SEKISUI SPR Europe sets European record in Paris: Spirally wound at the largest diameter

Le Pecq is a commune on the western outskirts of Paris, where sewage disposal is the responsibility of the "Syndicat Intercommunal d´Assainissement de la Région de Saint-Germain-en-Laye" sewage board, an amalgamation of 9 communes around Saint-Germain en-Laye. In the local area of Le Pecq, immediately alongside the exclusive "Les Pyramides" private leisure centre and under the busy main road Rue Nationale 10, Lyonnaise des Eaux, a company acting as network service provider for the Syndicat, operates one of the largest sewers in the district: a 281-metre-long DN 3000/3300 corrugated metal pipe that discharges the region's collected rain water to the western side of the Seine river. The voluminous pipe, however, was not large enough in practice. The poor hydraulic characteristics of the corrugated metal pipe meant that it would surcharge time and again. In order to resolve this problem, the operator had a rehabilitation plan drawn up by the engineering company SAFEGE. The goal set out for the rehabilitation was to ensure sufficient discharge capacity for at least 50 years.

 

It soon became clear during the rehabilitation planning that an open new construction would not be possible due to the boundary conditions. Trenchless rehabilitation in this locality also presented new challenges though, and this drastically reduced the range of technical possibilities. The only option for accessing the sewer was to create an insertion pit measuring approximately three by four metres with a depth of 5 metres, which could be set up on a narrow pedestrian lane next to the Rue Nationale 10. From here, with whatever process was to be used, the entire project would take place for both stretches that were to be rehabilitated. CIPP technology was rejected because there are not yet any processes that offer liners of this nominal diameter. The surface structure of the corrugated metal sheet also prevented a CIPP liner from being employed. The trench dimensions that were possible were not sufficient for relining with short GRP pipes.

 

The planner's thoughts turned to the spiral-wound pipe process as the solution. This process has been tried and tested since 1978 and the current types with the brand name SPR™ are virtually exclusively linked to SEKISUI SPR Europe GmbH, and in practice are implemented by its subsidiary the KMG Group. The process involves winding an endless PVC or HDPE profile strip into a sewer pipeline. The watertight connection of the individual windings is created either by key-and-slot joints in the profile strip or with a welded connection. With the SPR™ PE technique used in Le Pecq, the HDPE profile is manufactured with vertically oriented steel reinforcement, completely encapsulated within the plastic. The gauge of this steel reinforcement depends on the individual case, in particular on the diameter of the liner that is to be created. In Le Pecq, KMG LinerTec GmbH acted as a sub-contractor to the local HPBTP (Paris) rehabilitation company.

 

The main player in the process is a circular, stationary winding machine positioned in the sewer with an attached extrusion welding unit. While the drive of the machine feeds the profile strip, continuously supplied from an above ground reel, into a winding cage to form the required nominal diameter, the spiral-winding machine simultaneously welds the profile together to form a watertight pipe. The newly created liner is thus continuously wound into the old sewer until it reaches its end point. The end points at Le Pecq were, at one end, the outlet into the Seine and at the other the underground structure into which two collectors feed into the corrugated metal pipe.

 

Once the first 211 metre section had been successfully rehabilitated, the spiral-winding machine was quickly turned 180° within the trench and then converted for an upstream reach of 70 metres, including the necessary scaffold for the operators of the mighty machine, itself weighing around 1 tonne. From then it was a further 4 working days before the second section was fully fitted with the SPR™ PE liner. In the last working stage the annular space between the liner and the corrugated pipe was filled with liquid mortar, with approximately 600 cubic metres of this being needed. First of all the liner was secured with a mechanical bracing against buoyancy, deviation in position and buckling.

 

All in all, the Le Pecq project was considered a resounding success by all those involved, particularly the client. With the specified nominal diameter of the liner and its extremely smooth internal surface the hydraulic capacities of the sewer have been improved in such way that surcharge will be a thing of the past for years and decades. For SEKISUI SPR Europe and the KMG Group the extreme dimension of the spiral-wound pipe renewal in Le Pecq is not the first technical record in the rehabilitation market and the company directors are confident that it won't be the last.