Point Repairs – What’s The Correct Way To Perform Them?

” I have a point repair to do and I’ve shopped around for the best way to do the repair. I’ve talked to so many different people who’ve each given me their idea on the best way to perform the work and now I’m so confused, I don’t know which to choose that will give me the best solution. My customer is a great customer and I don’t want to make an error and give him something that won’t hold up. Any help in choosing one would be helpful?”

As I’ve stated in the past, there are many ways to get a liner in the ground that are perfectly acceptable and the same applies to point repair methods. With that said, let’s explore the various methods that meet the ASTM’s that apply to CIPP methodology.

Materials For Point Repairs

Many years ago, contractors began employing pipe plugs and scraps of lining material to repair broken joints in clay pipe. They would choose a pipe plug (packer) of the correct size to slide into the pipe and use air to expand it to hold the point repair material until it was cured. Depending on the amount of flow in the pipe, they may elect to choose a packer that has a flow-through port to allow liquid to continue flowing while the curing process is occurring. Some packers can allow heated water to circulate through the packer to accelerate the curing process. To save the pipe plug or packer, they would wrap plastic food storage wrap around the packer. They would cut a piece of lining material of the size of line they were doing. Usually they’d use scraps of material from other lining jobs, and hand invert or turn it inside out. With the inverted material, they would fully saturate the scrap of liner with resin and since no vacuum impregnation process was used, they would void the air pockets by troweling the resin back and forth insuring that all of the material was coated with resin. Once complete, they would slide the wetted out patch over the packer followed by a tube of 6 mil polyethylene tube or more “Saran Wrap” to keep the resin in place as they dragged the packer and patch into place. They would use masking tape to compress the assembly into the smallest profile they could. To get the packer into place they’d employ either ropes to pull it in from downstream or push rods to push it into place from upstream, depending on how far the patch was from the entry. To insure that they hit their mark, they would use their camera to locate the start and stop points for the patch and transfer that information to their push rods or pull rope. Once in place they would send the camera in again to verify they ended where whey wanted the patch to be. If not, adjustments could be made then. Once set in place they would expand the packer pressure with enough air pressure to break the masking tape and allow the assembly to hit the wall of the pipe. Usually a fast resin is employed for these repairs but if a larger point repair is needed, many contractors employ the recirculated heat option to accelerate the cure. Air or water is used to inflate the plug and is held at a minimum of 8 psi after the masking tape is broken.

Fiberglass Wet Out

As the industry evolved and new contractors entered the market, fiberglass matting began working its way into the industry. It offered the contractor a stronger patch with a thinner profile finished. It also allowed vendors to pre-package kits that contained all of the materials for a particular size point repair that was boxed and ready to use in the field without gathering materials prior to a job. All you needed was the kit and the packer. The rest of the process is the same as above and employees the same families of resins.

Along came lining contractors who had left over calibration tube from prior jobs. They also had left over material scraps from prior jobs as well as resin. These guys decided to put their scraps either around an old calibration tube and pull it into place or weld it to the calibration tube and invert it into place. Then they would use a new calibration tube to inflate it and cure it.

Quik Shot™ Unit for inversions

This approach gave them the ability to do longer point repairs. As an example our Technical Sales Manager aided a customer who had a 10′ patch located 70′ into a 4″ pipe. He welded the 10′ liner to a 70′ calibration tube, wetted out the 10′ patch using normal vacuum impregnation used in the standard lining process, then inverted the assembly through the Quik Shot ™ inversion gun. Once in place, they shot a calibration tube that was 84′ long and held it in place until it was cured.

So, in answer to your question, any of the methods will work. You should know how much flow you will encounter during your job and if you need to address it by bypassing or allowing the material to flow through. You will need to know access and pipe diameter. You will need to clean the pipe prior to the point repair. If still in doubt ask your supplier for details and assistance through the process.

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