The document discusses the applications of thermography in condition monitoring, emphasizing its advantages such as non-contact measurement and the accessibility of infrared imaging technology. It outlines various applications including the detection of electrical faults, building defects, and machinery issues particularly in bearings and couplings. The importance of accurate temperature measurement through specialized infrared instruments for predictive maintenance in industrial settings is also highlighted.

1. Aircraft Condition
Monitoring
UNIT-III
Condition Monitoring Analysis-Thermography
Prepared by Jhumki Nandy
Department of Aeronautical Engineering, Sanjay Ghodawat University Kolhapur

10. Industrial Applications of Thermography
Thermography has found many industrial applications for two obvious reasons: First, thermography is
noncontact in nature, and temperature can be measured from a distant location. Second, light,
portable, and precise IR image cameras are commercially available. The recent advances in
instrumentation along with the availability of user-friendly software has made thermography useful in
many engineering applications. Figure 10.2 shows a hand-held thermal imaging camera being used for
temperature monitoring of an engine.

12. Electrical and Electronic
Component Heat Generation
In many electrical and electronic systems and circuits,
due to flow of current in a conductor, heat is
generated that is proportional to the square of the
current. In many instances, due to an increase in the
load resistance, the current in the circuit increases as
a result of which there is a temperature rise, which
can be easily detected with infrared imaging. The
increase in resistance could be due to oxide
formation at the electrical contact points, electrical
sparking due to loose contacts, and so on, which in
turn increases the current flowing through the
conductors. In a plant control room or a system of
machineries where several electrical conductors
connect the various power sources with electrical
loads through switchgears, thermography aids in a
quick survey to detect a conductor at a higher
temperature. Electrical motor defects like broken
rotor bars, stator short circuits, and so on, can also
be detected by thermal imaging. Figure 10.3 shows
the heated electronic components in an amplifier

13. Building Condition
In many instances, several defects can occur in buildings, like roof leakage, cracks at building joints,
mold growth due to dampness, and so on. These result in different temperatures in different parts of the
building. Through infrared imaging of such building structures, variations in temperature can be
measured and clues as to cause of the building defect can be obtained.
Machineries
IR imaging is used for thermal imaging of processing equipment. Figure 10.4 shows the thermal image
of a reciprocating compressor. It can be seen that

14. Applications of Thermography in Condition Monitoring
Shafts are important machine components that are supported on bearings. The bearings are designed
to provide low frictional resistance to the rotating shafts and to support the loads on the shafts. Due to
defects in the rotating machines, many times the loads on the shaft increase, which in turn increases the
normal reaction at the bearings. Due to an increase in the normal load, the components in the bearing
undergo deflection along with an increase in frictional torques. The heat generated at the bearings thus
increases, which is responsible for the increase in temperature at the bearings. The rate of heat
generation is proportional to the rotational speed of the shafts. With an increase in the generated heat
at the bearings, the grease that is present to lubricate the bearings liquefies and flows out. Due to
excessive heat generated at the bearings, the remainder of the grease can become baked and form hard
particles. These particles score the bearing races, which leads to further deterioration of the bearing. To
extend the life of the bearings, the temperatures of rolling element bearings are not allowed to rise
above 70°C.

15. Infrared thermal imaging can be used to monitor the temperature of bearings, particularly in distant
locations. Similar to the phenomenon of heat rise in rolling element bearings, flexible couplings, in which
flexure elements are present in the coupling, experience frictional heat generation because of excessive
forces at the couplings due to shaft misalignment. This heat generation is responsible for the increase in
the coupling temperature.

16. Infrared Thermometer
On its most basic design an infrared thermometer consists of a lens to focus the infrared (IR) energy on to a
detector, which converts the energy to an electrical signal that can be displayed in units of temperature after
being compensated for ambient temperature variation.
This configuration facilitates temperature measurement from a distance without contact with the object to be
measured. As such, the infrared thermometer is useful for measuring temperature under circumstances where
thermocouples or other probe type sensors cannot be used or do not produce accurate data for a variety of
reasons.
Some typical circumstances are where the object to be measured is moving; where the object is surrounded
by an EM field, as in induction heating; where the object is contained in a vacuum or other controlled
atmosphere; or in applications where a fast response is required.

17. TYPES OF INFRARED INSTRUMENTS
Most infrared-monitoring systems or instruments provide special filters that can be used to avoid
the negative effects of atmospheric attenuation of infrared data; however, the plant user must
recognize the specific factors that will affect the accuracy of the infrared data and apply the correct
filters or other signal conditioning required to negate that specific attenuating factor or factors.
Collecting optics, radiation detectors, and some form of indicator are the basic elements of an
industrial infrared instrument. The optical system collects radiant energy and focuses it on a
detector, which converts it into an electrical signal. The instrument’s electronics amplifies the
output signal and processes it into a form that can be displayed. Three general types of
instruments can be used for predictive maintenance: infrared thermometers or spot radiometers,
line scanners, and imaging systems.