Many companies predict bundle life by analyzing the history of each shell and tube heat exchanger bundle. The problem with this approach is that many exchangers may experience few, if any, bundle failures during their lives. Some failures may not apply to current operating conditions or practices. Additionally, this approach is not based on a significant enough data set needed for accurately predicting future performance and/or Probability of Failure (POF).

To overcome these shortcomings, the API RBI methodology analyzes the failure data of similar heat exchanger bundles. Consequences are based on financial losses due to lost production from downtime associated with repair or replacement of the bundles.

To predict POF, the method utilizes a Weibull distribution based on the bundle’s inspection history or set of matching bundles from the bundle failure database. Matching criteria to determine similar bundles includes the following:

  • Exchanger Type
  • Tube Metallurgy
  • Tubeside and Shellside Fluid Categories
  • Operating Conditions, Temperatures, Pressures, Velocities
  • Process Unit
  • Controlling Damage Mechanism
  • Fluid Damage Modifiers (e.g., H2S, Sulfur, Caustic)

The failure rate curve is modified based on knowledge of the current condition of the bundle and the effectiveness of the prior inspections. Recommendations are made during the plan period to reduce the overall risk of bundle failure to an acceptable value.

Download RBI Case Study: Aging Bundles

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