TEPPFA - Structured Wall Pipes in Civils

Plastic structured wall pipes and fittings have been used in Europe for over thirty years. As their name suggests, these pipes are differentiated by a pipe wall that has a structured external profile or are composed of different layers to give an improved performance and to meet the stringent requirements of a drainage and sewer system.

The growing market share of plastic pipe systems in Europe is partly the result of continuous innovation, resulting in more effective and efficient concepts. These concepts, like structured wall pipes, can only be successful when serving the basic customer need: quality!

Standards have now been set and TEPPFA is confident that performance will endure.

The standard EN 13476 “Plastics piping systems for non-pressure underground drainage and sewerage - Structured wall piping systems of PVC-U, PP and PE” covers the performance requirements for high quality Structured Wall Pipes (SWP)

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Performance

The characteristics and requirements of the pipe systems described in this standard are performance based (table 4) See table below for system performance and the adequate characteristic:

System performance	Characteristic
Handling, transport, storage and installation robustness	- Impact strength
Resistance to soil load including traffic load both during and after installation	- Ring stiffness - Ring flexibility - Tensile strength of seam - Creep ratio - Mechanical strength
Ability to hold fluid inside and outside the system (leak-tightness)	- Dimensions and tolerances - Tightness - Long-term performance of seals - Water tightness - Tensile test of welded and fused joints
Resistance to high temperatures	- Elevated temperature cycling test
Cleaning and maintenance	- Resistance to jetting
Durability in processing	- Material characteristics
Durability in material	- Resistance to internal pressure - Chemical resistance - Thermal stability

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Structural Design

Because of the large variations in construction combined with the materials, the structural design is given as a design graph based on the deflection history of pipes installed under different conditions up to 25 years ago (see also the TEPPFA-Buried Pipes study). The design graph specifies the long-term deflection in relation to the pipe ring stiffness based on the compaction of the surrounding soil.

This design graph is valid from an installation depth from 0.8 m to 6.0 m with three classes of compaction: well (proctor density of >94%), moderate (proctor density from 87 – 94%) and none. The installation categories should reflect the workmanship on which the designer can rely.

For all applications and installation conditions the calculated structural design must use the parameters as defined in CEN/TS 15223.

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Stiffness Class

The stiffness has been classified as SN (nominal stiffness) values in the categories SN 2, SN 4, SN 8 and SN 16. No other values are allowed. The stiffness as measured shall be rounded to the next lower stiffness class and marked accordingly.

For the stiffness of the system composed with pipes and fittings the stiffness of the pipes is most relevant. Therefore fittings with a compact wall (EN 1401 PVC-U, EN 1852 PP and EN 12666 PE) may be one stiffness class lower.

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Cleaning Techniques

For a long lasting performance of piping systems in the field of gravity drains and sewers, a regular cleaning regime is appropriate. One should refer to the European standard for the management and control of these cleaning operations. Conditions are specified for a recommended practice for pressurized jetting to clean and unblock sewer pipelines while minimising any risk and damage to the pipe system.

New plastic pipes, as well as those, which had been in service for years, were subjected to 120 bars water pressure with a 2.8 mm nozzle over 50 cycles without any damage to the plastic pipe.

Reference is also included for supplementary cleaning techniques as cleaning ball, flushing, rodding, winching and root cutters.

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Interchangeability

The nominal diameters for the various constructions are based on the outside diameter (OD) in case of the type A (smooth inside and smooth outside and hollow wall). In the case of type B (smooth inside and profiled outside), the nominal diameters can be based on the inside diameter (ID) or the outside diameter (OD) of the pipe. The internal diameter shall be used as given in the geometry tables for calculations involving the capacity of the system.

In general, the OD-systems show a good interchange ability from one manufacturer to another. In this case, standardised fittings can be used everywhere.

For ID-systems, each manufacturer has to deliver his pipes with special designated fittings for his system. In principal, there is no interchange ability at all. In many cases, special adaptors can be obtained from the manufacturer.

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National Foreword

A possible deviation from the preferred requirements for Ring flexibility (30%) and for Impact requirements (0°C round the clock) must be referred to in the national foreword of all EU-member states that are publishing this norm. If there are climatic or other regional habits, a member state can specify a ring flexibility of 20% and impact requirement at 23°C or -10°C.

Read more … Abstract, SWP acc to EN13476

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