HDPE Krah Pipe

A structured wall pipe or profiled pipe has a very low weight, but at the same time can be used for high external load applications. The supportable static load is determined for every profile geometry by the factors; elastic modulus [N/mm²] of the respective material and the moment of inertia of the profile geometry [mm4/mm] referring to the pipe diameter. The result is called ring stiffness. By using a profile design pipe, the weight can be reduced up to 65% compared to a solid wall pipe with the same ring stiffness. Krah pipes offer the best security and durability. The wall thicknesses of our pipes can be adapted in various sizes to cater the respective load. The main properties of the structured wall pipes is the smooth inside and the profiled outside. The fields of application for these kinds of profiles are pipeline systems like sewer, drain, storm drain and ventilation.

Material:

The base material, high-density polyethylene (PE80, with a minimum MRS of 8.0 N/mm² or PE100, with a minimum MRS of 10.0 N/mm²), is normally stabilized by the addition of carbon black. On special request and for special applications other polyolefin can be used, like for example polypropylene grades.

Pipe ends:

The pipe ends are cut in-line, in 90° angle to the pipe axis. Should electrofusion joints or bends be produced, the pipe ends are produced accordingly with socket and spigot.

Surfaces:

The internal and external pipe surface is smooth. Slight corrugation (especially on the outer surface), which necessarily involves variations in the wall thickness, is acceptable providing that the thickness of the pipe wall is at no point less than its given nominal value. The inner surface can be produced of electro conductive or inspection friendly coloured material.

Production process:

HDPE Krah pipes are produced according to the Krah spiral cross-winding extrusion process. During the production process, the pipe is produced seamless and all sub-processes are continuously controlled by the integrated CPV and control visualizing software. The first layer is produced on a heated calibration mandrel, the next layers are produced cross-over accordingly on top of the previous layers. The previous layers are heated by an IR-Heating system to provide a surface temperature between 170°C and 200°C. With the help of the co-extruder the inner surface can be produced with an inspection friendly, coloured polyolefin material. The orientation of the molecules is in radial direction, which has a positive effect on the internal pressure. Another important quality advantage is, that due to the slow cooling down process no frozen stresses will occur in the pipe wall.