Pipeline Rehabilitation: Performing Under Pressure in India

Dec 15, 2011

There has long been a common myth to the effect that no spiral wound liner can perform when used as a method of rehabilitation/liner in pressure pipelines. This perception is born perhaps from the perceived fact that the majority of such liners are machine wound from a starting pit, or manhole, from where they are also grouted, often under less that ideal conditions, leading to voids behind the liner which subsequently result in the distortion of the liner when the pipeline is pressurized, which in turn then leads to tearing of the joints and a general catastrophic liner failure. This myth is further perpetuated by the fact that most spiral wound liner manufactures state in their product data that the lining of pressure pipes cannot be recommended with their system.

Installing Panel Lok flush against the inner wall of the metallic pressure main (Source: NoDig Media Services)
There is however, as always, an excerption to the proverbial general rule, which in this case was recently exemplified by the use of the Danby Panel Lok spiral wound lining system. Danby spiral wound liners have in fact been used very frequently and successfully in pressure pipe environments, since the first pressure pipeline liner Danby installations in Australia in 2000, where it was used with great success for the rehabilitation of over 10 km of 1,370 mm rising main operating at pressures of up to 7 bar.
 
This success was quickly followed by numerous even more ambitious projects in India, where the Danby Panel Lok product also began to find favour for use in both large diameter rising mains and pressure water pipelines operating at up to 9 bar in 2001, since when many kilometers have been installed and have demonstrated fully satisfactory service.
  
Cross-section through the composite line/grout/pipe wall showing the grout penetration into the pipe defect (Source: NoDig Media Services)
Installing the System
The secret to this success lays purely in the method of installing the liner and grout. Danby, never having been great advocates of mechanization, has always endorsed the manual installation of its products, by which means the spiral wound material can be easily expanded to ultimately form a tight fit liner positioned against the wall of the host pipe, regardless of any diameter deviations.
 
The grout fill, consists of a high strength (28 to 35 MPa), low viscosity, free flowing, rapid setting and non-shrink mix of fly ash and OPC which is injected through grout ports in the liner wall at intervals along the installed liner length. This is often achieved in multiple lifts, meaning that this crucial process can be closely monitored and controlled so as to ensure that 100% penetration is achieved with no voids, which can be inspected and verified from within the pipe bore. In this manner, it is possible to achieve a classic full composite structure through the liner/grout/host pipe wall ensuring the total transfer of all stresses throughout the pipe wall structure.
 
Savita Allied industries, Danby’s Mumbai licensee has been able to use this fact to great effect in many projects involving the rehabilitation of badly corroded and leaking metallic water supply pipelines, even when only intermittent shutdown periods have been available during non-supply hours.
  
The competed Liner in the pressure pipe (Source: NoDig Media Services)
With careful planning and organisation of the cleaning, installation and grouting crews the company has recently been able to undertake the installation of up to eighteen (18) 50 m long liners coils in a single shift, which is representative of over 70 m of 1.2 m diameter pipe work, a remarkable achievement by any measure.
 
The current projects in India continue to demonstrate the fact that the Danby Panel Lok spiral wound uPVC system has a valuable role to play in the rehabilitation of not just large diameter sewer pipelines, for which it has had an excellent track record, but also in the lesser known, but equally important role of being able to ensure the continuous supply of precious water, even working under pressure.
 
Danby Panel Lok is owned and distributed through Europe, the Middle East and Asia by APS Holdings.
 
>> This article is presented with permission of Trenchless Works / NoDig Media Services. <<

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