The Shale Oil Company contains several operating units that comprise its Aston, Ohio, manufacturing complex. These units process the crude oil that is pumped through and transform it into a multitude of hydrocarbon products. The units run 24 hours a day, seven days a week, and must be shut down for maintenance on a pre-determined schedule. One such unit is Distillation Unit No. 5, or DU5. Studies have shown that DU5 can operate only 3.5 years without major equipment breakdowns and excessive loss of efficiency. Therefore, DU5 is shut down every 3.5 years for cleaning, inspection, and repairs.
DU5 is the only distillation unit for crude oil in the Aston complex, and its shut down severely affects all other operating units. Some of the production can be compensated by Shale refineries in other locations, but the rest must be processed before the shutdown and stored. Without proper planning, a nationwide shortage of Shale gasoline could occur. The timing of DU5's shutdown is critical, and the length of time the unit is down must be kept to a minimum to limit production loss. Shale uses PERT as a planning and controlling tool to minimize shut-down time. The preventive maintenance for DU5 is as follows.

	Time Estimates (days)
Activities	Opt	Most Likely	Pess		Pred(s)
1. Circulate wash water throughout unit	1	2	2.5		-
2. Install blinds	1.5	2	2.5		1
3. Open and clean vessels and columns	2	3	4		2
4. Open and clean heat exchangers, remove tube bundles	1	2	3		2
5. Open and clean furnaces	1	2	4		2
6. Open and clean mechanical equipment	2	2.5	3		2
7. Inspect instrumentation	2	4	5		2
8. Inspect vessels and columns	1	2	3		3
9. Inspect heat exchanger shells	1	1.5	2		4
10. Inspect tube bundles	1	1.5	2		4
11. Inspect furnaces	2	2.5	3		5
12. Retube furnaces	15	20	30		5
13. Inspect mechanical equipment	1	1.5	2		6
14. Install new pump mechanical seals	3	5	8		6
15. Repair instrumentation	3	8	15		7
16. Repair vessels and columns	14	21	28		8
17. Repair heat exchanger shells	1	5	10		9
18. Repair tube bundles, retube	2	5	10		10
19. Repair furnaces	5	10	20		11
20. Repair mechanical equipment	10	15	25		13
21. Test and close vessels and columns	4	5	8		16
22. Install tube bundles into heat exchanger shells	1	2	3		18
23. Test and close heat exchangers	1	2	2.5		17, 22
24. Test and close furnaces	1	2	3		12, 19
25. Test and close mechanical equipment	1	2	3		14, 20
26. Test instrumentation	2	4	6		15
27. Pull blinds	1.5	2	2.5		21, 23, 24, 25
28. Purge all equipment with steam	1	3	5		27
29. Start up unit	3	5	10		28

Determine the expected shutdown time and the probability the shutdown can be completed one day, two days, three days, four days, five days, six days, or seven days earlier? Shale Oil is considering increasing the budget to shorten the shutdown. How do you suggest the company proceed?

Answer rating: 100% (QA)

To determine the expected shutdown time and the probability of completing the shutdown earlier by specific durations we can use the PERT Program Evaluation Review Technique method PERT calculates the ... View the full answer