We wanted to do an interview with an engineering company to find out the crucial points to use our pipes for their projects. Therefore, we have contacted the in Germany well known engineering office Müller GmbH Co. KG in Grünberg, Hessen. On a wednesday morning, I met  Dipl.-Ing. Maik Ginsberg in his office to have a coffee and a chat with him. He has been working with Polyethylene pipes for over 20 years. In his engineering office in Grünberg, he plans projects for sewage systems, drinking water, tanks, water treatment plants and road construction. 

Which kind of projects do you work with?
I work with large diameter pipes, mostly in the sector of canal construction, drinking water canals, tanks, water treatment plants and road construction.  Which requirements do you have for modern sewer pipe systems and which on suppliers?
First of all, the most important feature for sewer pipe systems is the tightness, which is given by plastic pipes with a  welded socket. Other important features concern the installation and handling. Especially for large diameter pipes the weight is a key factor - that‘s where plastic pipes come in handy. In terms of requirements for suppliers it is especially important that they stick to the stated delivery terms, which can be achieved by pre-fabricated pipes that only have to be connected together. 

How important are storm water retention tanks for you?
Depends on the factors, which volume of water do we have, what kind of receiving water do I have? Can I drain off enough, do I have to install storage space? It must be designed accordingly. With today‘s punctual heavy rainfall events, there is an increasing need for a buffer so that the water bodies are not completely polluted. It is noticeable that more reservoir channels are being installed. There are also demands from the licensing authorities to install more. The significance is growing all the time.

How do you estimate the follow-up costs of leaks in sewers?
Leakage is bad in any pipe. The first goal is to lay the pipes in such a way that we do not have any leaks. In the case of completely welded pipes without rubber gaskets that can become leaky, we have produced a homogeneous product without any foreign material (rubber gasket), theoretically nothing can happen. If it is properly welded, nothing can happen.

Which pipe materials do you use for water and sewage projects?
Depends on the client. There are municipalities where we specify this, but some operators also have specifications. Water: cast iron and Polyethylene, in our area we were a bit heavy on cast iron because we have the Buderus cast iron here. When I started here 20 years ago, Polyethylene was only rarely used, water pipes were all made of cast iron. That has now changed, the proportion of Polyethylene is currently increasing.Sewage: mainly plastic pipes, but not always just Polyethylene. Polypropylene or PVC are also used. A small niche product, although this is becoming more and more common, is a combination of concrete and plastic pipe. Here in Hessen, a new system has been developed, Polyethylene pipe wrapped in concrete. This is very much in vogue at the moment. In terms of cost it is somewhat more expensive than Polyethylene, but the advantage is its high stability. The problem with our bending soft pipes is the deformation. This is always controlled by the calibration, which gives the 6% short- and long-term deformation. If you have a client who really pays attention to this, it is difficult to keep to this. The pipe doesn‘t mind, but explain this to someone: it‘s crooked now, but it still works. 

How long have you been using Polyethylene pipes in your projects?
For 20 years, since I came here. The Polyethylene pipe was introduced here via Alexander. The older colleagues had nothing to do with it. When I started here, a bit of fresh wind came in, and with it the Polyethylene pipes. 

Where do you see advantages and disadvantages in Polyethylene  pipes?
Advantages: Handling due to low weight, sustainability due to the long service life, tightness through welding or sleeves, if it is done sensibly, nothing can happen. Disadvantages: partly with higher nominal diameters the long welding time and cooling time, because this is a downtime factor on the construction site. In the case of large storage ducts, this is already reflected in the long minute times. I am not allowed to do anything else on the pipe during this time, neither backfill it nor attach the next pipe. This also partly cancels out the price advantage. On the one hand, I come cheaper because I have a cheaper pipe, but on the other hand I have to charge the working time of the column, which almost cancels it out again. 

In your opinion, has the cost structure for sewage systems changed?
With larger pipes, we have lower wall thicknesses, correspondingly less excavation and less disposal. Today, the disposal factor is the factor that has a considerable impact on the cost structure due to the grouping into the storage classifications at the Arbeitsgemeinschaft Abfall.  This saves excavation, disposal costs and backfill material due to the smaller trench width. What are your customers‘ current expectations of pipe systems?Durability, tightness, low cost, low maintenance (less deposits).

Corona - how does Corona change your current plans?
Is there more or less planning, is there less money from the municipalities?No. At the moment it is not visible. Of course, it‘s impossible to predict what the future holds. At the moment the municipalities receive subsidies from the federal states and the federal government because of the defaulted trade taxes and so on. At some point, the federal government won‘t have anything left or will have to bring it back in. But at the moment nothing has hit us, we do not notice anything yet. 

What project are you currently working on?
Currently we are planning and building a reservoir sewer with 1800 DN ID large capacity profiles and an elevated drinking water tank with a capacity of 600m3 in Hessen.

Thank you very much for your time and your interesting answers. Finally, I have an important question: Do you have a dog?
Hm... no! Okay, nice to know! We hope that your company will get through the Corona crisis well and wish you and the company all the best!  
Jenny, Krah Pipes

Life goes on…

For more than 7 months, COVID-19 has had the world firmly under control. When the virus first appeared in December 2019 in Wuhan, probably nobody over here expected that this virus would present us with major challenges of any kind.  A strong economy, a well-functioning health system and trust in politics – what could happen to us? But with the latest occurences of COVID-19 in the Western countries we were taught better. Italy and Spain were on the brink of disaster, thousands of new infections daily, the number of deaths increased by several hundred persons a day. The hospitals are completely overloaded, trucks full of dead bodies and desperation all over the country. The USA, which initially thought it was safe, was also hit very hard. 

Of course, Germany was not spared either. 200.000 infected and 9.000 dead by COVID-19 are currently reported for our country. Despite these numbers, we still got off relatively lightly in Germany, thanks not least to our good healthcare system and the rapid intervention of politicians. Nevertheless, our company also had to take measures at the beginning of March to slow down the spread of the virus. Therefore, all office staff were sent to work from home and the production staff worked in shifts to have as little contact with each other as possible. This change was well-received by everyone and worked without any problems. Production continued throughout the whole period and we were able to stay on schedule. Many companies did not have this luck and had to close for several weeks or months, for some it has cost them their existence.

In the meantime, life has returned to normal so far, but some restrictions still exist and will probably keep us busy for some time. Nevertheless, everyone is happy about a certain normality, even if nothing will be the same as before COVID-19. A certain caution and fear will remain in each of us. The virus has shown us how vulnerable we actually are and how quickly the world can be shaken. But it also showed us, what kind of luxury we live in. Seeing family and friends at any time, going out for dinner in the evening, going to school and work every day, just going on holiday for a short time - all this has not been possible in the last time. Perhaps the virus also did reset us a bit, slowed down life a bit, appealed to humanity and taught appreciation - let’s hope that this lasts longer than the virus itself!

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The static calculation tool in the Krah Mickey software provides structural static calculations following either the design manual M55 of the American Water Works Association (AWWA) or the Australian/New Zealand standard AS/NZ2566.1. Both documents are worldwide spread and accepted.
The Mickey static tool is now getting completely revised and provides in future also a reviewable print out with input data, intermediate and final results. To simplify the handling the input can be done in imperial or in metric units. 

All results are calculated accordingly. Reasonable assumptions are already preadjusted, so for example the recommended bedding angle of 120° and in general good bedding situation is already premised. The values for strength and flexural modulus are suggested for the typical pipe materials and all considered load-times. For native and embedment soil the modulus of soil reaction is considered accordingly relevant tables of the standard. But the user has always the possibility to make changes in the values. After all inputs are made, the software follows the equations and tables of the manual to calculate all external dead and live loads. For the dead load a practical and conservative approach for the designing is considered, arching is ignored and it is assumed that the dead load on the pipe equals the weight of the column of soil directly above the pipe. Arching tends to transfer some of the weight of the backfill to the soil beside the pipe and thus reduces the load on the pipe. The main live loads are traffic load, surcharge load, groundwater table and vacuum load.

Following final results are calculated:
- Wall buckling proof (AWWA M55,  equation 5-10)
- Ring deflection proof (AWWA M55, equation 5-8)
- Vacuum stability proof (AWWA M55, equation 5-14)
- Compressive stress proof (AWWA M55, equation 5-15)

Furthermore additional proofs and interesting key-factors of the pipe are calculated, like stiffness and internal pressure load capacity. All proofs are made for different loading-times: short term, mid term (3 month) and long term (50 years). Due to calculation for different load times any peak-loads for example by internal vacuum load or by changing ground water table can be better considered. Of course more proofs and analysis can always be made, but the results provide already a good basis. We are open to integrate more proofs or to make changes if needed – just send us your ideas and comments.
This structural calculation is done according to AWWA M55, PE PIPE - DESIGN AND INSTALLATION, chapter 5 “External Load Design”. All mentioned numbers for tables (Tab) and equations (Eq) refer to this standard. The results provide a good basis for further statical considerations and examinations. Some additional aspects like e.g. internal pressure resistance, pipe stiffness etc. are scanned and mentioned. The user is requested to verify the input data and results according to local requirements and if applicable for kind of project.
The structural calculation presumes adequate handling of pipes according to manufacturer’s recommendation  and installation of pipes according EN 1620 or equivalent. For pipe bedding, Krah Pipes recommend a standard bedding angle of 120° and backfilling with compactable granular soil with little or no fines (GW,SW).

Author: Krah Pipes GmbH  & Co. KG

Sustainability hasn’t just become a trend in the past few years – it is also urgently needed. The demand for sustainable products is continuously growing faster. The improvement of energy and resource efficiency in companies all over the world will play an even greater role in the future.

Krah cutting mill for more sustainability
As a large mechanical engineering company, we are of course also thinking about how we can become even more sustainable. Therefore, we have now developed our Krah cutting mill. It enables a direct reuse of processed material. Even if there is hardly any waste during the production of our plastic pipes, it can happen now and again that pipes are not used or have been processed incorrectly and are therefore not used. 
In addition, during pipe production, so-called lumps are formed when the raw material is heated in the extruder, which can then not be used. These lumps can be shredded up to a size of 500x200x400 mm in the cutting mill. Pipe segments can be processed up to a size of 500x1500x150 mm. For this purpose, the material is thrown into the feeder and then homogeneously crushed by a single-stage mill. The grinding mechanism is made of a metal part and therefore guarantees enormous stability and a long service life. Depending on the material, the grinding capacity of the mill is between 250 and 500 kg/hr. With a motor power of 75 kW, the mill crushes the raw material into homogeneous free-flowing and sharp-edged material with an average size of about 8 mm. It can then be used directly for pipe production via the machine’s dosing system without the material first having to be processed in a granulator. The shredded material is filled into big bags or suitable containers by an automatic suction system with a hose. A filter system ensures that fine dust is absorbed directly and does not get into the environment.

Comfortable and easy operation
To make working with the cutting mill even more comfortable, a sound insulation can be bought accordingly to reduce noise. But prefarably, the machine is operated in a separated room/hall. Furthermore, the filling level of the material can be checked through a window. The robust cutters can be used double-sided and guarantee a long lifetime and low maintenance costs of the machine. Additionally, the mill only needs a working space of 3x3 m. 
With this mill we can finally offer a machine which makes our products even more sustainable and environmentally friendly. The first mill has already been delivered to one of our customers, who is more than happy with its performance. From August 2020 on we will offer the mill for everyone and are looking forward to receiving further positive feedback.  For an offer, please feel free to contact us at This email address is being protected from spambots. You need JavaScript enabled to view it..