Preparation of the network

The first function of the planner in conjunction with the project manager is to divide the project into manageable blocks. The name is appropriate since, like building blocks, they can be handled by themselves, shaped to suit the job, but are still only a part of the whole structure to be built.

The number and size of each block is extremely important since, if correctly chosen, a block can be regarded as an entity which suits both the design and the construction phases of a project. Ideally, the complexity of each block should be about the same, but this is rarely possible in practice since other criteria such as systems and geographical location have to be considered. If a block is very complex, it can be broken down further, but a more convenient solution may be to produce more than one network for such a block. The aim should be to keep the number of activities down to 200-300 so that they can be analysed manually if necessary.

As the planner sketches his logic roughly, and in pencil on the back of an old drawing, the construction specialists are asked to comment on the type and sequence of the activities. In practice, these sessions - if properly run - generate an enthusiasm that is a delight to experience. Often consecutive activities can be combined to simplify the network, thus easing the subsequent analysis. Gradually the job is 'built', difficulties are encountered and overcome, and even specialists who have never been involved in network planning before are carried away by this visual unfolding of the programme.

The next stage is to ask each specialist to suggest the duration of the activities in his discipline. These are entered onto the network without question. Now comes the moment of truth. Can the job be built on time? With all the participants present, the planner adds up the durations and produces his forward pass. Almost invariably the total time is longer than the deadlines permit. This is when the real value of network analysis emerges. Logics are re-examined, durations are reduced and new construction methods are evolved to reduce the overall time. When the final network - rough though it may be - is complete, a sense of achievement can be felt pervading the atmosphere.

This procedure, which is vital to the production of a realistic programme, can, of course, only be carried out if the 'blocks' are not too large. If the network has more than 300 activities it may well pay the planner or project manager to re-examine that section of the programme with a view to dividing it into two smaller networks. If necessary, it is always possible to draw a master network, usually quite small, to link the blocks together.

One of the differences between the original PERT program and the normal CPM programs was the facility to enter three time estimates for every activity. The purpose of the three estimates is to enable the computer to calculate and subsequently use the most probable time, on the assumption that the planner is unwilling or unable to commit himself to one time estimate. The actual duration used is calculated from the expression known as the j8 distribution:

where te is the expected time, a the optimistic time, b the pessimistic time and m the most likely time.

However, this degree of sophistication is not really necessary, since the planner himself can insert what he considers to be the most probable time. For example, a foreman, upon being pressed, estimated the times for a particular operation to be

Optimistic = 5 days Pessimistic = 10 days Probable = 7 days

The planner will probably insert 7 days or 8 days. The computer, using the above distribution, would calculate

With the much larger variables found in real-life projects such finesse is a waste of time, and a single entry is all that is required.

Figure 21.7

Figure 21.7

Figure 21.8

Typical site problems

Once construction starts, problems begin to arise. Drawings arrive late on-site, materials are delayed, equipment is held up, labour becomes scarce or goes on strike, underground obstructions are found, etc.

Each new problem must be examined in the light of the overall project programme. It will be necessary to repeat the initial planning meeting to revise the network, to reflect on these problems and possibly help to reduce their effect. It is at these meetings that ingenious innovations are suggested and tested.

For example, Figure 21.7 shows the sequence of a section of a pipe rack. Supposing the delivery of pipe will be delayed by four weeks. Completion now looks like becoming week 14. However, someone suggests that the pump bases can be cast early with starter bars bent down to bond the plinths at a later date. The new sequence appears in Figure 21.8. Completion time is now only week 11, a saving of three weeks.

This type of approach is the very heart of successful networking and keeps the whole programme alive. It is also very rapid. The very act of discussing problems in the company of interested colleagues generates an enthusiasm that carries the project forward. With good management this momentum is passed right down the line to the people who are actually doing the work.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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