Sunday, July 14, 2024

Soaring through options

FFRP vs. CIPP in trenchless rehabilitation by Dion Pohorille

Both in Africa and Europe I have noticed many people birding these days, frankly for me birding can get a touch predictable. Sure, the sweet songs of warblers and the vibrant colours of hummingbirds are delightful. Coming from sub-Saharan African Savannahs we were less exposed to two more common Northern Hemisphere pitch black birds found on every church steeple or city fence. Personally, I prefer a touch of these enigmatic Corvidae, the raven and the crow. These black harbingers of change have perched themselves in myth and folklore for centuries, symbolising everything from wisdom to transformation. As we delve deeper into the world of trenchless pipe rehabilitation, a similar sense of revelation unfolds.

Just like watching a raven soaring through the sky or scaling a rickety crow’s nest affords a breathtaking panoramic view, understanding the intricacies of FFRP (Flexible Fabric Reinforced Pipe) and CIPP (Cured-in-Place Pipe) grants us a much wider understanding of pipeline rehabilitation. We are no longer limited to a narrow perspective. Instead, “just as these birds fly,” we can explore the most efficient and effective solutions for the rehabilitation of our underground infrastructure.

CIPP: The agile crow

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Much like the crow, a highly manoeuvrable bird known for navigating tight spaces, some types of CIPP can excel in tackling complex pipeline geometries. The resin-saturated liner, resembling the crow’s compact body and flexible wings, can in certain applications handle 90-degree bends with exceptional agility. This makes CIPP ideal for certain situations where the existing pipeline negotiates sharp changes in alignment, similar to a crow navigating a complex network of branches. Additionally, CIPP’s ability to access a pipeline from a single point to cure in place is much like a crow accessing shiny treasures in tight spaces with military precision.

FFRP: The soaring raven

The raven, with its impressive wingspan and ability to soar above for long time periods, mirrors the core strengths of FFRP. This method utilizes a long continuous, flexible liner with embedded fabric reinforcements, as the raven’s broad wings allow it to soar for long distances, the strength to allows for significantly longer pulling distances, often exceeding a kilometre in one go, thus minimising the need for additional access points. However, FFRP’s inherent tough bursting and temperature resistance composition limits its ability to handle sharp bends. While it can navigate 45-degree bends, complex 90-degree manoeuvres or tight spaces are better suited for CIPP’s agility. In situations where there are longer sweeping bends with radii exceeding five times the pipeline diameter, FFRP’s extended reach is achieved, similar to how a raven’s powerful wings allow for efficient soaring.

The importance of a close fit

Regardless of the CIPP or FFRP choice, achieving a close-fit liner allows for cost effective material options offering longevity and operating capabilities withstanding internal and external forces and protecting the host pipe from corrosion. This approach enhances the inherent strength of the existing host pipe, allowing it to contribute to the overall structural integrity of the rehabilitated system. The host pipe can then assist in handling internal bursting pressures and external loads, thus maximising the effectiveness of the rehabilitation process.

This philosophy underlies our core approach at ASOE. On demand liner solutions can be manufactured from nominal diameters of 50mm to 1400mm if requested to match the exact inside diameter of the host pipe. This unique ability to tailor the looms and extrusion process embraces the individual requirements of each pipeline, thus overcoming the outdated “one-size-fits-all” mentality. In today’s world of adaptability, the “one size fits all approach” limits budgets and trenchless design capabilities. This is why ISO 11295 below gives the interactive Class C specification for FFRP allowing the liner to interact with the host pipe as one entity, connected together by pressure.

This is not to say that there are not situations where in design an annulus gap is accounted for. This is where ASOE uses Kevlar (Aramid) in the lining manufacturing process.

As ASOE’s vision and core values centre around the environment and cost effectiveness we strive wherever possible to use less Kevlar. Hence the use of more cost-effective Polymer yarns are used in the manufacturing of linings for gravity pipelines. However, ASOE does use Aramid as all the ASOE oil, gas high temperature and pressure liners require this material for these applications.

Close fit allowing T connections: FFRP has previously struggled with T connections especially when air release, scour or other valves need to be installed. With a tight close fit liner the ability to install a T connection once the lining has been placed will now become possible as the final stages of certifying and testing this technology are taking place. Asset owners will soon be able to connect place T connections for smaller pipes or valves to T off the main FFRP. With an annulus gap connecting a T piece is not possible.

Ultrasonics (UT) & close fit: UT is a key non-destructive testing (NDT) method relying , it relies on sound waves. Dissimilar materials in liners and pipes, along with air gaps ( annuli), weaken these waves.

Water filling the gap certainly offers a slight improvement, but inconsistencies and complex wave interactions make it this unreliable. A close fit lining regardless of being CIPP or FFRP ensures a far better, direct sound path for accurate flaw detection through the liner and in the host pipe.

This is particularly important for smart pigging, a common oil and gas practice. Pigs are cleaning and inspection tools propelled through pipelines. A close fit lining allows for efficient pigging enabling comprehensive NDT inspections. Unlike municipal utilities, where internal inspections are less advanced and more focused on CCTV coding, whereas pigging’s prevalence in oil and gas pipelines demands higher resolution inspections making es a close fit system essential for reliable NDT.

Intelligent assessment: the key to choosing wisely

Through a combination of visual inspections, understanding the host pipelines environmental conditions, advanced surveying techniques, and the material testing has been done, engineers can pinpoint the exact nature and extent of the pipeline deterioration. This allows for a more nuanced approach to rehabilitation. For instance, if the primary concern is internal leaks and joint failures on these pipe assets with limited access, FFRP’s ability to handle high pressures and long lengths then ASOE becomes the ideal solution, similar to how a raven’s larger wingspan is perfectly suited for extended soaring. Conversely, pipes with multiple sharp bends, severe structural weaknesses, vacuum conditions or where external loadings exist, one would benefit from CIPP’s capabilities, mirroring the Crow’s resilient and efficient manoeuvrability.

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Trenchless Works bringing you balanced journalism, accuracy, news and features for all involved in the business of trenchless and no-dig from around the world

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