Example

We will use the same example as discussed previously in Chapter 4 for the time management. The project is to install a mechanical pack­age and connect it with piping as shown in Table (5.1). From this table we can define the relationship between the project activities.

Figure (5.6) shows the critical path of this project through the project plan. Table (5.2) shows the time frame for each activity. This is presented in the table by the total floating time (TF). The resources column indicates the number of personnel required for each activity per day. The last column shows the total number of days required for each activity. Thus, for example, in Table (5.2) excavation needs 7 workers per day, and work will last for 8 days, so this activity needs 56 working days in order to be achieved.

Figure (5.6) shows the distribution of time duration of this proj­ect, which is 25 days. Summing the total working days, shown in Table (5.2), the effort will actually consume 173 working days.

Table 5.1 Example for foundation

Item

Activity

Time

(Days)

Precedence

Activity

too

Mobilization

3

200

Excavation

8

100

300

(Pouring concrete foundation and piping support)

10

200,100

400

Install the piping

4

300,100

500

Install the mechanical package

1

300

600

Put the grouting

1

300,500

700

Connect the piping

5

400,500

800

Commissioning and start up

2

700

Figure 5.6 Preceding diagram define the critical path.

Figure (5.7) presents the time schedule and the number of employees if the plan is presented by the early start (i. e., all activ­ity starts in its first starting time). At the bottom of the schedule another option is presented of launching all the activities which are not on the critical path at the latest starting time. In our example, this is represented by activities 400 (installing the piping) and 700 (connecting the piping).

In the first case, the maximum number men on site will be 12, whereas under the second option, using the latest start, the maxi­mum will be 9 persons. Therefore, a decision needs to be made on whether to use the total float or free float to achieve the proj­ect target. In normal cases, it is preferable to keep the number of laborers on site as few as possible consistent with safety standards and project requirements, since, if the number of onsite laborers is increased, the probability of accidents and injury may increase. A similar consideration arises with siting laborers in remote areas such as those in which oil and gas projects are conducted: accommodations have to be provided by the company that may be onsite or nearby but in any case add to the project’s ongoing operating costs. If the optimum number of onsite personnel can be minimized, it will help rein to in these costs. (In some cases of this kind, there may be fiurther constraints, e. g., if the client can provides accommodation for only 10 persons per day near or on the site.)

When it comes ot staffing levels in the engineering design office, it is important for maintaining the project’s output quality that the work load is distributed so as to maximize the distribution of work and working time to full-time engineering staff, while minimizing the hiring of part-time, or six-month-contracts-at-a-time, engineer­ing staff. Too much part-time work eventually undermines overall project quality, so an appropriate distribution of work loads can be highly beneficial.

Figures (5.8) and (5.9) present the distribution of the resources in two cases, and the harmony of resources distribution is visible if we use the latest start activity as discussed before.

It is worth mentioning here that, in the case of large projects, a meeting be held between a representative of the owner, the consul­tant, and the contractor. In this meeting, the contractor should define the personnel and equipment that will be found at the site in accor­dance with the schedule plan. In this meeting all the representative engineers should reach a working agreement about the allocation

of resources. There are objective conflicts that have to ironed out. For example, the contractor in the negotiation may have his own reasons for supporting a particular distribution of resources, con – nectd with other plans he has for other projects using some of the same personnel and equipment. This is examined further in the later chapter on costs. From an owners point of view, not wanting to be exposed to potential liabilities from a project that increase with the time taken for its completion, it is frequently important to com­plete all the scheduled project tasks as soon as possible. This predis­position, however, leads to favoring a fatter payroll at the project’s inception in the hope that the risks of project delays down the road will thereby be minimized.