infrared thermogrphy CONTENT

Infrared Thermography

Seminar Report 2011

CONTENTS TITLE

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1. INTRODUCTION.

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2. THERMOGRAPHIC CAMERA.

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3. THERMOGRAPHIC TECHNIQUE.

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4. PROCESS OF THERMOGRAPHY.

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5. APPLICATIONS OF THERMOGRAPHY.

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6. ADVANTAGES & DISADVANTAGES

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OF THERMOGRAPHY. 7. CONCLUSION .

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8. REFERENCE.

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Dept. of Electrical and Electronics Engineering, MGUCE, Thodupuzha.

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Seminar Report 2011

1. INTRODUCTION

1.1. About the Thermography

Thermal or infrared energy is an energy, not visible because its wavelength is too long for the sensors in our eyes to detect. It is the part of the electromagnetic spectrum that we perceive as heat. Unlike visible light, in the infrared spectrum, everything everything with a temperature temperature above absolute zero emits infrared electromagnetic electromagnetic energy. Even cold objects such as ice cubes, emit infrared radiation. The higher the tempera temperatur turee of the object, object, the greater the infrare infrared d radiatio radiation n emitte emitted. d. The Infrared camera allows us to see what our eyes cannot. All objects, cold or hot, radiate heat in the form of infrared energy. As an object increases in temperature, it radiates more energy, and the wavelength gets shorter. Infrared radiation, visible light and ultraviolet light are all forms of energy in the electro electromagn magnetic etic spectrum spectrum.. The only differen difference ce is their their waveleng wavelength th or frequency.

Fig 1.1. Electromagnetic Spectrum

1.1.1. What is Thermography? Thermography?

Infrared Thermography is the technique that uses an infrared imaging and measure measuremen mentt camera camera to "see" "see" and "measur "measure" e" invisibl invisiblee infrared infrared energy being being emitted from an object.


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Thermography is a non-contact, non-destructive test method that utilizes a thermal imager to detect, display and record thermal patterns and temperatures across the surface of an object. Infrared thermography may be applied to any situation where knowledge of thermal profiles and temperatures will provide meaningful data about a system, object or process.

1.1.2. What principle used in Thermography?

Since infrared radiation is emitted by all objects based on their temperatures, according to the black body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore thermography allows one to see variations in temperature. Radiation also originates from the surroundings and is reflected in the object, and the radiation from the object and the reflected radiation will also be influenced by the absorption of the atmosphere.

If the temperature an object gets hot enough however, above 525°C the energy from that object will radiate energy in the visible spectrum and we will see it. This is when we see an object like the burner on an electric stove “glowing” red. In fact any time an object will emit or reflect energy in the same frequency of our eyes we will see it. Infrared energy is just one part of the electromagnetic spectrum that encompasses radiation from gamma rays, x-rays, ultra violet, a thin region of visible light, infrared, microwaves, and radio waves. All objects emit a certain amount of black body radiation as a function of their temperatures. The higher an object's temperature is the more infrared radiation as black-body radiation it emits. A special camera can detect this radiation in a way similar to an ordinary camera does visible light. It works even in total darkness because ambient light level does


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not matter. This makes it useful for rescue operations in smoke-filled buildings and underground.

1.1.3. Where Thermography is used?

Thermal imaging photography finds many uses. For example, firefighters use it to see through smoke, find persons, and localize hotspots of fires. With thermal imaging, power line maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver. Some physiological activities, particularly responses, in human beings and other warm blooded animals can also be monitored with thermographic imaging. Cooled infrared cameras can also be found at most major astronomy research telescopes.

1.2. Why Thermography?

Thermography is useful because: It is non-contact. •

Uses remote sensing.

•

Keeps the user out of danger.

It is two dimensional . •

Thermal patterns can be visualized for analysis.

•

Comparison between areas of the target is possible.


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It is real time •

Enables very fast scanning of stationary targets

•

Enables capture of fast moving targets

•

Enables capture of fast changing thermal patterns.

1.3. Benefit of Thermography?

Thermography is a non-contact, non-destructive test method. It is capable of catching moving targets in real time. It finds defects in shafts and other metal parts. It is used to take measurement in areas inaccessible or hazardous for other methods. It find deteriorating components prior to failure. It helps compare temperatures over a large area. When compared with other classical nondestructive testing techniques such as ultrasonic testing or radiographic testing, thermographic inspection is safe, nonintrusive and noncontact, allowing the detection of relatively shallow subsurface defects under large surfaces and in a fast manner.


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2. THERMOGRAPHIC CAMERA

2.1. Radiation from an Object

Every object whose surface temperature is above absolute zero (-273 °C) radiates energy at a wavelength corresponding to its surface temperature. Utilizing our highly sensitive infrared cameras, it is possible to convert this radiated energy into a thermal image of the object being surveyed. Infrared energy is just one part of the electromagnetic spectrum that encompasses radiation from gamma rays, x-rays, ultra violet, a thin region of visible light, infrared, microwaves, and radio waves. These are all related and differentiated in the length of their wave (wavelength). All objects emit a certain amount of black body radiation as a function of their temperatures. The higher an object's temperature is, the more infrared radiation as black-body radiation it emits. A special camera can detect this radiation in a way similar to an ordinary camera does visible light. It works even in total darkness because ambient light level does not matter. This makes it useful for rescue operations in smoke-filled buildings and underground. 2.2. Thermographic Camera

A thermographic camera, sometimes called a FLIR (Forward Looking InfraRed), or an infrared camera less specifically, is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible light. Instead of the 450–750 nanometer range of the visible light camera, infrared cameras operate in wavelengths as long as 14,000 nm (14 µm).


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Cameras - FLIR T250

Cameras - FLIR i60


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Fig2.1.ThermaCAM PM390

The ThermaCAM PM390 System utilized by Infra-red Analyzers, Inc. consists of an infrared camera with optics transparent only to infrared radiation and a video monitor capable of displaying the thermal image. The camera converts radiated heat energy into an electrical signal which is then displayed on the monitor as a real-time heat image of the object being scanned. This digital thermal image can be captured directly from the camera and processed for CD-ROM, printed report, or analog VHS videotape generation. There are two different types of images. Color Thermograms (photographs of the infrared image) and Control Photos (conventional digital images of the same scene taken during the inspection) are provided of problem areas uncovered during the inspection. In the thermograms, temperatures are displayed in a spectrum of colors.

Fig2.2. Hierarchy of colors


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This chart illustrates the hierarchy of colors used to represent the relative temperature differences of the problems found during the inspection. Black and white, and color, are properties of visible light that do not exist in the infrared world. Because we need to convert these images into visible light, the IR camera assigns black to the coolest temperatures in an image, white to the hottest temperatures in an image, and graduating shades of gray in between. Similarly, different colors can be used to portray different temperatures. The higher the temperature, the more energy emitted. The typical infrared thermography camera resembles a standard camcorder and produces a live TV image of heat radiation. The camera provides a basic grey scale image which is converted to false color images to make interpretation of thermal patterns easier. The thermal image produced by an infrared camera is called a thermogram.


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3. THERMOGRAPHIC TECHNIQUE The basic principle of thermography is that all types of surfaces will emit some degree of heat. The thermographic equipment will detect heat which differs from the temperatures in the surrounding area of a surface. These higher temperatures might be an indication of a potential malfunction of the scanned object i.e. faults in electrical circuitry or overheating of bearings in mechanical equipment, i.e. pumps, motors, compressors, etc. Thermographic imaging can detect insufficiently insulated hot spots in engine rooms, which create a large fire risk. If material under inspection is heated with radiators (active thermography), the temperature of the surface will rise suddenly. The speed at which the heat front dissipates into the material depends on the thermal properties like density, heat capacity, thermal conductivity and the bonding quality between top surface layer and the base material. A defect in the sub-surface creates a barrier for the heat diffusion process and, therefore, the surface temperature above the defect will decrease more slowly than the temperature in other regions. The surface above such a defect will show a hot spot for a longer time as its vicinity covering good bonded material. The principle of this effect is shown schematically in Fig.3.

Fig.3. The uniformly distributed heat impact on the surface.


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In contrast to the fast dissipation of heat in metallic materials, the dissipation of heat in wood-based-materials is comparable slow. The detection of defects can take a few seconds or even some minutes after the heat impact depending on the material and depth of the defect.

3.1. Active and Passive Thermography.

If the inspected material is heated during the production process (passive thermography), the surface temperature will decrease after leaving the production line. Invisible defects within the material will appear as cold spots on the surface, because of the good insulation between the hot core material and the colder surface. In both cases, active or passive thermography, the defects can be either detected as hot (active) or cold spots (passive) on the surface.

3.2. Results of active and passive thermographic measurements.

For first tests with active on-line thermography, different panels of laminating floor were

placed on a conveyor belt and heated by a few degrees

centigrade while moving along three infrared heaters.

The result can be seen in Fig. 3.2.1. & Fig.3.3.2. where a blister shows up in the thermographic image as circular hot (red) spot. But moreover some extended areas show also a warmer behavior as its vicinity. Destructive tests showed that these areas have a decreased adhesion bonding in comparison to the rest of the material.


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4. PROCESS OF THERMOGRAPHY Infrared thermography is the technique of converting infrared energy (radiant heat) into an image that a person can see and understand. We ordinarily see in visible light. We can compare infrared to visible light - they are not the same, but they are analogous. We are familiar with the idea of a video camera creating images on video monitors or television. The electronics in the camera convert the light energy that enters the lens into a video signal and displays that signal on a monitor or TV. We see shapes, colors, textures, shadows, and reflective surfaces in the image as a result of the camera's ability to capture light.

Fig 4. This image shows the radiant heat rather than light. The light areas are warmer than the dark areas

In a similar way, an infrared camera creates an image by converting radiant heat energy into a signal that can be displayed on a monitor (and later printed). The infrared energy emitted from an object is directly proportional to its temperature. Therefore temperatures are accurately measured by the infrared camera.


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The ability to measure temperature from an IR image is called radiometry. This requires sophisticated and expensive electronics.

The ability to measure a

temperature anywhere on the image is available only on the high-end cameras. 4.1. Colorizing Infrared Images

Black and white, and color, are properties of visible light that do not exist in the infrared world. Because we need to convert these images into visible light, the IR camera assigns black to the coolest temperatures in an image, white to the hottest temperatures in an image, and graduating shades of gray in between. Similarly, different colors can be used to portray different temperatures. Using colors to represent different temperatures, a knowledgeable technician adjusts the color image to optimize clarity and best reveal the high temperatures of interest.

Fig 4.1. This image of shows a hot coffee mug and a plate of cookies. The colors bear no correlation

with visible light, rather the colors correspond to the radiant heat.


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5. APPLICATIONS OF THERMOGRAPHY Infrared Thermography is the technique for producing a visible image of invisible infrared energy emitted by objects. The higher the temperature, the more energy emitted. The thermographic camera provides a basic grey scale image which is converted to false color images to make interpretation of thermal patterns easier. The thermal image produced by an infrared camera is called a thermogram. 5.1.ElectricalThermography

It is used virtually around the world to evaluate the condition of electrical systems and equipment. When an electrical system is energized, current passes through the entire system, a byproduct of this current flow is heat. When there is a defect in the system, more heat is generated because of high resistance, and the camera will see the difference between the normal components and the one with a problem.

Fig 5.1 Thermal image showing a failing connection on an electrical component.


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5.2. Tank Inspections

Manufacturers concerned with non-destructively testing product quality and performance are also among those employing, infrared radiometric technologies. An automobile manufacturer might use IRT to measure the real-time thermal dynamics of a prototype engine block or a plastics manufacturer might be interested in monitoring its extrusion process. Many industrial processes implicate the use of IRT where temperature and heat flow are a useful indicators of how a process is operating.

Fig 5.2. Infrared Inspection for tank leaks and to verify tank level.

5.3. Concrete Inspections

Another example is the inspection of concrete bridges. Over the years, a concrete bridge deck can develop subsurface delaminations, which can lead to holes in the deck. When a hole develops, it is already a big problem. What is important is to find the problem before the hole appears. Using the energy from the sun as an active heating source, we look at it with the infrared camera. The region with the subsurface delamination will have a different level of heat than the solid parts of the concrete deck structure. The infrared camera will show the differences.


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Fig 5.3. This shows that even though the bridge deck doesn’t generate heat it can still

be analyzed with thermography. 5.4. Aircraft Inspections

Composite aircraft materials are extremely sturdy and lightweight. These materials are vital to aircraft performance and airworthiness. However, the honeycomb structure of this material presents a potentially dangerous problem: water ingress.

Fig 5.4.Aircraft inspection 5.5. Medical Thermography

Clinical IRT is applied to the care of horses. Many minor injuries to muscle tissue may go unnoticed until the problem is more severe. However, infrared imagers used today can pick up the smallest change in temperature as a result of increased blood flow to damaged tissues. In this way IR imaging aids the expert trainer in caring for the horse.


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Fig.5.5. Race horse sustained an injury in a fall. The infrared image shows where

the problem is, and monitored the process of the healing.

There are three main areas in veterinary medicine where thermography can play a major part: 5.5.1. Preventative Medicine - particularly effective for competition animals in

detecting strains or areas of abnormal heat after an event 5.5.2. Diagnosis - assisting the veterinary surgeon by quickly and easily locating

the source of a problem 5.5.3. Treatment - a visual method of monitoring the effectiveness of treatment

allowing changes to be made as the case progresses.

Fig 5.6 Horse showing lameness after exercise. Thermography revealed localised

inflammation at the bottom of the tendon. Dept. of Electrical and Electronics Engineering, MGUCE, Thodupuzha.

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Fig 5.7.This horse which was being treated for Navicular disease had suddenly

gone lame. A thermal scan showed inflammation in the foot centred on the right part of the frog. Investigation revealed an abscess which was subsequently treated. Thermography can be applied to treat human beings also. They are used in treating: 5.5.4. Respiratory Dysfunctions

Infrared thermography is useful for monitoring asthma, allergies, bronchitis, influenza etc. 5.5.5. Digestive Disorders

Infrared thermography has demonstrated excellent results in helping in the diagnosis of urgent gastrointestinal pathology, especially appendicitis and hyper and hypo gastric secretions. 5.5.6. Urinary Diseases

Infrared thermography helps to save patient's and doctor's time in waiting for laboratory data and is successfully used to monitor urinary tract infections, kidney pathology etc. 5.5.7. Cardiovascular & Circulatory Disorders

Infrared thermography is periodically applied for differential diagnostics and is useful in preventing heart disease and serious circulatory problems such as varicose veins. Dept. of Electrical and Electronics Engineering, MGUCE, Thodupuzha.

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5.5.8. Lymphatic Dysfunctions

Infrared Thermography tests therapy effectiveness in severe cases of lymphoma, leukaemia and reliable to monitor lymphatic involvement in breast cancer patients. 5.5.9. Nervous Dysfunctions

Infrared Thermography analyses the brain, spinal cord and nerves, gives doctor a reliable and safe method of problem location and for monitoring improvements. 5.5.10. Endocrine Disorders

Infrared Thermography helps to evaluate hormonal changes, thyroid disorders such as hypo and hyperthyroidism, and diabetes 5.5.11. Locomotors Disorders

Infrared Thermography helps in the clinical evaluation and detection of serious and difficult disorders such as musculo-skeletal syndromes, neuropathy, neurovascular compression, nerve injury, soft tissue injury, arthritis, inflammatory pain, and disk injury. 5.5.12. Surgical Assistance

Surgeries can be assisted safely before and after using Medical Thermographyhelps to locate tumours size and locates surgical area and monitors the healing process after surgery. 5.5.13. Skin Problems

Infrared thermography gives a more precise level of information - skin tumours and skin cancers, and wound healing.


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5.5.14. Ear, Nose & Throat Dysfunction

Infrared thermography can assist in identifying areas with disorders when radiation should not be used such as tonsillitis, swelling of the lymphatic glands, teething problems, and sinusitis. 5.5.15.Dentistry

Dentists recommend the use of Medical Thermography in monitoring control in the inflammation process into oral cavity and reaction of the regional lymphatic nodes and other chronic diseases of the bones, nerves, located in the maxilla facial area. Medical Thermography can also measure temperature changes in the application of new methods and dental materials applied by dentists. 5.6. Non Destructive Testing

Nondestructive Testing (NDT), also called nondestructive examination (NDE) and nondestructive inspection (NDI), is testing that does not destroy the test object. To detect different defects such as cracking and corrosion, there are different methods of testing available, such as X-ray and ultrasound. While destructive testing usually provides a more reliable assessment of the state of the test object, destruction of the test object usually makes this type of test more costly to the test object's owner than nondestructive testing. That there is a tradeoff between the cost of the test and its reliability favors a strategy in which most test objects are inspected nondestructively; destructive testing is performed on a sampling of test objects that is drawn randomly for the purpose of characterizing the testing reliability of the nondestructive test. During their service lives, many industrial components need regular nondestructive tests to detect damage that may be difficult or expensive to find by everyday methods. For example:


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

Aircraft skins need regular checking to detect cracks.

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Underground pipelines are subject to corrosion and stress corrosion cracking.

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Concrete structures may be weakened if the inner reinforcing steel is corroded.

Fig 5.8. Composite material at aeroplane industry.

Violet color indicates parts visible at surface level and yellow indicates non visible parts at surface level.

5.7. Condition monitoring

It is the process of monitoring a parameter of condition in machinery, such that a significant change is indicative of a developing failure. It is a major component of predictive maintenance. The use of conditional monitoring allows maintenance to be scheduled, or other actions to be taken to avoid the consequences of failure, before the failure occurs. It is typically much more cost effective than allowing the machinery to fail. Serviceable machinery includes rotating machines and stationary plant such as boilers and heat exchangers.


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5.8. Night Vision

Night vision is the ability to see in a dark environment. Humans have poor night vision compared to many animals, in part because the human eye does not have a tapetum lucidum.

Fig 5.9. Two American Soldiers pictured during the 2003 Iraq War seen through an

Image Intensifier. Enhanced spectral range allows the viewer to take advantage of non-visible sources of electromagnetic radiation (such as near-infrared or ultraviolet radiation). Some animals can see well into the infrared and/or ultraviolet compared to humans, enough to help them see in conditions humans cannot. Thermal imaging cameras are excellent tools for night vision. Contrary to other technologies they do not need any light at all to produce a clear image. They produce an image in the darkest of nights and can see through light fog, rain and smoke. Thermal imaging cameras make small temperature differences visible. They detect what can not be detected by the human eye. Thermal imaging cameras are widely used to complement new or existing security networks.


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6. ADVANTAGES & DISADVANTAGES OF THERMOGRAPHY

6.1. Advantages of Thermography •

It shows a visual picture so that can help compare temperatures over a large area.

•

It is capable of catching moving targets in real time.

•

Able to find deteriorating components prior to failure.

•

Measurement in areas inaccessible or hazardous for other methods.

•

It is a non-destructive test method.

•

Make easier to find defects in shafts and other metal parts.

6.2. Disadvantages of Thermography •

Due to the low volume of thermal cameras, quality cameras

often have a high price range (often $6,000 USD or above) and are easily damaged. •

Images can be hard to interpret accurately even with experience.

•

Accurate temperature measurements are very hard to make

because of emissivities. •

Training and staying proficient in IR scanning is time

consuming. •

Ability to measure only surface areas.

.


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7. CONCLUSION When compared with other classical nondestructive testing techniques such as ultrasonic testing or radiographic testing, thermographic inspection is safe, nonintrusive and noncontact, allowing the detection of relatively shallow subsurface defects under large surfaces and in a fast manner.Thermography enables us to see and measure heat. Thermography is a method that utilizes a thermal image to detect, display and record thermal patterns and temperatures across the surface of an object. Thermography is the future in water damage and mold claims adjudication for the insurance industry. IR is going to allow the industry to be more exact in the data that it obtains, and to be able to resolve any claims that may be occurring now, as well as in the future, more quickly and cost-effectively, saving time and money.


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infrared thermogrphy CONTENT

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