Applying The Wrong Technology To Fix A Problem

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“I just heard about a new technology that can coat a pipe and I won’t need to reinstate any tie ins. The line is 200′ in length and is 4″ pipe and I’m told that I can do this with no problem at all even with missing section of pipe and ground water present! There are 30 tie ins within the first 25′ of pipe, then none from the last 175′. While the line is considered fully deteriorated, the one coat spray on material will make fully structural according to my supply vendor.” 

When something is new, we all test the limits to see what it will do and how far we can push it often applying it to situations outside of what it was designed to do. First things first, the technology described above is a great technology and we are working on a fully structural version. The devil is in the detail and as with all technologies, there are limitations. The first limitation is line preparation. While this technology was developed for rehabilitation of drain, waste and vent piping inside of a building the technic can be used in multiple sized pipe diameter changes, with turns and bends that have been cleaned to near new condition and have pinhole holes or less to coat. The surface must not only be clean to these levels, but then must be dried to apply the resin system. We’ve been introduced to systems that “rough up” the surface of the pipe while others attempt to get the pipe to new condition.

To be fully structural the entire surface should be covered with about 3mm of material to provide a fully structural pipe that doesn’t rely on the old pipe for anything more than a form. Brushing or spraying on the material should be accomplished in thin lifts in order to avoid globs of resin running before curing takes place. Further, thinner lifts will insure that you cover all of the pipe and not miss some spots.

The way this technology works, after cleaning and drying the pipe, is to lay down a coating of resin approximately 1/2 mm thick per lift to a total completed thickness of 3 mm when finally complete. That means that a minimum of 6 lifts must be completed to rehabilitate this pipe. The details of this method is to bundle two supply hoses of part A and part B resins delivered into the pipe, a camera with cable, and a sleeved cable that turns a sprayer or brush to spread the resin. The sleeved cable is run with a drill. this assembly is pushed to the end of the line to be rehabilitated, and the resin is pumped to the delivery system. The techs job is to watch the resin application, a using the video camera watch the application of the resin to the pipe while he manually pulls the assembly back toward him or her. The resin is designed to harden in 5 to 30 seconds depending on the temperature of the resin when it’s mixed, so you don’t have a lot of time to stop the process from the beginning of the pipe you are lining to the end. The second crew member is running the drill at the opposite end of the cable with instructions to start and stop coming from the tech who is running the camera and applying the resin. The technology is usually broken up into sections of about 30′ or less to line at a time. After the first lift is complete, a drying time of 5 to 10 minutes is required to let the resin harden so that the next lift can be applied. The resin is metered so that you know that you’ve applied enough resin to make the pipe structural.

With the parameters I’ve discussed, imagine pushing a 200’+ long cable down the line and having the operator pulling back that kind of weight while maintaining a 1/2 mm surface and giving orders to the drill operator 200’+ behind him. Add the ground water issue plus the missing pipe, they’ve set themselves up for a failure. While this process was set up for inside building drain, waste and vent pipe rehabilitation, applying it to those jobs designed for other technologies doesn’t make sense. In the example above, lining the last 175′ of pipe with conventional remote start CIPP liner, and the first 25′ with the tie ins with the new technology.

The point of this is to apply technologies for what they were intended for and don’t try to make something work that doesn’t fit the job. Several years ago I inherited a job that was to pipe burst an 18″ clay sewer pipe and replace it with 30″ HDPE in sand. It was designed to complete 600′ bursts, but we couldn’t get more than 200′. After haggling with engineers, agency owners and the equipment supplier, we were lucky to break even on the job. I could have had my excavating crew do the job with less heartache in half the time it took to burst. That lesson stuck with me through my career in construction. “Never attempt applying a technology to something that is outside of the scope of what that technology was designed for”!

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