Most sewer pipe lining technologies offer liners that are cured in place after insertion. Spiral-wound pipe rehabilitation is an emerging technology that offers trenchless repair with no curing.
The technology includes a system that uses a single panel of polyvinyl chloride (PVC) that has interlocking edges and is reinforced by encapsulated steel, and a system that uses high-density polyethylene (HDPE) that is welded together with a polyethylene joint. The liners, which come in profiles of various thickness to ensure rigidity, are installed manhole-to-manhole.
The liner is suitable for stormwater and wastewater lines, but not for potable water, because it isn’t pressure rated.
Hydraulic winder
In making a repair with spiral-wound technology, the damaged section of the host pipe is first camera-inspected, then jetted or otherwise cleaned of debris.
A hydraulic winding machine is then lowered into the manhole, and the panel material is fed into the winder from a spool that remains on the surface. As the material exits the winder, it forms the shape determined by the host pipe and construction variables by extruding along its own interlocking channel.
The winder continues to push the material shape along the pipe’s interior surface until the liner reaches the next manhole.
Once the liner has been locked into place at both ends, a temporary bracing system can be erected if necessary. Grout is injected into the annular space between the host pipe and the liner. In most cases, no shutoff or bypassing is required, as the host pipe can accommodate a certain degree of flow during installation.
The technology is suitable for circular pipes from 30 to 197 inches and for non-circular shapes, such as teardrops and culvert pipe.
“Even though the liner slightly reduces the inside diameter of the host pipe, we’re increasing the flow of the pipe because of the material’s Manning’s n value,” says Jonathan Vaccaro, business development manager with SEKISUI SPR Americas LLC, headquartered in Atlanta, Ga.
SEKISUI is the only company offering the machine-wound spiral technology, having purchased a majority stake in former competitor Rib Loc Australia about two years ago.
Smaller sewers
A PVC liner is designed for circular sewer and stormwater pipes from 6 to 30 inches. The grade of PVC is similar to that used in new sewer and drainage lines. Liners are chosen according to the structural requirements of the pipe: Thicker liners can offer greater stiffness.
After a camera inspection in which lateral connections and branch lines are mapped, the line is cleaned and jetted. The winding machine is lowered into the access chamber and set in place. Then the liner is extruded. A wire mounted inside the liner allows it to retain the shape of a pipe until the spiral liner reaches the next upstream access point. There, it is fixed into place as the material continues to feed into the interior of the pipe, stopping only when the liner expands to its maximum diameter.
“Essentially, you’re getting a circular liner in the shape of the pipe, but somewhat smaller so that it moves freely to the next manhole or access point,” says Vaccaro. At the access point, the end of the spiral is locked into place and the wire is cut to allow further expansion of the liner so it can fit tightly against the profile of the pipe, smoothing out jogs, offsets or imperfections.
A lubricating sealant allows the liner to slide smoothly as it expands along its own interlocking channel. When the liner expands to its maximum diameter, the liner is cut and sealed at both ends. A robotic cutter then reinstates the lateral connections.
Larger pipe
PVC material is also used in larger pipes from 30 to 197 inches. It can be fitted to circular, custom or rectangular shapes and can be installed vertically in access shafts or wells. The hydraulic winder can either be fixed or moved along the profile of the pipe as the liner is extruded.
“We can do pretty much any shape,” says Vaccaro. “For odd shapes we customize the hydraulic winding drive unit to follow pre-determined shapes. So if we’re creating a 96-inch-tall teardrop, the winding frame is built to the shape of the pipe, but slightly smaller so that we have a predictable annulus space and know the grout thickness required as part of the rehab design.”
For these profiles, the winder bends the metal reinforcement inside the liner to permanently shape it to the host-pipe profile. These liners require a bracing system to provide structural support during grouting.
Extrusion-welded
A pipe-grade HDPE material is used to provide optimum stiffness for lining sewers, storm drains and culverts from 30 to 120 inches. Here, the profile of the liner is sealed using an extrusion welder that fuses the material together.
“We use HDPE pellets in a pre-heated condition to provide the molten material for the weld,” says Vaccaro. “This liner uses HDPE because it has a higher chemical resistance and is designed for the industrial market. Because the welded liner provides the structure here, a non-structural grout fills the annulus space.”
Careful in the cold
While the spiral-wound liner is suitable for all climate conditions, application requires care during extreme cold. The material must be kept supple while being wound so that it conforms perfectly to the desired profile.
The first U.S. installation was a 2005 test by the City of Los Angeles to install a corrosion barrier in a semi-elliptical, large-diameter sewer pipe. The earliest use of spiral-wound technology was recorded 25 years ago in Tokyo, Japan.
“They’ve had zero significant failures either there, or anywhere else where it’s been used,” says Vaccaro. “One reason is that feed rates, winding profiles and HDPE welding information is programmed into the computer. After that, the results are completely independent of the skill of the human operator.”
The product is being licensed in the United States on a territorial basis. “Typically, the smaller contractor is attracted by the idea that he can enter the market for an attractive price,” Vaccaro says. A typical start-up package consists of a TV truck, supervisor truck and a winding truck.
The technology is versatile: “For each new project, we can adjust the material profile, the grout thickness and the shape of the annulus space to meet the parameters of the job,” says Vaccaro.
