CALCULATION OF EXPANSION LYRES
Calculation of expansion loops: REPOLEN pipes are subject to thermal expansion just like all other building materials. This necessitates compensating for this expansion during the installation calculations. Several formulas exist according to UNE ENV 12108: 2015 IN.
INITIAL INFORMATION
SECTION CALCULATION
(m)
ΔL (mm)
- ΔLes is the increase in length that the tube will have due to the expansion, in millimeters.
- L is the length of the tube over which the expansion is calculated, in meters.
- α is the coefficient of linear expansion in mm/mºC.
- ΔT is the temperature difference between the transported fluid and the ambient temperature.
- LB is the total flexible arm
- LD is the length of the cross arm
- LA is the length of the longitudinal arm – LA = 0.5 LD
- k is the specific material constant; for PPR, k = 20
- D is the nominal diameter of the pipe
CONSIDERATIONS ON THE CALCULATION AND INSTALLATION OF EXPANSION LOOPS
- If there are many fixed anchors, the capacity to absorb movements is reduced.
- Repolen pipes usually require expansion joints starting at 10-15 mm. Up to 10 mm, expansion is absorbed in elbows and anchors.
- The greater the free length, the greater the expansion. If the expansion joint is not installed, the pipe will “push” on the anchors, potentially damaging supports or insulation.
- Expansion is usually taken into account starting from 8-10 meters in length of pipe.
These expansions must be calculated between fixed points or changes in direction. Depending on the geometry of the installation, the temperature difference between the temperature of the transported fluid and the ambient temperature, the pipe type, the arrangement of moving or fixed points, and the length of each section, the installation will absorb the expansions and contractions it may experience during its service life to a greater or lesser degree.
As stated in the Technical Building Code:
The laying of cold water pipes must be done in such a way that they are not affected by heat sources and therefore must always run separate from the hot water pipes at a distance of at least 4 cm.
In any straight section without intermediate connections exceeding 25 meters in length, appropriate measures must be taken to prevent excessive stress on the pipe. The best location for these measures is equidistant from the nearest branches on the risers.
The most common practice is to insert U-shaped expansion joints along straight sections. It is recommended to position the U-joint horizontally or upwards, but never in an inverted U shape. Another possible option is the installation of compensating expansion sleeves, which is very viable in installations where there is limited space to adjust the pipe layout.
The compensators or sleeves used must be manufactured for use in polypropylene or polyethylene piping. Clamps marked PF are clamps that fix the pipe (anchor or fixed point), preventing any movement. Clamps marked PD, on the other hand, allow movement in the same direction as the pipe (guide or moving point). The size of the fixed points depends on the axial and transverse forces generated by the expansion of the piping, plus the forces generated by hydraulic pressure.
