Dating back to the 1940s, slip lining has been used as a pipeline liner to restore structural stability to an existing pipeline or repair leaks by stopping infiltration. It is one of the oldest methods of trenchless rehabilitation. The most common material used in slip lining in an existing pipe is high density polyethylene to prevent internal pipeline corrosion.
Pipeline Liner and Slip Lining Installation
The slip lining method does not rely on the strength of the host pipe for pressure containment. A smaller pipe, typically known as a carrier pipe, is slipped into or installed into a larger piper, known as the host pipe with the aid of a winch. The space between the two pipes is then sealed with grout. Then then upstream and downstream ends of the pipe are also sealed with grout.
The most difficult part of any slip lining installation is selecting the grout. The grout has the potential to cause the new and host pipe to act a single entity which can increase the stiffness of the pipe and its resistance to external hydrostatic loads. The grout should only be considered a filler and so be low in strength and have a low viscosity. There are some structural grouts that link the pipeline liner to host pipe and these have compressive strengths which are higher than grout used only to confine the liner.
Using slip lining as a pipeline liner, the liner can accommodate the trenchless reinforcement of pipe from 8 to 60 inches in diameter.
Slip Lining Advantages
One of the major benefits of slip lining is that installation is faster than that of standard HDPE lining in that liner compression equipment is not required and only uses tools and equipment that any pipeline contractor typically would have on hand. Consequently, it can usually be done while the existing line is working. If done in segments, then bypassing or diversion of the existing flow is not required.
It is also a very cost effective rehabilitation method. Excavation and trenching costs are eliminated as a new pipeline does not need to be installed. Additional costs and risks are avoided and eliminated as existing pipeline is not abandoned and every foot of pipeline trench does not need to be protected and backfilled.