TABLE OF CONTENTS There are dozens of predictive maintenance technologies, and some have become a standard in many industries. The standard technologies include vibration analysis, ultrasound, oil analysis, wear particle analysis and thermography. In the earlier topics, we discussed in detail the predictive maintenance techniques of vibration analysis and oil and wear particle analysis. In this chapter, we will discuss the other predictive maintenance techniques like ultrasound and thermography. These techniques are quite useful for some applications and complement the major techniques very well.
Many condition-monitoring techniques can be used to monitor the same fault condition. For example, a problem identified by an oil sample can also be cross-checked with vibration analysis or thermography. An electrical problem, identified with ultrasound, can be confirmed through the use of thermography. Hence, a confirmation of the diagnosis is possible through the use of the different predictive maintenance techniques. This fact makes the predictive maintenance more convincing, especially when critical machinery is involved.
Most machines emit consistent sound patterns under normal operating conditions. These sound patterns (sonic signatures) can be defined and recognized, and therefore changes in these signatures can be seen as components begin to wear or deteriorate. In a certain sense, it is a different form of mechanical vibrations. Sound is a microscopic oscillation at the molecular level of a substance. Vibration is a macroscopic oscillation of structures in other words, physical structures that move. Ultrasound is defined as sound waves that have frequency levels above 20 kHz, higher than...
