Infrared Thermography as Condition Monitoring

 

Infrared Thermography:

Infrared Thermography is one of the most versatile and desirable tools in condition monitoring program – a technique that’s used to monitor the health of the equipment and associated structure by detecting infrared energies emitting out of the system, assets, and structure – any abnormality in the temperature indicates the developing fault in the system.

Infrared thermography is considered a valuable tool in the range of non-destructive testing techniques. A thermography technique is based on the fact that all objects emit energies or radiations of some kind and infrared is one of them – an energy of the longest wavelength, which is invisible to human eyes, require a special instrument to capture and convert this to a surface temperature.

Infrared energy is the function of the surface temperature, it is developed due to the vibration of the atoms and molecule in the object – the higher the temperature, the more molecules in motion, the more infrared energy is emitted. Thermography cameras are designed to detect the thermal radiations of the objects surface and their subtle differences in temperature.

Thermography is a non-intrusive technique that can be used even when the equipment is energized and without the need of taking equipment shutdown. it’s an effective periodic equipment inspection program that ensures that the component is operating within its acceptable thermal range. It has the ability to record all the thermal photographs of the equipment for the analysis purpose. Infrared thermography is contactless temperature monitoring device that uses infrared sensors for the simultaneous temperature measurements of the multiple points – because of its contactless and line-of-sight characteristics it is best suited for identifying the hot and cold spots in an energized electrical equipment.

Temperature measurements using infrared sensors requires an understanding of radiant energy, emittance, and reflections. There are three types of thermal energies that can be detected from any object – energy that is emitted from the object, energy that is reflected from the object, and the energy that is transmitted by the object. Out of three, only emittance is of great importance in condition monitoring program. It is essential to filter out reflected and transmitted energies since reflected energies makes surface temperature way higher than it really is.

Two kinds of inspections can be made from thermography device,

1- Qualitative Inspection

2- Quantitative Inspection

Quantitative Thermography Inspection:

Quantitative inspections refer to the accurate temperature measurement of the object. It is required where numerical data is essential to determine the severity of the component.

Qualitative Thermography Inspection:

In qualitative inspection thermography camera spots the accurate temperature variations, hot and cold spots, and the uneven heating surfaces. It is less time consuming and used for quick analysis where severity of the component is not needed.

Applications of Infrared Thermography:

Infrared Thermography is an effective way of determining the degraded condition of the equipment and system. It can be used in condition-based maintenance and predictive maintenance program to periodically inspect the plant equipment – motors, pumps and fans etc.

It can be used in many facilities such as:

• In electrical system, it can be used on power transformers, power lines, equipment contacts, switchgears, and its associated components. The primary use of infrared thermography in electrical system is to find electrical deficiencies. For example:
• It is mainly used to identify the overloaded components that may cause functional failure of the equipment.
• Overloading in power cables may deteriorate its insulation and cause to puncture.
• On energized equipment, it is used to identify the loose and corroded connections. High resistance path causes to create hotspots on the surfaces which is easily identified by the IRT device.
• it is used to identify the blockage in transformer radiators, heat exchangers, and pipes. It is also used to spot heated surfaces which happens due to extreme friction, bearing inspections.
• Infrared thermography can be used to identify the roof leakages, cracks, and crevices in the building.
• Infrared thermography is also used to detect the insulation degradation of the building walls and roofs.
• Infrared thermography is also used to detect energy loss of the directly ground-buried pipes by monitoring the soil temperature through thermograph lens.
• In medical science, it is used to detect the blood flow in human tissues. A special kind of infrared thermography can be used to diagnose the breast cancers.
• Another usage of IRT device is the surveillance of people and security imaging.
• Thermal imaging is an efficient way of locating fluid – gas, liquid, and sludge level.

Benefits of Infrared Thermography:

There is an endless benefit of using infrared thermal imaging device in condition monitoring and predictive maintenance program. Some key benefits are enlisted below:

• Due to contactless by nature it requires no equipment shutdown for the inspection.
• Due to thermal imaging qualitative inspection program developing faults are easily identified before the equipment breaks down. It saves time and money.
• Early diagnosis of incipient faults prevents hazardous equipment failures and risk of fire, which allows to mitigate severe safety issues before it becomes a personal risk.
• With the use of thermal imaging quality of the product can be greatly increased.
• Since it’s a non-destructive testing technique so it allows you to test a large area of the equipment in a quick way without destroying it anyway. It saves major saving in time, people, and machinery.

Limitations of Thermography:

Despite being effective and handy, thermographer must pay heed to many factors that greatly affects the accuracy of the reading. Variations like, shiny surfaces and paint and other many variables such as the atmospheric condition between the object and thermography device. It is as moisture and water vapor in atmosphere absorbs the infrared radiations and dust particles and lighting distort them. However, most of the devices uses built in filter to attenuate the affects of environment.