The municipal waste disposal company Speyer gave the project contract to sewer rehabilitation specialists Ehnes GmbH, who is based in Germersheim. The project included the complete repair of 1.7 km of damaged concrete sewers. The project was carried out from March to April 2011.

The sewage pipes from the 1960s lie in a residential area near the centre of town. Speyer’s St. Vincentius hospital is also located nearby. The sewers with circular profiles of DN 300–800 mm as well as oval profiles of 400/600–700/1,050mm showed serious corrosion and structural damage, plus extreme fat deposits in places. Speyer called for tenders in 2010 for the comprehensive installation of pipe liners to prevent possible collapsing and to achieve long-term preservation.

Working at night

Segments were rehabilitated at lengths of 20–160 m during the 40 day project. A strict schedule was mandated by the city to limit the traffic problems and inconveniences for local residents, as well as the hospital operations. Therefore the Ehnes team did part of the work at night. In addition, due to the great amounts of wastewater in the larger sewers, extensive water drainages needed to be installed.

Project Manager and Director of Ehnes Hans Kreuzer said that due to the prevalent fat residues in the sewer, callibrating and cleaning the pipes thoroughly was not an easy task. Obstacles such as protruding ports or intrusions were removed by milling robot equipment owned by the rehabilitation company.

Once the sewer pipes were prepared to be rehabilitated, the pipe lining commenced with Brandenburger’s light-curing technology in sections, installing an average of 150 m, approximately one section, per day.

After the liner was installed, the necessary partial projects followed. The previously dimensioned side inlets were milled open using robots and their ports reconnected the next day. The connection of the liner ends to finish the shaft rehabilitation also used the robotic equipment.

Rapid execution

The rapid execution of the liner can be shown through the rehabilitation of the longest section, which was 160 m, in the Hafenstraße of Speyer. The, first step after the DN 300 mm pipe under the quiet residential street was rinsed, was to insert the protective foil for the liner. Once complete, the GFRP liner, which was impregnated in the factory with light-curing polyester resin and delivered ready for installation, was drawn in by a cable winch, sealed with packers and pressed against the old pipe walls by pressurised air.

A camera inspection showed the flush and non-wrinkling position of the 4.2 mm thick liner. For curing at a pressure of 500 bar, a light chain with eight lamps, each with 400 watt, was drawn in. Completed in 3.5 hours, the curing speed was at a rate of 0.9 m per minute.

Reducing administrative expenses

With the tight times frames, the quick curing times, as well as the good preperation and routine working methods of the construction team, allowed for the other sections to be rehabilitated on schedule.

An engineer appointed by the waste disposal company Mr Riedel said “The Ehnes company provided very good work.”

The company said that the advantages of the liner procedure with UV light curing are clear, “In addition to the quick curing, the setting up and dismantling of the construction site is carried out quickly and above all, contrary to the usage of needled felt, all ports can be opened up immediately after the curing.

“That is an advantage for the construction supervision, because the construction site does not need to be visited a second time, which reduces the documentation and administrative expenses. And of course, the client prefers to have a quickly completed construction site,” said Mr Riedel.

Sewer rehabilitation from one source

Owner and Director of Ehnes Roland Herr emphasised the good co-operation with the Speyer municipal facilities, in particular with the engineer responsible for planning and executing rehabilitation projects, Stephan Wittner. To ensure a continuous exchange of information, the construction site consultation and the taking of sample pieces were done on a weekly basis.

Mr Herr considers the professional qualification of the employed personnel a central factor for the cost effectiveness and quality of pipe lining projects, along with the good co-operation with the client.

“In 2010, we sent in about 70 samples of cured pipe liner for inspection and there was not a single complaint,” Mr Herr said.

Since 2009, Ehnes has relied on the Brandenburger procedure with good rehabilitation results.