The means to detect, visualize and survey different kinds of gases within industrial and energy processes, technical infrastructure, landfill bodies, indoor and outdoor environment are discussed. The current status and future plans for IR imaging technologies in the U.S. and in Sweden are described. Primary consideration is given to mobile and airborne remote sensing systems, such as current laser-based imaging technologies, advanced IR systems with and without filter techniques, and two-dimensional gas-correlation techniques, being used or under development. Results of recent laboratory and field experiments involving the imaging of natural gas leaks under both controlled and actual conditions are presented and discussed. Plans for future field testing and technology improvements are described.
Many utilities throughout the United States have added infrared scanning to their arsenal of techniques for inspection and predictive maintenance programs. Commercial infrared scanners are not designed, however, to withstand the searing interiors of boilers, which can exceed 2500 degrees Fahrenheit. Two high-temperature lenses designed to withstand the hostile environment inside a boiler for extended periods of time were developed by the EPRI M&D Center, thus permitting real-time measurement of steam tube temperatures and subsequent analysis of tube condition, inspection of burners, and identification of hot spots. A study was conducted by Sunderland Engineering, Inc. and EPRI M&D in order to characterize the radiative interactions that affect infrared measurements made inside a commercial, coal- fired, water-tube boiler. A comprehensive literature search exploring the existing record of results pertaining to analytical and experimental determination of radiative properties of coal-combustion byproducts was performed. An experimental component intended to provide data for characterization of the optical properties of hot combustion byproducts inside a coal-fired furnace was carried out. The results of the study indicate that hot gases, carbon particles, and fly ash, which together compose the medium inside a boiler, affect to varying degrees the transport of infrared radiation across a furnace. Techniques for improved infrared measurement across a coal-fired furnace are under development.
The infrared radiometer is widely used to detect invisible internal flaws of industrial structural elements, as one of the remote sensing devices. The thermal image method (TIM) was carried out to analyze the location and dimension of the flaw numerically. The method was applied to detect the obscured and underground structural elements, like piping, vessel, concrete slab and ancient tomb using solar and radiation heaters. Detection characteristics are numerically and empirically estimated using a model test piece. The detection limit and heat transfer mechanism pertaining to the present technique is also discussed quantitatively. It was clarified from a series of experiments and analysis that our proposed method was useful to detect the buried object and carried out the verification of heat transfer analysis. We examined experimentally to detect the buried ancient tombs as the application tests. We verified the existence of the invisible buried tomb by observing the non-uniform temperature distribution, as in the case of the test results using radar and electric resistance methods.
A two channel scanning system for the visualization and storage of thermal images has been constructed. The system may be installed in aircrafts for the acquisition and storage of aerial images or used in surface for terrestrial images. Detection in the 3-5 micrometer spectral region with indium antimonide (InSb) detector and in the 8-14 micrometer spectral region with mercury cadmium telluride (HgCdTe) detector is provided in normal use; detection can be extended to near infrared by replacing In Sb detector by silicon or germanium detectors. Images are acquired in real time through an acquisition board, stored in the hard disk of a Pentium PC and displayed in a SVGA monitor. Characteristics of the system and the software developed are described. Some thermal images obtained are shown.
Through an experimental research work, the authors succeeded in defining a methodology for the in-situ determination of the thermal losses of building envelopes, using IR techniques combined with thermo-fluximetric and monitoring techniques. The problem of thermal losses determination in existing external envelopes is extremely important in all those countries where the aging of the existing buildings makes it necessary to work on the improvement of the environmental control and the thermal insulation. The paper presents the results of the research works that have been carried out. Special consideration is given to the problems concerning the non-steady state thermal conditions of the building and to the quantification of the thermal losses value. The paper also describes the methodology that has been set up, discussing on its possible large-scale applications.
The paper deals with how to improve the thermal performance of prefabricated multistory houses in Tallinn, Estonia, built in the 1960s and 1970s based on the results of thermal scanning during 1995 - 1996. The thermal scanning was performed by VTT Building Technology and reported by Helsinki Univ. of Technology. Based on the results of the first tests, some light renovation works were made, and the second tests showed how the repair work had succeeded. The aim of the project was to develop and test less-expensive and easy repair methods for large prefabricated multi-story house areas. The houses have been planned based on uniform design, when the existing problems can be generalized.
Performance of IR building thermography has reached its limits in analyzing qualitative IR images only. Future progress could be traced in using new thermal pattern characterization algorithms applied both to quantitative static and dynamic IR images.
Damage due to moisture and particularly to evaporation is one of the major causes of decay of wall surfaces in ancient buildings. The evaporative rate of water in building materials can be related to the alteration (chips, gallets) caused by salts crystallization when the water evaporates through the surface of the wall. Current and future usage of NDT heavily depends on the possibility to precisely measure physical variables which present large sensitivity to small variations of water content. A NDT thermography allows us to exactly determine the evaporation rate because of both the high value of water latent heat and the high sensibility of thermographic devices. The research has been carried out both in the laboratory and on the field measuring relative humidity and temperature in a frescoed wall of the castle of Malpaga (Northern Italy). In laboratory a climatic room has been set up using a thermovision system and a temperature & RH% probes, to analyze the evaporative phenomena. A mathematical model, although approximate, is proposed to describe the energy balance of the surface where evaporation is present. The model has been applied to the fresco to correlate the temperature to the evaporation rate. This method allows us to correlate the decay, due to the capillary raise of water in the masonry, to the transpiration phenomena.
The Parliamentary Precinct in Ottawa, Canada is comprised of a number of historic buildings that include the House of Commons, the Senate Chamber, the Parliamentary Library, the Peace Tower, and other buildings that provide offices for parliamentarians and their staff. The majority of these buildings have exterior walls that are made of solid masonry with thicknesses ranging between 400 mm and 800 mm. In some cases, special wall areas are more than 1200 mm thick and are comprised of various types of masonry materials. With winter design temperatures of minus 25 degrees Celsius, more than 170 cm of snowfall, and numerous thaws during the five month heating season, the exterior environmental conditions acting on the exterior wall assemblies of these historic buildings are severe enough to cause masonry and mortar deterioration wherever moisture accumulates during winter months. Infrared thermographic inspections were carried out to locate and identify the casual mechanisms of moisture accumulation within masonry wall assemblies. This paper discusses the types of thermal patterns produced by various mechanisms of heat loss and identifies some of the typical areas where possible masonry deterioration occurs. Knowledge gained from these extensive investigations is used to develop a non destructive test methodology to locate areas of freeze thaw damage as part of a predictive and preventative maintenance program to reduce preservation costs of these historical structures.
The American Society of Nondestructive Testing (ASNT) has recently established a new central certification program. This program will allow individuals who meet the requirements to receive a 'portable' certificate. Augmenting the existing employer-based certification, this program will have significant impact on industries that may ultimately require nondestructive testing (NDT) personnel to have central certification. This paper explains show ASNT has structured central certification and when and how it will effect thermal/infrared thermography (T/IRT) personnel. The paper also discusses the industry specific certification process.
In the copper electrorefining process short-circuits between the anodes and cathodes are harmful. They cause decreasing production rate and poor cathode copper quality. Short- circuits should be detected and eliminated as soon as possible. Manual inspection methods often take a lot of time and excessive walking on the electrodes can not be avoided. For these reasons there is a lot of interest to develop short-circuit detection and quality control. In this paper an IR based method for short circuit detection is presented. In the case of the short-circuited anode and cathode pair especially cathode bar becomes significantly warmer than bar in the normal condition. Using IR camera mounted on a moving crane these hot spots among the electrodes were easily detected. IR imaging was tested in the harsh conditions of the refinery hall with various crane speeds. Image processing is a tool to interpret the obtained IR images. In this paper an algorithm for searching the locations of the short-circuits in the electrolytic cell using imaging results as test material is proposed. The basic idea of the developed algorithm is first to search and calculate necessary edges and initial lines of the electrolytic cell. The second step is to determine the exact position of each cathode plate in the cell so that using thresholding the location of the short-circuited cathode can be determined. IR imaging combined with image processing has proven to be a superior method for predictive maintenance and process control compared to manual ones in the copper electrorefining process. It also makes it possible to collect valuable information for the quality control purposes.
As the automotive industry continues to develop advanced materials and manufacturing processes, infrared imaging has the potential to become a major tool in process monitoring and closed loop process control. This paper reviews five novel applications of infrared imaging in applications such as product testing, component manufacture, and vehicle assembly. Infrared was found to be effective as a diagnostics tool for characterizing disc brake systems and electronic engine control sensors. The effectiveness of infrared to qualify fuel nozzle backspray was used to optimize hardware design for fuel systems. Finally, infrared was found to be useful in vehicle assembly operations in the installation of windshield glass and instrument panel hardware where visual inspection was impractical. The speed of image capture and the availability of image processing software for real time image processing and closed loop process control will no doubt find more applications as infrared imaging finds its niche in the automotive industry.
This presentation provides an overview summarizing several applications of infrared thermal imaging and the non-imaged instrumental detection of infrared radiation to in-process quality control in manufacturing. Past and potential applications of this technology to a range of process quality issues also are discussed, with concomitant requirements and constraints. The requirements and constraints imposed by the high-volume, low-margin, mass- production environment and economics of the automotive industry are outlined herein to encourage technological developments that meet those needs.
Infrared electrical inspections have been performed regularly for more than 30 years. They are now conducted in almost every country in this world. Millions, if not billions, of electrical components are inspected each and every year. Despite the level of use there is much misconceived, mistaken and outwardly false information circulating within the industry regarding how to accurately perform an electric inspection. We call these items 'myths' since a myth is a fictitious story or an unfounded belief. Of the many myths being propagated today, the four main ones that unfortunately can still be heard regarding infrared electrical inspections are: (1) Infrared inspections are not necessary because each year all the connections are tightened. (2) Infrared inspection of electrical components can accurately be made through cabinet doors and other covers. (3) It is not necessary to obtain the current flow reading of the electrical system. (4) Temperature measurement is accurate as long as you can 'see' the hot spot. These myths are reviewed one by one.
The problems of construction, reliability in operation, control and maintenance in modern iron and steel mill industry are discussed. The advantages and limitations of traditional inspection methods are evaluated. The results from infrared inspections and field control of reheating furnaces with different construction, damage conditions, before and after retrofitting are analyzed and evaluated. Repeated infrared investigations were performed with short and longwave IR-systems. The results from the investigation indicates that infrared technology has an information potential which could be used for priority measurements within e.g. regular control programs, and as input in development of constructural standards, and for warranty inspection. The research needed to develop accurate and cost-efficient operative methods is discussed. The research project is planned to be continued.
Predictive maintenance practitioners readily diagnose steam leaks through drain using infrared thermography, often supplemented with ultrasonic probe verification. Typically, a pipe carries the leaking steam to a flash tank or directly to the condenser. Thus, the energy used to create the steam is what is lost, not the steam itself. However, the cost of steam production is not inexpensive. We have found steam leaks we estimate cost $30 K/year. As a part of the Electric Power Research Institute's (EPRI's) Boiler, Condenser and Steam Cycle Applications Project, the EPRI M&D (Monitoring & Diagnostic) Centers have begun acquiring steam leak data at several electric utilities. Estimates of steam leak costs are key to evaluating cost savings and recommendation of corrective action, but are hampered by lack of knowledge of the steam flow in the line. These lines are usually not instrumented because typically there is no flow. Consequently, we must derive an indirect method of estimating steam flow. This can be done for uninsulated pipes given knowledge of the pipe surface temperature gradient over a known distance. For single phase conditions, the mass flow of steam equals the heat lost from a length of pipe divided by the temperature drop along the length and the heat capacity of the steam. Pipe heat loss is calculated knowing the pipe diameter, pipe surface temperature, ambient air temperature and using American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) tabulated values. The temperatures are derived from thermographic data. Distances can also be derived from thermal imaging radiometer data, depending on the type of system employed. To facilitate calculation of steam leak cost estimates, we have developed a Microsoft ExcelTM spreadsheet macro. The user can interface directly with the spreadsheet, entering appropriate temperatures, distances, pipe diameter, heat rate, cost of power, etc. Or, the analyst can use thermal imaging radiometer analysis software to semi-automatically input the temperatures and distances.
Proper training and a full understanding of substation components are necessary to effectively perform IRT surveys and analysis of components in high voltage substations. Most thermographers cannot be expected to have extensive substation equipment and operations knowledge. Therefore, this paper and tutorial presentation are designed to aid the thermographic community with the identification and the expected thermal signatures from these components. Technologies complementary to IR are also included in this presentation. Equipment discussed in this paper includes transformers and their cooling systems, load tap changers, circuit breakers, potential transformers, current transformers, lightning arresters, bushings, and standoff insulators.
The benefits of using infrared thermography in monitoring a facility for maintenance purposes have been documented for many years. Adding the capability of displaying previously collected, or baseline, images for online comparison with live images would reduce the time needed for problem identification, improve the accuracy of problem diagnosis, and assist in confirming that all failures have been addressed, without requiring the thermographer to carry and sort through volumes of hard copies of previous reports in the field. A new generation of modern instrumentation makes this method of thermographic analysis not only practical but efficient.
Infrared thermography, a proven technology used for nondestructive testing in industrial facilities, has many applications. Typically industrial facilities only use the technology for electrical applications such as switchgear, substations and transformers. Most facilities fail to realize the tremendous impact of infrared because they only focus on electrical applications. This paper addresses the reasons infrared is not more widely utilized. It also examines methodologies by which the utilization challenges can be addressed such that industrial facilities can realize greater utilization of the infrared sensors and thus achieve greater returns on the investments they have already made.
Recently, the fundamentals of the 'pulsed phase thermography' approach were described. As it is recalled, this approach somehow combines together practical advantages of both the well-known 'pulsed-transient thermography' and the 'lockin thermography' for which specimens are submitted to a periodical excitation. Some advantages of this novel approach were demonstrated as well. In the present paper, the discussion about 'pulsed phase thermography' includes theory and reviews the possibilities of defect detection in terms of minimum diameter-to-depth ratio in aluminum components. Experimental results include both academic and real corroded specimens from the aircraft industry.
The advantages of phase sensitive modulation thermography (also called lockin thermography) are here illustrated together with some applications of nondestructive evaluation (NDE) on advanced materials and large structures. Lockin thermography has shown to be a versatile tool for rapid inspection of large surfaces and detection of defects in materials where other NDE techniques are not able to give good results. Besides this, the phase angle image eliminates many undesired effects like inhomogeneous distribution of surface heating that make images obtained with pulse thermography difficult to interpret.
The paper aims to illustrate the relevant use of infrared thermography as a nondestructive, noncontact and real time technique (a) to observe the progressive damage processes and mechanisms of leather failure, and (b) to detect the occurrence of intrinsic dissipation localization. The parameter, investigated in this paper, is the heat generation due to intrinsic dissipation caused by anelasticity and/or inelasticity of leather. Thanks to the thermomechanical coupling, this useful technique offers the possibility of scanning processes of leather mechanical degradation before reaching the ultimate strength. It allows a measure of the limit of a progressive damaging process under load beyond which leather is destroyed.
We have studied the possibility of applying infrared thermography to the problems of fracture mechanics. First of all we have shown that the stress intensity factor, K, can be analyzed by measuring the distribution of the elastic component of the sum of the principal stress around the crack tip by an infrared stress measuring device, SPATE- 8000. Next, the increase of temperature produced by the plastic deformation at the crack tip has been measured by a thermal video system (TVS). It has been found that the distribution of the temperature increase (Delta) Tp in the plastic zone is proportional to 1/r where r is the distance from the crack tip. Then a method of measuring the J-integral by the TVS has been proposed. Finally, we have developed an experimental and computational hybrid measuring system for the purpose of nondestructive detection of cracks embedded in the structural members. The system consists of TVS and an engineering work station (EWS), by which image processing of the thermal image can be carried out by the developed expert system. It has been shown that fatigue cracks in the steel specimens and delaminated defects in the honeycomb sandwich structures can be detected fairly well through the developed system.
In the past decade, nondestructive testing techniques using infrared thermography, i.e., thermographic NDT techniques, received a lot of attention in many engineering fields in Japan. The first national symposium that specialized in thermographic NDT techniques was held in Tokyo, Japan on November 28-29, 1995, organized by the Research and Technical Committee on Surface Method of the Japanese Society for Nondestructive Inspection (JSNDI). At this symposium, twenty eight presentations including two keynote addresses were given. Over three hundred thermography researchers and engineers (thermographers) attended the symposium. Further, an exhibition of newly developed equipment for infrared thermography featuring the equipment of eleven companies took place concurrently. This symposium played an important role as the first national symposium dedicated to sharing information, ideas and experiences about thermographic NDT among thermographers from both the user and supplier sides. Sessions within the symposium were as follows: Advances in Infrared Imaging Systems; Applications for Composite Materials and Coated Materials; Diagnosis of Equipment/Monitoring, Applications for Structural Materials; Backup Techniques for Thermographic NDT; Infrared Stress Measurement and Contact Problems. This paper briefly describes presentations given in the symposium.
This paper reports a comparison among different thermal techniques and shearography applied to a sandwich panel of composite material containing simulated defects. In particular, the detectability of the defects and the evaluation of the planar extension are examined. An important feature is also the classification of different kinds of defects. The experimental and data processing procedures are described for all methods. For the thermal method, a mathematical simulation of the thermal problem allows us to better design the test. Automatic processing of data are presented giving outputs very simple to understand.
Particle boards are very common products in the wood industry. However, increasing use of this product with its derivatives, imposes new challenges in terms of inspection techniques. Lockin thermography is an attractive tool for such a task. In this paper, fundamentals of lockin thermography are presented followed by several representative examples of particle board inspection.
A new variation of forced-diffusion thermography, coating tolerant forced diffusion thermography, is described. This new thermal method is specifically designed to inspect large steel bridge structures. To increase effectiveness in the field coating tolerant thermography separates the effects of structural defects from variations in emissivity. The technique is a derivative of forced diffusion thermography which uses patterned radiation to force heat flow in-plane to specifically target cracks. This paper presents the fundamentals of coating tolerant forced diffusion thermography including the mathematical bases for the separation of thermal gradients and emissivity gradients. Also, presented are case studies including the inspection of a bridge girder samples at FHWA Turner Fairbanks Lab.
The service water piping system at nuclear power plants provides cooling for a variety of safety and non-safety related components and systems. Reliability of service water piping systems is a key consideration for safe and reliable plant operations. Conventional inspection techniques for detection of pipe wall thinning usually involve the time- intensive process of ultrasonic thickness measurements, based on a grid system, of the entire pipe length. An alternative to this process may lie in the use of active infrared thermography techniques for detection of thin wall areas in the pipe. Infrared thermography (IR), in a passive mode, has been widely used by utilities for a variety of predictive maintenance applications. For assessment of service water piping, an active IR technique, thermal injection, can be used. Application of this IRNDE technique for material evaluation can provide a rapid screening technique for identification of thin wall areas in service water piping. The EPRI NDE Center participated in a preliminary evaluation of this technology at Vermont Yankee Nuclear Power Plant. Based on the promising results of the Vermont Yankee activity, the Center worked with Thermal Wave Imaging, Inc. in an effort to optimize the IR thermal injection technique for service water piping applications. A series of representative pipe mock-ups were used for evaluation. Subsequent modification of the thermal injection hardware and technique yielded more uniform thermal energy transfer, improved detection capabilities, and increased effective inspection area.
A new experimental technique using an infrared stress measurement system and an infrared transmitting material is proposed for the visualization of a contact stress distribution. An infrared transmitting material is employed as one of two contacting materials, and is brought into contact with a cyclically loaded sample. Infrared emissions from the contact surface are measured through the infrared transmitting material, and thermoelastic stress analysis (TSA) is applied to measure the contact stress distribution. First, a flat contact is investigated, in which a barium- fluoride window is in contact with an embossed plastic letter. Stress distribution on the contact area in the letter can be measured accurately. Further, a spherical Hertz contact is examined by using an infrared transmitting sapphire convex lens and a flat plastic plate. The obtained contact stress distribution is compared with the stress distribution predicted by the Hertz theory. An excellent correspondence is found between those stress distributions, indicating the feasibility of quantitative analysis using the present technique.
Complex (magnitude and phase) measurements of the near field of a radiating antenna over a known surface (usually a plane, cylinder, or sphere) can be used to determine its far-field radiation pattern using near-field to far-field Fourier transformations. Standard gain horn antennas or open-ended waveguide are often used to probe the near field. This requires the time-consuming positioning of the probe antenna to several thousand positions in the radiating near field of the antenna under test. Experimental errors are introduced into the near-field measurements by mechanical probe position inaccuracies and electrical probe interactions with the antenna under test and probe correction errors. A minimally perturbing infrared (IR) imaging technique can also be used to map the near fields of the antenna. This measurement technique is much simpler and easier to use than the probe method and eliminates probe position errors and probe correction errors. Current IR imaging techniques, which have been successfully used to rapidly map the relative magnitude of a radiating field at many locations (mXn camera pixels per image captured) over a surface, however, suffer from an inability to determine phase information. This paper describes a method for determining the absolute magnitude and relative phase data from these phaseless IR measurements by using techniques derived from optical holography. Form a pair of microwave holograms and magnitude only measurements, the complete near field (magnitude and phase) of the antenna can be determined. Once obtained, this data can then be used to determine the antenna far field pattern by conventional Fourier near-field to far-field transformation techniques.
Thermographic technique can be used to measure temperature distribution of body surface in real-time, non-contact and full-field, which has been successfully used in medical diagnosis, remote sensing, and NDT, etc. The authors have developed a thermographic experiment that can be applied to inspect the effect of action of acupuncture and qi-gong (a system of deep breathing exercises) by measuring the temperature of hand and arm. The observation is performed respectively by thermography for the dynamic changes of temperature of the arm and hand after acupuncture therapy and qi-gong therapy. Thermographic results show that the temperature on the collateral channels increases markedly. In the meantime, it can be seen that the above therapies of Chinese medicine can stimulate the channel collateral system. This also contributes a new basis to the effect of action of the therapies of Chinese medicine. The work shows that thermographic technique is a powerful tool for research in Chinese medicine. In this paper, some thermal images are obtained from the persons treated with acupuncture and qi- gong.