1. Mova Oil Company\'s Dallas, Texas, manufacturing complex comprises several op
ID: 371886 • Letter: 1
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1. Mova Oil Company's Dallas, Texas, manufacturing complex comprises several operating units. 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, 7 days a week, and must be shut down for maintenance on a predetermined schedule. One such unit is Distillation Unit No. 5, or DUS Studies have shown that DU5 can operate only 3 years without major equipment breakdowns, and excessive loss of efficiency. Therefore, DUS is shut down every 3 years for cleaning, inspection and repairs DU5 is the only distillation unit for crude oil in the Dallas complex, and its shutdown severely affects all other operating units. Some of the production can be compensated for by Mova refineries in other locations, but the rest must be processed and stored before the shutdown. Without proper planning, a nationwide shortage of Mova gasoline could occur. The time 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. Mova uses PERT as a planning and controlling tool to minimize shutdown time The first phase of a shutdown is to open and clean the equipment. Inspectors can then enter the unit and examine the damage. Once damages are determined, the needed repairs can be carried out Repair times can vary considerably, depending on what damage the inspection reveals. Based on previous inspection records, some repair work is known ahead of time. Thorough cleaning of the equipment is also known to improve the unit's operating efficiency. The table below lists the many maintenance activities and their estimated completion times. a. Determine the expected shutdown time and the probability that the shutdown can be completed 1 week earlier earlier? company proceed? b. What are the probabilities that Mova finishes the maintenance project 1, 2, 3, 4, 5, or 6 days c. Mova Oil is considering increasing the budget to shorten the shutdown. How do you suggest the Preventive Maintenance of DU5 Immediate Predecessor Time Estimates (in Days) Activities ptimistic Most Likelv PessimisticExplanation / Answer
(o+p+4m)/6 (P-O)/6 Task Pre O M P Mean Std Dev ES EF Critical LS LF Slack Std dev A 1 2 2.5 1.92 0.25 0.00 1.92 Yes 0.00 1.92 0.00 B A 1.5 2 2.5 2.00 0.17 1.92 3.92 Yes 1.92 3.92 0.00 C B 2 3 4 3.00 0.33 3.92 6.92 Yes 3.92 6.92 0.00 D B 1 2 3 2.00 0.33 3.92 5.92 17.17 19.17 13.25 E B 1 2 4 2.17 0.50 3.92 6.08 4.92 7.08 1.00 F B 2 2.5 3 2.50 0.17 3.92 6.42 8.08 10.58 4.17 G B 2 4 5 3.83 0.50 3.92 7.75 13.75 17.58 9.83 H C 1 2 3 2.00 0.33 6.92 8.92 Yes 6.92 8.92 0.00 I D 1 1.5 2 1.50 0.17 5.92 7.42 21.33 22.83 15.42 J D 1 1.5 2 1.50 0.17 5.92 7.42 19.17 20.67 13.25 K E 2 2.5 3 2.50 0.17 6.08 8.58 14.58 17.08 8.50 L E 15 20 30 20.83 2.50 6.08 26.92 7.08 27.92 1.00 M F 1 1.5 2 1.50 0.17 6.42 7.92 10.58 12.08 4.17 N F 3 5 8 5.17 0.83 6.42 11.58 22.75 27.92 16.33 O G 3 8 15 8.33 2.00 7.75 16.08 17.58 25.92 9.83 P H 14 21 28 21.00 2.33 8.92 29.92 Yes 8.92 29.92 0.00 Q I 1 5 10 5.17 1.50 7.42 12.58 22.83 28.00 15.42 R J 2 5 10 5.33 1.33 7.42 12.75 20.67 26.00 13.25 S K 5 10 20 10.83 2.50 8.58 19.42 17.08 27.92 8.50 T M 10 15 25 15.83 2.50 7.92 23.75 12.08 27.92 4.17 U P 4 5 8 5.33 0.67 29.92 35.25 24.58 29.92 -5.33 V R 1 2 3 2.00 0.33 12.75 14.75 26.00 28.00 13.25 W Q,V 1 2 2.5 1.92 0.25 14.75 16.67 28.00 29.92 13.25 X L,S 1 2 3 2.00 0.33 26.92 28.92 27.92 29.92 1.00 Y N,T 1 2 3 2.00 0.33 23.75 25.75 27.92 29.92 4.17 Z O 2 4 6 4.00 0.67 16.08 20.08 25.92 29.92 9.83 AA X,Y,W,Z,U 1.5 2 2.5 2.00 0.17 29.92 31.92 Yes 29.92 31.92 0.00 AB AA 1 3 5 3.00 0.67 31.92 34.92 Yes 31.92 34.92 0.00 AC AB 3 5 10 5.50 1.17 34.92 40.42 Yes 34.92 40.42 0.00 Total process 146.67 Mean 40.42 Std Dev 5.42 A Regular completion 40.42 Days For 1 week earlier 39.42 Days Probability 43% NORM.DIST(39.42,Mean,Std Dev,TRUE) B Earlier days Prob 1 39.42 43% NORM.DIST(days,Mean,Std Dev,TRUE) 2 38.42 36% NORM.DIST(days,Mean,Std Dev,TRUE) 3 37.42 29% NORM.DIST(days,Mean,Std Dev,TRUE) 4 36.42 23% NORM.DIST(days,Mean,Std Dev,TRUE) 5 35.42 18% NORM.DIST(days,Mean,Std Dev,TRUE) 6 34.42 13% NORM.DIST(days,Mean,Std Dev,TRUE) C The company should focus in shortening the critical tasks, like A,B,C,H,P,AA,AB,AC as these are critical and will affect the overall shortening
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