Norman Neitzel, Rink's Lease Service
High Density custom designed pull through polyethylene liner programs for new and existing steel pipelines started in Canada in the late 70"s. High pressure salt water injection steel pipeline buried 6 to 7 feet deep in Northwestern Alberta prompted a major manufacturer of HDPE pressure pipe to try custom sizing a thin wall liner pipe. Custom tooling first had to be programmed to the front of the pipe extruder at the plant to fit all the various steel sizes and wall thicknesses. Once this was done the technology came along to install the system inside existing steel pipelines for renovation of the pipeline. This system development was the start of pipe rehabilitation for pipelines buried and suffering from internal corrosion. The polyethylene plant made the outside diameter of the thin wall liner pipe 2 to 5% smaller than the inside diameter of the steel pipeline inside diameter. Excavations where dug at each end of a section of the pipeline (normally 2,500 to 3,000 ft). Modified steel flanges were welded at each end to house a custom liner flange. A weld-o-let or thread-o-let was also welded to the top of the steel line and a small hole drilled through the steel pipeline wall. This weld-o-let or thread-o-let played an important role because this first system of HDPE liners would be "expanded" against the host pipe carrier by using air, water, or gas pressure inside to expand the HDPE liner. This "vent station" played an important part in vacating the annulus of any trapped air or produced water to the atmosphere as the liner expanded against the steel pipe wall. This system came to the USA in 1981 and was perfected as the "EXPANDED LINER SYSTEM" for the oil, gas and petrochemical industry. It is still being used today as a pipe rehabilitation technology with some variations and also has applications for the water and sewer trenchless techniques. In 1986, a newer method of HDPE Poly liners entered the commercial market place with a technology that places the custom liner "AGAINST THE STEEL WALL" after its insertion. Excavations, welding steel flanges that will house a custom liner flange to tie each pull section together are the same as the previous systems. This system changes at the liner pipe manufacturing plant, however in that the outside diameter of the liner is made slightly larger than the inside diameter of the steel host pipe. This system uses a series of power driven rollers to temporarily size down the outside diameter of the Poly Liner as the winch truck pulls it inside the steel host pipeline. After it is positioned in the steel pipe line, it reverses to a snug fit. In the 90's two more systems using "AGAINST THE STEEL WALL" technology were commercially developed. The first system uses a "Folding Technique". This form is manufactured at the Poly Liner plant typically a "U-Shape" sometimes with structural reinforcement tape around the outside to maintain its reduced diameter until it is inserted. The latest newest system employs a series of hydraulic downsizing "cells" that are controlled by pressure and lubrication to reduce the outside diameter as it is inserted into the steel pipeline. It is called "PRESSURIZED DIE System"" or "PDS" . The "PDS" system is easier to change equipment from one size to other on different sized steel pipelines. It also shows great potential when dealing with different steel wall thickness from a repair or liner rehabilitation for "cement lined" steel pipelines. All of the liner systems presented here use a