World first for sewer rehabilitation in Dorset

The first installation of a new MIPP system for pipe lining has taken place in Dorset. On behalf of Aqualiner, Ian Clarke reports

Portland in Dorset has just seen the world's first commercial application of the latest development in pipeline rehabilitation technology, the Melt-In-Place Pipe (MIPP) system known as Aqualiner. The lining operation itself comprised the rehabilitation of just 23m of existing 225mm diameter clay sewer pipe, which runs beneath Castle Road at between 1.5 and 2m deep.

The work was scheduled to be completed in one working day including set up, clean, survey, line and site break down, all of which had to be completed with full traffic flow allowed alongside the working area. All works were completed using access via existing manholes serving the sewer ensuring no excavation work was required on the busy Castle Road.

Castle Road forms part of the main one-way system serving traffic entering and leaving Portland Bill, which is the land mass which is almost an island on the end of a narrow land spit off the Dorset coast near Weymouth. The 'island' has one entry and one exit route handling two-way traffic flows to and from the mainland running alongside the eastern end of Chesil Beach. Therefore, any work that could disrupt the traffic flow along this sole access route could have very serious consequences for the local population, businesses, Portland prison and the Naval Base.

According to OnSite's engineer, to complete this same project using traditional open cut techniques would have required 7 to 10 days with much greater potential for traffic disruption, noise and environmental impact for the local population. In the event, the installation began was completed in two hours and 15 minutes.

The Aqualiner system is similar to other rehabilitation systems currently available, but differs in some very significant ways. Firstly, the Aqualiner system does not utilise resins or chemicals as part of the lining process. This is achieved because the liner material is specially designed to eliminate this aspect of an installation. The MIPP technique uses a liner material which comprises a combination of glass fibres (for stiffness and strength) and thermoplastic polymer fibres (which, after processing, becomes the matrix that surrounds the reinforcing fibres). The liner installation technique follows what at first glance is a relatively simple process.

Once the old pipe is prepared, the Aqualiner material is winched through the host pipe over the length to be rehabilitated. The main liner is normally installed with a protective outer preliner to prevent wear against the host pipe wall during the pull-in operation.

A power umbilical is then fed through the liner from the reception manhole end to the launch manhole. The umbilical is then connected to a heater pig which is placed just inside the liner. A liner inversion drum is positioned at the launch end of the process which is fitted with an appropriate length of inversion calibration tube. The drum is then connected over the end of the host pipe anchoring one end of the liner material in place.

The heater pig is a vital component in the lining process. Once up to temperature, around 200°C, the heat from the pig melts the thermoplastic component of the liner material which pushed against the inside wall of the host pipe by the pig. The melted plastic then permeates the structural glass fibre material.

As this process occurs, the calibration hose from the inversion drum pushes the heater forward into the host pipe melting the next 'section' of thermoplastic material. Once started the process operates continuously.

At Castle Road, the advance rate of the heater pig was about three minutes/metre. As the heater pig advances the umbilical is collected at the reception end of the lining run. On short runs this can be achieved by hand or for longer runs the umbilical is wound on to a cable drum. Once the heater pig passes out of a section of liner, the temperature of the thermoplastic material drops quickly causing the plastic solidify in place. Thus the liner is formed.

This process occurs over the full length of the liner until the heater pig emerges at the reception manhole completing the lining installation. The inversion hose is retrieved, equipment is removed from the manholes and the liner ends are cut into the ends of the host pipe. If lateral connections exist along the pipe length these can be reopened using standard robotic cutters.

In the case of the Castle Road project only one connection existed on the lining run. Once this work has been completed a final as built survey can be completed and the pipeline put back into operation.

The absence of chemicals in the lining process means that odour emissions are significantly reduced, if not eliminated, during the installation process. The shelf life of the liner is unlimited because the materials do not react over time and are not altered until the installation process is under way.

A further significant advantage of the Aqualiner system, given the absence of chemicals in the liner process, is that its standard material content and the strength this offers makes it not only suitable for installation in sewer systems, but also pressure pipes including potable water pipes.

A significant advantage that is claimed by the developers of the Aqualiner system is that the fully structural liner that is formed using the technique comprises very strong component materials. This means that for any given load bearing requirement the liner material for an Aqualiner lining can be significantly thinner walled than more conventional lining systems. In the case of the Castle Road project, a 3mm thick liner was required, whereas for a conventional CIPP lining a wall thickness of around 4.5mm would have been required.

Not only does this mean that there is less material to handle at a lighter weight, but also the cross-sectional loss in the final lined pipe is significantly reduced. With the low friction coefficient inner wall of the Aqualiner this may have the effect of not just maintaining but possibly improving overall flow capacity within the renovated pipe. The project to install the Aqualiner system was undertaken for Wessex Water by its main rehabilitation contracting partner OnSite, which holds the exclusive Aqualiner installation licence for the UK.

Commenting on the operation for Wessex Water, Julian Britton said: "It has been a long road to get to the point where Aqualiner has become a commercial system that we are able to utilise. However, this first commercial project in Portland may well mark a significant milestone for the technology. In the same way that lining engineers remember the first ever commercial CIPP lining installation, this project could well occupy a similar place in the rehabilitation industry's history for MIPP technology."

For Aqualiner, Gerry Boyce said: "This is a very auspicious day for the Aqualiner system. We have overcome some very demanding technological obstacles to get here but now we feel that we have a world-beating system to offer to the pipe renovation industry."

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