Organic “High-Build” Spray-in-Place Liners – An Emerging Class of Rehabilitation Methods

By Erez N. Allouche, PhD, P. Eng. and Eric J. Steward, Trenchless Technology Center, Louisiana Tech University | June 2009 Vol. 64 No. 6

A pressure supply system was designed to provide up to 1500 psi of water pressure to the frame. The system consists of a high pressure nitrogen tank supplying pressure to an interface chamber which in turn pressurizes the water within the cavity on the pressure side of the frame. A series of regulators, gauges and relief valves were installed for safety and pressure regulation. To measure the deformation of the exposed panel at the opening as pressure increases, a pivot system was designed to transfer the movement of the panel to a linear variable displacement transducer (LVDT) (Figure 7). This system protects the LVDT from damage when panel failure occurs. During testing, data from both the LVDT and the pressure transducer was collected using an Agilent data acquisition unit.

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Fig. 6: Assembled testing frame with panel.

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Fig 7. LVDT installed at panel opening

Sample Preparation
Specimens tested consisted of 31-inch square panels of the polyurethane and polyurea materials. Flat plates were used to simplify the testing apparatus. Also, the majority of current applications in the USA involve the lining of large diameter pipes that permit person entry for manual spray application of the material. The vendors provided a total of 28 of panels with thicknesses ranging from 0.14 inch to 0.42 inch. To accommodate the 26 threaded rods required to assemble the testing frame, 1⅛-inch holes were drilled into the panel along the edge using a steel frame template (Figure 8).

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Fig 8. Test panels of poluyrea (left) and polyurethane (right)

Testing procedure
Once the panels were prepared and installed in the test frame, the transducers were mounted and the data acquisition system was powered to begin acquiring data. The pressure cavity was then filled with water to evacuate the air. Once the cavity was filled, the pressure system was transferred to the nitrogen side of the interface chamber to begin applying pressure to the water behind the panel. The pressure was applied in 50 psi increments with approximately 60 seconds between increments, allowing the pressure to stabilize and form a uniform distribution of the load across the panel. These increments of pressure were applied until failure occurred.