PREMANT district heating pipe
Installation guidelines
Sheet 3
Pipe bends, minimum bending radius
If district heating pipes have to be laid along roads, it may be necessary to use pipe bends in
order to keep close to curves. In this case, the bends can be assembled from several straight
lengths of pipe. Up to an angle of 3°/5, these bends can be produced with mitre cuts but for
larger angles, only preformed parts can be used.
This pipe curvature causes bending stresses in the pipe which make it mandatory to set a
minimum bending radius in relation to the pipe dimension. The minimum bending radius and the
resultant maximum deflection are calculated as follows:
PRE 6.265
Bending radius for elastic-plastic strain on site
DN
da
R
min
mm
m
20
26.9
19
25
33.7
23
32
42.4
29
40
48.3
33
50
60.3
41
65
76.1
51
80
88.9
60
100
114.3
77
125
139.7
95
150
168.3
115
200
219.1
150
250
273.0
170
R
zul
S
Installation with small bends (kinks)
h=R·
[1- 1-(s/(2·R))2 ][m]
R
permitted
= minimum bending radius [m]
S = chord length [m]
h = maximum deflection [m]
d
a
= outerdiameterofsteelpipe[m]
Sliding zone: Bends up to a maximum of 3° are allowed in mitre cuts.
Adhesion area: Bends up to a maximum of 5° are allowed in mitre cuts.
The bends must be installed without expansion pads.
Reductions in the adhesion area
In accordance with the various stress cross-sections, there is inevitably a sudden rise in the axial compressive force
progression in the reduction.
The greater compressive force in the area of the larger dimension may result in an overload in the smaller stress cross-
section, as a reactive force. This can be excluded either by avoiding reductions in the adhesion area, or by positioning a
fixed point on the side with the larger dimension.
Fixed point
Reductions in the adhesion area
d2
d1
23.5.2023 BGP
Subject to technical changes
h
