PE drainage pipe systems

PE drainage pipe systems

- Flow resistance. Regression curves
- Ageing
- COESTILEN® specification





COESTILEN® is a high molecular weight HPDE with a density of 0.952 g/cm2 and a melt fluid index of 0.5 g/10 mm with a 5 kg load.

These properties grant excellent resistance to thermal and mechanical stress and make it usable for both domestic and industrial plants which are technically adequate under the most difficult working conditions.



1. Flow resistance. Regression curves

The life of HDPE waste pipes depends on their flow resistance under stress.

According to the internal pressure and the working temperature, it is represented by curves which provide the stress time values, at different temperatures, minimum acceptable values according to the DIN 8075 type 2 provisions.

At different temperature values, the pipes undergo variable pressure values at which stresses are obtained on the walls. They are given by the following formula:

p = P(De - s)/2s
p = stress kg/cm2
De = External pipe diameter
P = Pressure
s = Pipe thickness

The curves show that the life of a pipe depends on the values of both mechanical and thermal stresses that it undergoes.

The concomitance of both stresses results in short life.

COESTILEN® pipes, designed to work without pressure, have a practically unlimited life.

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2. Ageing

Polymers are subject to deterioration mechanisms because of degradation and oxidation.

Degradation is mainly due to light, especially to the ultraviolet one, as its photons have sufficient energy to fragment the macromolecules in other small molecules, thus worsening the material properties.

These inconveniences can be overcome by adding to raw material carbon black, which, by absorbing luminous radiations before they can interact and degrade the polymer, acts as a stabilizer. The carbon black used in COESTILEN® pipes meets the following requirements:
- quantity 2.0 <NOTE> unknown </NOTE> 2.5%
- density 1.5 <NOTE> unknown </NOTE> 2 g/cm3
- average particle size 0.010 0.025µ

CO.E.S. spa only uses initially pigmented polyethylene and does not make use of any regenerates or extruded neutral granule polyethylene.

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3. COESTILEN® specification

Thermal stability
COESTILEN® keeps its physical state and its characteristics unaltered at temperatures ranging from -40 °C to +100 °C. This allows it to be used without any mechanical stress, for applications where other materials would not give the same results and guarantees.

Low thermal conductivity
Like all plastic materials that do not have any free electrons able to carry energy with them by a thermal gradient, COESTILEN® is a bad heat conductor. This characteristic allows the material to be subject - for short intervals - to higher thermal stresses than the operating ones, because, due to delayed heat transmission, the material does not reach a uniformly distributed temperature which is close to critical values. For the same reason, the temporary passage of low temperature fluids does not cause condensation.

Dimensional stability
After extrusion, the COESTILEN® pipe undergoes a stabilization process by annealing. This avoids - once it has been laid - shortening due to heat reversion.

Elasticity

COESTILEN® is elastic enough to withstand external stresses, impacts and deformations. Besides, should the pipes full of water freeze, the material can increase its volume and then get back to its original shape.

User-friendly
COESTILEN® is lighter than water. Its low specific weight makes working and laying on site easier and it allows the material to be quickly laid.

Smoothing and abrasion resistance

COESTILEN® has very smooth walls which prevent the formation of deposits causing the pipes to be clogged, and facilitate the water outflow, thus eliminating any abrasion phenomena that solid substances might cause.

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