Agru America's SureFIT® is a close fit liner that is specially designed for rehabilitating damaged potable water pipelines. When heated up by steam, it regains its original round shape and adjusts to the wall of the existing pipe, reducing internal stresses and increasing resistance to crack initiation. |
Trenchless water main rehabilitation is an emerging field and new techniques and materials are continually being developed. Water main linings can be structural, semi-structural, or nonstructural. AWWA Manual M28 – Rehabilitation of Water Mains identifies four types of linings with respect to their structural capabilities:
Class I Linings: Essentially nonstructural in nature, these linings are used to restore water quality in water mains that are structurally sound, but suffer from corrosion and tuberculation. Class I linings might be an economic and easy-to-install option for rehabilitation projects that are aimed at improving water quality and, for some cases, hydraulic capacity by increasing the Hazen-Williams coefficient. They do not provide a viable solution if there are apparent holes and gaps in the host pipe or structural support is sought. Examples include thin-wall polymeric (epoxy and polyurethane) and cement mortar linings.
Class II and III Linings: These types of linings are considered semi-structural, and designed to give structural support in addition to improving water quality and hydraulic capacity. However, hydraulic capacity improvement is dependent on initial condition of the host pipe and lining thickness. Class III linings have adequate ring stiffness to withstand external loads by themselves; however, they are not designed to withstand the maximum allowable operating pressure (MAOP). High-build polymeric, spray-applied linings (e.g., epoxies, polyurethanes, polyureas) and thin-walled extruded linings (medium density polyethylene installed by swage lining, die lining, etc.) are examples of Class II and III linings.
Class IV Linings: A Class IV lining is essentially a pipe within a pipe. They are designed to withstand MAOP for the design life of rehabilitation (typically 50 years). Class IV linings will work as a replacement pipe in case the host pipe fails and may provide a more economical and easier to install option in comparison with conventional replacement (open-cut) or pipe bursting. The downside of fully-structural linings is that they are thicker than semi-structural or nonstructural linings, which means a smaller internal diameter (ID) for the rehabilitated pipeline and, depending on the lining type, restoring service connections may require excavation. Polymeric linings (typically high density polyethylene or PVC) installed by slip-lining and cured-in-place pipe linings are examples of Class IV linings.
About the Author: Firat Sever is a Senior Engineer with Benton & Associates Inc., based in Illinois. He has more than 10 years of experience in the water and wastewater industry. Sever's doctoral dissertation was based on the use of polymeric linings for pipeline rehabilitation. He may be contacted via email at [email protected].