Gas 2024 Issue

10 out of 352 tubes

Percentage expansion

Figure 7 Tube harvesting graph

rather than replacing all tubes at the same time, regardless of the severity of damage (see Figure 7 ). To apply an effective tube harvesting program, the NDT inspection method applied must produce quantitative test results. Simply bundling the tubes into A, B, C, and D type categories does not provide enough detail to adopt a har- vesting strategy. Ideally, each tube should be ranked, and then a histogram should be applied to determine where tube replacement thresholds are set. Integrating availa- Performing baseline QA/QC inspections proactively at the tube manufacturing facility provides a means to ensure the quality of tube fabrication prior to shipping and installation ble temperature measurement data into this process also helps prioritise where to harvest and test for damage. It is easy to perform destructive testing on the correct tube but incorrect elevation on the tube if temperature data is not integrated into this effort. Conclusion Performing baseline QA/QC inspections proactively at the tube manufacturing facility provides a means to ensure the quality of tube fabrication prior to shipping and installation, in addition to collecting important baseline data for future comparison during routine inspections once they are placed in service. Failure to do so may result in installing tubes that contain manufacturing flaws, in addition to reducing the accuracy of future inspection data comparisons. Once tubes have been installed and placed into service,

routine tube skin monitoring is critical. It is imperative that plants develop and maintain a temperature monitoring program. This frequently requires a combination of tech- nologies (infrared imaging and pyrometer with Goldcup) to verify the accuracy of temperature data. Time interval periods between planned reformer shut- downs are critical. Often, trends are to extend plant shut- downs as far out as possible, mainly due to economic drivers. For a nominal 100,000-hour (11.4 years) design life and a shutdown cycle of four years, the tubes can only be inspected at year zero (baseline), year four, and year eight before some may require replacement. To plan for this, the plant owner will only have the year four data on which to base critical replacement decisions. Therefore, the inspec- tion technique(s) applied must produce quantitative test results and be sensitive enough to assess all tubes at this early stage. Qualitative inspection techniques that produce results report ranking tubes in ‘good’, ‘moderate’ or ‘poor’ condition (A, B, C, and D) are of little value. Remaining life assessment approaches should have the ability to apply historical operating, monitoring, and inspec- tion data. Combining remaining life assessment calculation analysis with a tube harvesting program provides plant engineers with a step up in maximising the operating life of tubes in addition to spreading out capital spend. Becht partners with owner-operators to establish such programs, ensuring online monitoring data and inspection data ben- efits are maximised over the life of the steam reformer’s tube network.

Richard D Roberts is Inspection and Fixed Equipment SME at Becht. He holds a BS in mechanical engineering from Ohio State University.

Grant Jacobson is Division Manager, Fired Heater Services Division at Becht. He holds a BS in chemical engineering from University of Nebraska-Lincoln.

Gas 2024