Drainforce Limited working in collaboration with Alun Griffiths Contractors have installed a first time in the UK water industry UV liner, cured in place with a specification of 23.6mm thickness delivering the project for asset owner Dwr Cymru Welsh Water.
A surface depression appeared in the road on a busy bus route in central Cardiff, investigations carried out identified a large brick sewer had started to collapse. A solution was developed to minimise disruption, shortest duration of works and reduced excavation in an area with lots of utility services in the area that would have to be excavated.
A solution was developed to minimise disruption and progress a quicker solution than full open cut excavation.
The solution to achieve this was to excavate the deformed section of brick sewer, then install a Cured In Place Pipe Lining, the steps on progress is summarised below:
Measurements were taken of the pipe size and the liner was designed to withstand the total load imposed on the existing pipe by external groundwater pressure, internal service pressure, ground and traffic loading – thus achieving ‘a new pipe within an old pipe’ structural solution. The outcome was to manufacture a bespoke liner which was 890mm in diameter and 23.6mm thickness which is the highest specification liner that would be installed in the Water Industry in the UK, this was fast tracked through the production process in Germany. The iMPREGLiner tube material is a combination of non-woven felt and fibreglass, impregnated at the manufacturer’s plant.
The liner was transported to site from Germany in a refrigerated vehicle that was used to ensure that curing would not be triggered by premature heat and the liner also had double peroxide applied. The liner was 45m in length with a weight of 6.5tonne.
Prior to the lining, the existing pipe was cleaned using a state of art recycler to ensure a close fit could be achieved to the existing sewer, a CCTV survey confirmed the pipe was clean and was also used to mark-up lateral connections.
The liner was winched into place through the existing sewer, inflated with air to allow a UV light train to pass through the inflated liner. The light train is controlled by computer and allows UV light to penetrate the polyester resin impregnated liner, with the resin having a light sensitive catalyst added. Once the UV light comes in contact with the lining, curing commences, this technique is fast and once the light train has passed through the liner, the liner is cured and consequently the engineer does not have to wait until a number of hours for curing of the full pipeline.
After the lining was cured, lateral connections were reinstated using a specialist robotic cutter and the pipeline returned to service with a new pipe which has a 70-year guarantee within in an old pipe.