Entrance building of Krah Misr. The total production area has 10.000 m²

Every now and then Krah Group employees visit different Krah Pipes production plants. In April 2018 Alexander Krah went to visit the factory Krah Misr in Egypt.
Having arrived in Cairo he is warmly welcomed by the owners at the airport. The owners and managing directors are the two brothers Peter and George Yussuf Sadek.

Peter and George Yussef Sadek

The two brothers have been producing Krah Pipes for almost 10 years. Since the political changes in Egypt during these years, the factory was able to produce and sell large pipe systems successfully.
From the airport the group went straight to the production plant, where in a very modern and big office the two brothers held a company presentation. They showed how the company has been growing since 1975 – it was very impressive and inspirational to see how proud the two brothers were of what they had achieved. The whole production plant is in a very neat and maintained condition and the products (pipes, manholes, fittings and tanks) correspond to the international quality standards. Later this afternoon Alexander had the possibility to talk to Peter privately regarding several topics in a nice club-house.

Sinkhole in the United States, Source: Nationalgeographics, by Octavio Jones

Introduction

Anywhere in our world different kind of erosions happen which form our landscape – on the surface as well the subsurface. The most significant factor of erosion is water (beside wind, landslide and abrasion) which is causing a challenge in engineering problem. The ability of water to move soil and rock depends on several factors. The faster and more turbulent the flows of water, the more erosive characteristics are appearing. Larger particles like gravel are more resistant to erosion than small particles like silt or clay. Finally, rather than physical erosion, some materials dissolve in water, just like sugar or salt. It can be eroded just by dissolving into the ground water from time to time.

Some kinds of soil are more affected than others – i.e. dolomite areas, etc. Most natural sinkholes occur in areas with large deposits of carbonate rocks like lime stone. Over long periods of time, ground water flowing through the subsurface can dissolve the rocks, creating voids and open tunnels. In fact, this is how most caves are formed – a creative name of sinkholes is also „Internal erosion“. A sinkhole is a feature that occurs suddenly and manifests as a hole in the ground.

Huge sinkhole, Source: Nationalgeographics, by Octavio Jones

Around 100 km from Stockholm you will find Västeras, a large city at Lake Mälaren, the third biggest lake in Sweden. Västeras is a big industrial city that was founded over 1000 years ago. In the past year they had some trouble with leakages in the sewer system. High rainfalls had led to full pipes which resulted in an overflow into Lake Mälaren.

Sewage collection tank during installation

Krah Pipes Manhole

Therefore a quick, durable and reliable solution was needed. The engineering company Mälar Energie AB contacted Krah pipes yet again in January 2017 to plan the project for a 950 m³ sewage collection tank of DN/ID 1600 mm with a DN/ID 2000mm manhole. The first pipes were shipped already in October 2017, the project was finished in March this year. The manhole is equipped with a flow regulator 150 l/s from Mosbaek A/S. The incoming flow to the manhole is 350 l/s if the incoming pipe is working with full capacity. The pipes were delivered in lengths of 6 Meter including rubber gasket. In a whole, 41 trucks were needed to deliver the whole amount to the construction site.

Skyline of Jakarta

1. Basis

The development respectively the renovation of waste water ischarge system is always associated with high investments and extensive civil engineering works. Beside the purchase costs for the pipelines itself, also high proportionate costs arise for the grounds works and the pipe installation. 

Especially in topographical flat Asian metropolitan areas like Jakarta, the pipelines can often only be installed with a low longitudinal slope. Thus, the hydraulic capacity of the pipelines is decisively limited. Increasing the longitudinal slope again means expensive, extensive, technically sophisticated excavation works. In Asia, most sewage and drainage systems are made out of concrete. Those pipes have a very rough pipe wall and have a lot of connections, due to their production process and quality. By using suitable pipe materials that guarantee smooth walls and need much less pipe connections, the longitudinal slope can be reduced while maintaining the dimension and the hydraulic capacity. Thus, also the costs for excavation and civil works can be reduced considerably. Smooth walls also optimize the discharge conditions and especially avoid depositions during dry weather flow.

2. Dimensioning of the pipeline