When the tender for a renewal project in Szczecin, Poland was first issued at the beginning of 2008, GRP short-pipe lining was specified. However, after some extensive research by the customer it was found that it would be very difficult to maintain the required water flow rates using the chosen technique. Severe deformation of the old pipe, which was not identified during the planning stage, meant that if a GRP short-pipe lining was used, the diameter of the renewed pipe would be much smaller, and so reduce the capacity of the new pipeline.

Another challenge was posed by the fact that the pipeline being renewed in Szczecin was a main collector in the city centre, where it would be impossible to construct a dewatering system. Even though a large pit for the GRP lining had already been dug, at the last minute the customer decided – based on the new demands faced – to opt for the first ever European use of SPR technology.

The masonry-lined combination sewer was built over a century ago. The condition of the sewer had deteriorated severely in recent years. As a result of continuous traffic and other external loads, longitudinal cracks had formed along the crown of the pipe, leading to increased deformation.

Renewal had become a matter of urgency. There were also a large number of deposits and other obstacles protruding as much as 50 cm into the pipe. Consequently, it was clear that thorough cleaning and jet-grouting work would have to be carried out prior to the renewal process. The SPR installation process can be divided into three key stages: the winding of the PVC profile, the construction of the bracing system and the grouting of the annulus

Winding process

The winding was executed starting from the manhole access shaft downstream to the next shaft. Based on the local conditions and the existing 18 metre long pit, the stretch of pipeline scheduled for renewal was divided into four segments. The winding machine installed the profile in the existing pipeline guided the profile and formed it into the desired shape, with an inner diameter of 2,240 x 1,600 mm. The winding machine moved one profile width forward on each rotation of the profile, locking the profile edges to form a water-tight pipe in the process.

As soon as the machine’s forward momentum had taken it to the next shaft, the winding process was stopped and the profile separated. The team from the Polish construction company, together with the Japanese engineers, laid the winding machine and the profile reel to the next shaft, which then served as the new starting point for the next installation phase and as the conduit through which the profile was again guided by the winding machine, as in the first phase.

Bracing system

In the next step, when the winding process was complete, the expert team constructed the bracing system. The braces were introduced through the shaft into the spiral wound pipe and carefully installed. The constructed cross-section of the bracing system prevents lifting of the new spiral wound pipe during subsequent grouting and prevents deformation.

Grouting

The grouting process for each renewal segment comprised injection of the grout into the annulus between the old pipe and the spiral wound PVC profile and curing of the grout. The team executed the grouting work in three stages. Then the braces were dismantled and installed in the next renewal segment. The pit area was grouted to a statically determined height above the spiral wound PVC profile. Summary

All work was carried out by the team comprising workers from the local Polish agent of Sekisui CPT and Japanese technical specialists. The renewed sewer is beneath one of the main streets in Szczecin, and collects the rainwater and sewage from all the smaller surrounding systems. Work was interrupted several times due to flooding and above average rainfall, and lost time had to be made up for at night. However, since SPR can also be applied with drainage, the installation could be resumed without problem following the enforced breaks.

Headed by Christopher Moritz, an expert team provides technical know-how and support covering all aspects of the new technology. “One of the key benefits of the SPR PVC profile from Sekisui is its environmental sustainability – including 60 per cent less fossil fuel consumption, 30 per cent less energy use and four times lower CO2 emissions in production.

“That is one of the factors that will enable us to achieve our goal of delivering premium renewal solutions and becoming the market leader in the renewal of large-diameter pipelines in Europe,” said Mr Moritz.

Despite the very difficult weather conditions, the European premiere of SPR technology was successfully completed within approximately two months.