CIPP for Tomorrow: What Is Needed?

Washington Suburban Sanitary Commission (WSSC Water), one of the largest users of carbon fiber reinforced polymer (CFRP) liners for large diameter pressure pipe, is considering expanding its use of FRP liners to include small diameter pressure pipes using the cured-in-place pipe (CIPP) technology. However, the lack of a well-established AWWA design standard for CIPP with strong analytical and experimental basis, similar to AWWA C305 developed for CFRP lining of large diameter pipe, has limited the use of CIPP to pilot projects and precludes applications at larger scale. The ASTM standards currently used for design of CIPP in the industry are known to have been originally developed for gravity pipe but are now increasingly used as Class IV (fully structural) liners for pipes with relatively high internal pressure without additional material qualification and design requirements. The number of CIPP products in the market increase continuously, and they differ in materials, architecture, susceptibility to imperfections, curing methods, etc., which cannot be evaluated on a uniform basis. Material test data are still being developed on a project-by-project basis. Having been involved in the decade long research program and in development of the AWWA Standard for design of CFRP liners for large diameter pipe, WSSC Water is currently evaluating the current state of the art of the CIPP technology in general, and some proposed CIPP products, for potential use in pressure pipe. The results generally indicate inadequacy of the current state of the art in addressing critical strength and stability design limit states (in both circumferential and longitudinal directions) according to WSSC Water design criteria and loads. Also, the evaluation demonstrated a deficiency in ensuring durability and reliability. This paper emphasizes the need for development of an AWWA standard for design of CIPP for small-diameter pressure pipe, and recommends additional design limit states, material qualification, and testing requirements that are not currently addressed by typical designs in the industry. Case studies on evaluation of CIPP for pilot projects will be discussed to demonstrate the need for more detailed design procedures and considerations which, when incorporated, will likely increase the use of CIPP for pressure pipe applications.

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