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Water hammer and how PE pipes react

For designing a pressure pipeline all pressure load phases must be considered and in reference to the loading time be evaluated. Besides the test-pressure, the maximum operation pressure (MOP) and also the water hammer effect have to be considered and implemented in the static design! This procedure is valid for all pressure pipe materials and systems, but flexible pipe materials provide some advantages.

What is a water hammer? 
A water hammer is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly. A water hammer commonly occurs when a valve closes suddenly at the end of a pipeline system, and a pressure wave propagates in the pipe. This pressure wave can cause major problems, from noise and vibration to pipe collapse. But it is possible to reduce the effects of the water hammer pulses with bypasses, expansion tanks, surge tanks, blowoff valves and other features. Rough calculations can be made e.g. by using the Zhukovsky equation, also known as Joukowsky equation.

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A new section of our newsletter will from now on be the “Frequently asked questions”, shortly FAQ. 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:

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Short news

Big & Beautiful calendar for 2018

Following the tradition of the past years we will publish a new calender by the end of 2017.
The pictures will be taken in October this year, with new models and pipe applications. If you know
someone who would look good between large pipes please let us know and he/she will eventually feature this year’s issue for 2018!

Krah Calendar 2018

Postal subscription to ImProfil
From now on you will be able to submit to a postal subscription for the “ImProfil” - Newsletter on the homepage - just click here.
Should you also have any matters you would like us reporting about or have any suggestions for our newsletter we would be happy about a short feedback from you - just send us a quick mail via our contact form or under This email address is being protected from spambots. You need JavaScript enabled to view it. and we will implement your suggestion in the next issue. We will publish a third edition of ImProfil in December 2017.

Top story from the Pipe and Profile Extrusion magazine

The Pipe and Profile Extrusion magazine wrote an article about our pipe production.
Here is an excerpt of the text:

It may seem like a case of sheer brute force, but the technology needed to produce large pipe – often more than 2m in diameter – requires sophistication and close control. After all, even a small increase in pipe wall thickness will mean a lot of material is being given away.

Krah Advanced Technologies (KAT) has recently developed new technology to produce large diameter pipes. It says that the equipment can be used to make structured wall pipes and solid wall pipes at high output – but without sagging problems or frozen stresses.
The company says that its KR800-Max production line has been used to make 1,000mm internal diameter SN8 pipe, at an output of 1,300kg/hour – including co-extruded inner layer with electrofusion and spigot.
Also, it was used to make 2,000mm, SDR11 pipe – for pressure or outfall applications – at an output of 1,400kg/hour.
The same machine has been able to extrude a pipe DN/ID2000mm, SDR11, for pressure or outfall application.
Also the solid wall had no frozen stresses and no sagging...

If you want to read the full article, just click on the download below.
The complete magazine can be read through this link.

New investments are almost completed (DN/ID5000mm)

From May 2017 on the Krah Group is able to produce machines which can fabricate a maximum pipe diameter of 5000mm.
For this purpose new machines were purchased and the infrastructure of the company building was changed accordingly.
The reason for these investments were several specific enquiries for polyethylene pipes DN/ID5000mm.