AEP's Experience With Failure Modes In Fiberglass Cooling Towers

摘要

There are a total of 15 hyperbolic and 31 mechanical draft cooling towers on the American Electric Power (AEP) system. These towers utilize a cross-flow or counter-flow thermal transfer design, and a majority of the cross-flow towers are treated wood structures. AEP replaced eight cross-flow, mechanical draft towers during the period of 2008 through May 2013. Two new counter-flow, mechanical draft towers were built for new generating units in 2009 and 2012. A counter-flow, mechanical draft tower (which was built around 2001) was finished and placed into service in 2011. A natural draft, hyperbolic tower had the heat transfer and water distribution areas converted from a cross-flow configuration to a counter-flow design in 2011. All twelve of these new towers used polyester or vinyl ester fiberglass structure from at least three different pultruders, and were designed and constructed by four different cooling tower companies. These twelve towers are the only fiberglass structure cooling towers on the AEP system. The intent of this paper is to share information on how pultruded fiberglass members can fail or be structurally compromised. Failed or cracked fiberglass columns were found in five towers during construction or after 18 months of operation. The failed or cracked columns were attributed to misuse of fiberglass bearing pads or poor construction procedures. Several failed columns and horizontal members were also damaged from ice on the counter-flow, natural draft tower in January 2013. Surface blisters were noticed in two of the new towers after 2 to 18 months of operation. A summary of these events will be discussed in this paper along with the probable reasons and actions AEP is taking to prevent a reoccurrence. CTI Paper TP11 -19 was presented at the 2011 CTI Winter Conference and provides more details on four of the mechanical draft fiberglass towers constructed in the 2008 to 2010 time frame. A brief summary of the failed columns in those four towers are included in this paper.