In the world of CIPP lining, light curing technology is proving to be a game changer. Light curing cuts CIPP installation times dramatically, from several hours to just minutes; a benefit that pertains to all light curing system types. In addition to speed of installation, and the improved productivity that comes with it, there are other benefits that accrue to both lining contractors and their clients.
The virtually unlimited pot life and the ability to wet out liners off- site, for example, ensures that technicians are not racing the clock in the way they are when working with a two-part epoxy, since curing does not start until the lights are illuminated.
Light curing also provides more consistent quality in the end product. With non-light cured CIPP there can be differences in the quality of the final product produced due to variation in curing elements. Differences in temperature, circulation, and time period applied to the curing medium can vary during every installation. This means that the end product can vary, which could mean that it does not meet the required standard and may cause issues later on.
When exposure to light controls the cure, the variable site conditions have far less influence and crews must make fewer site-specific method adjustments, so light curing results in a much more consistent cure across installations. The result is a high-quality end product that meets specifications and gives the long-term performance planned.
But there are some important differences between light curing systems that should be considered. For instance, to cure properly all systems require a wavelength of light that is appropriately matched to the properties of the resin used. Some wavelengths utilised are in the UV region of the spectrum, while others are technically not, but the critical consideration to ensure a full and dense cure is that the resin and light wavelength need to be calibrated to each other.
In developing the NuCure Cold Cure UV system, the NuFlow engineering team calculated the specific requirements needed to cure three-layer fibreglass material. Optical power density was measured as a function of different voltages applied to the LED strips, and Differential Scanning Calorimetry determined the percentage of liner cured as a function of irradiance. This resulted in a precise calculation of the micro-watts per square centimetre required to ensure complete irradiance
and a full and dense cure along the length of the liner. Dual power supplies ensure sufficient light power will fully penetrate the entire liner.
‘Density of cure’ refers to the levels of uncured resin present after the curing process is complete. The NuFlow NuCure system features an extremely high curing density (above 99%) with laboratory tests indicating no detectable levels of uncured resin. In any light cured system, any uncured resin that remains will likely remain uncured indefinitely and can be difficult to clean out. The dense cure of the NuCure system also results in exceptionally high heat deflection temperature (HDT), enabling the NuCure CCUV liners to be utilised in very high temperature applications. At an Ohio brewery in the USA, a NuFlow certified contractor lined over 600 ft (183 m) of 6 in (150 mm) diameter PVC pipe that had cracked as a result of extreme temperature fluctuations. The ability to tolerate high temperatures opens new markets that other lining systems cannot adequately serve.
Different lining systems will also throw off varying levels of heat while curing. The NuCure resin/light wavelength calibration results in a more controlled reaction, with a low peak exotherm and a short exotherm duration, resulting in minimal excess heat and a true ‘cold cure’. Cold cure is energy efficient, but just as importantly, does not require additional active cooling techniques or equipment. Curing processes that require active cooling can depend on additional cooling equipment which can present challenges in smaller work areas. Perhaps more significantly, active cooling can cause condensation along the length of the light train and the resulting light refraction can hinder the curing process.
Beyond resin and light wavelength, the methods by which the liner is installed also matters. Precise liner placement is the principal feature of NuFlow’s Precision PIP (push or pull in place). The process ensures installers can avoid under-shots or over- shots during liner installation, which is particularly important for ‘blind shot’ branch pipe lining. It also ensures that joints and fittings near the end of the liner are properly sealed. In other processes air can be compressed up the pipe, which may result in ‘burping’ traps and toilets and releasing aerosolised contaminants into buildings.
In addition, the design of the liner tube itself is also critical to the success of light cured CIPP systems. Liner design can inadvertently increase the risks associated with resin bleeding, migration, and resin slugs up remote branch connections. NuFlow’s Resin Protection System (RPS) helps contain the resin, which, along with fast cure times, greatly reduces the chance of these kinds of issues. The RPS also protects the liner from inadvertent light exposure, which prevents premature curing while preparing for installation.
The standard NuCure system is designed for pipes of 3 in to 6 in (75 mm to 150 mm) diameter but a briefcase-sized version is also capable of lining pipes with diameters as small as 2 in (50 mm). NuCure 2” CCUV consists of a lightweight control box and small diameter light train cores. Pipe Restoration Solutions, a NuFlow Certified Contractor, recently used the small diameter UV system on a condominium project. “The shower drains in this building were improperly installed, so there were leaks coming through floors below each unit. The units were occupied, so we needed to get in and out of them as quickly as possible.” said Project Manager Frank Rucco. He added: “We applied short repairs to over 50 PVC shower drains. We also used the NuCure Adhesive for Plastic Pipes to make sure we had both a structural and adhesive bond to the pipe. We were in and out of each unit within 20 minutes. It went as smooth as it can go.”
Light curing is a leap forward in CIPP lining, improving consistency in the final product, speeding installation times, lowering technician labour costs, and limiting risk by enhancing control over the lining process which in turn reduces warranty time and effort. “In the end, we are capturing more revenue.” Rucco concluded. “It has been a game-changing technology for us.”