A flexible pipe, like Hebeish’s spiral pipe is by definition, a pipe which will deflect when subjected to external loads ( traffic, ground water changes,frost actions, soil settlement etc.) – as opposed to a rigid pipe, which carries all external loads by itself. The degree of deflection of a flexible pipe will depend on the pipe stiffness, support from the surrounding soil, and external loads.
|Properties||Property||Test Method||Typical Value|
|Melt index 190/5||g/10min1||DIN 53735||0.3-0.7|
|Yield stress||N/mm2||DIN 53455||24|
|Elongation at yield point||%||ISO/R 527||15|
|Elongation at break||%||125 mm/min||>800|
|Flexural stress at a given deflection||N/mm2||DIN 53452||28|
|Modulus of elasticity||MPa||900|
|Shore hardness D||DIN 53505||60|
|Notched impact strength||DIN 53453||no failure|
|Coefficient of linear expansion||K-1||ASTM 696||1,7.104|
|Thermal conductivity at 20oC||W/(m.k)||DIN 52612||0.43|
HDPE pipes are used in transporting liquids by natural sloping such as :
Compliance with the Egyptian code of practice for the design and installation of potable and sewage pipes.
Connection by butt welding through heating both ends of the pipes with hydraulic pressing by using welding machine.
The pipe stiffness is chosen in regards with soil type, bedding and backfill material, depth of installation and external live and dead load ( groundwater, traffic etc. ) on the pipeline. Please refer to national codes of practice for installation of plastic wherever applicable.
The bedding soil should be free from stone within the breadth of the pipe trench. On the trench bottom, a 10-15 cm thick bedding layer is prepared and well compacted. The bedding shall be at least 20 cm wider than the pipe’s outside diameter. For installations in soft/wet soil, a geotextile is placed under the bedding.
The primary backfill material should be friction soil or macadam. Backfilling should be made over the whole width of the trench. Compaction of the backfill material should be made in layer of 15-30 cm. The final layer or the primary backfill should extend 30 cm over the pipe crown. Note: No compaction is to be done directly above the pipe until the backfill has reached 30 cm above the pipe crown.
The final backfill is done in regard with the original soil and external loads ( traffic ). When deemed necessary, the compaction is carried out in several layers. The final backfill material can be compatible as dug materials. However, the material must be free from stones.
The recommended installation depth is 0.6m – 6m depending on external loads ( groundwater, traffic etc. ) For pipe sizes above 1200mm, detailed static calculations are normally necessary to determine