Defining, Understanding Lateral Rehab Options

Part 1 In A Series
By Jeff Griffin, Senior Editor | April 2011 Vol. 66 No. 4

Epoxy Resin Systems -- The structure of epoxy resin can be engineered to yield a number of different products with varying levels of performance. A major benefit of epoxy resins over unsaturated polyester resins is their lower shrinkage, and they emit little odor compared to polyesters. Generally, epoxies have short working time with long cure times.

Vinyl Ester Resin Systems combine the advantages of epoxy resins with the better handling/faster cure, which are typical for unsaturated polyester resins. These resins are produced by reacting epoxy resin with acrylic or methacrylic acid. The resulting material is dissolved in styrene to yield a liquid that is similar to polyester resin. Vinyl ester resins typically cost two to three times more than polyester resins.

Silicate Resin Systems provide good adhesion to properly prepared, cleaned and compatible surfaces. They have similar curing issues as an epoxy where the work-time is short and the cure-time is long, yet unlike an epoxy, silicate resins are typically not suitable to external heat sources as commonly used in CIPP applications. For these reasons, silicate resins are well-suited for short liners, main/lateral connection liners or injection grouting.

Synopsis of resin systems
In most residential sewer systems, all of these resins would be suitable for a CIPP application, providing the cured-in-place pipe meets the minimum requirements as set forth in relevant ASTM standards. However, depending on the chemical makeup of the effluent, one resin may be preferred over another, and resin suppliers can recommend the correct resin for specific applications based on the type of pipe on a project.

Liner Tubes
Lining tubes typically are constructed from a needle punched felt or a knitted tube. These liners vary in density and flexibility in order to negotiate small diameter pipe, bends and to reduce pressures for inverting the liner so the tube is not overstressed. Sometimes liners stretch, but advanced technology allows both types of liner tubes to be reinforced to eliminate stretching and increase flexural properties.

Regardless of tube construction, good installation practices combined with the right material are keys to successful lining repairs. Trained and seasoned installers know how to accommodate for stretch and ensure quality control during inversion to prevent over stressing the tube and squeezing resin, critical when the liner is installed from a single access point, sometimes called a “blind shot.”