A combination of computational and imaging tools was developed to characterise the performance and assess the lifetime of flare tips, the top portion of stacks used to burn off excess gas in the gas and petroleum industry. Integrating the use of (1) an infrared imaging study to obtain temperature profiles of flare tips in operation and (2) finite element modelling of stress distributions based on temperature profiles allowed lifetime prediction for creep and fatigue failure. The techniques were successfully applied to a complex flare tip design that included a venturi shaped windshield. It was concluded that in this instance, the flare tip lifetime would be limited by a combination of creep and fatigue of the support brackets and by plastic deformation at the top of the windshield. Design methodologies for producing flare tips with improved lifetimes are suggested, including the use of computational fluid dynamics modelling to assess the combined effects of gas flow rates and wind conditions on combustion behaviour. Thus, the prediction prior to installation, of both the performance of a new design and the long-term behaviour, can be a valuable assessment process for a proposed flare tip assembly.

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This study investigated the susceptibility of alloy 625 to embrittlement in the temperature range 600-800 C using simulated thermal treatments, specimens from ex-service petroleum industry components and subsequent remedial heat treatment. Embrittlement was quantified by conducting impact testing using the Charpy V-notch method and the results discussed in terms of precipitate formation and ageing. The results of annealing the exposed samples at high temperature are presented, demonstrating that embrittlement is most detrimental at intermediate temperatures (i.e. 650 C). The study confirms that a 24-h remedial heat treatment of embrittled alloy 625 leads to significant recovery of impact energy on ex-service samples.

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