Since ancient Roman aqueducts, water management has been continuously developed to become pipeline system and plastic appeared as the rising star material. With benefits of lightweight and flexibility, plastic was first used for pipes in the early 1950s, with continuous development of higher strength all along since then. Starting with PE63, the first generation of HDPE pipe material, followed by PE80 with an improvement of pressure resistance, the plastic pipe industry is now in the era of PE100, the third generation of HDPE pipe that was significantly developed in its key properties. In the present, PE100 is used to convey various types of flowing substances including water, gas (fluids), and slurries.
In 2014, SCG Chemical Co, Ltd. has successfully developed EL-Lene H112PC, an innovation with higher pressure with an MRS of 11.2 MPa. Our own developed polymerization process and special catalyst were selected to produce this advanced material, resulting in PE112 with no knee that perform beyond current conventional PE100.
The high flexibility is already very known for Krah-Pipes, and a basic reference for the bending is given by R=50 x DN/ID for long term and even R=25 x DN/ID for short term.
So technically these two cases have to be diveded, in long and short term examination. The long term is to reduce fittings (bends) and the shirt term aspect is during the installation e.G. using the S-sinking method in water applicaitons, relining. What is a easy way to make a detailed calculation, to be sure that the pipe will not fail. How to calculate the minimum bending radius for a Krah-Pipe with profiled wall structure, in helical style?
Rmin = α x DN [mm]
Rmin = minimum bend radius [mm]
The minimum bend radius is defined as the smallest radius to which the pipe may be safely curved.
A maximum of total strain elongation should not exceed:
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.
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:
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!
Postal subscription to ImProfil
From now on you will be able to submit to a postal subscription for the “ImProfil” - Newsletter on the www.krah.net homepage - just click here.