What are the best trenchless rehabilitation procedures to consider?
Many private and public sector organizations are turning to trenchless rehabilitation procedures to repair and maintain underground piping due to their numerous benefits. However, not all trenchless pipe rehabilitation techniques are created equal.
It is, therefore, crucial to understand the benefits and limitations of each procedure to select the most appropriate solution for a specific application. Some of the most popular trenchless rehabilitation techniques are listed below:
Pipe bursting, also known as in-line expansion, involves demolishing the existing pipe using a bursting tool while simultaneously installing the new pipe. During pipe bursting, the existing pipe acts as a guide for the path of the bursting device. (Read An Introduction to Pipe Bursting.)
As the tool advances, it pushes the existing pipe radially outward until it shatters into fragments. The bursting tool also pulls the new pipe behind it during this operation.
Pipe bursting is ideal in situations where existing pipes exhibit excessive deformations or are damaged beyond the repair capabilities of other rehabilitation techniques, such as sliplining or cured-in-place pipe liners. They are also commonly used when larger-diameter replacement pipes need to be installed.
While pipe bursting is one of the fastest trenchless rehabilitation techniques, the dynamic movement of some bursting methods can disturb the surrounding soil, resulting in heaving and settlement in some soils. Also, during bursting operations, the rehabilitated pipe must be taken out of service. Therefore, temporary rerouting infrastructure is typically required.
Sliplining is one of the oldest trenchless pipe rehabilitation techniques. During this process, a new, smaller diameter carrier pipe is inserted into an existing larger host pipe. The annular space between the two pipes is typically grouted to improve structural integrity and prevent leaks. (Read An Overview of Sliplining.)
Sliplining is also relatively fast compared to other trenchless methods and can install pipes in long runs with minimum connections. However, in most sliplining projects, manholes do not provide adequate access for the procedure.
As such, insertion pits are required for each pipeline segment. While the quantity of excavation for the pits is less than that required by conventional dig and replace methods, it can still result in disruptions to surface activities.
Cured-In-Place-Pipe Liner (CIPP)
CIPP is a renewal process which involves inserting a flexible liner into a host pipe. The fabric liner is saturated with a thermosetting resin and inserted into the pipeline using a liner inverter. This procedure is typically done using an existing manhole as the access point. (Read A Look at CIPP and Aging Drinking Water Infrastructure.)
The inverter expands the liner until it presses against the outer walls of the existing pipe. When the resin cures, it hardens to form a new structural pipe within the host pipe.
CIPP is the best way to install a structural liner without any excavation. One of the main disadvantages of CIPP is that the liner follows the alignment of the host pipe. Therefore, the liner will not correct any distortion-related defects.
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