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FAQ - Part 3

This is the third 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.


Can Krah pipes be used for outfall and intake pipelines?
Yes, Krah pipes are 100% applicable for marine applications and have a multitude of successfully reference projects worldwide. Both Krah profiled wall pipes and Krah solid wall pipes can be used for outfall and intake pipelines. However, the profiled wall in combination with the Krah Electrofusion technology is mostly used.Notice: The Krah marine pipe profile provides a higher stiffness and buckling stability than normal solid walls. And also an axial strength is excellently given by using this special Krah profile!
How is the chemical resistance of Krah pipes against acid and lyes?
Krah pipes and Polyethylene products in general have been successfully used for decades in the chemical industry for transport of chemicals as well as for storage tanks. Notice: Polyethylene has a very good chemical resistance against most of acids and lyes.
Will Krah pipes float in the water?
Yes, Krah pipes are made of Polyethylene and Polypropylene, and due to being slightly less dense than water, they will float even when they are full of water. For underwater anchored pipeline installations, it is important to specify the proper weights and distance of the weights. Whenever possible, an underwater pipeline should be installed in a trench with a protective crushed rock cover.Notice: Krah can support you with designing marine pipes!
What is the maximum recommended flow velocity for possible fluids going through Krah pipes?
In a pumped system the maximum operating velocity is limited by the surge pressure capacity of the Krah pipe. If surge is not a consideration, water flow velocities exceeding 7,5 meter per second may be acceptable. This number can also be used as a maximum for gravity applications.
Will sunlight adversely affect Krah pipes?
Sunlight is not a concern if black PEHD material is used.Carbon black, utilized for black compounds, is the most effective ultraviolet stabilizer. Therefore, black is the recommended pipe colour for an exposed long-term service or storage. Krah pipes, made of a black PE pipe compound will provide decades of outdoor use!
ome applications require explosion protection, especially in explosive gas atmosphere – how can Krah pipes avoid a static charge?
Krah pipes can be made of electrical conductive Polyethylene for an anti-static behaviour. Mostly it is sufficient to produce the coextruded inner or outer layer with electrical conductive Polyethylene!
Are Krah pipes applicable for landfill technology?
Yes, Krah pipes provide a perfect chemical resistance against almost all hazardous media you will find in landfill application. Krah pipes are used for leachate drainage pipes, telescopic shafts for manholes, gas collectors etc.
Is thermal expansion and contraction of Krah pipes a problem?
No. All pipes expand and contract with change of temperature. The key is the management of the resultant thermal strain. As with all materials, expansion and contraction must be taken into consideration when designing a HDPE piping system. However, for above ground applications thermal effects must be considered - the unrestrained coefficient of thermal expansion for HDPE pipe is 0,18 mm per meter and degree temperature change (mm/mK).
Notice: Buried pipelines usually do not move due to soil friction, especially in the case of a Krah profiled wall structure!
Can Krah pipes also be used as tank shell for vertical installation?
Yes, we make a difference between vertical and horizontal tank applications. Vertical tanks are mostly used for an industrial application as like a storage tank for water or chemicals. For the design we provide the static software “PROFITank” which considers all load case scenarios (wind, sun, earthquake etc.). Horizontal tanks, made of Krah pipes are either buried in the ground or installed on saddles!
Systematic drainage is important to avoid flooding and soil stabilization! How can Krah pipes be used for drainage?
Krah Pipes for drainage application have already been used for decades. According to project requirements either slots or holes are implemented in the wall structure between the profiles. The holes/slots can be implemented at fully or partially circumference and can be covered by Geotextile ex work. Krah drainage pipes and manholes are available in all stiffness classes from DN/ID 300 until DN/ID 5000 mm.