Open-cut replacement was out of the question for a 400-ft long fire suppression line running beneath a loading dock of a paper mill an hour’s drive from Montreal in the Lanaudière region of Quebec. The 10-in. diameter line had been leaking under a steady 170 psi of water pressure, threatening damage to the dock that would render it unusable. The plant needed repairs to the line but plant activities could not be disrupted during the repair.
The pipe was ideal candidate for an advanced form of cured-in-place pipe (CIPP) method designed specifically for pressure pipe applications, including water mains. Plant officials called Rehabilitation DUO of Quebec, specialists in this advanced form of CIPP renovation.
The principles of CIPP have not changed much since it was first introduced as an in situ sewer pipe rehabilitation technique in England in 1971. But it wasn’t until 2000 that a European manufacturer produced the first technically advanced CIPP felts and resins that were both certifiably safe for both the environment and for potable water customers and that, properly installed, formed a structurally sound pressure pipe. For most of North America, that means NSF/ANSI Standard 61: Drinking Water System Components – Health Effects, which certifies among other things pipes and joining/sealing materials as safe for contact with potable water. None of the styrene-based CIPP resin systems have NSF 61 certification.
Yet by 2010, CIPP pioneers like Rehabilitation DUO were still hesitant to enter the niche market with these earliest products and their various installation methods, since the installing contractor bears responsibility for the successful installation and performance of the pipe repair. Manual wet out processes and even the early designs of off-site wet-out facilities introduced opportunities for human error, with no way of assuring an installation met the demanding requirements of pressure pipe applications. Therefore, wet-out processes in many sewer main installations had to take place in regional facilities, being shipped by refrigerated truck to the job site. But this placed the wet-out process entirely beyond the contractor’s control.
Two years later DUO found the quality consumables and precise installation control they had been waiting for in the RS Lining product line, recently acquired by HammerHead Trenchless Equipment. DUO launched its CIPP division in 2012. Now a 15-member CIPP team operating primarily in the provinces of Quebec and Ontario, DUO crews installed more than 30,000 ft of RS BlueLine CIPP in potable water pressure pipe applications within their first years of operation.
Cedric Bergeron, general manager of the DUO division, said the paper mill’s leaking fire suppression line is a prime example of the value of CIPP for pressure pipe rehabilitation, as well as the rapid-response capabilities of its mobile RS MobiPreg CIPP impregnation station. The facility is a purpose-made, pull-behind unit, also now available through HammerHead Trenchless. The patent-pending MobiPreg is designed to exceed ASTM standard F2994: Standard Practice for Utilization of Mobile, Automated Cured-In-Place Pipe (CIPP) Impregnation Systems. DUO crews carry everything they might need in the MobiPreg trailer, arriving on site fully prepared to complete the job even when they might not know exactly what they’re up against – as in this case.
This site had a high soil water level. Water infiltration can potentially interfere with a CIPP installation.
Immediately after excavating a small working pit to access the pipe and confirming the points of leakage, DUO eliminated the potential for water infiltration at five leakage points using CIPP point repair kits they had brought. The point repairs are tolerant of moisture. The pipe does not need to be completely dry before a point repair installation.
The crew spread out the sections of CIPP liner on plastic tarps included in the kits, mixing the two-part resin, saturated the fabric and placed it over a bladder. Pulling a repair into position at a leak point, the crew filled the bladder with 11 psi of air. The spot repairs took just one day to complete. DUO finished prepping the full run of pipe, verifying its readiness with a live CCTV inspection.
Then, Bergeron said, the MobiPreg facility gives his installation crew unprecedented onsite quality control through its fully computerized mixing and resin impregnation processes. “It’s a state-of-the-art rig,” he said. “It guarantees consistency and repeatability of a high-quality installation from design to layout.”
The MobiPreg operator simply inputted basic data such as product types, diameter and length of liner, and resin type on a touchscreen. The computer configured the wet-out process based on this job’s unique information and then measured and mixed the resin. The computer also controlled and monitored the wet-out operation, giving instantaneous remote readouts about the mix, the application and the rate of wet out.
Immediately following wet out, the crew loaded the liner into an inversion drum, securing one end of the liner to an exit flange and the tail end to a strap that was used to control inversion speed. They pressurized the drum from its integrated compressor and progressively inverted the liner into the existing pipe at a controlled rate. Once the liner had been fully inverted, they introduced steam to activate the resin and begin its cure.
CIPP liners use a fiberglass component to give the cured pipe its high structural robustness independent of the existing pipe material. Unlike other liner designs, however, RS Blueliner is a felt-fiberglass composite that stretches radially. This permits the liner to form itself more completely to the pipe surface, rather than stretch across any irregularities in the surface of a run of pipe.
Dave Kozman is a CIPP specialist with HammerHead Trenchless Equipment who has been closely involved in the company’s development of CIPP products in pressure-pipe applications. “A tight fit between liner and host pipe is critical to pressure pipe performance from a structural standpoint, as is achieving a watertight seal throughout,” he said “Any gaps between a liner and host pipe can cause liner failure across unsupported areas during pressure testing or while in service. Additionally, these gaps provide a path for water to travel, which is not desirable.”
After the installation had cured, DUO pressure-tested the line. Standard disinfection processes were made before returning the system to service. The entire project took less than 10 days from access excavation to backfilling. Plant operations were not disrupted.