CIPP Best Practices

By By NASSCO member Ed Kampbell, PE, Jason Consultants | October 2011, Vol. 66 No. 10

There are four key elements to having a really good Cured-in-Place Pipe (CIPP) installation:
1. Proper saturation of the tube;
2. Proper inflation of the resin saturated tube in the host pipe;
3. A full and thorough curing of the resin system used; and
4. A proper cool-down of the CIPP.

Proper Saturation
Whether the CIPP’s tube consists of only polyester felt fiber material, is a hybrid of polyester fibers and glass fibers, or is the product of only glass fibers, proper saturation with the resin system is key to a water-tight, structural performance of the CIPP throughout its intended service life.

The most commonly employed method for the resin saturation process is serial vacuum with calibration rollers. Looking at a felt fiber tube it is hard for most to fathom that approximately 90% of its volume is simply empty or void space. What this means to the wet-out technician is that the void space or pathways for the resin to fill are very small, and the only real way of coaxing the resin into them successfully is by the use of a negative pressure, or vacuum.

The level of the vacuum at the tube varies somewhat with the thickness and type of fiber matrix used. The air must be evacuated from the tube to make room for the resin. When adding resin to the tube, the technician must be careful not to add air back into the tube. Once the required amount of resin is in the tube the tube can be transported through the calibration rollers at a speed consistent with the resin’s migration into the fiber matrix.

Proper Inflation
The current state of the art for CIPP installation is to either invert the resin saturated tube into the host pipe using a column of water or pressurized air or to pull the tube into position followed by the inversion of a polymeric membrane or simply inflating the tube with air.

When the installation is made using a column of water for the inversion process it is key that the advancing nose of the inverting tube sees a pressure equal to or greater than the tube manufacturer’s stated “minimum inversion head”. The minimum inversion head provides for the proper full expansion of the tube and tight contact with the host pipe.

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