Krah Pipes under difficult conditions - Field report from Egypt
Since our existence in Egypt we have realized many projects, with kilometres of pipes in several sizes, as well as fittings and manholes. All pipes, fittings and manholes are according to the newest version of DIN16961. Basically, all pipes have an inspection friendly bright (yellow) smooth inside surface and they are jointed with our special integrated electro-fusion jointing system. Overall, the number of failures due to unexpected loads or wrong handling at site is fairly low, but they exist. One of the major question is always: “How to repair the pipe, the fitting or the manhole?”, and from time to time we must also show our repairing skills to the project owner. One of the biggest issues in Egypt is the existence of very soft, cohesive soil, so all pipes and system components are based on extensive structural analysis, to be on the safe side, because a proper backfilling is not easy at all.
A typical view of our loose soil
In the day to day business inadequate transport procedures, wrong handling and/or storage can cause pipes damages. External mechanical force may also damage pipes which are already installed. Another origin of leakage can be a bad or wrong jointing of the pipes, for example the power generator stopped during the electro-fusion joining and the worker didn´t check, even the welding report will show a failure (not enough energy in the joint) or manual welding was carried out in dirty conditions.
Depending on the project, the product, the failure and the environment we have different solutions to fix the problem. All products are produced out of 100% virgin PE100 material – and they passed the requested quality control program, according to DIN16961 and our additional internal guidelines. All manholes are pre-fabricated at the plant and installed on site, by using the electrofusion system. From time to time, special connections are done on site.
The way of repair must consider the origin of the damage, the type of product, the jointing-procedure and the on-site-conditions. That’s why we provide several repair-procedures and always choose the best solution accordingly. In this report four different solutions (cases) will be explained, to show the range of possibilities. An important issue is that each solution is a long-term solution (minimum 50 years) and the pipe properties like stiffness and internal pressure rating shall be kept.
Case 1: A lake connection pipe DN/ID 2500 broke at one position
Project description: High-way is executed in order to connect Suez Canal Economic zone (SC Zone) to Cairo but it will set aside many agriculture lands as it crosses many lakes. Road culvert are required up to 2500mm. First it was decided to use the concrete pipes with ID 2500mm but due to loose soil and a high weight of the pipes, the pipes were replaced with HDPE profiled pipes - Krah pipes, namely two adjacent pipelines with an inner diameter of DN/ID 2500 mm and a ring stiffness of 32 kN/m. The depth of installation was 6 m.
Case: Due to wrong handling during alignment and after welding one of the pipes was broken. The broken part was the spigot of one pipe.
Challenge: There was no (payable) way to remove the complete backfilling and change the pipes.
Solution: Internal coupling equipped with two sets of electrofusion wires are installed inside the pipe to be welded to the pipe by electrofusion followed by hand welding. In cooperation with a contractor the ground water level was lowered to guarantee the welding area was completely dry.
Tip: Consider and respect the Krah installation guideline!
Outlet of the Project Internal Krah-Electrofusion sleeves Welding under progress
Case 2: A sewage pipe DN/ID 1000 mm was physically destroyed by excavation
Project description: A primary care families’ project, planned by the Government to help homeless people who had lost their homes in catastrophes or who live in very bad conditions near Giza Pyramids, the project is designed for 12,500 unit of capacity for 60,000 habitants. It was the first project delivered by Krah Misr and it went into service in 2010 and consists of 3 Km profiled pipes from ID 500 to ID 1000 mm connected by Electrofusion- In an operating sewage network with an inner diameter of DN/ID 1000 mm (stiffness of 8 kN/m²), maximum installation depth 8m, minimum 0,5 m of a pipe got destroyed.
Case: During the installation of some new electrical cables, the already installed pipe was broken. So, it did not happen during installation, it was a post-installation effect.
Challenge: A very time critical issue, since the pipes are part of an operating sewage network, the maximum time for the repair can be 3-4 hrs.
Solution: As the damage is not repairable and it’s not possible to weld within the pipe length, it was decided to change the complete pipe. Thanks to the flexibility in Krah pipe production process, the new pipe was produced with two special ends of solid wall with thickness of minimum 25 mm, so it could be welded by hand welding. Also, the pipe could be cut on site exactly to the needed length.
The broken pipe The broken pipe, cut by a standard chain saw
The new pipe will be placed Manual welding under progress
Case 3: Storm water pipeline with inner diameter DN/ID 700 mm with ring stiffness 16 KN/m²
Project description: An industrial area built on 331 acres with an authorized capital that reaches 5 billion Egyptian Pounds
The new city will make a qualitative leap to transform the local furniture industry into a global one. 1500 small and medium workshops of 50 to 150 meters with about 150 large and complete factories, in addition to providing more direct and indirect employment, which is expected to exceed 25,000 employment opportunities. The industrial area is built close to a fishing lake, so the ground water level is almost on finish level and the soil is very loose. No other pipe material than welded Krah-Pipes could be installed in this region as the settlement expected is significant. The total project was approx. 5.5 Km of pipes with an inner diameter of DN/ID700 and DN/ID 1000 mm, all jointed by electro fusion, also 550 manholes (in different shapes) were installed.
Case: During installation some pipes were damaged due to crossing heavy vehicles directly on pipes, before proper backfilling. The damages were discovered after the pipeline was tested -after complete backfilling.
Challenge: To stop the leakage with ground water existence and guarantee the pipe flexibility as no welding procedure can be applied with note that pipe might be defected more than allowed due to lower compaction proctor density.
Solution: Amex-liner (Amex Sanivar AG is a German company – www.amex-sanivar.com) offers a very cost-effective way to solve the leakage, during running condition. The range is from DN/ID 600 mm – DN/ID 5000 mm. The solution can even be used, when the pipes is not fully round anymore and under inside pressure conditions – we haven’t had this problem, but it might be a good information for other pipe failures.
Tip: The pipe section or at least the pipe joints should be tested before you make final backfilling, to avoid time consuming and expensive work afterwards.
Ground water situation Infiltration of water
Installed AMEX-Liner Worker inside the pipe, during installation of the AMEX-Liner
Case 4: A leaking Krah-Pipe manhole, surrounded by a high ground water table
Project description: Integrated in the stormwater network of case 3 also 550 manholes are installed with inlet and outlet according to the connected pipeline.
Case: During installation procedure some manhole connections were damaged due to wrong handling on site.
Challenge: The manhole is already installed and the surrounding ground water table is 30 cm below the surface level and no welding can be done in water presence , and the ground water is infiltrating constantly.
Solution: Using a single-component injection resin on polyurethane base, which is employed for stopping water ingress, for stopping flowing water in combination with acrylate gel grouting, for ground and rock hardening, as well as for numerous other sealing requirements in civil and mining engineering and in tunnel construction.
The material is injected through drilled holes from one point to the adjacent as picture. After water stop hand welding is completed in manhole benching, the manhole is totally repaired.
Heavy infiltration of water in the manhole (video screensahot) A manhole filled by gravel, due to leakage Mixing of components Manual welding of broken part after infiltration stopped
Failures can always happen, even if the pipe passed all quality control tests during production and after shipment. Everywhere where people are working, human mistakes can happen, and the good news is, that we have solutions to eliminate the problems with several solutions. And in case we haven’t had a specific failure before, we are sure that the Krah-Community will find a solution for the problem.
CEO of Krah MISR