SYGEF Product Catalogue

Calculation of change in length and flexible sections
The change in length caused by temperature can be the installation temperature, then the pipe expands. If,
calculated using the following formula:
on the other hand, the operating temperature is lower
than the installation temperature, then the pipe contracts
in length.
with:
Ï ”L = temperature-related change in length (mm)
Ï L = length of the pipe section (m)
Ï ”T = difference of temperature (K)
Ï ± = coefficient of linear expansion (mm / m K)
Some coefficients of linear expansion of polymers:
Material
± = mm/m*K
ABS 0.10
PA 0.10
PE 0.15 - 0.20
PP 0.16 - 0.18
PPS 0.15
PVC-U 0.07 - 0.08
PVC-C 0.06 - 0.07
PVDF 0.12 - 0.18
The installation temperature must therefore be
incorporated into the calculations as well as the
maximum and minimum operating temperatures.
1. Pipe at installation temperature
2. Operating temperature above installation temperature
3. Operating temperature below installation temperature
Important:
Ï It is preferable to use + to indicate expansion of the
pipe and - to indicate contraction.
Ï The larger change in length is the one to be used for
determining the required length of the flexible section.
Important: If the operating temperature is higher than
Calculating the length of the flexible section
The required length of the flexible section can be
calculated using the following formula:
with:
Ï da = pipe outside diameter (mm)
Ï ”L = change in length (mm)
Ï E cm = average bending creep modulus for t = 25 a
(N/mm²)
Ï Ã b = permitted bending stress for t = 25a (N/mm²)
Boundary conditions for using the diagram
For easy determination of the required length of flexible
section please use the following diagram. Please take
into account the given boundary conditions.
Ï Assembly temperature T M = 20 °C
Ï T B Operating temperature
Ï ”T = T B - T M
Ï allowable bending stress 15 % of à v
Ï PN 6 .. 16
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