Sewer rehabilitation with Brandenburger pipe liners with 16.5 millimetres wall thickness

Pipe lining with light-curing GFRP liners are among the most important options of the sewer rehabilitation planers because of the very brief construction times, the minimised construction site set-up, and finally the outstanding characteristics of the finished liner. Brandenburger Schlauchliner, based in Landau, has set a new standard in the renovation of walkable, large-profile sewers with this technology: Four pipe liners had 16.5 millimetre wall thickness, which where used to rehabilitate a brick egg-shaped profile in Hamburg-Osdorf in combination curing procedure under commission of the sewer system operator, the Hamburg water works in December 2005.
 

The brick storm sewers (class V) 650/1100 in the Dörpfeldstraße in Hamburg-Osdorf had become conspicuous in the course of the Hamburg sewer rehabilitation program. The damage assessment encompassed in addition to washed-out joints and encrustations, also isolated longitudinal fractures and faulty points in the masonry. In the end there were 345 metres of sewer channels under the Dörpfeldstraße to be designated as a subject for rehabilitation. As is usual for Hamburg, these sewers should also be rehabilitated in the pipe lining procedure as far as sensibly possible. Trenchless technology was definitely desired here, simply because the apex cover of the sewer was up to 8.50 metres.

Left: Weighing in at 10 tons, this 92 metre long pipe liner was the longest of the four that Brandenburger installed in Hamburg-Osdorf. Right: The existing inspection shafts were big enough for drawing in the large-calibre liners into the sewer.

In light of the documented damage assessment and the special boundary conditions, Brandenburger decided to offer a liner with a unique size to solve the problem, which eventually was commissioned by the Hamburg water works (HSE). A 16.5 millimetre thick GFRP pipe liner was used with a resin system based on light peroxide combination curing. In this process a peroxide hardener is mixed to the conventional photoreactive UP resin, which doesn't "react" until 65 °C. This means that such a liner can be stored with no problem for many months at moderate temperatures and definitely when cooled.

But when the photoreaction is initiated by UV light during the curing process, then it also ignites directly the peroxide reaction - which is self-supporting then -, so that practically two simultaneous reactions lead to the reliable curing of the liner. While you have different curing limits at hand today with the various light-curing pipe liners based on reduced transparency or uneven optical refraction indexes, the above-mentioned combination curing is deemed necessary by various light-curing pipe liner manufacturers for thicknesses of already 5-6 mm so that the curing is reliable and economical as well (slow drives take too much time!). Brandenburger employs combination curing starting at 10 mm because of the extremely good transparency of the material used in coordination with the applied UV curing equipment. The dimensions realised in Hamburg-Osdorf have so far never been attained in all respects.

Secured by a water pumping of 250 l/sec peak pump performance, the pipe liners were installed into the rehabilitation sections always in the same procedure: In each thoroughly cleaned section a preliner was first drawn in that should reduce the friction of the heavy liner, which weighs tons, as it is drawn in across the base. It is of note that for a liner of this dimension made of GFRP neither excavations needed to be made nor even the shaft cone needed to be removed – an enormous acceleration of the entire process. A UV lamp train was then brought though a pressure lock into the pipe liner, which had been expanded by air pressure to form-fit in the sewer. The lamp train has an output of 6000 Watt.

The lamp train travelled through the pipe liner in the Osdorfer class V sewers at an even speed of 40 cm/min. An interesting and important insight from the Brandenburger engineers' point of view was that the 16.5 millimetre liner cures just as fast as otherwise the liners with 12 millimetre wall thickness; the curing time with the combination reaction evidently does not increase proportionately with the wall thickness. Even the liner in the Dörpfeldstraße, which was the longest at 92 metres and the heaviest with about 10 tons, was fully cured in just around four hours. At four hours installation time, four hours curing, and then five hours disassembly including the opening of the connections, each section of the construction could be completed within one long work day. Ultimately the entire time and technical effort with this procedure in the walkable diameters is therefore hardly greater than for a sewer DN 500. This makes a significant difference to some other pipe-lining system in which the process effort increases with the diameter of the sewer. Some advantages of the GFRP light curing are:

• no water consumption
• minimal power consumption with light as opposed to hot water
• conceivably low vehicle use even at greater diameters
• no scaffolding installation in the traffic area of the shafts during the installation and curing phase
• notably quicker curing of greater diameters than with hot water, thus quicker project execution 
• no waiting period before opening of the connections, because shrinkage in the GFRP pipe liner is nearly ruled out

In Hamburg-Osdorf the 4 construction sections, which where altogether 354 metres long, were completely executed within 2 workweeks, including all the preparation and other related tasks. The independent inspection of the project confirmed to the client's satisfaction that all the required technical specifications according to the regulations of the qualification requirements and the quality assurance plan of the Hamburg water works had been observed.

A further record for light-curing GFRP pipe liner was set by Brandenburger during various tests in Landau in December 2005. DN 1000 liners with wall thicknesses of up to 28 mm were cured. Curing was done here too with the combination curing UV light/peroxide.
In the presence of managers from the DIBt or a materials testing facility, pipe liner samples or ring samples for long-time apex pressure trials where taken and tested later. The measuring results showed the following values: Outer diameter 992.83 mm; wall thickness 28.77 mm, short-time Young modulus 13543N/mm2.
In this test series the new Brandenburger BLUETEC UV curing equipment was tested that offers advantages especially in larger diameters and wall thickness as compared to the standard conventional equipment.

For the GFRP pipe liner technology in general and for Brandenburger in particular these successes with the greater wall thickness signify the first step into a new and increasingly interesting market segment of trenchless sewer rehabilitation.

Contact
Dipl.-Ing. Jens Goll
Technischer Service
Brandenburger Liner GmbH & Co.
Taubensuhlstraße 6
D-76829 Landau/Pfalz
Tel:(+49) (0) 63 41 51 04-0
Fax: (+49) (0) 63 41 51 04-155
E-Mail: Info@brandenburger.de oder j.goll@brandenburger.de
www.brandenburger.de

All Photos: Brandenburger

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