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FAQ - Part 2

This is the second part of our “Frequently asked questions” section. In every issue we will answer some of the most asked questions we get from potential customers and interested parties about the Krah Technology.
Also feel free to send us some new ideas for our FAQ in he form below. We will try to publish as many as we can.


What is the stiffness of Krah manholes?
The minimum stiffness is defined as SN2 in EN13598. Further all other stiffness classes can be manufactured if required and necessary!
Can Krah pipes resist inner pressure?
Yes, due to the tailormade design any Krah pipe provides a certain solid waterway wall-thickness for the requested inside pressure.
What is the maximum size and height for Krah manholes?
Typical Krah manholes are used in a maximum depth of 10-12 m. For bigger depths Krah recommends the telescopic manhole design which is used for landfill application as well. The biggest manhole diameter is DN/ID 5000 mm.
What kind of fittings do the Krah system povide?
Krah fittings are manufactured in the Krah factory. All necessary fittings and even customized design can be manufactured: bend, elbow, stub-end, flanges, reducers, T-branches, Y-branches etc.
How high is the vacuum / buckling pressure resistance of Krah pipes?
Krah pipes provide a very high buckling pressure resistance due to their structured wall design. The bigger the pipe stiffness, the higher the buckling pressure resistance.
What is the installation speed of a Krah pipe?
The installation speed of a Krah pipe is very high and a big cost-advantage for the contractor. Because of the Krah Electrofusion system the pipe strings can be installed in final position and be parallelly or later on welded. That guarantees no time loss!
Is the load capacity of buckling pressure and inner pressure the same?
No, it isn’t comparable! The inner pressure capacity mainly depends on waterway wall thickness and material strength. The buckling pressure capacity mainly depends on geometry (moment of inertia) and the flexural modulus.
What is the most efficient manhole design for larger pipe diameters?
The most efficient manhole design are tangential manholes – the tangential manhole design is becoming more and more popular, because it considers all the advantages in fabrication of Thermoplastics and helps to save costs!
What is the welding time of Krah pipe electrofusion?
Krah designed the Electrofusion process to guarantee maximum quality at minimum of welding time. The welding time of Krah Electrofusion Joint is not more than ca. 20 minutes or any diameter!
Is it possible to recycle Krah pipes after usage?
Krah pipes are made of Polyethylene (PE) or Polypropylene (PP) and can be recycled! Important is cleaning and separation of the contents. Multitude of professional recycling companies are established worldwide. PE and PP are also after their first product life worthful resources!
How is the axial load capacity for Krah manholes?
The axial load capacity has the same importance for the design of manholes as the stiffness! Axial loads by direct load induction from the top or down drag forces gets transferred and absorbed by the solid wall thickness. Krah manholes can be produced with any required solid wall thickness to fulfil a maximum of axial load capacity!
How is the fitness of purpose for potable water applications?
Krah Pipes can be made of approved raw material for potable water application and fulfil all requirements! The high pressure-capacity and the homogeneously jointing method complete the fitness!
Why is the nominal diameter of Krah pipes an inner diameter and not outer diameter like the PE pipes?
Krah pipes are calibrated to an inner diameter. The inner diameter is the important diameter for hydraulic aspects and general planning! The stiffness and pressure capacity can be adjusted without any change of the inner diameter.