Effect of close-fit sliplining on the hydraulic capacity of a pressurized pipeline

A full-scale laboratory testing setup was used to examine the flow conditions through a new steel pipe with relatively smooth interior (no tubercles, encrustations, holes, scales, etc.) before and after sliplining with a high density polyethylene (HDPE) liner. Results of the tests indicate that the relative roughness of the lined pipe section was generally lower than that of the new steel pipe at Reynolds Numbers of 200,000 to 500,000. The average friction factor (Swamee–Jain) for the lined pipe was 0.0180 compared to 0.0185 for the original steel pipe. The minimum and maximum friction coefficients were 0.0146 and 0.0208 for the lined pipe and 0.0148 and 0.0241 for the new steel pipe, respectively. This indicates that a deteriorated pipe with significant roughness could be restored back to its original condition using close-fit sliplining. Meanwhile, installation of the 6.35 mm (1/4 in.) thick liner in the 152.4 mm (6 in.) pipe reduced its cross-sectional flow area by about 16% and, accordingly, would decrease the flow by about 20% under the same head loss. To further explore this condition, two design parameters, the liner thickness and its buckling resistance, were examined analytically using a practical application of 152.4 mm (6 in.) pipeline with an internal negative pressure due to a water hammer. Results of the analysis indicate that a 3.4 mm (1/8 in.) thick HDPE liner with average quality installation would provide about 100 kPa ( 10 m or 33 ft water column) of buckling resistance, but would also reduce the flow capacity by about 12.7%. While the laboratory tests were only performed on one type of liner material (i.e., HDPE), the general concepts and findings of this study would apply to other types of polymeric liners.