“I’ve read articles in the past about the value of resin and tube systems, but can’t you use any resin with any tube and achieve a rehabilitated pipe that’s just as good as one that has passed testing?”

Let’s explore the factors that go into the finished product. For CIPP, there are two components to manufacturing the product in the field. We’re in essence building the pipe on site using the old pipe as the form for making the new one.

Digging deeper, there are three resin systems acceptable for use in the CIPP process: polyester, vinyl ester, and epoxy resin. Performing this process using another resin system takes you outside the acceptable realm of CIPP construction. A tube can be made up of woven and non-woven materials that will absorb the resin and hold it in place through the curing process.

Typically we deal with two different manufacturers of the components, one making raw resin and the other a textile producer that makes fabric. At Pipe Lining Supply, our piece of the process is to assemble the components we supply to customers, balancing the resin and tube product to provide the best performance.

If the tube is woven or made with too much fiber, not enough resin can be absorbed into the fabric to make it strong enough to meet the long-term flexural modulus prescribed in the ASTM standards. That minimum is 250,000 psi, and if it doesn’t carry enough resin, the composite will fall below that number as the material portion holds no value to carry the load. It does provide flexibility to the resin in the finished product and serves to hold the resin in suspension during the curing cycle.

The resins, on the other hand, are the components that carry the loads the pipe is subjected to. The resins cured independently of the tube can reach flexural modulus numbers over 450,000 psi, well above the 250,000 psi called for in the standards.

This is where the balance of these two components becomes a factor in the finished product.

Too much fiber in the tube means less resin can be absorbed in the material. This may cause the combined products to fall below the 250,000 psi flexural modulus called for in the standard. On the other side, if the tube has much fewer fibers, your composite will achieve higher numbers. But the trade-off may be a product that is too brittle and subject to stress cracking.

This is where testing comes into play. If you don’t balance the two, you may get a product that doesn’t serve you as well as those that are tested.

Obviously, there are other factors to consider such as cost, availability, shipping costs, and working/curing times. But the information discussed here will give you the power to control risk. If you buy one component from a supplier and another component from someone else, you can have the finished composite tested. That way you can be satisfied that the product will meet the standard and can sleep easy at night not worrying about a failure.

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About the author: John Heisler is the owner of Pipe Lining Supply and Quik-Lining Systems. He has more than 20 years of experience in the CIPP lining industry and 40-plus years in the underground construction industry.