ABSTRACT

The overwhelming majority of steam boilers and fired heater tubes that operate at elevated temperatures are ageing and within creep threshold temperature with an inherent potential risk of stress rupture if not adequately monitored. Traditionally, degradation rates (i.e., creep damage) of these components can only be assessed during shutdown through non-destructive testing to determine the metallurgical conditions upon exposure to elevated temperatures. Typically, in the past creep damage cumulation is evaluated and predicted reactively using single maximum operating data when observable anomalies and incidences occur, leading to very conservative results. Furthermore, a piecemeal manual calculation method would require specific skills in material performance behavior at elevated temperatures. This paper presents a real-time creep life prediction system for steam boilers and fired heaters using available online operating data and develops creep modelling to provide dynamic creep damage accumulation and remnant life prediction. This solution deploys data analytics to proactively notify plant operators in the event of online monitoring parameters deviating from the preset integrity operating window parameters. By having real-time dynamic calculation from a continuous data feed from online operating data, it empowers plant operators to evaluate multiple scenarios feeding into plant operation for optimum planned maintenance and shutdown windows which is a game changer to the industry.

INTRODUCTION

Creep is a continuous degradation of metal under applied stress at high temperature with critical factors of temperature, stress, type of material and exposure time. Most of our steam boilers and fired heaters tubes are operating within or sometimes operated slightly above the creep threshold temperature with an inherent potential risk of stress rupture if not being monitored properly. Traditionally, degradation rates (i.e., creep damage) of these components can only be assessed during shutdown through non-destructive testing (NDT) to determine the metallurgical conditions upon exposure to elevated temperatures. Conventionally, creep damage cumulation is evaluated and predicted reactively using single maximum operating data when observable anomalies and incidences occur, leading to very conservative results. Furthermore, this manual calculation method would require specific knowledge and skills in material performance behavior at elevated temperatures.

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