 51″ 19f”
36 49f” 54″ 21w”
38 52i” 57″ 22r”
40 55w” 60″ 23i”
42 57s” 63″ 24p” 8r”
44 60r” 66″ 25s”
46 62f” 69″ 27″
48 65i” 72″ 28i” 9p”
50 68w” 75″ 29r”
52 70s” 78″ 30i”
54 73r” 81″ 31p” 10f”
56 75f” 84″ 32f”
58 78i” 87″ 34″
60 81w” 90″ 35w”
62 83s” 93″ 36y”
64 86y” 96″ 37i”
66 88f” 99″ 38p”
68 91i” 102″ 39f”
70 94w” 105″ 41″
72 96s” 108″ 42r”
78 104i” 117″ 45s” 15r”
84 112y” 126″ 49i”
86 115″ 129″ 50y”

Notes:

  • All Miter Pipe Bend dimensions are given in Inches.
  • Welding shall be in accordance with the job specifications.
  • These Miter Elbow Pipe are to be used when authorized by the piping spec’s.
  • Use “A” dimension only where necessary to meet close clearance requirements or when connecting to flange or fitting.
  • Miter Pipe Elbow Material shall be as specified in the job piping materials specification class.
  • “M” dimension does not include taper bore length.
  • The “M” dimension must be calculated for Miter elbows other than 78″, 54″, 48″ and 42″.

45 Degree Mitered Elbow Dimensions

TWO WELD 45° LONG RADIUS MITER ELBOW

45 deg mitered elbow - What are miter elbows?

DIA
NOM
A B C
(1)
D
(1)
M
Min (3) LR Ell Dim
3 2 2 1s 1w t
4 2i 2i 2y 1t u
6 3s 3s 3i 2 p
8 5 5 4s 2p d
10 6r 6r 5f 3t 1q
12 7i 7i 7w 3g 1r
14 8s 8s 8r 4p 1y
16 10 10 9i 5r 1o
18 11r 11r 10s 5f 1s
20 11i 1 – 0i 11f 6o 2
22 1 – 0r 1 – 1i 1 – 1w 6g 2e
24 1 – 1r 1 – 3 1 – 2r 7f 2y
26 1 – 1s 1 – 4 1 – 3i 8r 2o
28 1 – 2s 1 – 5y 1 – 4q 9q 2s
30 1 – 3i 1 – 6i 1 – 5f 9o 2g
32 1 – 4i 1 – 7f 1 – 7 10y 3e
34 1 – 5i 1 – 9w 1 – 8r 11 3y
36 1 – 6r 1 – 10r 1 – 9i 11i 3o
38 1 – 7 1 – 11i 1 – 10p 1 – 0e 3s
40 1 – 7s 2 – 0s 1 – 11f 1 – 0d 3g
42 1 – 8i 2 – 2 2 – 1 1 – 1i 4w 8y
44 1 – 9i 2 – 3r 2 – 2r 1 – 2w 4y
46 1 – 10i 2 – 4i 2 – 3y 1 – 2d 4o
48 1 – 11r 2 – 5s 2 – 4p 1 – 3u 4s 9p
50 2 – 0r 2 – 7 2 – 5s 1 – 4w 4g
52 2 – 1 2 – 8r 2 – 7 1 – 4s 5w
54 2 – 1s 2 – 9i 2 – 8r 1 – 5y 5y 10f
56 2 – 2s 2 – 10s 2 – 9y 1 – 6q 5o
58 2 – 3i 3 – 0 2 – 10i 1 – 6s 5s
60 2 – 4r 3 – 1r 2 – 11s 1 – 7y 5g
62 2 – 5r 3 – 2i 3 – 1 1 – 8 6w
64 2 – 6 3 – 3s 3 – 2w 1 – 8o 6t
66 2 – 7 3 – 5 3 – 3y 1 – 9t 6o
68 2 – 7s 3 – 6r 3 – 4i 1 – 10 6s
70 2 – 8i 3 – 7i 3 – 5s 1 – 10p 6g
72 2 – 9i 3 – 8s 3 – 6f 1 – 11t 7w
74 2 – 10r 3 – 10 3 – 8e 1 – 11f 7y
76 2 – 11 3 – 11r 3 – 9y 2 – 0o 7o
78 3 – 0 4 – 0u 3 – 10i 2 – 1e 7s 150
80 3 – 0s 4 – 1q 3 – 11s 2 – 1d 7g
82 3 – 1s 4 – 2g 9 – 0t 2 – 2i 8e
84 3 – 2i 4 – 4e 4 – 2w 2 – 3w 8y
86 3 – 3r 4 – 5u 4 – 3t 2 – 3s 8o
88 3 – 4r 4 – 6g 4 – 4i 2 – 4u 8s
90 3 – 5 4 – 7f 4 – 5o 2 – 5q 8g
92 3 – 6 4 – 9e 4 – 6f 2 – 5o 9w
94 3 – 7 4 – 10y 4 – 8w 2 – 5y 9y
96 3 – 4i 4 – 11p 4 – 9r 2 – 7 9o
98 3 – 8i 5 – 0f 4 – 10i 2 – 7p 9s
100 3 – 9 5 – 2w 4 – 11q 2 – 8t 9g
102 3 – 10 5 – 3f 5 – 0f 2 – 8q 10w
104 3 – 11 5 – 4p 5 – 2q 2 – 9o 10t
106 3 – 11s 5 – 5f 5 – 3r 2 – 10r 10o
108 4 – 0i 5 – 7w 5 – 4u 2 – 10f 10s
110 4 – 1i 5 – 8t 5 – 5o 2 – 11i 10g
112 4 – 2r 5 – 9o 5 – 6d 3 – 0e 11w
114 4 – 3 5 – 10d 5 – 8 3 – 0d 11t
116 4 – 4 6 – 0q 5 – 9e 3 – 1u 11i
118 4 – 5 6 – 1t 5 – 10y 3 – 2w 11s
120 4 – 5s 6 – 2o 5 – 11p 3 – 2s 11g
122 4 – 6i 6 – 3d 6 – 0d 3 – 3t 12w
124 4 – 7y 6 – 5q 6 – 2 3 – 4 12y
126 4 – 8r 6 – 6r 6 – 3e 3 – 4q 12o
128 4 – 9 6 – 7i 6 – 4y 3 – 5r 12s
130 4 – 10 6 – 8s 6 – 5o 3 – 6 12g
132 4 – 10s 6 – 10 6 – 6s 3 – 6o 13w
134 4 – 11i 6 – 11r 6 – 8 3 – 7r 13t
136 5 – 0i 7 – 0i 6 – 9w 3 – 7q 13i
138 5 – 1r 7 – 1s 6 – 10y 3 – 8o 13s
140 5 – 2r 7 – 3 6 – 11i 3 – 9r 13g

Notes:

  • All Pipe Miter elbow dimensions are given in Inches.
  • “C” and “D” dimensions are approximate. Do not use for fabrication.
  • These Miter elbows are to be used when authorized by the piping spec’s.
  • Use “A” minimum dimension only where necessary to meet close clearance requirements.
  • Use butt-weld “A” only where necessary to connect to flange or fitting. Use Miter weld for pipe connection.
  • Miter elbow Material shall be as specified in the job piping materials specification class.
  • Welding shall be in accordance with the job specifications.
  • “M” dimension does not include taper bore length.
  • The “M” dimension must be calculated for Miter elbows other than 78″, 54″, 48″ and 42″.

Mitered Elbow Equivalent Length

Miter Fittings Steel
e = 0.05 mm
Spiral Weld Steel
e = 0.1 mm
Threaded Miter elbows
90° elbow, r/d=1 30 26
45° elbow, r/d=1 16 14
Welded Miter elbows
90° elbow, sharp bend 55 49
90° elbow, r/d=1 19 16
90° elbow, r/d=1.5 13 12
90° elbow, r/d=2 11 10
45° elbow, sharp bend 18 16
45° elbow, r/d=1 14 12
45° elbow, r/d=1.5 9.4 8.3

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 sales@steeljrv.com

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

What is a Mitre angle?

A mitre cut refers to an angled cut on the face of two structures that will be joined to create a corner, which would then be called a mitre joint. A true mitre joint requires two pieces to be cut at 45 degree angles, so when they are joined the corner created will be 90 degrees.

What is the standard of mitered elbow?

ASME B31.3 – Process Piping
Process Piping is the piping that convey fluids under pressure or vacuum within the limits of a Petroleum refinery, Chemical plant, Gas Processing plant, Pharmaceutical, Textile, Paper, Semiconductor and Cryogenic plants and related processing plants and terminals.
This standard contains rules for piping typically found in the above-mentioned plants and it prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping.

What is angle of miter elbow?

Miter pipe elbows bending angle (θ):
15°, 30°, 45°, 60°, 90°, 135°, 180°

What is Miter bend in piping?

Another type of bend is a Miter bend. A Miter bend is a bend which is made by cutting pipe ends at an angle and joining the pipe ends. A true miter bend is a 90 degree bend made by cutting two pipes at 45 degrees and joining them by welding.

Summary
what are miter elbows - What are miter elbows?
Article Name
What are miter elbows?
Description
Miter elbows are not standard fittings they are fabricated from pipes. High skill pipe fitter is required to fabricate this type of elbows and Usually, they are preferred for size 10” & above because large size elbow is expensive.
Author
Publisher Name
www.steeljrv.com
Publisher Logo

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