Most water main lining technologies require that the existing pipe be thoroughly cleaned and prepared for application of the coating. Some cleaning techniques include: hydraulic, mechanical, chemical, swabbing, scraping, pigging and air scouring.
Generally, a type I/II or type V Portland cement is used, depending upon the salinity of the liquid flowing through the line. Specialty cements are available to withstand high temperatures, heavy salinity concentrations, and hydrogen sulfide gas and associated corrosives.
This system is used for the internal sealing and corrosion protection for water lines first installed as early as 1930 in the USA.
Cured-in-place liner systems are typically installed in pipe sizes of 6”-12”. These liners span and seal leaking joints, pinholes and minor cracks. Services/laterals are reinstated from inside the pipe with no excavation typically required except for access pits. Resins used with potable water are typically NSF 61 approved resin systems. Installation lengths of up to 500 feet are not unusual and liners can negotiate bends in the existing main.
Larger liners up to 48 inches in diameter are also available and can be a structural solution to rehabilitate water mains. Glass fiber reinforcement gives the liner static, self-supporting properties and allows it to withstand higher internal and external pressures than traditional liners. An individual pipe can be up to 800 feet in length.
Spin cast pipelining technology combines specially designed equipment with proven processes for the cleaning, preparation and application of an ANSI/NSF Standard 61 approved epoxy to deteriorated 3” to 36” diameter pipes. Metal and cement-based gravity and pressure pipes can be lined in both horizontal and vertical configurations.
In 2007, the AWWARF study, “Service Life Analysis of Water Main Epoxy Lining” [Project #2941] estimates a 50-year design life for epoxy. The epoxy will provide a high level of water quality that will not affect pH levels.
Internal joint seals require worker-entry for Installation. The seal bridges the existing joint with a rubber material allowing continued movement of the pipe joint. Internal seals typically provide a bottle-tight, leak-proof joint repair and can withstand both internal and external hydrostatic pressures.
The PE or PVC material is either site or factory folded or radially reduced prior to insertion into the host pipe. With the pipe liner profile reduced in size, allowing for an easier installation, the pipe liner is inserted utilizing techniques similar to that used in traditional sliplining applications. Air or water pressure and/or steam are used to revert the liner back to its original round shape, thereby forming a close fit with the host pipe. The new liner isolates the flow stream from the host pipe wall, eliminating internal corrosion and typically providing a full structural renovation solution.
In addition, the new liner allows for service connections to either be reinstated externally to the new liner or reinstated internally with newly developed robotic technologies.
The sliplining method incorporates the installation of a smaller or reduced size steel, ductile iron, polyethylene, PVC or other pipe materials inside the existing pipeline. Pressure rated pipe capabilities can be selected for most main applications. In some cases, grouting is required to fill the gap between the host pipe and the new PE pipe. Very long lengths can be installed using this method. Service taps are typically excavated and directly reconnected. Sliplining can be applied in transmission and distribution mains of 6”-60” in diameter.