Rehabilitation with close-fit PVC-U pipe lining

Rehabilitation of sewers with close-fit pipe lining involves the use of modified polyvinyl chloride (PVC) pipes manufactured at a reduced dimension. Due to its construction and parameters PVC-U lining is used only to rehabilitate gravity sewers. Appropriate static strength calculations determine the selection of the lining’s ring stiffness (SN 4 to SN 8).

TECHNICAL EVALUATION OF THE SEWER
Before the rehabilitation the pipeline is jet-cleaned with a sewer cleaning machine placed on a truck. After that the pipeline is inspected with a remote-controlled camera. The analysis of the video from the sewer inspection forms the basis to create a detailed computer report on the technical condition of the pipe. On the basis of the above data the sewer is classified depending on its technical condition.

SELECTING THE REHABILITATION METHOD
Depending on how the sewer is damaged or destroyed, and its classification to a specific group, an appropriate rehabilitation method is selected. After the evaluation of the sewer’s technical condition one should analyze geodetic data, groundwater level with respect to the base of the sewer, road traffic exposure, and other parameters that have influence on the selection of parameters of the liner that is to be used. On this basis, knowing the Young (E) modulus characteristic for the recommended carrier, during the design phase the designer can select a PVC-U close-fit pipe that has the right thickness (given the load on the ring stiffness) and diameter.

STORAGE AND TRANSPORTATION TO THE CONSTRUCTION SITE

The lining is wound on a spool and delivered to the construction warehouse using normal means of transport. Spools are stored vertically, on a hardened service yard. The lining is delivered to the insertion point in a pipe-sauna, to prevent the cooling of the lining.

To install the pipe liner in the rehabilitated sewer it must be plugged above the section undergoing repair. If the flow of water is large, before the plug a pump or set of pumps is installed, to create a by-pass and remove wastewater beyond the rehabilitated section.
Then, into the cleaned and prepared sewer PVC-U lining, preheated in the pipe-sauna, is inserted using a winch with controllable and recorded towing force.
Once the lining has been inserted steam plugs are installed in a special construction at the start and end manholes. Once the plugs are in place the lining is evenly heated up to ca. 90°C using hot steam. Having heated the lining, it must be inflated using compressed air at a pressure of 0.5 bar. Following that the lining is cooled down using cold air. When the lining has been cooled down the steam plugs are cut off and the lining undergoes CCTV inspection. All lateral drains are connected directly, without any T-pipes, using a milling robot.
During the process installation parameters, such as temperature of preheated lining, towing forces, and all temperature readings from control points during the main heating cycle are recorded.

CCTV INSPECTION

Once the installation is finished and drains are opened a CCTV acceptance inspection is made and recorded on a DVD or another storage medium. At the same time an inspection report is prepared.

TESTS

In accordance with PN-EN ISO 11296-1, 11296-4 and PN-EN 1610.

Any defects are made good with the help of a camera-controlled robot and/or by patching with short sections of the pipe liner.