How task considerations dictate the choice of equipment?

The task objectives at the construction sites are stated in terms of the nature of the task and the quantity of work to be accomplished economically, within the specified time, and under given site conditions.

The nature of the task dictates the type of equipment needed and the time allowed in the work schedule determines the rate of work. This rate of work indicates the output capability of the required equipment. The equipment productivity determines its cost effectiveness.

1.1. Nature of Work

The tasks that can be performed with equipment in building construction projects include excavating, hauling, transporting, filling, compacting, grading, fabricating, hoisting, concreting, pre-casting, block-making, plastering, finishing, trenching, pipe-laying, cable-laying, and road-making and so on. In addition, the support equipment at the project site consists of generators, pumping sets, treatment plants and other utility services equipment.



1.2. Rate of Daily Output

The forecast of the quantity of work to be completed in a specified period, conforming to the schedule of work under given job conditions, defines the rate of daily output and the peak production level. The output of the equipment under site conditions will have to be equal to or more than the average planned hourly rate at which the task is to be executed economically.

1.3. Equipment Performance Capability

The equipment performance at the site of work depends upon many situational factors that influence the output. It is neither feasible nor desirable to evaluate the resultant impact of each of these situational factors as, overall, only a few may matter and the remaining may overlap. In order to simplify this evaluation, the prominent situational factors, other than those considered while computing equipment output norms, can broadly be grouped under two headings, viz. controllable factors and uncontrollable factors.

Controllable factors. These are the factors, whose effect can be controlled by the site management. The prominent contributing factors include, but are not limited to the following:

· Equipment operational worthiness.

· Operator's skill to operate the machine effectively for performing the given task.

· Available equipment repair and maintenance facilities.

· Planning and supervision effectiveness.

· Level of motivation.

Uncontrollable factors. These include impact of the work site altitude and environments:

Performance efficiency factor. The performance efficiency resulting from various controlled and uncontrolled factors can be determined as follows:

Performance efficiency factor = Controllable factor × Uncontrollable factor

The equipment efficiency thus determined can be either expressed as a fraction or as a percentage. It can also be stated in terms of effective time in minutes per hour, e.g., the efficiency factor of 0.6 can be stated as 60% or 36 minutes effective output of the hourly optimum production rate.

It may be noted that the given piece of equipment does not operate in isolation. Generally, it follows a sequence, i.e., one machine is followed by the next machine or related activity. Thus, the performance of each equipment influences the outcome of the subsequent equipment or activity. The standard output of the machine, therefore, has to be viewed in the light of the system and the adjustments made, if required, as any imbalances in related activity will adversely affect the overall output of the system.

1.4. Equipment Productivity

The production of a given piece of equipment is optimum when it is employed on the primary task for which it is designed, e.g., a bulldozer is most productive when it is used for cutting earth and hauling by dozing action up to 60 meters. In case equipment is to be used on secondary tasks, its productivity will have to be suitably modified.

1.5. Future Use of Equipment

If all the expenses connected with the ownership and operation can be amortized/repaid on the project on which it is to be employed, there is no need to consider the future use of the equipment. However, if the equipment is to be utilized only for a part of its economic life in the project, the recovery of cost on its balance life will have to be considered in terms of future use or disposal after part use. This involves evaluation of the equipment owning and operating costs.