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Author: Mahen Das
Location: 2.1.3 Petroleum Refinery
The refinery had a 3000 tons/day fluidized catalytic cracking unit (FCCU). The performance of the FCCU Regenerator cyclones, which recovered catalyst from the hot gases leaving the vessel, had deteriorated significantly over the years. A new set of cyclones had been ordered from a European vendor. There were five primary and five secondary cyclones, lined internally with an abrasion resistant refractory.
These would replace the existing five pairs of cyclones during the next FCCU Turnaround (or shutdown as it is called in Europe). The new cyclones were larger than the existing ones, and Figure 30.1 shows one such unit. Each cyclone weighed about 6 tons, and all ten were of the same size and geometry.
Cyclone Replacement Procedure
In most other locations, where availability of hoisting machinery is no constraint, the execution would have been as follows (see Figure 30.2):
- • Order the new cyclones ready for mounting on the dome.
- • Erect a derrick for removal and refitting the dome.
- • Cut the dome of the regenerator beyond the mounting periphery of the cyclones.
- • Remove the dome together with the 10 old cyclones; use a large capacity crane to lower the dome along with the cyclones to ground level.
- • Place the dome on a steel structure at ground level, high enough to enable working under the dome.
Figure 30.1 Cyclone
- • Remove the old cyclones from the dome and attach the new ones.
- • Lift the dome and place it back on top of the regenerator shell, using track crane and derrick.
- • Weld the dome to the shell.
- • Repair internal insulation.
At this location, it was not feasible to apply the conventional procedure, as it needed a long boom 200-250 ton capacity crane and a large derrick. At the time of these events, such a large crane was not available, and space constraints were such that a derrick could not be installed. So we knew we had a major problem on our hands.
Figure 30.2 Cyclone Replacement Process—Conventional Method