1500 mm diameter main sewer line renovated under sports ground - Use of the Rib Loc Rotaloc spiral wound liner system

Sep 28, 2007

A 1500 mm diameter main sewer line in the town of Tiel in the Netherlands was renovated along a length of 626 m by KMG Benelux B.V. using the Rib Loc Rotaloc spiral wound liner system. The location of the pipe beneath a soccer pitch, the length, dimension and condition of the pipe combined to produce an unusual challenge, which was successfully mastered using the Rotaloc method. Advantages of the SWO liner system, such as high static load-bearing capacity, uniformly high quality of the prefabricated liner material, the avoidance of cost-intensive open cut activities, rapid installation, relatively little expenditure on over-pumping and lack of styrene emissions were all positive factors in the success of this project. In recent years, the town of Tiel in the Netherlands has carried out several rehabilitation measures using the cured in place liner method. In April 2006, it issued another invitation to tender for a sewer renovation. The decision was made in favour of the Rib Loc Rotaloc method. KMG Benelux was able to beat the competition in terms of both price and technology with this special proposal.

Description of the method
The Rotaloc spiral wound liner method is a member of the family of Rib Loc SWO liner systems, and can be employed for the rehabilitation of old pipes with nominal diameters of DN 800 to 1800.
This method makes use of the close-fit process, in which the spiral wound liner lies snugly against the old pipe. This makes the grouting of the annular gap unnecessary in most cases.
High rigidity despite minimal wall thickness
The high annular stiffness of the circular new pipe guarantees high static load-bearing capacity. The cross-sectional height of the profile, which is available in two system dimensions (21 mm and 37 mm) is adapted to suit the static requirements and covers a nominal diameter range of 800 to 1800. The load-bearing capacity of the Rib Loc liner can be statically proven. Furthermore, the reduction in cross-section is minimal, so that the hydraulic capacity of the sewer line is not impaired.
Work steps for installation (Figure 1)
  1. The pipe that is to be renovated is cleaned and extreme deposits and incrustations are removed. Next, a CCTV inspection of the pipe is carried out, to check whether cleaning was successful.
  2. Any house drains can be localised and calibrated with the aid of the CCTV inspection.
  3. The Rotaloc machine is positioned at the beginning of the pipe and calibrated to the pipe wall.
  4. The Rib Loc PVC profile is introduced into the manhole to the winding machine from the material drum. The machine rotates and simultaneously moves through the pipe, winding the PVC profile in a spiral fashion close-fit against the old pipe, so that it forms a load-bearing pipe (Figure 2).
  5. If the host pipe is oversized and the diameter needs to be reduced, the PVC profile may be wound with a smaller con- Quelle: Rib Loc, Australia REHABILITATION 27 3R international · Special-Edition 1/2007 stant diameter. The resulting annular chamber is then subsequently grouted with porous lightweight concrete.
  6. The winding machine travels through existing pipe deformations in a controlled manner. It can also change without problem from one nominal diameter to another without a crease.
  7. The machine can also travel through several intermediate manholes, so that entire pipe runs can be renovated in a single operation (Figure 3).
  8. After renovation of the pipe is complete, a pressure test is performed.
  9. Lateral and manhole connections are connected.
  10. The quality of the work is verified by a CCTV inspection.
Rehabilitation of a 1500 mm diameter main sewer in Tiel (NL)
The challenge
The challenge here was the rehabilitation of eleven reaches of a DN 1500 main combined sewer along an overall length of 626 m.

The ageing concrete pipes displayed obvious leakage points at the socket joints, which allowed the penetration of significant quantities of outside water and extreme root growth, as the pipes lay in ground water up to a height of 1.5 m above the invert level. Altogether, the damage status of the sewer had been classified as Class 1. The line lay at a depth of between 2.55 m and 3.10 m. Along these eleven conduit reaches are four lateral connections with a nominal diameter of 125 mm, which had to be reconnected properly when renovation work was complete.
Preparatory underground work
Although a manhole opening of only 62 cm is normally required for all Rib Loc spiral winding methods, here the manhole covers and cover plates had to be removed in two cases, because in Holland the standard diameter of manhole openings is only 52.5 cm. The manhole works were bricked using conduit klinkers (Figure 4). However, in the end these two openings were sufficient for installing the Rotaloc spiral winding machine and recovering it after renovation. The Rotaloc profile was inserted and the Rotaloc machine installed and removed exclusively via a start and an end manhole.
The first section had a length of 106 m. Since part of the pipe lay beneath a sports ground with a 400 m grass racetrack and a football field, steel plates and digger mattresses had to be laid to protect the lawn (Figure 5).

The two concealed manholes first had to be localised electronically. One of them was situated at the edge of the football field and had to be exposed, to allow access to the pipe. For this operation, the excavator was placed on sheets of plastic to protect the grass. Thus the preparation of this section was somewhat more time-consuming than in “normal conditions”.
Over pumping
According to the invitation to tender, the conduit’s dry-weather flow inside the pipe could be regarded as insignificant; however, we had to be prepared for rain and so set aside and maintain a head-bay for approx. 150 m3/h. Volumes of water in excess of 150 m3/h were to be buffered in an existing retention basin. In practice, however, due to the leaky coupling sleeves combined with the high ground water level, there was a relatively high flow.
Permanently free cross-section
A major advantage of the Rib Loc spiral winding process became apparent even during drainage measures. For the cross-section of the main line did not have to be closed off at any time throughout the rehabilitation process. Thus, if inclement weather should cause the pumps to be overloaded, bringing the threat of an overflowing buffer basin, the sewer could be used as an outfall at any time. This therefore eliminated the risk of neighbouring land and cellars being flooded as a result of accumulated water in the uppermost sections of the conduit.
Renovation possible under running conditions
If it becomes necessary to flood the pipe during the course of the work, once the water level has sunk once more it is essential in all cases to inspect the pipe and clean it if necessary. With the Rib Loc method, it is also theoretically possible to renovate the pipe while it is in use. The prerequisite here is that the water level is in the lower third of the cross-section, in order that the work can still be reliably monitored. However, precautions have to be taken to ensure that mud or solids brought in with the water do not deposit themselves in the bottom of the pipe, thereby posing a risk to the success of the process.

The building schedule set aside one week for the construction of the entry pits. Flanged steel pipes with a 6" diameter were laid parallel to the sewer. The total length of the sewer line was 600 m. An inflatable stopper prevented water from escaping from the retention basin that acted as a buffer reservoir. The collected sewage was then sucked up by a diesel-operated pump assembly and fed back into the line 600 m further on.
Cleaning the old pipe
The cleaning of the sewer pipe turned out to be more time-consuming than anticipated, for a large quantity of mud and gravel had deposited itself in the bottom of the pipe over time, and had in part to be shovelled out by hand. The removal of the roots also entailed hard manual labour and took longer than originally planned. And the removal of the roots that had grown in the joints over the years necessitated underground logging activity. The roots – which had intertwined and were as thick as a forearm – had to be sawn off with a battery-powered foxtail saw and hauled to the next manhole. They then had to be pulled out of the manhole with the help of a tripod and winches.
Installing the Rib Loc Rotaloc spiral wound liner
After two weeks’ preparation, we were able to commence with the renovation of the leaky concrete pipe. The 5-man renovation team were glad to get started on the actual work at last.

Once the hydraulic power pack had been put in place, the team could start to use the Rotaloc spiral winding machine. The advantage of this machine is that it can be used where there are standard manhole covers (625 mm internal diameter), without the need for any open cut work, thereby dispensing with the time and cost that such work entails, regardless of the nominal diameter of the pipe requiring renovation.
After the profile has been inserted in one side of the Rotaloc machine, which is powered by a hydraulic motor, a new, circular pipe is wound on the other side of the machine, along the route of the old pipe. The individually controlled hydraulic cylinders ensure that the endless PVC profile is positioned with uniform pressure close-fit against the pipe wall, while the machine rotates along the helix of the resulting new PVC pipe through the sewer line. An inliner length of 91 mm is produced with each revolution. In this way, 50 to 60 m of 1500 mm diameter pipe can be renovated every day, on average.
Constant CCTV camera surveillance
The winding of the profile is monitored by two cameras (see Figure 3). Whilst one CCTV camera in front of the winding machine checks the winding process moving backwards against the direction of installation, the second camera, which is mounted on the machine perpendicular to the direction of flow, monitors the joining of the profile around the joints. The plant operator surveys these processes via a monitor. If the operator at his monitoring post sees deposits or obstructions inside the pipe, the installation process can be interrupted until the obstacles have been removed without the formation of mysterious bumps or dents, which would have to be discussed upon a later viewing of the video.

Even if the operator discovers on screen that the profile is not connected precisely in the joint, this is no problem: the Rotaloc machine can be turned back against the direction of installation to the point in question. The position of the machine can then be recalibrated, and the problem spot corrected.
Endless liners produced on-site
If more profile is required than is available on a material drum, due to the length and diameter of a renovation section, it is necessary to join the end of the profile from one drum to the beginning of a new one. During this process, first the two pieces are connected by a mechanical clamping device. Once this profile connection reaches the winding machine, the clamp is removed and the machine winds the profile in the old pipe. Next, the joint is sealed with CIP in epoxy resin. It is thus theoretically possible to produce “endless” liners.
Even major deformations are no problem
If a local deformation is encountered in the old pipe during the course of renovation work, the pressure of the hydraulic cylinders is reduced, in order to adapt the diameter of the liner to the reduced cross-section. Even in the case of major deformations (> 5% of the old pipe dimension), the new pipe always has a completely circular cross-section. In order to ensure the static load-bearing capacity of spots with significant local deformations, these pipe sections can be grouted from the inside out, thereby guaranteeing optimum load transfer.

In Tiel, however, these benefits of the Rib Loc method did not come into their own, because there were no deformations whatever in the pipe.
Manhole connection
The Rib Loc liner is cut using the batterypowered foxtail saw or angle cutter so that it lies flush in the start, end and intermediate manholes. The transitions to the manhole are filled with special plastic-containing mortar. This work can be carried out immediately after installation of the liner, since there are no thermal stresses to be reduced in the liner.
Connecting the lateral connections
As with the manhole connections, the 125 mm diameter laterals were opened and re-connected manually. In inaccessible locations, the connections were produced using a robot or the CIP-hat-profile technique. Here, too, the connections can be established immediately following the renovation of the main pipe.
Acceptance test
In order to check the quality of the work, the entire stretch was examined by a CCTV camera and verified during an acceptance test. In addition, each individual reach of the line was subjected to a pressure test with compressed air to DIN EN 1610. These tests confirmed the successful, flawless installation of the new pipe.
Conclusion
Despite two weeks of continuous rainfall during the final stages of the project, the work was completed on time and to the customer’s full satisfaction. When the rehabilitation work was over, the football field was returned to its former, exemplary condition, so that matches and training can be resumed as normal after the Christmas break.

Finally, it should be mentioned at this point that in December 2006, Rib Loc Australia Pty Ltd. applied for DIBt (German Institute for Construction technology) approval for the Rib Loc spiral winding method.

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Contact

Dipl.-Ing. Martin Gerhardt (KMG Pipe Technologies GmbH)

Nürnberg

Phone:

+49 (0)911 955127-14

Fax:

martin.gerhardt@kmg.de

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