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Specifying the right trenchless products

Innovative new products, systems and methods of trenchless repair are being launched all the time. Glenn Cartledge, managing director at Source One Environmental, explains how you can specify the right trenchless technology for the job in hand

Cleaning up

The first part of most repair jobs is to clean the pipeline of any debris or blockages. As well as general debris, this can include the removal of fatbergs, tree roots and hard substances such as concrete that have been ‘tidied up’ by washing down the nearest drain.

Traditionally, water jetting has been used. This has limitations, particularly with more stubborn blockages, which can take days to remove, and runs the risk of bursting the pipe if too high a pressure is used.

Now increasing in popularity is the use of milling machines, which mechanically rotate tools at the end of a cable inserted into the pipe. These tools can cut through blockages in minutes. 

Milling machines come in a range of sizes, specified by the nominal OD of the target pipeline. A wide range of tools is available, many designed to clear specific types of blockages, such as concrete or failed liners. Special tools for PVC pipelines are available, which will scour, but not cause damage. The ranges of manufacturers such as Picote, Renssi and Seweri give an indication of what can be achieved.

The specification for cleaning jobs should therefore include the pipe size, material and type of blockage but could also include the desired method of cleaning.

Avoiding a rough patch

Localised patch repair is achieved by installing a resin-impregnated fibre glass mat into a pipeline using an inflatable packer. Until recently, only perfectly circular pipes were repaired. Now, non-circular assets like egg-shaped culverts can be patch repaired using new rectangular packers.

The quality of matting and resin varies between suppliers. In addition, more flexible matting material should be used if the repair includes a bend of more than 45°, to ensure a smooth patch.

Resins are available with a range of working and cure times. As these are affected by ambient temperature, the right resin needs to be matched to general weather conditions. Rapid-setting resins are available but are only recommended for defects close to the manhole, as otherwise patches can begin to set before they are fully in position.

On the right lines

Lining a whole section of pipe is sometimes necessary when the pipe has been badly compromised. 

The lining system will consist of the liner and the resin, similar to systems for patching. Liners are available in various materials and thicknesses. Specification will need to take account of the depth of the pipeline, load weight upon it and level of the water table.

In the UK, polyester resin is used as standard. Alternatively, vylester is available for improved chemical resistance. Epoxy resin creates an improved bond but also has reduced odour during installation and is often specified, for example, around schools or hospitals.

Fully qualified

Some of the more established products are approved by independent bodies such as the Water Research Centre (WRc), WRAS or DibT (in Europe).  The US NSF approval indicates suitability for potable water following repair. 

Tests such as long-term durability or resistance to chemicals may be available from manufacturers, even where no approval exists, and these have usually been carried out by independent test houses.  

Overall, the quality of lining and patch repairs will depend on the installers’ skills. Training is available, some of which is independently verified, in the above techniques. This is often delivered by product manufacturers, but proof of training may well be available.

Trenchless technologies save time and cost on site and the huge disruption of excavation. Their reach is ever expanding. Now, there are efficient no-dig tools and systems for all sorts of refurbishment applications.  Matching the tool to the job is the key to a good result, as well as using approved materials installed by trained operators.

This article first appeared in the May issue of WET News and was sponsored by S1E

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