Discuss the role of network techniques in project planning, scheduling and controlling.?

Ans. Projects are successful if they are completed on time, within budget, and to performance requirements. Management of any project involves planning, coordination and control of a number of interrelated activities with limited resources, namely men, machines, money and time. Furthermore, it becomes necessary to incorporate any change from the initial plan as they occur, and immediately know the effects of the change. Therefore the managers are compelled to look for and depend on a dynamic planning and schedule system which will not only produce the best possible initial plan and schedule, but will also sufficiently dynamic to react instantaneously to changed in the original plan and schedule. The question of such a dynamic system/ technique led to the development of network analysis. It provides a framework which :

􀂾 defines the job to be done,

􀂾 integrates them in a logical time sequence and finally,

􀂾 affords a system of dynamic control over the progress of the plan.

Network analysis is a generic name for a number of associated project planning and control procedures that are all based on the concept of network. PERT, an acronym for Program Evaluation and Review Technique and CPM, an acronym for Critical Path Method are the two widely used techniques of project management that were developed, independently and simultaneously, during the 1950s.

. PERT and CPM- both techniques use similar network models and methods are have the same general purpose. They were developed during the late 1950s. PERT was originally developed by the U S Navy’s Special Product Office in cooperation with the consulting  firm of Booz, Allen and Hamilton. It was developed as a network flow chart to facilitate the planning and scheduling of the Polaris Fleet Ballistic Missile Project, a massive project with about 250 contractors and about 9000 sub contractors and its application is credited with saving two years from the original of five years required to complete the project. Designed to handle risk and uncertainty, PERT is eminently suitable for research and development and programmes, aerospace projects, and other projects involving new technology. In such projects the time required for completing various jobs or activities can be highly variable. Hence the orientation of PERT is ‘probabilistic’.

CPM, is akin to PERT. It was developed (Independently) in 1956-57 by the Du Pont Company in the US to solve scheduling problems in industrial settings. CPM is primarily concerned with the trade-off between cost and time. It has been applied mostly to projects that employ fairly stable technology and are relatively risk free. Hence its orientation is ‘deterministic’.

As both PERT and CPM approaches to Project Management use similar network models and methods, the term PERT and CPM are sometimes used interchangeably or collectively as PERT-CPM methods. The differences between those tools come from how they treat the activity time. PERT treats activity time as a random variable whereas CPM requires a single deterministic time value for each activity. Another difference is that PERT focuses exclusively on the time variable whereas CPM includes the analysis of the time/Cost trade-off. The PERT/CPM is capable of giving answers to the following questions to the project manager :

􀂾 when will the project be finished ?

􀂾 when is each individual part of the scheduled to start and finish ?

􀂾 of the numerous jobs in the project, which one must be timed to avoid being late ?

􀂾 is it possible to shift resources to critical jobs of the project from other non-critical jobs of the project without affecting the overall completion time of the project ?

􀂾 among all the jobs in the project, where should management concentrate its efforts at one time ?

Methodologically, PERT/CPM were developed from traditional GANTT Charts used for scheduling and reviewing the progress of activities. Developed by Harry Gantt in 1916, these charts give a time line for each activity. They are used for planning, scheduling and then recording progress against these schedules. Basically there are two basic types of Gantt Charts : Load Charts and Project Planning Charts.

Load Charts : This type of chart is useful for manufacturing projects during peak or heavy load periods. The format of the Gantt Load Chart is very similar to the Gantt Project Planning Chart, but, Load Chart, uses time as well as departments, machines or employees that have been scheduled.

Project Planning Chart

It addresses the time of individual work elements giving a time line for each activity of a project. This type of chart is the predecessor of the PERT. It is really easy to understand the graph, but in developing it you need to take into consideration certain precedence relationship between the different activities of the project. On the chart, everyone is able to see when each activity start and finishes but there is no possibility to determine when each activity may start or if we can start a particular activity before finishing the immediate predecessor activity. Therefore, we

need somehow know the precedence relationship between activities. This is the main reason for using the PERT/CPM tools instead of using exclusively Gantt Charts. Widely diverse kind of projects can be analyzed by the techniques of PERT/CPM. In fact they are suitable for any situation where :

(a) the project consists of well-defined collection of activities or tasks.

(b) the activities can be started and terminated independently of each other, even if the resources employed on the various activities are not independent.

(c) the activities are ordered so that they can be performed in a technological sequence. Thus precedence relationships exist which preclude the start of certain activities until other are completed. For instance, road leveling cannot start unless the roadbed is laid.

The network analysis underlying PERT and CPM helps to support the three phases of effective project management

Planning

􀂾 identify the distinct activities,

􀂾 determine their durations and interdependencies,

􀂾 construct a network diagram,

􀂾 determine minimum overall project duration (using the network diagram), and

􀂾 identify the tasks critical (i.e. essential) to this minimum duration.

Scheduling

􀂾 construct schedule (‘time chart’),

􀂾 schedule contains start and finish times for each activity, and

􀂾 evaluate cost-time trade-offs (evaluate effects of putting extra money, people or machines in a particular task in order to shorten project duration).

Controlling

􀂾 monitor/control project by use of network diagram,

􀂾 follow progress of the various activities ; and

􀂾 make adjustment where approp