Sliplining is a technique for repairing leaks or restoring structural stability to an existing

pipeline Pipeline may refer to: Electronics, computers and computing * Pipeline (computing), a chain of data-processing stages or a CPU optimization found on ** Instruction pipelining, a technique for implementing instruction-level parallelism within a s ...

. It involves installing a smaller, "carrier pipe" into a larger "host pipe",

grout Grout is a dense fluid which hardens to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting secti ...

ing the annular space between the two pipes, and sealing the ends. Sliplining has been used since the 1940s.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 The most common material used to slipline an existing pipe is

high-density polyethylene High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...

(HDPE), but fiberglass-reinforced pipe (FRP) and PVC are also common. Sliplining can be used to stop

infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

and restore

structural integrity Structural integrity and failure is an aspect of engineering that deals with the ability of a structure to support a designed structural load (weight, force, etc.) without breaking and includes the study of past structural failures in order to ...

to an existing pipe. The most common size is (8"-60"), but sliplining can occur in any size given appropriate access and a new pipe small or large enough to install.

Installation methods

There are two methods used to install a slipline: continuous and segmental. * Continuous sliplining uses a long continuous pipe, such as HDPE, Fusible PVC, or

Welded Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as braz ...

Steel Pipe, that are connected into continuous pieces of any length prior to installation. The continuous carrier pipe is pulled through the existing host pipe starting at an insertion pit and continuing to a receiving pit. Either the insertion pit, the receiving pit, or both can be

manhole A manhole (utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel. Manholes are often used as an access point for an underground public utility, allowing inspection, m ...

s or other existing access points if the size and material of the new carrier pipe can manoeuvre the existing facilities. * Segmental sliplining is very similar to continuous sliplining. The difference is primarily based on the pipe material used as the new carrier pipe. When using any bell and spigot pipe such as FRP, PVC, HDPE or Spirally Welded Steel Pipe, the individual pieces of pipe are lowered into place, pushed together, and pushed along the existing pipe corridor. Using either method the annular space between the two pipes must be grouted. In the case of

sanitary Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems ...

sewer lines, the service laterals must be reconnected via excavation.

Advantages

Sliplining is generally a very cost-effective rehabilitation method. It is also very easy to install and requires tools and equipment widely available to any pipeline contractor. Segmental sliplining may not require bypassing of the existing flow.

Limitations

The new pipe will generally have a significantly reduced

cross sectional area In geometry and science, a cross section is the non-empty intersection of a solid body in three-dimensional space with a plane, or the analog in higher- dimensional spaces. Cutting an object into slices creates many parallel cross-sections. T ...

because of the size difference between the inside diameter of the existing pipe and the outside

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...

of the new pipe, as well as the wall thickness of the new pipe. Sewer laterals must be reconnected via excavation. Laterals can be welded to liner without excavation if man entry size pipe. Installation usually requires excavation at the insertion and receiving pits. Continuous sliplining generally requires bypassing the existing flow. Storm

culverts A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdo ...

are often installed without bypass pumping. If the HDPE pipe has been butt welded, the external bead must be removed from the pipe, which is done with an 'external de-beader' tool. This provides a smooth exterior on the HDPE pipe, allowing it to pass through the existing pipe easily. Because the weld bead does not contribute any strength to the butt-welded join, removing it is no detriment to the strength or pressure rating of the pipeline.

References

{{Reflist
Center for Underground Infrastructure Research and Education CUIRE
* 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 Trenchless technology