To absorb the linear elongations, some compensation breaks are necessary by the direction changes (elbow 90°) and by branches (tee), to balance the expansion of a pipe piece, in case of fixed points.
Through the diagrams, the compensation break of the expansion (LAS) can be calculated, according to the pipe length and the working temperature. Length L is given by the fixed points (FP).
The minimun length (LAS) of the break for the dilatation compensation is to be calculated by the following formula:
LAS = length of compensation break
d = outside diameter in mm
Dl = linear elongation in mm.
K = constant for pipe = 20
NB: the compensation break is done through fittings of the same material (see pictures).
PRETENSIONED COMPENSATION BREAK
Installing the pretension arms, lengths become much shorter.
By the installation, one should tension the compensation arm; once the system starts working, this arm can absorb twice the linear expansion (see the pictures).
The calculation is identical to the previous one, taking into consideration that compensation is twice for the same break. A necessary preliminary remark is to know the data on the system future working in a precise way.
Calculation of the pretension arm LAS on The basis of the linear expansion dl/2
Examples of Pretensioned Arm
By the project, in case of installations out of the wall, one should provide for a right compensation of the axial movement. Most of the compensations can be reached through the direction changes.
If compensation through the direction changes only is not possible, the elongation can be balanced by an expansion joint made by the fittings selves
Example of Calculation for a Warm Water Network (60c)
PPR Pipes (Simple)
PPR Pipes with Fiber Glass + Aluminum