Ultra Flex Liner & A Difficult Job – Minimizing Risk

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Here’s a tough job and the advice I gave the contractor to accomplish the job. The contractor’s customer had a job that included 75′ (22.8m) of 3″ (75mm) pipe, a transition to 4″ (100mm) pipe and continued on for 25′ (7.3m). He was particularly concerned about covering the transition when the diameter changed from 3″ to 4″. While this is a high risk job, it is doable, but needs consideration. Trying to get 4″ (100mm) material down a 3″ (75mm) host pipe is difficult in itself. And using a stretchy material that expands 30% would leave the risk of splitting the seam using a 3″ material stretch to a full 4″ diameter. We have tested the stretch limits of many materials and found the 30% factor works for most of these materials. While some suppliers tout a liner that will stretch from 3″ to 8″ pipe, the reality is that even if you find that material, the
3″ portion will be exceedingly thick while the 8″ section will be dangerously thin. Using the 30% rule shows a 3″ material will stretch to 3.9 inches without worrying about splitting and still hold the minimum design thicknesses dictated by the ASTM’s. So trying to get a 3″ liner to stretch to a full 4″ inside the 4″ clay host pipe 75′ out, may fail due to stretching the material beyond the safe 30% rule. The 3″ material is ABS pipe, so it, like the clay is full diameter unlike cast iron. One final curveball is there are three 45 degree turns in the 3″ section of pipe. So what to do?

TPU Welded to Liner

To minimize risk, I suggested the following steps in this scenario. By welding on a 75′ leader plus the distance from the Quik Shot to the beginning of the host pipe, to a 25′ x 4″ section of liner. This will allow the 4″ section to be lined and cured first. To speed up the process, it can be cured with heat, so the second shot can be completed right after the 4″ section is cured.At this point we have a 4″ cured line coupled to a 75′ leader that can be left in place and used as a pre-liner. If there is a desire to remove it, that can be accomplished by sanding the connection with one of our reinstatement drill driven sanding devices. Either way, a 3″ stretchy liner can be wetted out and installed. The end should end somewhere inside the 4″ section of pipe. Being we’ve lined the 4″ pipe, the diameter is no longer 4″ and can be lined with a 3″ material that will stretch the 30% without worry to the new lined diameter. Curing should be accomplished with a 4″ calibration tube to insure that the liner in the 4″ section is stretched to the wall of the lined 4″ pipe. Again, this can be heat cured to speed the process.

While there are other options to line this pipe, this method reduces the risk to the lowest scenario.

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