Root Cause Analysis (RCA) related to the roof hot spots repairs and their problem eliminated forever.
Article Type: | Root Cause Analysis (RCA) |
Category: | Mechanical |
Equipment Type: | Pipelines and Miscellaneous Problems |
Author: | S. Raghava Chari |
Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.
20 to 30% of the cast bricks thermally insulating the reformer room fell off randomly yearly, after two years of service. Hazardous emergency repairs of welding cast refractory lined box over the hot spots (HS) avoided plant shutdowns.
The hot spotted parent roof portions plus some adjacent areas disintegrated in time. The plant felt a keen need to stop the recurring, annoying, expensive, and hazard-prone emergency hot spot boxing for safety-enhancing and eliminating the repeated expensive roof metal renewal at the two-yearly turnarounds (TA).
The plant lined the revamped roof during the IN 529 RT change (earlier Problem) with the vendor suggested 12600C grade non-ceramic Fiber blankets (FB). More details follow:
Below listed are pre-TA tasks:
Reformer Tubes were out of the reformer for new HK-40 RTs insertion. Technicians tore off the old roof and welded the lined panels to form the lined roof.
The 50-mm blanket protrusions beyond the panel sides butting into dense layer prevents hot flue gases wetting the roof plates at the joints assures cooler root top metal. After an area blanketed roof top completion, the crew moved to another far away area.
Other crews installed the new RTs and welded the outlet pigtails. They welded the inlet pigtails new flanges. The operation started filling catalysts in OPT welded RTs.
Roof crews packed fiber blanket pieces in the RT annuluses to prevent leaks, positioned 20 mm thick CS split cover halves, and tack welded to the roof metal.
Thus, many crews working simultaneously w/o interfering with one other in a coordinated manner completed the RT and Roof change in 14 record days.
FB lining an existing good roof with RTs in position though not as easy and quick as above, is practical, cheaper, lot easier and quicker than cast blocks restoration and living with the expenses and hazards of frequent hot boxing.
Below listed are the benefits:
The conventional sidewall refractory was in very good condition. The crew shutdown the reformer at two-year catalyst change intervals only. Hence, it stayed.
However, a much larger 1987-built Saudi 1500T/d Ammonia Plant reformer and a near equal-sized 1998 built world’s largest petroleum refinery reformer are FB lined all over – walls and roof.
Both perform exemplarily maintenance-free even after 5-years of their 20 years life expectancy. Their much lighter structural supports save 30 to 35% steel than that of the author re-roofed reformer.
Author: S. Raghava Chari
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