Trenchless sewer pipe renovation using the new tight-in-pipe method in the congested streets of the City of Dortmund, Germany

Jun 05, 2008

This paper introduces the Tight-in-Pipe Method. Tight-in-pipe is the term of a method for renovating sewer pipes and laterals with new, slightly smaller pipes in the same path without the need for filling the annullus between new pipe and host pipe. Deformation and misalignment can be compensated to a certain extent during pipe installation. Excavations can be abandoned almost completely when working from one manhole to the next. By this means, slight to medium deformations and misalignments are compensated, leaving circular pipes underground. The Tight-In-Pipe method is mainly used in projects for which a slight reduction of the original diameter is acceptable.Furthermore, this paper describes the application for this method on a larger project in the German City of Dortmund, 2006, where 4 sections of sewer pipe in Hertastraße had to be renovated, over a complete length 186 m. Installation with open trenches was impossible due to narrow site conditions and congested streets. Furthermore, this application method saved approximately 2/3 of the initially calculated costs had the project been carried out by open trenching. The contract was awareded to Paul SPEECK Rohrleitungs- und Tiefbau GmbH from Dortmund.

1. INTRODUCTION
Short length Polypropylene sewage pipes with high Modulus of Elasticity (PP-HM) can be in-stalled trenchlessly without excavation from manhole to manhole, fitting tightly within the host pipe by using the “Tight-In-Pipe-Method”. As the outside diameter of the new pipe is only slightly smaller than the internal diameter of the host pipe, there is no need for filling the an-nulus. The cross-sectional reduction is minimal, and trenchless connection of laterals is also possible.
An essential advantage of the Tight-In-Pipe technique is the fact that during the installation, small to medium sized offsettings can be evened out by means of a patented guiding sleeve. Thus the method can be applied for all common damages, such as e.g. cracks, leakages, de-formations up to 20% of the pipe’s cross section, misalignment, tree root infestation, ground water infiltration, etc.
2. STATE OF THE ART: CLOSE-FIT-LINING WITH PRE-FABRICATED PIPES
When close-fit-lining is applied, plastic pipes, reduced in their cross section by deformation, are pulled into the host pipe. Heat and internal pressure widen the liners after their installation, causing them to lie flush inside the host pipe. Reduction and deformation are the two most common methods. Reduction (e.g. Swagelining or Roll-down method) means that the diameter of the plastic pipe is reduced by about 10-12% immediately before it is pulled in, while the deformation method uses pre-deformed pipes (i.e. U- or C-shaped).
Key advantages:
  • minimal reduction of original pipe cross section,
  • use of pre-fabricated pipes,
  • completely fusion welded pipe string (PE, PP, PVC),
  • plastic pipe liners have smooth inner walls and show high resistance against mechanical
  • wear or chemical reactions,
  • liners can also be utilized on sites with groundwater infiltration, 
  • independent of soil cover depth and soil conditions if laterals are connected from inside,
  • short installation times with little traffic disturbance,
  • structural load capacity if the dimensions are sufficient (material, wall thickness),
  • long service life if the dimensions are sufficient (material, wall thickness).
  • minimising the reduction of the original pipe cross section compared to sliplining,
  • no annulus to fill up,
  • no starting pit requirement when using the deformation method (U-, C-Liner)for pipes up to
    ND 450 mm / 18” 
     
Essential disadvantages:
  • can only be used for circular host pipes,
  • sags cannot be compensated for,
  • blockage debris needs to be removed,
  • possible movement of the liner in temperature fluctuations,
  • exact knowledge of the location of the laterals is crucial for trenchless re-connection, otherwise connection of the laterals, particularly in the non-accessible nominal diameter range, is very elaborate and has to be carried out with open-trench methods,
  • no sufficient long term experience about the re-shaping of the pre-formed pipe,
  • movement of the liner under temperature fluctuations possible,
  • sewer has to be taken out of service for the duration of the project.
The application of the close-fit method is somewhat restricted due to deformations, sags and nominal diameter tolerances, because these host pipe deficiencies cause difficulties when the original circular form of the liner is re-shaped. This, in turn may lead to negative results where structural load bearing capacity and functionality are concerned. Nominal diameter reductions in the host pipe obstruct the re-shaping of the liner to its original circular form. This may lead to increased residual stress in the liner (reduction method) or, when applying the deformation
method, to additional wrinkling of the liner. On the other hand, nominal diameter expansions can form an annular gap between the liner and the sewer. The liner may become overstretched during installation whereby later on, longitudinal shrinkage could be the outcome.
3. TIGHT-IN-PIPE METHOD
Tight-In-Pipe is the term of a method for renovating sewer pipes and laterals with new, slightly smaller pipes without the need of filling the annulus (gap) between new pipe and host pipe. Only pre-fabricated, circular pipes which ensure tight-fit inside the host pipe are used. Deformation and misalignment can be compensated during pipe installation, depending on the extent of damage. Excavations can be abandoned almost completely when working from one manhole to the next thereby making this application simple and timesaving. The short pipes in
use are slid onto QuickLock rods and pushed into the host pipe with the help of a guiding head and a pulling rig already known from pipe bursting. By this arrangement, slight to medium deformations and misalignments of the host pipe are compensated, leaving circular pipes underground. The Tight-In-Pipe method is mainly used in projects for which a minimal reduction of the original diameter is acceptable. For example, a new pipe OD 192 x 12.0 mm (7.6”x0.47”) can be pushed into a host pipe ND 200 mm (8”) (Fig. 1). The new installation is carried out from manhole to manhole over lengths of up to approx. 70 m (230 ft).
Difference between Tight-In-Pipe and sliplining / close-fit-lining: The Tight-In-Pipe method combines key advantages of the conventional short-pipe-lining, sliplining and close-fit-lining methods. Especially the key advantages of close-fit-lining can be employed without any of the previously mentioned disadvantages. Tight-In-Pipe is thus less susceptible towards misalignment, deformation, sags and nominal diameter tolerances of the sewer than close-fit-lining. Correspondingly, this decrease in susceptibility positively effects the load bearing and functional performance of the pipes installed by the Tight-In-Pipe method. Using pre-
fabricated, circular pipes, there is no need to investigate long-term effects caused by the relaxation of the pre-shaped pipes (e.g. U-Liners, C-Liners). Additionally, the filling of the annulus which is sometimes necessary when operating sliplining or short-pipe-lining can be disregarded.
Difference between Tight-In-Pipe and calibre pipe bursting: The main difference between Tight-In-Pipe and calibre pipe bursting is within the range of damages which each method can eliminate. Caliber pipe bursting can elimainate damages as extreme as collapses. Also, the installed pipes do not necessarily have to lie tightly inside the host pipe walls. Generally, an annulus remains when calibre pipe bursting which mostly has to be filled.
4. FIELD OF APPLICATION
Tight-In-Pipe can be used under the following circumstances:
  • cracks, fractures, breakages, slab-outs (missing pipe fragments),
  • corrosion, roots (remove, if necessary), leakages,
  • deformations up to a maximum of 15% of the host pipe diameter,
  • misalignment up to a maximum of 10 % of the host pipe cross section,
Limitations of the Tight-In-Pipe method:
  • can only be used for circular host pipes,
  • a relatively straight course of the existing defective pipe line is a pre-condition. The method is not suitable for sewers with several different invert levels in the same renovation sections,
  • sags cannot be compensated for,
  • trenchless connection of laterals is possible from host pipe ND 250 mm / 10” or larger,
  • blockage debris needs to be removed,
  • misalignments of the manhole bases must be compensated for,
  • mounting the pulling device into a manhole is not always possible (due to misalignment of the entry and emerging angles of the pipe line).
Advantages of the Tight-In-Pipe method:
  • Re-shaping of a circular profile: slight to medium deformations and misalignments are compensated for by the guide head, thus re-shaping the circular form of the pipe. This improves the hydraulic properties compared to the defect host pipe.
  • The new pipe lies tight inside the host pipe (without annulus): there is no annulus over the entire length of the pipe required to be filled . Only the end sections of the mains (manholes) require sealing.
  • Trenchless connection of laterals: the laterals can be connected without working pits using common trenchless re-connection methods (robot).
  • Load bearing properties of a new pipe: the load bearing performance of the new pipe does not depend on the host pipe (Fig. 2), that is, the structural calculation is carried out without relating to the remaining bearing capability of the host pipe.
  • Long service life: the pipes are industrially produced under the best conditions possible. The pipe materials of highest quality, according to the manufacturer, offer a long service life of 80-100 years (DIN 8078, appendix B). With this solid wall pipe, the defective sewer system is renovated for the coming generations.
  • Smooth pipe walls: short pipes have dense, stable, plug-in joints, smooth inside and outside. The inner pipe walls are regular and very smooth, deposits are avoided. Due to the improved hydraulic properties, the frequency of flush cleaning, among others, can be reduced, which also results in reduced operation costs.
Not only should the existing host pipe damage aspects be considered for the application of the Tight-In-Pipe method, but also, whether the installation of a new pipe with all its advantages may be perhaps the more economical alternative.
5. “LAUNCH – EXIT – APPLICATIONS”
Basically, there are three possibilities for installing the new pipes:
  1. operating from manhole to manhole (short pipe installation only), 
  2. operating from pit to manhole (short pipe installation from manhole),
  3. operating from pit to pit (long or short pipe installation from pit). 
The procedure depends on several conditions, e.g. the geometry of the manhole as well as the depth, type, damage extent, nominal diameter and material of the existing host pipe. 
 
5.1 Operating from manhole to manhole
Short pipes up to OD 585 mm (23”) can be installed applying the “Tight-In-Pipe” method from manhole to manhole with the aid of a manhole pipe bursting rig (fig. 3); section lengths of up to 70 m (230 ft) in one go can be achieved. Concrete host pipes with massive corrosion of the inner pipe walls, require more pulling power compared to smoother vitrified clay host pipes.
5.2 Operating from pit to manhole
The Tight-In-Pipe method can also be used in relatively small pits, just like the static pipe bursting method. Here, too, the short pipe sections are pulled with QuickLock rods (Fig. 4). This kind of application is recommended when higher demands are made regarding the equipment, e.g. when working on corroded concrete sewers or when laterals are beyond repair and have to be renewed using an open trench method (key hole). The working pit can be used both for the pulling rig and for installing longer pipes. As before, the maximum installation lengths are 70 m (230 ft) for new pipes up to OD 585 mm (23”).
5.3. Operating from pit to pit
Long pipes can also be pulled “Tight-In-Pipe“ into an host pipe. The method is similar to the principle of the static pipe bursting method with QuickLock rods. Of course, if the renovation section is shorter, then short pipes can be installed from an existing launch pit (Fig. 5). The advantage of an installation from existing pits is in the utilization of longer pipes and a wider application range. When using this installation method, pipes up to OD 585 mm (23”) can be laid over maximum lengths of 100 m (330 ft).
6 EQUIPMENT
6.1 Pulling rig
Manhole bursting rigs, already known from static pipe bursting, operate with pulling forces between 200 and 400 KN (45,000 – 90,000 lbs), depending on pipe size and also use QuickLock rods. The rig can be used for bursting as well as calibre pipe bursting and the Tight-In-Pipe method. 
After the rig has been fixed inside the manhole (target manhole), the QuickLock rods are pushed into the host pipe to the launch manhole. Here, the guide cone (Fig. 8) and the following new pipe segments are slid over the rods and tensioned with a pre-tensioning system, for example, Burstfix (Fig. 7). 
 
6.2 Burstfix tensioning system
The Burstfix tensioning system (Fig. 7) ensures a safe pipe pulling-in process behind the guide cone and tight socket connections. It forms a unit consisting of the rod guiding system with slide rollers and the tensioning unit itself with pipe adapter, locking plate and pressure ring. The Burstfix tensioning system is operated with a portable hydraulic power unit – the functions are activated via remote control. The permissible tensioning force for each pipe can be preset at the hydraulic unit.
Working principle: First of all the bursting rod is extended and the new short pipe segment is fitted into the short pipe already pulled-in. The tensioning unit then automatically drives over the tensioning rods to the rear, the pipe adapter with the locking plate is inserted and the pressure ring is fixed in place with a bolt inside the rod. With the pipe adapter any size of short pipe modules can be adapted. The cylinders are now driven out up to a maximum length via a remote control. The pipe pulls itself together to form a string and can be tensioned up to max. 200 kN. Gradually, as the renovation progresses, all short pipes are pulled in.
6.3 Guide Cone
The guide cone (Fig. 8) is the key to successfull installation by means of the Tight-In-Pipe Method. The rollers in the front of the guide cone align it centrally in the host pipe and assist to restore the circular profile of the host pipe. The new pipe can then follow along in a relatively friction-free environment.
7 PIPE MATERIALS
Due the material properties, PP-HM is the preferred new pipe material (Fig. 9). The pipes are mass produced in a factory under conditions that are subject to constant quality control (both external and internal pipe inspection). The new pipes offer: 
  • excellent material properties,
  • uniform wall thickness,
  • precise dimensional accuracy of the pipes and pipe joints,
  • reliable impermeability,
  • proven suitability for sewer applications.  
8. RENOVATION OF A 300 MM (12“) VCP SEWER PIPE WITH SPECIAL OD 292 MM (11.5”) PP-HM SHORT PIPES IN DORTMUND, GERMANY
8.1 Development of the Sewer System in Dortmund

1842: Construction of the first sewer system in the Hanseatic City of Hamburg (Fig. 10). Start of the sewer works in Dortmund.

1853 to 1879: The first single sewer systems are installed beneath streets with extremely terrible sanitary conditions.

1880 to 1907:Installation of the first coherent sewer system for the old central city of Dortmund in the river basin of the Emscher. The sewerage was collected in the sewer system and thus quickly disposed off. In this way, the plight was shifted from the city to the area of Huckarder Bruch.

1887: Construction of a mechanical sewer system in the Franziusstraße with 2 slurry tanks and 4 Dortmund wells (6.50 m diameter and 12 m deep).

1889: Two additional Dortmund wells are built. However, industries and population are growing so quick that the new purifying plants are unable to stop the increasingly deplorable state of affairs.

1891: A commission of officials of government visits Dortmund. At that time, the regulation of the river Emscher was considered to be impossible, therefore the commission decreed: “The supervisory authorities must strive with emphasis towards coercing the city to carry out a project which had formerly been planned, the installation of sewage farms on the outskirts of the city" (Fig. 11).
1892:The city starts the development of sewage farms in the terraine of the Waltrop community. The plants are constructed in the area of the river Lippe because the irrigation properties of the soil in the Emscher area are insufficient.

1894/97: The 13.5 km long inlet system of the sewage field is built (Fig. 12). The profile ND 90/135 cm was calculated for the waste water of 150.000 inhabitants at a dilution factor of 2.5.

1898/99: The eastern part of the sewage farms is put into operation. The waste water of the city centre is lead from its natural drainage area (river Emscher) into the river Lippe area via inlet system of the sewage farm (Fig. 13).
1889 until 1900: 6.1 million Marks were raised for the improvement of the outfall ditch and waste water disposal in the complete Emscher area, the greatest part of the sum came from the mining industries, the remaining money was funded by the community. These measures did not achieve drastic improvements, however. Gradually it became obvious that the deplorable state of affairs could only be helped by a uniform regulation of the river Emscher from its source to the estuary.

1904: The Prussian king confirmed the law for forming a cooperative society for the regulation and sewage clarification in the Emscher area (Emscher Law). All parties involved in the area (communities, mining companies and other commercial enterprises) are forced into membership. Their contributions are needed to pay for the tasks of the cooperative.

1926: In an attempt to achieve a uniform regulation of the waste water conditions and to prevent the extreme soiling of the river Lippe and its side branches, the Lippegesetz (Lippe law) was passed and the Lippeverband (Lippe alliance) was founded on the 19th of February 1926. Adjacent communities, mines and other industrial enterprises are also forced to become members here. The tasks of the Lippe alliance are the same as those of the Emscher cooperation. Both associations are managed in administrative and personal union.
1924 to 26: The upper reaches of the Körne river are expanded and deepened. The plan was to drain parts of the city centre in direction of the river Körne, thus disburdening the sewers in the north-west.

1935 to 36: An 1800 m long deep sewer is installed between the quayside railway in the Brackeler Street and Borsigplatz. The sewer is 420 cm in diameter and lies as deep as 15 m beneath the level of the terrain. At the time, the sewer was excavated using the shield tunnelling method, a procedure which attracted the greatest attention of the experts because of the difficult site conditions.
After 1945: The air raids during the Second World War destroyed the sewer networks of the city of Dortmund almost completely or shut them down. When the war was over, the civil engineering department located approximately 2300 damaged spots in the sewer net. For reasons of sanitation and in order to take up the industrial production again as quickly as possible, repair of the damaged spots was crucial. This attempt was hampered by the lack of sufficient manpower, the badly required tools and materials where nowhere to be found. Therefore, the occupation authorities ordered workers from industrial companies to contribute their services towards the repair of the sewer network.
The sewer conditions in the north of Dortmund were particularly precarious. Destruction and break-down of the sewer pumping stations caused the lowest points of the northern part of the city to be flooded by waste water. The threat of epidemics caused severe worries, the authori- ties even considered evacuating the population living in the endangered regions. Beating all the odds, the civil engineering authorities, powerfully assisted by the Hoesch Bergwerke AG, managed to reactivate the waste water pumping station in Borsig street in a provisional fash-ion in the summer of 1945. The main damage of the sewer network could not be repaired be- fore 1948, after the currency reform, when sourcing of material improved and work was accel- erated considerably. On the 1st of July 1949, approximately 90 percent of the damage was repaired.
After 1950: When the Federal Republic of Germany was founded in 1949, reconstruction in Dortmund also commenced to the full extent. For municipal sewer disposal, this meant: renewal of existing sewer plants and also new construction. Since 1950, built-up areas with a population larger than 300,000 are being canalised. The sewer network was expanded from roughly 800 km (state of 1950) to approx. 1750 km (state of 2000). With the exception of 6,000, all inhabitants of the city are connected to the municipal sewer network which work with biological waste water treatment plants.
1989: Due to the continuous modification of the municipal drainage net in the past 30 years, first in the western central part of the city of Dortmund, later on in Dortmund-Brechten, the outflow of waste water in direction of the sewage farms of Dortmund was steadily reduced, finally ceasing completely in 1989. The waste water now flows back to the natural catchment areas, Emscher and Süggelsbach. It was necessary to give up the sewage farms because this waste water treating method is no longer up to the standards of modern sewage technology and the laws pertaining to water.
1994 and 1995: Within a boundary of between the Emscher and Körnebach / Seseke systems, two large sewage plants were built in Dortmund by the Emscher cooperation and the Lippe alliance. These have been operating since 1994 and 1995, respectively.
Beside the new construction of drainage plants, the civil engineering department (Fig. 14) is also maintaining a drainage net in a length of 1,770 km on a municipal terrain the size of 280 km² for 588,000 inhabitants.

Open trench renewal of the sewer net in Dortmund means higher building costs and definitely higher indirect costs due to the management of the heavy traffic in the city. Therefore, the civil engineering department is increasingly inclined towards the application of trenchless sewer renewal methods.
8.2 Jobsite Situation:
In May 2006, tenders were invited for the installation project Klosterbredde / Hertastreet, using the Tight-In-Pipe method. The job site is located in the centre of Lütgendortmund, a suburb of Dortmund (Fig. 14 - 16).
The specialist contractor PAUL SPEECK Rohrleitungsbau und Tiefbau GmbH from Dortmund was awarded the contract on the 23rd of May 2006.
The sections (Fig. 16) 74 / 121, 121 / 120, 120 / 119, 119 / 221 to be renovated using the trenchless Tight-In-Pipe method. The complete length was 186 m (610 ft). According to Dr. Christan Falk, head of the sewer department of the municipality of Dortmund and GSTT Board member, installation with open trenches was impossible because of narrow site conditions and the risk for a 2 m high house wall, which was in danger of collapsing. Also, the project would have taken much longer.
On the first section, the bursting rig Grundoburst 400 S was installed in a manhole and the QuickLock rods were pushed into the starting pit in a distance of 64 m. The patented QuickLock connection forms a flexible rod string which followed even slightly curved paths.
The Grundoburst was placed on top of a height-adjustable working platform, 1 m above the bottom of the manhole and was secured against the manhole walls. In the starting pit, a guide cone was connected to the rod string (Fig. 17). The first new pipe section was then attached to the guide cone and safely tensioned using the Burstfix (Fig. 18). The Burstfix kept the short pipe sections safely together during the pulling-in operation. The rollers in the front of the guide cone aligned it centrally in the host pipe and assisted to restore the circular profile of the host pipe. The new pipe could then follow in a relatively friction-free environment.
After the second pipe section, there was sufficient room to install a spacer on roller tracks which kept the rods centred in the new pipe. It was connected to the Burstfix. The Burstfix was driven by a small, portable hydraulic power unit. After each pipe section had been pulled in, the Burstfix drove back to the next pipe section at the push of a button, reached automatically into the joint of the previously installed pipe and tensioned the whole pipe string. By this pro- cedure, the installation of one pipe section of approx. 60 cm (24”) length took less than 3 minutes.
After one working day, the complete pipe string of one renovation section was completed, in- cluding all set-up times and side jobs (Fig. 19). A sewer robot was put into action in the after- noon and reconnected the laterals.
The municipality of Dortmund and the contracting company PAUL SPEECK Rohrleitungsbau und Tiefbau GmbH have recognised the advantages of this method and want to utilise it in their networks wherever it is possible. According Dr. Christan Falk, in addition to the advantages mentioned before also saved approximately 2/3 of the initially calculated costs had the project been carried out by open trenching
9. CONCLUSION
There are various techniques for trenchless pipe installations resp. replacements available, which are competitive to open cut regarding economy and environmental acceptability and far superior in indirect (social) costs. Using these techniques means protection of valuable sur- faces with only very small interference of traffic, residents and business. Varied alternatives of trenchless techniques even make it possible to pay attention to local conditions, requests of residents, utility supply and sewer companies.

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57368 Lennestadt, Germany

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+49 (0)2723 808187

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+49 (0)2723 808216

E-Mail:

meinolf.rameil@tracto-technik.de

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