4.25
Baseline - 1993 Tube A - 2004
Tube A - 2000 Tube A - 2006
4.20
Comparison location
4.15
4.10
4.05
4.00
3.95
0
50
100
150
200
250
300
350
400
450
500
Tube length (in)
Figure 4 NDT inspection methods
applied via the data sets obtained with the Goldcup and proper procedures with training are implemented for the pyrometer use. ‘Offline’ inspection methodologies During routine plant shutdowns, ‘offline’ tube inspections can be facilitated. Whether the catalyst is being extracted from the tubes or not will dictate which internal or external inspection option can be applied. The internal approach can only be applied once the tube is fully evacuated of cata- lyst and preferably the catalyst support cone (if present) at the bottom of the tube, providing access to the full tube length, top flange to bottom cone or flange, depending upon tube design. Inspections facilitated from the tube interior surface while applying an internal probe mechanism often provide more accurate test results, as the internal bore of the tube is machined smooth with tight profile tolerances, as opposed to the rough ‘as cast’ exterior tube surface profile. The full tube length can also be accessed from the tube’s interior
bore. Often, many obstructions near the tube’s exterior, such as floor and roof refractory penetrations and narrow tunnel walls, limit an external crawler’s travel, ultimately leaving a portion of the tube uninspected where obstruc- tions exist. Leveraging inspection results The amount of inspection data collected with today’s instrumentation technologies can be overwhelming if not managed correctly. Complex software has become essen- tial, allowing scrutiny of individual tubes and the ability to combine data from all tubes into one image. Overlaying the combined data sets onto one viewing platform is powerful in discerning general damage patterns well in advance of experiencing unexpected localised or broad area failures. Producing inspection results quickly while a steam reformer is offline enables engineers to focus on necessary repairs or modifications quickly prior to the asset being brought back online. For example, a partially collapsed tunnel may result in localised elevated temperatures, ultimately accelerating
1
2
3
1. Primary creep 2. Secondary creep 3. Tertiary creep
Macrocracking
Microcracking
Aligned cavities
Steady-state creep rate
Isolated cavities
Time
Figure 5 Tube failure prediction
23
Gas 2024
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