Figure 5 Chimney tray fouling
recommended to mitigate significant hazards. The process engineering turnaround report should have highlighted issues and recommendations from previous turnarounds. Operations would also have noted changes/suggestions from prior unit shutdowns/start-ups. The shutdown for the turnaround is often a good opportunity to test the unit feed-outage trip. Any parts that were not fully activated as intended should be added to the turnaround scope. Hydrocarbon isolation valves should be checked in particu- lar, since poor activation can result in a significant hazard if they fail to fully isolate. With current practices requiring the prevention of hydro- carbon releases to the atmosphere, purging hydrocarbons from the unit requires better planning with chemical clean- ing for any significant shutdown (see Figure 6 ). Effective execution depends on comprehensive planning to identify all purge, vent, and drain locations and to ensure proper containment of hydrocarbons. Planning must also address the disposition of vents and drains to maintain hydrocarbon containment and the management of venting to minimise or prevent flaring. Initial catalyst removal should be carefully planned to minimise delays in turning equipment over for turnaround
Figure 6 Typical chemical cleaning manifold
maintenance. The prior turnaround report should identify areas where equipment or piping presented challenges with hydrocarbon removal, as these lessons can be directly applied to improve the current shutdown plan. Key regenerator/reactor levels/pressures, along with the effectiveness of catalyst removal, should be documented and reviewed. Catalyst withdrawal from the regen/spent standpipes can be particularly difficult. Effective removal may require using blast streams in standpipes, periodic transfer from the reactor to the regenerator, or even with- drawals from standpipes using cooling equipment (see Figure 7 ). These can aid operations in effective catalyst removal prior to stopping catalyst withdrawals. Shutdown timeline A shutdown timeline is often tracked by operations, noting times when various sections of the shutdown procedure are complete. However, an abbreviated shutdown timeline
Disengager and risers
972.441 931.2 973.201 963.885 968.616 965.298
1000
950
01/11/2013 02:24 963.738
900
850
150F/hr cool down on Disengager catalyst bed
800
750
700
650
600
550
500
450
03:00
04:00
05:00
06:00
07:00
08:00
09:00
10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
1/11/2013
Figure 7 Equipment cooling down rate
50
PTQ Q2 2026
www.digitalrefining.com
Powered by FlippingBook