Fold & Form Lining

Published: April 30, 2018 | Last updated: July 5, 2023

What Does Fold & Form Lining Mean?

Fold and form lining is a type of thermoformed pipe lining method. In trenchless rehabilitation, the liner made of polyethylene (PE) or polyvinyl chloride (PVC) is introduced into the host pipeline with the cross-section in the shape of the alphabets H, U or C.

Using trenchless methods for the purpose of rehabilitation are advantageous because they do not require digging up a stretch of road or property in order to access the defective pipe. The entire operation can be conducted from manholes.


Trenchlesspedia Explains Fold & Form Lining

The host pipe is first inspected using video cameras that are sent inside the system to check for obstructions. The pipe is then cleaned and a winch cable is used to pull the folded liner into the pipe from the downstream manhole.

Once the liner is pulled in, any stress transferred to the liner is relieved. Steam is delivered to the liner from a heat source equipment for a uniform rise in temperature through the liner. Once the liner is formed, compressed air or a mix of water and compressed air is used to cool the liner. When the temperature of the exhaust air or water and air mixture is a constant 110°F for at least 20 minutes, the curing is considered complete.

A robotic cutting machine aided with closed-circuit television cameras are used to trim the ends and open the laterals and service connections.


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