6. The economics of choice

The economic elements usually taken into account are :

• the purchase cost of the instrument ;

• installation cost;

• maintenance costs.

Unlike the technical aspects, which are normally certain elements, the economic criteria consist, in part, of a projection into the future of subjective data; among other things, a somewhat vague notion of "expenditure efficiency" is added. A type X flowmeter, for example, costs 8,000 euros per unit, but once installed, it will be "forgotten" by the maintenance department, and three years later will have become more economical overall than a type Y instrument sold for 5,000 euros but requiring more maintenance. If necessary, type X can be used on several lines or processes, making maintenance easier and quicker,...