The measurement of levels of liquids and, even, solids, are frequently used in visual inspections for predictive maintenance, due to the fact that it monitors the degree of occupation of tanks, containers, containers or deposits.

While there are different ways to measure levels in the industry, we will focus on the ones most commonly used in visual inspections for predictive maintenance.

Among the direct level measurements, the most widely used is the one performed by means of sight glasses, although measurement by rod or probe, float measurement and plumb measurement can also be performed.

In cases of systems with oil, the sight glasses allow to evaluate in a simple way not only the oil level, but also the condition of the oil (color, bubbles and contamination).

Figure 17: Column type oil level sight glass. Source: Luneta.
Figure 18: Oil level sight glass. Source: Luneta.

Within the indirect level measurements, we can find hydrostatic measurements (manometric, membrane, bubbling, diaphragm differential pressure, displacement) and electrical measurements of the liquid (conductive, capacitive, ultrasonic).