Polymer Degradation – Deterioration of Celcon Plastic Water Pipe Fittings

Our firm was selected as experts for the insurance defense group in Hoechst Celanese Corp. vs. National Union Fire Insurance Company et. al. This matter related to the premature field failure of residential plastic pipe fittings throughout the southern and western regions of the United States and involved losses of hundreds of millions of dollars. Our firm was engaged to determine if premature fitting failures would be expected based on the available file documents. We inspected failed fittings, performed stress analyses, analyzed file test data, and reviewed thousands of documents to assess whether or not Hoechst Celanese knew or should have known that the fittings were unlikely to survive the intended service life expectancy prior to releasing the product.

Acetal resins are sensitive to chorine and low levels of chlorine in potable water supplies (1-3 ppm) can be sufficient enough to promote stress corrosion cracking. Widespread failure of acetal fittings in potable and hot water supplies resulted in one of the largest class action lawsuits in the US when acetal plumbing fittings cracked and caused flooding of homes. The accompanying photograph illustrates chlorine attack in the threaded portion of an acetal fitting. Chlorine attack caused the material to become brittle and resulted in crack initiation at the thread roots. The discoloration on the fracture surface was caused by deposition of carbonates from the hard water supply, indicating that the joint had been partially cracked for a while prior to component failure.

Return to Case Studies