Modern pipe rehabilitation

  • Two recent projects featuring trenchless pipe rehabilitation
  • Spiral-Wound pipe lining, Cured-in-Place-Pipe & Fold-and-Form method
  • Detailed project description

Sekisui SPR has a comprehensive portfolio of technologies for the rehabilitation of water, sewage and gas networks, such as the Spiral-Wound pipe lining, Cured-in-Place-Pipe and Fold-and-Form method. Two recent projects show that these technologies fulfill the various requirements to maintain worldwide the water and sewage infrastructure. In addition, they offer benefits such as short construction times, low costs and little strain on local residents and the environment.

Spiral-Wound pipe project in Ansbach, Germany

The city of Ansbach, located in Southern Germany, is a 1,250 year old city with numerous buildings of historical value as well as a substantial underground infrastructure for the supply and disposal of water, wastewater and energy of a city with 40,000 inhabitants. The high concentration of residential houses meant that neither traditional methods of excavation nor conventional trenchless methods could be used for the rehabilitation of an aged sewer system made of bricks and dating from 1936. The sewer section in need of rehabilitation was located under the busy promenade in central Ansbach. As part of a major construction project at the Promenade only a small amount of space was available for the rehabilitation equipment that made SPR the obvious choice because it does not require much equipment.

The sewer section in need of rehabilitation was located under the busy promenade in central Ansbach. With the Spiral-Wound technology SPR only a small amount of space for the rehabilitation equipment was required.


Sekisui SPR recommended the Spiral-Wound technology SPR to the utility company Awean, responsible for the wastewater network of Ansbach. The Spiral-Wound product is based on the world’s first, unique concept of “composite with existing pipe” to make effective use of the structural strength remaining in the existing pipe. The possibility of installing under live flow conditions reduces construction time, costs and the impact on the residents, society and environment, compared to methods that require the excavation of roads.

The rehabilitation process with SPR

The winding machine wound the profile to the requested egg-shaped form and diameter of 1,200/1,500mm while it moved with every rotation towards the end point.


After inspection and cleaning of the 220m sewer section, the winding machine was placed through a manhole into the host pipe. The spool with the endless PVC profile strip was located directly next to the manhole to continually feed the profile into the winding machine in the sewer. The winding machine wound the profile to the requested egg-shaped form and diameter of 1,200/1,500mm while it moved with every rotation towards the end point. With every winding the profile strip was interlocked to a new egg-shaped watertight pipe. When one profile spool was empty a new profile was welded onto the Spiral-Wound pipe until the complete 12,000m of profile were wound. After the winding process the deliberately created annular space between the old and the new pipe was filled with high-strength grout, which gave the new pipe its required static characteristic. The new stand-alone pipe operates with an increased hydraulic performance and prevents future deposits or deterioration. The trenchless rehabilitation project was successfully completed in July 2013 after a three-month construction period.

After completion of the winding process a new high-performance, watertight liner is formed.


For the Ansbach rehabilitation project Sekisui Chemical received, on September 10, 2013, the 6th Junkan no Michi Wastewater System Prize awarded by the Japanese Minister of Land, Infrastructure, Transport and Tourism as well as the 59th Okochi Memorial Prize for the Development and Practical Application of the Automatic Spiral Pipeline Forming and Pipeline Rehabilitation Method in March 2013.

Pilot project with CIPP technology in Shumen, Bulgaria

Shumen is a northeastern city in Bulgaria where the drinking water supply is the responsibility of the “Water Supply and Sewerage Company of Shumen”. The main drinking water supply pipe runs from the waterworks in the southeast of Shumen across the city. The pipe was built in the 1950s and showed pinholes, corrosion and leakages. The deteriorated steel pipe was in urgent need of rehabilitation to guarantee a 24h faultless drinking water supply.

As an open construction solution was not possible because of the appalling grounds which are very muddy when it rains and the excavation pits run full with water, a fast trenchless technology solution with less equipment was required. The construction company Stroitelna Mehanizatsia was awarded the contract for the trenchless rehabilitation.

Nordipipe as Pull-In version

Sekisui NordiTube Technologies, member of Sekisui SPR in Europe, recommended Nordipipe, a fully-structural solution for the trenchless rehabilitation of water pipes. Instead of an inversion method, the technology was designed as Pull-In version in response to the specific requirements of the project: pipe diameter of 920mm including 15° bends, installation length of 164m and an operating pressure of 16bar. Additionally, calculating the amount of resin required is more accurate and therefore injecting the resin is more consistent; in addition irregularities like air bubbles are also excluded. The Pull-In installation is also said to reduce the risk of wrinkling and increases the quality of the final pipe.

Nordipipe on a mobile impregnation setup close to the construction site


Nordipipe as Pull-In version consists of a main hose and a calibration hose. The laminate is embedded into an inner and outer polyethylene (PE) coating and is impregnated with the same epoxy resin to form a homogenous material combination used for potable water approved under various regulatory schemes.

Inversion of the calibration hose


The main hose is a fibreglass reinforced needled felt liner with a specific number of glass layers selected according to the internal pressure. If needed, the wall thickness can also be increased to address other loads, for instance vacuum. Its durable PE coating on the outside protects the liner from external influences.

Arrival of the calibration hose into the intermediate pit


The calibration hose, a needle-felt liner with PE coating, raises the main hose into its position within the old pipe and provides a smooth surface with increased hydraulic performance compared to the old host pipe.

The installation process

Three construction pits provided access to the 328m long pipe section which was at a depth of 3m under a farm field alongside a main road. Heavy rain fell prior to the rehabilitation which increased the silting-up and soaked the loamy soil so that no heavy load such as rehabilitation equipment could be carried. This also confirmed the decision to use the Pull-In method as one truck with the liner spools and pressure drum, a roller bed as well as the roller setup for liner guidance were sufficient. The impregnation process took place at a road near the construction site. A lengthy space was needed for laying out the liner during impregnation by a mobile impregnation setup and it was then directly wound onto a transport spool. The main and calibration hose were impregnated with the specially designed NordiPox D epoxy resin at about 4°C.

After the pipe cleaning, the main hose of the Nordipipe was drawn successively into one of the two 164m long pipe sections by means of a winch. The calibration hose was then installed with a pressure drum. This hose positioned the liner in the old pipe and both hoses were steam cured to a new stand-alone pipe. After the temperature at the coldest spot reached 70°C, the temperature was maintained for 2h. The inner side of the new pipe consists of a PE coating that forms a smooth surface. As a result, drinking water is transported at a higher flow rate, improving the efficiency of the pipe function which is expected to last for the next 50 years.

The inner side of the new pipe consists of a PE coating that forms a smooth surface.


After the endsealing of the four liner ends at the two 164m long liner sections, the entire rehabilitation process was concluded within two weeks by applying a two-component epoxy resin. After a pressure test with 18.5bar, the pilot project for the Nordipipe Pull-In liner at a 920mm diameter drinking water pipe was successfully finished and the supply pipe could be put back into 24/7 operation.


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