SEKISUI SPR Americas, LLC provides mechanically-wound PVC liners with 3 methods of installation.
The Spiral Wound Category
Spiral Wound Lining is a trenchless technology that uses continuous strips of plastic (typically PVC or HDPE) to fully restore gravity pipelines. This rehab method has been successfully utilized for over 40 years with millions of feet installed in the United States and across the globe. Two methods of installation exist for this category; machine-wound and manually-wound liners. These methods vary by manufacturer and possess unique features and benefits.
Differences aside, Spiral Wound technology boasts innovative qualities as a category. These include being 100% trenchless, involving no chemicals, and creating a minimal construction footprint – to name a few. Both machine-wound and hand-wound liners provide flexibility when it comes to pipe offsets and job site unpredictability. However, there are many resulting differences as well; this article will first overview each method and then compare/contrast the two regarding design & structural capacities, industry standards, and capabilities.
Mechanically-Wound PVC Liners
For both manual and mechanical Spiral Wound Lining, the process begins with a continuous strip of plastic material (typically PVC or HDPE, referred to as “profile”) that is fed from above ground through the access. The mechanically-wound process uses spools to unreel the material. The strip is then fed into the machine located within the pipe or at the entrance. Mechanically-wound PVC liners are installed using stationary or traversing machines that continuously wind the profile into the host pipe by interlocking each subsequent strip of profile. The profile edges interlock to form a mechanical seal impervious to I/I and root intrusion. This is done by rollers or a winding cage that is powered hydraulically. Watch a live winding video to see how this occurs.
A traverse winding machine is typically (but not always) used for large diameter pipe renewal. The machine travels the entire pipe segment locking the strip’s edges together to form the liner. A larger diameter (32” – 217”) mechanically-wound project involves man-entry inside the pipe. This is to guide the PVC strip towards the machine and ensure the liner is locking properly.
For small diameters (6” – 42”), the machine is placed at the entrance of the host pipe. The liner’s edges are wound and locked within the cage of this machine, and subsequently pushed towards the far-end manhole. In short, winding machines perform the forming and locking of the liner for mechanically-wound rehab.
Manually-Wound PVC Liners
Alternatively, manual, or hand-wound liners use manual force to lock the profile’s edges and form the liner. The continuous plastic strip lays coiled near the access and is manually fed inside the pipeline. For certain hand-wound projects, the material comes in plastic panels, which are simply lowered through the access.
The edges of the strip are then pulled to become perpendicular to the liner. From here the male and female locks are joined and subsequently locked together by installing a strip within the joint. The strip is made from gasketing material and creates a water-tight seal. The strip is installed by the crew using a pneumatic palm hammer.
Again, this process will continue the entire segment required. The hand-wound liner is then subsequently grouted-in-place. With this method using manpower, it will also require man-entry inside the pipe. This means that hand-wound liners are typically used to restore pipes from 36” in diameter and above.
Comparing Design & Structural Capacities
Manual and mechanically-wound both feature a ribbed profile design, which provides added stiffness to the liner material. Although these processes typically use the same material (PVC) and ribbed design, the height, thickness and inner components of the PVC strip vary by manufacturer.
For instance, machine-wound PVC may be steel-embedded depending on the project. The steel not only structurally reinforces the liner, but it also allows non-round applications to keep their shape. Additionally, the hand-wound PVC strip is typically wider than the machine-wound strip.
While both methods provide fully structural renewal, the machine-wound liner is a fully structural, stand-alone liner for circular pipelines. This is partially due to machines being capable of winding rigid and thick profiles. The result is the actual PVC liner being structural, as opposed to the hand-wound composite system which typically requires both liner and grout for structural integrity.
Certain machine-wound applications require grout to be fully structural, such as larger diameter non-round shapes.
Comparing Industry Standards
Spiral Wound adheres to ASTM standards for trenchless rehabilitation projects. The main difference is the machine-wound standard compared to the hand-wound; SEKISUI and other machine-wound manufacturers comply with ASTM 1741-18; the standard practice for installation of machine spiral wound poly (Vinyl Chloride) (PVC) liner pipe for rehabilitation of existing sewers and conduits. This is in contrast to hand-wound manufacturers following ASTM F1735-09; the standard specification for poly (Vinyl Chloride) (PVC) profile strip for PVC liners for rehabilitation of existing man-entry sewers and conduits.
Both manual and mechanical-winding renew sewers, storm drains and culverts. Manual-winding, however, is also applicable beyond restoring gravity pipelines. The method is utilized for new pipe construction as well as manhole rehabilitation. Hand-winding is also possible for structures as a partial-lining solution, not the entire 360°. This contrasts mechanically-wound liners, which exclusively serve 360° pipeline rehabilitation.
The two methods are both capable of renewing non-round shapes. The diameter ranges, however, differ. Hand-winding typically renews 36” pipe and above due to the required man-entry. Mechanical winding starts at 6” and spans to over 200”.
Furthermore, hand-winding requires grout in the annular space. This is opposed to machine-winding within circular pipelines from 6” – 60”. At this range of diameter, certain mechanical-winding methods allow the liner to be in intimate contact with the host pipe, resulting in no annular space.
The ability to install liners in live flow is a key feature for both methodologies. That being said, the acceptable live flow conditions vary. For machine-wound liners, typically up to 30% low-velocity flow is permittable for installation.
It is important to note these comparisons when considering a Spiral Wound technology for a pipe rehabilitation project. While there are certain similarities between machine and manual spiral wound lining, the fundamental differences make for two very distinct trenchless lining solutions.
SEKISUI SPR offers mechanically wound PVC liners for trenchless pipe rehabilitation.
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