Spiral-wound lining is an established trenchless technology to renew gravity sewers, storm drains and culverts. Like cured-in-place pipe (CIPP) or sliplining, spiral-wound liners provide a structural lining solution for fully deteriorated pipelines with minimal site disruption.
The features and benefits of spiral-wound liners, however, differ significantly from its trenchless technology counterparts.
Let's take a closer look at spiral-wound pipe lining and its constructability features and benefits.
Spiral-Wound Technology Basics
Spiral-wound liners are a specialty extruded plastic ribbed profile made from pipe-grade PVC. The liners are constructed directly onsite using mechanical winding machines and the PVC profile is shipped to the job site on spools.
The profile strip is wound into the existing pipe via stationary or traversing winding machines with the edges of the profiles joining to form a continuous liner. The result is a new PVC pipe within the existing pipeline. (Look: INFOGRAPHIC: The Lifespan of Steel, Clay, HDPE, and PVC Pipes.)
Spiral-wound rehab is a fully structural repair solution that can be designed for fully deteriorated pipe conditions capable of withstanding all applied loads. This method is designed for tight fit or fixed diameter grouted solutions for 6” to over 200” diameters.
Spiral-wound liners are used on gravity pipe systems, such as sewers, storm drains and culverts and rehabilitate a wide range of pipe materials including concrete, brick, clay, CMP and others.
Additionally, spiral-wound liners are capable of renewing round and non-round shapes as well as pipelines with radius bends.
Trenchless Lining Process
The lining process for spiral wound rehab is typically as follows:
Pipe Cleaning & Inspection
The pipe is cleared of debris and inspected to confirm pipe conditions. If laterals are present their locations are marked via closed-circuit television (CCTV). (Read: Using CCTV to Inspect Pipes.)
Spiral Wound Installation
An above-ground spool feeds PVC profile strips directly inside the pipeline where the liner is constructed.
Sealing & Reinstatement
The PVC liner’s ends are sealed, and services are reinstated.
The PVC liner is inspected via CCTV to ensure the rehabilitation process was a success.
The installation set-up typically includes a continuous strip of PVC profile that is on a spool above ground. This strip will then be led from the reel, through the manhole and fed into the winding machine. The machine will then construct the liner through a continuous winding process, interlocking the profile edges to form successive wraps of PVC.
The PVC profiles contain gasketing materials that form a tight-fitting continuous mechanical lock that is impermeable to water or root intrusion. (Read: The Harmful Effects of Tree Root Infiltration on Potable Water Piping.)
Depending on the project and manufacturer, spiral-wound liners can be designed as tight fit or as fixed-diameter grouted solutions. For smaller and medium diameters (6” – 72”), installation methods exist to where the PVC liner is installed as a tight fit liner and doesn't require annular space grouting.
For larger diameters and non-round shaped pipes, fixed diameter solutions are available. Some profiles have optional steel reinforcement and can be designed using structural or non-structural grouts.
Ongoing research and development by spiral-wound liner manufacturers has recently introduced PVC profiles and installation equipment that can rehabilitate larger diameters without the need for annular space grouting.
Features & Benefits of Spiral Wound Lining
PVC pipe lining is a different approach than conventional lining methods, allowing for unique features such as:
Live Flow Installation
In most cases, Spiral Wound can be installed in up to 25% - 30% flow inside the pipe. This allows for limited or even no bypass for pipe rehab projects that would otherwise require mandatory bypass pumping.
Minimal Above Ground Footprint
Spiral-wound construction's carbon footprint is extremely minimal, even for a trenchless technology. The staging area includes the spool of PVC, power unit and CCTV truck. For larger scale projects, multiple spools of profile would be on site to meet the daily production requirements.
With spiral-wound rehab being an entirely mechanical process, there's no styrene or contaminated process waters to dispose of. The installation process also allows the contractor to start or stop at any point during the installation as needed.
Structural & Hydraulic Renewal
Spiral-wound rehab is a fully structural rehab solution that is designed to relevant ASTM standards such as ASTM F1697-18 and ASTM F1741-18.
Truly Trenchless Lining
Spiral Wound uses existing access points to complete rehab projects. This means no pit excavation or backfill. The winding machine can be disassembled to pass through existing manholes and subsequently reassembled directly inside the pipeline.
Spiral-wound lining is a continuously evolving trenchless technology. Capabilities within the United States have increased significantly over the past few decades as new manufacturers have entered the market.
Liners are now available for a wider range of diameters. New profiles and state of the art installation equipment are continuously being introduced to meet a wider range of applications.
Contractors understand the constructability and environmental advantages of using spiral-wound liners and are now are part of their trenchless toolbox.