• TECH TALK •
Isolation of Fluidized Catalytic A Process
Fluidized Catalytic Cracking Units remain one of the most complex processing units within modern petroleum refineries. They play an essential role in converting heavy gasoil fractions into lighter, highvalue products, making them indispensable for profitability and operational flexibility. This second installment of FCCUs continues to address a series of pertinent topics including fractionator section isolation, isolation system design, and digitalization / smart isolation systems.
• By Gobind N. Khiani. P. Eng., M. Eng./ Fellow-Piping / Pipelines
By further recognizing key operational elements of FCCU’ s and isolation philosophies, as well as safety protocols, current standards, and the growing benefits of digital technology, refineries can more effectively identify and manage the inherent hazards of FCCU’ s and become better positioned to meet regulatory requirements and maintain consistent production throughout the lifespan of these units.
* 4. Fractionator Section Isolation
In the fractionator section of an FCCU, isolation is influenced by maintaining continuous operation where possible while allowing for maintenance of individual components. The presence of catalyst fines in the bottom streams introduces challenges, as they cause erosion and fouling of equipment and valves.
By adopting and continuously improving a modern isolation philosophy, refineries operating FCCUs can better manage the inherent hazards and meet regulatory expectations.
Strainers installed upstream of fractionator bottoms pumps are common and maintenance requires frequent isolation. In modern practice, double block and bleed arrangements are preferred. They provide optimal safety and allow for verification prior to opening equipment. Valve selection is critical and the materials chosen are required to resist abrasion and maintain sealing performance over cycles.
The layout of the isolation system in the fractionator section must also consider operator safety, ensuring that valves are accessible and that personnel are not exposed to hot or hazardous fluids in the event of leakage. The reactor overhead vapor line isolation valve, which separates the reactor from the main fractionator, is a particularly safety-critical device.
The American Fuel and Petrochemical Manufacturers( AFPM) technical forum indicates that in North America, approximately 22 to 23 of approximately 99 cat crackers have such dedicated overhead vapor line isolation valves installed with sizes ranging from 24” to 66.” These valves can provide the ability to isolate the catalyst section for unplanned repairs without shutting down the gas recovery section. They can also reduce turnaround preparation time by eliminating manually pulling a vapor line blind while equipment is hot.
5. Human Factors and Isolation System Designs
A significant advancement in isolation philosophy has been the incorporation of human factors into design.
28 Valve World Americas | May 2026 | www. valve-world-americas. com