- Cured-in-place pipe
-
A cured-in-place pipe (CIPP) is one of several trenchless rehabilitation methods used to repair existing pipelines. CIPP is a jointless, seamless, pipe-within-a-pipe with the capability to rehabilitate pipes ranging in diameter from 0.1–2.8 meter (4"–110"). As one of the most widely used rehabilitation methods CIPP has application in water, sewer, gas, and chemical pipelines.[1]
Contents
The CIPP Process
A resin-saturated felt tube made of polyester is inverted or pulled into a damaged pipe. It is usually done from the upstream access point (manhole or excavation). It is possible to invert the liner upstream (e.g. from the downstream access point) but this carried greater risk. It is possible to install a liner from the downstream access point, upstream to a blind end however this carried the highest risk of all the CIPP installation methodologies. Little to no digging is involved in this trenchless process, making for a more environmentally friendly method than traditional "dig and replace" pipe repair methods. The liner can be inverted using water or air pressure. The pressure required for inversion can be generated using pressure vessels, scaffolds or a "Chip unit". Hot water, UV light, ambient cured or steam is used to cure the resin and form a tight-fitting, jointless and corrosion-resistant replacement pipe. Service laterals are restored internally with robotically controlled cutting devices. These can be sealed with additional seals into the lateral connection (Lateral Junction Repair). The rehabilitated pipe is then inspected by closed-circuit television (CCTV). CIPP is considered a trenchless technology.
History
In 1971, Eric Wood implemented the first cured-in-place pipe technology in London, England. He called the CIPP process insit u form, derived from the Latin meaning "form in place." Wood applied for U.S. patent no. 4009063 on January 29, 1975. The patent was granted February 22, 1977 and was commercialized by Insituform Technologies until it entered the public domain on February 22, 1994.
Advantages
As a trenchless technology, CIPP does not require excavation to rehabilitate a pipeline that is either leaking or structurally unsound. Depending upon design considerations an excavation may be made, but the liner is often installed through a manhole or other existing access point. Anything larger than 60" must be excavated in order to install. Liner is installed as it is wet out on site in these instances. In the case of sewerlines, lateral connections are also restored without excavation via a remote controlled device that drills a hole in the liner at the point of the lateral connection. If larger than 24" and it is safe to do so someone will reinstate laterals by hand. CIPP has a smooth interior and no joints. While CIPP can repair a pipe with bends, special design considerations must be taken into account to prevent wrinkling and stretching. CIPP can effectively reduce infiltration and leaks in pipeline systems without digging.
Disadvantages and Limitations
Except for very common sizes, liners are not usually stocked and must be made specifically for each project.[1] CIPP requires bypass of the flow in the existing pipeline while the liner is being installed. The curing may take from five hours to 30 hours depending on pipe diameter and must be carefully monitored, inspected, and tested. Obstructions in the existing pipeline, such as protruding laterals, must be removed prior to installation. Cost should be compared with similar methods such as Shotcrete, thermoformed pipe, close-fit pipe, spiral wound pipe and sliplining as these other methods can provide a similar design solution for similar or less cost in certain situations. CIPP must also be carefully monitored for release of chemical agents utilized in the reaction process for contamination downstream of rehabilitated pipes. The liner material used for common sizes is normally a felted fabric (weave) and does not go around bends well without wrinkling and going out of round on corners. Liners used for pipes with bends (particularly 100 mm pipes) are made from a woven fabric allowing it to go around bends with minimal wrinkling. The more flexible the liner, the more care needs to be taken during inversion to ensure the liner remains on the correct alignment.
References
- ^ a b Mohammed Najafi, PhD, PE and Sanjov Gokhale, PhD, PE, Trenchless Technology (New York: McGraw Hill, 2004), p. 295–311. Available from Water Environment Federation at http://www.e-wef.org/timssnet/static/OM/WPM404.htm.
External links
Categories:
Wikimedia Foundation. 2010.
