The epros®DrainMtH system is a method for the trenchless rehabilitation of property drainage lines by means of the cured-in-place pipe (CIPP) lining technology. The difference from the usual method is the lining direction: It works from the main pipe to repair lateral connection pipes. (MtH: Main to House)
The "MtH" lining method from Trelleborg provides a solution to some of the – still unsolved – technical problems in the trenchless CIPP rehabilitation of branch lines. For the very first time, it is now possible to renew laterals by working from the public sewer main towards the connected building (main to house) over a distance without needing to access private property, but this is by far not the only advantage.
Under the critical eyes of interested experts from the sewer rehabilitation industry, the new MtH method demonstrated its practicability during a second project performed for the European Patent Office in Munich. The result: Much acclaim and the breakthrough for the launch of the product in the German market.
During regular sewer inspection, leaks were detected in some of the house connection pipes surrounding the building in a star-shaped arrangement – cast iron pipes dating from the 1970-ies. 7 out of 12 lateral pipe runs were in need of repair; each damaged portion was some 4 to 5 metres in length.
What the pipes had in common was that they were hardly accessible or not accessible at all; neither was there sufficient room for installing any technical equipment whatsoever as would have been necessary in most rehabilitation methods.
Trenching was not possible either, because the sewer laterals are partially located beneath the building and embedded in concrete. Also, digging up the ground was out of the question for the project owner because of the complex design and rich art decorations of the outdoor facilities. The challenge was to repair the sewer laterals without disturbing the cultural and natural environment while keeping social disruptions to a strict minimum.
The contractor for this difficult relining project was Stingl, a specialist company for heating, ventilation, sanitary and sewer technologies which has been known and renowned in the south German regions for more than 100 years.
At IFAT in Munich in 2012, Stingl took notice of the existence of the novel MtH system offered by Trelleborg, because sewer and pipe rehabilitation projects with no or almost no access to the host pipe are not exactly rare in the field. So the solution presented by Trelleborg left a lasting and positive impression – but would it finally prove itself in practice?
The large project for the European Patent Office in Munich was the proper occasion to try and test the system, which had already been successful for some time in America, over a longer period under real site conditions. Supported by Trelleborg’s engineering team, the operations took place during the first two weeks in June 2013.
With the kind permission of the project owner, the construction site was opened one day to a technical audience in order to share the performance potential of this forward-looking technology with members of the sewer rehabilitation industry.
The technical components
The MtH system is generally composed of three basic packers for different main pipe diameters with respective calibration hose variants.
Each packer is equipped with wheelsets both at the inversion end and at the steam swivel joint end. Another major component is the camera attached to the MtH packer for exact positioning of the system within the main line or in front of the lateral junction prior to the inversion of the MtH liner. Not to forget the MtH inversion hose, which is adjusted to the length to be relined and will accommodate the MtH liner.
The packer carries the control unit supply hose, which contains pneumatic and electric lines for operating the system, and is also equipped with the hose connection port for the steam-air mixture. A winch is used to bring the packer into the correct position, which is additionally.
The wheelsets, which are adjustable to the given pipe diameter, and the optimized centre of gravity ensure optimally balanced movement and positioning of the packer within the main line. A winch at the exit manhole pulls the packer along the main line to the lateral junction. The system design includes a specific steam generator (epros®SteamGen M 150) tailored to the curing needs and technical parameters of the MtH system.
The Munich project in front of the specialist audience used the packer system I for a main pipe size of DN 200 to DN 225 (8"-9").
Resin system and liner
The MtH liner is a tube of the proven epros® carrier material, which is accurately adjusted – between 1 and 30 metres – to the length of repair of the host lateral. To seal the main pipe in the same operation, the tube ends up in a multidimensional open liner in the form of a short (or patch) liner.
MtH uses the EPROPOX HC120 epoxy resin system, a pure resin with outstanding mechanical properties, which has no fillers and can provide a long-term flexural modulus of ≥ 2,500 N/mm² while ensuring high resistance to chemicals. The resin system was specifically designed for steam cure.
The EPROPOX HC120 as a system component was granted General Technical Approvals (DIBt Approval No. Z42.3468, Z42.3488) both for the epros®DrainLiner method (DN 100 – DN 600) and for lateral connection repairs (epros®DrainLCR) with nominal sizes between DN 100 and DN 250. An application for obtaining the general technical approval for the MtH system in its entirety has been filed with DIBt.
The packer type I for small pipe diameters was thoroughly prepared as best suited for this application. The visitors watched with great interest how the final adjustments were made to the wheelsets and the calibration hose.
The properly calculated amount of resin was gently mixed with a double stirrer without any air entrapment.
The blue-coloured two-component epoxy resin system EPROPOX HC120 is used in the MtH process for two reasons: one is the rapid steam cure, the other one is the long pot time of 2 hours at 25° C, which made the operation convenient for the installers despite the hot temperatures in Munich on that day.
There even was enough time left to answer questions of the attending experts.
While the installation crew of Stingl was wetting out the MtH liner with the resin system, the technical guests were amazed at the extraordinarily easy and quick impregnability of the MtH liner material, thanks to the obviously perfect adjustment of the resin system’s viscosity.
The next process step is to place the LinerEndCap onto the liner tube. For this purpose, a steam outlet valve is attached to the end of the wetted MtH liner with the liner end thus being closed. The properly prepared liner tube was then pulled into the MtH packer and the inversion hose and extended to full length. Finally, the multidimensional liner piece for the main line portion was cut to size, wrapped around the packer and properly attached. Then the packer was lowered into the manhole.
The so-called "LinerEndCap" makes it possible to install an openend liner tube in the same way as a closed-end liner tube without using an additional calibration hose. The LinerEndCap will be removed after complete cure in a specific operation at the end of the job. So the final pipe will be opened with no need of cutting.
Like in all steam-curing systems, it is important to ensure permanent drainage of condensates. This can be done by installing a specific device in the epros®DrainMtH packer. This guarantees for perfect cure. (read the details in the printed version you can download below).
After expiry of the regular cure time, the CCTV inspection showed an excellent picture of the lining operation.
The objective of rehabilitating the lateral drain pipe by the quick removal of sewer leakage and sealing of the annular space in the region of the main/lateral junction was achieved.
Productivity & efficiency
A well-trained and coordinated crew of properly skilled and mutually supportive installers as well as perfectly matched materials and tools are crucial to
achieve the desired productivity. Good job preparations in association with ease of installation and simple steam cure of the MtH liner allow installers to complete up to 3 lateral lining jobs a working day.
The modern lining technique saves municipalities or public sector customers a lot of time and administrative effort under both technical and legal aspects and is in addition a resident-friendly approach in all respects. This solution meets the organisational and financial interests of owners or estate management corporations of large-size residential and commercial buildings, office complexes and industrial facilities: in most cases, the installation of the MtH system goes unnoticed by the users of the building, without any disruption of operations, avoiding expensive shut-down times. High-value physical assets like paved areas or green spaces, gardens, parks or streets remain untouched and will thus need no investments for restitution.
The MtH method is a state-of-the-art solution, technically convincing and especially interesting for municipalities, consultant engineers and highly professional large-size sewer rehabilitation companies with a high potential of customers in the public sector.
For municipalities, it provides fewer points of contact with property owners and thus constitutes a resident-friendly and administratively convenient alternative to conventional methods.
For engineers, it offers the technical solution to some rehabilitation problems left unsolved in the past, e.g. in cases of inaccessible pipe runs.
For renowned sewer rehabilitation specialists, the MtH offer provides a unique selling proposition in terms of an innovative technical solution that leaves almost nothing to be desired during practical application.