More recently, the industry has introduced systems that allow the installation of folded plastic pipe relining products through manhole entrances. These systems, known as FFP systems, utilize thermoplastics that have been deformed from a circular shape (i.e. folded) to produce a smaller net cross-section that can Easily feed it into existing sewers. These FFP products are typically extruded PVC or high-density polyethylene (HDPE) pipes, flattened and folded longitudinally. The plastic pipe is fed from the spool into the existing pipe, where hot water or steam is applied until the lining temperature rises enough to round. After rounding, allow the installed liner to cool. The FFP process can produce tight fitting liners in the main tube. However, no bonding occurs between the inner liner and the main pipe.
This is a process of inserting a new smaller diameter pipe into the defective pipe and grouting the annulus. It has the advantage of being simple and relatively inexpensive. However, a significant loss of hydraulic capacity may occur.
Improved slip liners, commonly referred to as snug liners, include rolled liners and swaged liners, utilizing the properties of PE or PVC to allow a temporary reduction in diameter or change in shape prior to insertion into a defective pipe. The inserted pipe is then expanded to form a snug fit against the original pipe wall, thus avoiding the need for annular grout as in traditional slip liners. Temporary reduction in diameter is achieved by mechanical rolling (rolling) or by drawing through reducing dies (swaging).
The basic helically wound sewer repair system involves the use of extruded rigid PVC tapes of varying widths with interlocking edges. The strip is fed from a reel to a winder, which produces a helically wound tube that is smooth on the inside and ribbed on the outside. The winder can work from the bottom of the manhole and feed the liner directly into the pipe. The annular space around the tube is grouted.
