Curved pipes
S&D
Projecting with Curved Pipes
To convert the information of a pipeline plan to a usable curved pipe can be
difficult because both the projected and the bent radii and the straight pipe
ends have to be considered. Furthermore, it can be difficult to mark out a
curved pipe in the field, and this info is, therefore, meant as an assisting tool.
For production reasons a curved pipe is manufactured with a straight pipe
piece at each end. The length of the straight pipe ends will appear from the
catalogue.
Radii:
The projected radius Rp and the manufactured bent radius RK will not be the
same (see enclosure 1 for definitions). As the angular motion will always be
the same the radii can be calculated according to the following formulas:
Rp 
180  L
V
Rk 
180  ( L  2  L 1 ) R p  ( L  2  L 1 )

V
L
Where:
Rp = Pojected radius
Rk = Bent radius
V = Angular motion in degrees
L = The total pipe length
L1 = The length of the straight pipe piece.
Theoretically there will be a difference between the radius of the outside and
the inside pipe of a bend. However, this is of no importance as curved pipes
can only be produced with a tolerance of ± 1°. Our Catalogue, states the
maximum angular motions possible.
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Curved pipes
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GEOMETRY:
Defining an angle:
When the pipeline is marked out in the field it is possible to define the angle.
The easiest way to do so is by means of an isosceles triangle (see enclosure
2)
b = The length of the two straight legs.
c = The length of the third leg.
V = The angular motion in degrees.
c 

V  180   2  argsin


2  b
Example:
Find the intersection of the two directions in the field. Measure out 40.00 m in
both directions. The chord between is measured to 77.275 m and the angle V
can be calculated in this way:
77,275 


V  180   2  argsin
  30

2  40,00 
See enclosure 2.
Defining the distances:
The distances may be defined according to the below formulas. Use the
projected radius or the bent radius as the case may be (see enclosure 3).
Radius:
Rf
cos( V / 2)
1  cos( V / 2)
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Curved pipes
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The distance from the vertex to the bent:
f 
R
R
cos( V / 2)
Arrow height:
p  R  R  cos( V / 2)
The distance between the tangent point and the vertex:
A  R  tg( V 2)
The distance between tangent points (chord length):
k  2  R  sin( V 2)
Arrow length:
S
RV
180
End displacement:
Where more curved pipes in succession are required to obtain the necessary
angular motion the length of the bend is adjusted to an entire number of pipe
lengths. The angular motion is divided by the necessary number of pipes. To
get the right curve out in the field, it is very important to define the midpoint of
the curve and work from the midpoint to both sides.
In connection with large dimensions and angular motions there will be an end
displacement between the external and the internal pipe. This is of special
importance when several curved pipes in succession are used. In these cases
it may be necessary to insert a middle piece on the pipes at the ends or to
shorten the straight pipe of the internal pipe.
The displacement can be calculated approximately:
L f  ( D  a )  tg( V 2)
Where:
a = The distance between the district heating pipes.
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Curved pipes
S&D
D = The casing diameter.
See enclosure 4
Ordering curved pipes:
When ordering curved pipes it is important to state the correct information:






Dimension
Series
Monitoring system
Length (12 or 16 m)
Angular displacement per pipe length (is stated in jumps of 1°)
Number
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Curved pipes
S&D
Enclosure 1.
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Enclosure 2.
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Enclosure 3.
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Enclosure 4.
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