Draw the Network Diagram for the Following Project
Before starting to draw the network, following measures should be taken serially:
1. Ready a list of the activities included in the project and their dependence on other activities.
2. Draft the network roughly, usually by soft pencil and an eraser on a large piece of paper.
three. The guess of time required for each activity is made because manpower and equipment's available and in certain cases assumptions are based on statistical approach and experience.
4. These time estimates are and so written on each activity.
5. So scheduling computations are washed to get earliest and latest allowable get-go and finish times for each activeness, to identify critical path and to indicate the corporeality of slack on non-critical paths.
6. Now this is prepared in final class for employ in the field. Projection is controlled by checking the progress against the schedule.
The construction of C.P.Thou. diagram can exist explained past the following examples:
Instance 1:
For the construction of wall the consummate procedure tin exist cleaved into the post-obit operations:
(i) Brick laying A
(2) Preparing mortar B
(iii) Earthworks foundation C
(4) Planning the foundation D
These above operation have not been written in a logical sequence. These operations can exist denoted by the symbols ABCD.
The C.P.M. diagram tin can exist drawn as shown in Fig. 28.35.
The operations D, C, B and A have now been shown in the logical sequence. From the study of these operations, it is establish that preparing mortar is independent of digging foundation and planning operations. Therefore a modified C.P.M. diagram is drawn in Fig. 28.36.
In this effigy numerals (one, 2, 3, etc.) are used commencing from the kickoff column on the left and so proceeding towards right.
Example ii:
A ladder is to be synthetic. The various operations involved in information technology are:
(i) Fixing of Nails A
(ii) Cut Wrings B
(iii) Drilling Wrings C
(iv) Drilling holes in 2 Bamboos D
(five) Cutting two Bamboos E
Solution:
The operations are non given in logical social club. At that place logical order will be according to Fig. 28.37.
The modified network of Fig. 28.37 is shown in Fig. 28.38.
The cutting and drilling of the bamboos and wrings are different operations, and these are contained of each other. Therefore cutting ii bamboos and cut wrings can be started concurrently. Thus after the end of operation East, operation D can begin and similarly later on the terminate of performance B, functioning C can kickoff.
After the finish of functioning C and D, the last operation of fixing nails can brainstorm. Thus the network is fatigued from left to right and each circle representing an operation is numbered from left to correct. All the circles in the extreme left are commencement numbered and so on.
Information technology is clear from the Fig. 28.38 that operation five tin can just brainstorm when the operation 3 and iv are over. Thus we tin say that functioning one immediately preceding operation 3, and operation 2 immediately precedes operation 4. Also the operation 3 and 4 must immediately precede the functioning 5.
In the language of C.P.M., the operations 1 and 2 are chosen the pre-operations (or PRE- OPR) of 3 and 4 respectively. Similarly iii and 4 both are the PRE-OPR of functioning v. Also three and iv will be called mail operations (POST-OPR) of operations 1 and 2 respectively, 5 is the Mail- OPR of performance 3 and 4.
Example 3:
Suppose we desire to beginning a small calibration factory in a shed available in an Industrial area in which workshop is to exist prepared. Commencement step is and so to divide the project into operations.
The list of operations is given below, which is not in a logical social club:
A = Auto foundation
B = Electric fitting
C = Repair of floor
D = Installation of machines
Eastward = Procure workshop edifice
F = Whitewash
G = Make clean up
Solution:
Its logical order of operations should exist Eastward, A, D, B, F, C and G. (Refer Fig. 28.39).
If each operation is represented by a circumvolve then this work can be executed in a ameliorate way as follows:
Sketch shown in Fig. 28.forty is drawn as per circle and line method in which circles represents the performance or action and the line shows the human relationship between the 2 activities. The operation on the left of each line should exist completed before the starting of the operations on the right of the line.
Network shows that operation 3 and 4 are not afflicted by operations 2, 5 and 6. Hence the operations 3 and 4 can exist conducted at the aforementioned fourth dimension, when 2, 5 and 6 operations are existence conducted.
This reduces the time to complete the projection because after operation 1, operation 2 and 3 tin can exist started simultaneously. Operations half dozen and 4 should be completed before the brainstormning of the operation seven. In the final network, diagram operations should be represented by the numerals instead of alphabets.
Case 4:
Construct the network diagram for which operations and post operations are given as nether:
Solution:
As no operation precedes operation i, hence we shall start network from operation 1, keeping it in first vertical column. Operations ii and 3 are post-operations of operation one; hence these are kept in second vertical column as shown in Fig. 28.41.
As operation iv can be started when operation 2 is completed therefore, it will be kept in tertiary vertical column. Operations 4 and 5 are the mail-operations of operation 3 and tin be started simultaneously after completion of operation 3, hence operations 4 and 5 both can exist kept in the same third column. Equally operation half dozen is the post-operation of operations iv and 5, hence will exist continued by both 4 and five and volition exist placed in the side by side column, i.e., in the fourth column equally shown in Fig. 28.42.
In Fig. 28.42, line connecting operations iii and five crosses some other line; hence it may be arranged in a improve and clear grade as shown in Fig. 28.43.
Sometimes, information technology is not possible to avoid it and so the lines may cross each other but care should be taken that such lines should exist as minimum as possible and clear to understand.
Example 5:
Example illustrates a instance in which, operations and pre-operations are as under:
Solution:
As the performance 1 is the first operation, hence network will exist started by operation i denoted by the circle in first cavalcade. Operation 2 is the mail service-operation of 1 and therefore will be kept in 2d column.
Functioning 3 has pre-operations 1 and ii; therefore operation 3 cannot be started unless operations 1 and ii are complete. Hence operation 3 can be kept in third column, i.e. after operation 2, and not in second column immediately afterward performance i. It is shown in Fig. 28.44.
Example 6:
Draw a network diagram for painting in a two storey building.
Solution:
After dividing the project into some operations, network can be drawn equally per Fig. 28.45.
If sufficient men, equipment'due south and materials are bachelor the network would be meliorate to draw in the form as shown in Fig. 28.46 to reduce the timing required for selecting colours, ordering and testing paints and without waiting for the plaster on beginning floor, painting can exist washed on basis flooring and in the hateful-time plaster piece of work on first floor will exist completed and the painting on the same can exist washed. Therefore network shown in Fig. 28.46 is a ameliorate diagram from the point of view that it will relieve the time.
Example 7:
Describe the network diagrams for the projection in which PRE-OPR or Mail-OPR are given below:
The CPM network will be as in Fig. 28.47.
Example 8:
The example 7 for the higher up network diagram can also be framed in terms of Mail service-OPR as given nether:
Example 9:
Draw the network for the post-obit in which POST-OPRs are given:
Solution:
Fig. 28.48 (a) shows the sequence of operations A, B, C and D. Now the operation Due east is preceded by C and the operation F is as well preceded past C. Hence, when the circles are drawn to prove the operations E and F, the connecting lines of DE and CF intersect each other equally shown in Fig. 28.48 (b).
The intersection of lines DE and CF can exist avoided by placing the operation Fin the fourth sequence above the operation Eastward, as shown in Fig. 28.49 (a). At present the numbers may be placed in the operation circles beginning from left to right as shown in Fig. 28.49 (b).
As far equally possible, the crossing of lines should exist avoided. This makes the diagram less disruptive and easier to empathise. Still, sometimes it may not be possible or desirable to eliminate the occurrence of such crossing lines. The numbering should be washed starting from left and moving towards right, the kickoff vertical sequence of operation existence numbered start and and so the 2d and and then on.
Example 10:
Post-obit table shows the operation fourth dimension in working days for dissimilar activities. Describe the critical path on the diagram.
Solution:
The above activities are drawn in the network equally shown is Fig. 28.50. Each activeness is represented past the numeral in the circle. Numbers of days are mentioned on the left corner of circle representing the operation.
After drawing the network diagram, Earliest Finish for each operation is calculated and noted on the height right corner of the circle in the rectangles.
For the last operation vii, Latest time = Earliest finish fourth dimension, i.e. 59 days in this case. From this value, Latest Cease time for other operations is calculated and written on the correct bottom corner of the circle and inscribed in a triangle. For operations 2, 3, 4, 5 and half-dozen latest finish fourth dimension is calculated by subtracting the working days required from the latest of post operation.
For functioning 1, Latest Finish calculated past considering operation 2 is 25 – 10 = 15 days and past because operation 3 is 52 – 15 = 37 days. In such instance lower value is considered equally the Latest Finish. Hence for operation 1, Latest End = 15 days.
Operations which are having Earlier Finish = Latest Finish are joined with double line and represent the critical path every bit shown in Fig. 28.51.
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