Category
Most probable cause
Why 1
Why 2
Di culty in achieving correct ID of column throughout column length
Fabrication of column done in the sections
Height of column is more than the standard plate length available in the market
During plate rolling, ID mismatched with the required ID of column Non-co-ordination between column vendor and tray vendor during fabrication
Out of tolerance in column ID
Due to limitation of rolling machine
Fabrication
Fabricated tray bundle OD is not as per fabricated column ID
Both the items pro c u re d separately
Sti e ner/spider cannot be inserted to prevent distortion
Ovality in column due to self weight during transportation
Logistics
Due to small column ID
Non-co-ordination between column vendor and tray vendor during fabrication
Tolerances mismatch between tray and column OD/ID
Both the items procured separately
Installation
Tray bundle got stuck in column and modi cation required at site
Delay in tray bundle installation activity
Installation of cartridge tray at site
CONCLUSION: 05 root causes
Figure 3 Probable root causes
rework during later project stages. The cartridge tray bun- dle is shown in Figure 2 , which was being installed through the column body flange and failed during installation. Problem identification The design and engineering of cartridge trays, up to their installation at the site, involve multiple steps. At each stage, potential factors may contribute to on-site installa - tion failures. These potential causes have been identified and organised into different categories to provide a clearer understanding of the relationship between each cause and the observed installation issues, as shown in Table 1 . All the probable causes listed in Table 1 for each strat - ified category will be analysed to identify the root causes of the problem. Since the identified causes include a mix of valid (assignable) and invalid (chance-based) factors, it is essential to first apply a ‘valid and invalid filter’ to system - atically eliminate those that are invalid. For example, within the design and inspection categories, all the listed causes are considered invalid as they arise purely by chance and are therefore not actionable. Consequently, the remaining valid and assignable causes are found only within the fab - rication, logistics, and installation categories. Through this filtering process, engineers ultimately arrive at six valid and assignable causes, which have been consolidated and pre- sented in the second column of Figure 3 for focused analy - sis and further resolution planning. Root causes of installation problem All six valid and assignable causes identified within the fabrication, logistics, and installation categories require detailed examination using a ‘why-why analysis’ approach to systematically trace and establish underlying root causes contributing to installation issues observed on-site. These initial causes subjected to analysis are listed in the first col - umn of Table 2 . Following the completion of this analytical process, the
investigation resulted in the identification of five root causes, out of which three are found to be viable and actionable for mitigation. The remaining two are assessed as non-viable due to inherent limitations such as constraints posed by the rolling mill capabilities and the small diameter of the col - umn, which are beyond the scope of corrective intervention within the current operational framework. Proposed solution Proposed solutions for all identified and viable root causes, along with their respective advantages and limitations, are presented in Table 3 . Selection among these options may be made based on project-specific suitability and constraints. However, to mitigate risks, optimise installation time, and enhance HSE performance, installing cartridge trays at the column vendor’s shop emerges as an effective solution. The approach detailed under Point No. 4, ‘Single point responsibility vendor for column and tray under RFQ and installation at shop’, ensures compatibility and
Identified root causes
Id entified root causes Both the items procured separately Heig ht of column is more than the standard plate length available in the market Du e to limitation of rolling machine Due to small column ID Inst allation of cartridge tray on-site
Viable/non-viable
Viable P Viable P
Non-viable r
Non-viable r
Viable P
Table 2
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