This document discusses project scheduling and control methods. It describes critical path method (CPM) and program evaluation and review technique (PERT) which are used to schedule projects by breaking them into tasks, determining task durations, and identifying the critical path which represents the longest sequence of tasks that must be completed on time. CPM is used when task durations are certain, while PERT is used when they are uncertain. The critical path cannot be delayed or it will delay the entire project. Other topics covered include maintenance project backlogs, priority systems, and different types of maintenance.

1. ❑ Sequencing and Scheduling
Sequencing
•Determine the order in which
jobs or tasks are processed
Scheduling
•Assignment of start and
completion times to particular
jobs, people or equipment
•Sequencing with consideration
of time

3. ❑ Maintenance Project Control Methods
Two widely used maintenance project control methods are
• Program Evaluation and Review Technique (PERT) and
• Critical Path Method (CPM).
In maintenance and other projects three important factors of concern are
• Time
• Cost
• Resource availability.
CPM and PERT deal with these factors individually and in combination.
PERT and CPM are similar. The major difference between the two is that
when the completion times of activities of the project are uncertain, PERT
is used, and with the certainty of completion times, CPM is employed.

4. • Break a project into individual jobs or tasks.
• Arrange these jobs/tasks into a logical network.
• Determine duration time of each job/task.
• Develop a schedule.
• Identify jobs/tasks that control the completion of project.
• Redistribute resources or funds to improve schedule.
❑ The following steps are involved with PERT and CPM:

5. Critical Path Method (CPM) (Example)

6. CPM
Activity on Node
Start End
L
M
O
N
P
S
T

7. Start
O
P
S
T
L
M
O
N
START
S
P
T
END
0 0
0 12
0 2
14
12 18
18 21
12
21 30
30 45
45 45
45
45
45
30
30
21
21
18
21
19
18
12
12
0
19
17
0
0

8. CPM
Task Successor Time
F
E
D
C
B
A
C,D
B
B
A
-
-
5
4
6
2
5
8

9. CPM
Activity on Node
Start End
A
B
C
D
F
E

10. A
B
C
D
E
F
Start
0 0
0 0
0 5
0 5
0 4
5 9
5 11
5 11
4 6
9 11
4 9
14 19
11 19
11 19
End
19 19
19 19
Critical Path
A – C – F
CPM
Activity on Node
All activities in critical path consist same earliest and latest time

11. Note: [very important]
• Why is it called critical path?
Answer: Critical path is called critical because if they are delayed, the whole
project will be delayed.
• Critical path is the longest sequence of tasks
• Critical path represents activities which take the longest time to complete.
• The duration of critical path represents the minimum length of time
required to complete a project.
• No slack time or float or excess time in a critical path.
• slack time: the amount of time a job can slip
= Latest time-earliest time
In the critical path, as latest time and earliest time are equal, the
slack time is Zero.

12. ❑ Critical Path Method (CPM)
• Advantages:
• It is an effective tool for monitoring project progress.
• It helps improve project understanding and communication among involved personnel.
• It highlights activities important to complete the project on time. These activities must
be completed on time to accomplish the entire project on predicted time.
• It shows interrelationships in workflow and is useful in determining labor and
resources needs in advance.
• It is an effective tool for controlling costs and can easily be computerized.
• It helps avoiding duplications and omissions and determining project duration
systematically.
• Disadvantages:
• Costly
• Time-consuming
• Poor estimates of activity times
• Inclination to use pessimistic estimates for activity times

13. ❑ Activity Expected Duration Time Estimation
•
Acti
vity
Predec
essor
OT MT PT Ta
A - 2 3 4
B - 4 6 8
C A,B 6 7 10
D C 3 5 8

14. ❑ Elements of Effective Maintenance Management
• Backlog Control and Priority System
• Planned maintenance work waiting to be scheduled
• Bucket of future work
• Identification of backlogs is important to balance manpower and workload
requirements.
• decisions concerning overtime, hiring, subcontracting, shop assignments,
etc., are largely based on backlog information.
• It is not possible to start every job the day it is requested. In assigning job
priorities, it is important to consider factors such as importance of the item
or system, the type of maintenance, required due dates, and the length of
time the job awaiting scheduling will take.

15. ❑ Types of Maintenance
I. Preventive or condition based maintenance (Chapter-4_Class-4)
II. Corrective or breakdown maintenance ( Chapter-5_Class-5)
a) Fail repair
b) Overhaul
c) Salvage
d) Servicing
e) rebuild
III. Predictive maintenance
IV. Autonomous maintenance
V. Reliability based maintenance