TAPPI TIP 0402-36

Abstract

This Technical Information Paper provides guidelines for the detection, monitoring and prevention of flow accelerated corrosion (FAC) in the pulp and paper mill. FAC is a damage phenomenon that causes wall thinning of carbon steel piping, fittings, vessels and other equipment in systems that carry wet steam, high-quality boiler feedwater or condensate. FAC can occur under single- or two-phase flow conditions. <br>This TIP is a compendium of information about FAC. It is largely based on a paper by Petric and Ksiazek (1). With author permission, the compiling task group quotes the paper and has liberally inserted it into the TIP. Their goal is to review and update the original work with current information. <br>The power industry has found that the control of FAC requires corporate commitment, comprehensive implementation procedures, sound analysis and inspection programs, and a long-term strategy. This document addresses only the basic characteristics of FAC in the pulp and paper mill; the organizational focus on an FAC strategy is left to the individual company structure. <br>FAC wall thinning has resulted in catastrophic failures of high-energy piping systems for transport of water and steam/water mixtures. Based on research sponsored by the electric utility industry (2), the risk of FAC ruptures have been highlighted and the key parameters influencing FAC have been well identified. As a result, many of the nation's power plants have implemented organizational and technical procedures (sometimes assisted by computerbased modeling tools) to detect, monitor and hopefully prevent metal loss due to FAC. This approach uses FAC detection guidelines to inspect susceptible piping/process components for metal loss during scheduled outages. The results are then re-evaluated at regular inspection intervals to monitor the rate, if any, of FAC attack. <br>The piping and component systems of the pulp and paper mill are similar to those found in industrial power and steam plants. They include many of the same systems &#8211; boiler feedwater, condensate and extraction steam &#8211; which have been found to be susceptible to FAC in large power plants. Also, the pulp and paper mill has additional susceptible systems that are not found in electric utility plants. For instance, there are multiple boiler feedwater and condensate piping runs that are not isolated in the plant. Failure of these runs due to FAC related ruptures or leakinduced hot vapor/steam flashing hazards can lead to personnel exposure. <br>This TIP describes the FAC mechanism, process conditions required for FAC to be active, and guidelines to assess FAC in the plant as part of a systematic procedure. The procedure includes detection (covering system evaluation, susceptible piping systems and process components, inspection and testing), evaluation of FAC thinning damage, FAC monitoring and preventative practices that also address repair/replacement options.