Insight Vol 50 No 9 September 2008 1 IRT 1. Introduction Failures of electric or mechanical machines occur due to problems associated with stator, rotor misalignment, overheated bearings, improper lubrication and worn out components or mechanical loading anomalies. It has been observed that approximately half of all machine failures occur due to bearing failures (1) . Commonly used bearing condition monitoring techniques are vibration, temperature, acoustic emission, sound pressure, laser and current monitoring. Sometimes, chemical analysis is also employed by looking at the wear debris generated from the bearing, which is carried by the lubricating oil. Condition monitoring (2) is the practice of obtaining the basic operating characteristics from a working plant to assess its efficiency and predict its reliability. Practically every chemical and process industry employs predictive condition management to ensure the safety, reliability and also cost effectiveness of plant operation. A wide variety of Non-Destructive Evaluation (NDE) techniques such as acoustic emission (3) , vibration analysis, ferrography and oil analysis are used to determine mechanical problems while the equipment is in operation. Infrared Thermography (IRT) is becoming another promising technology in verifying conditions found with vibration and oil analysis. With thermography, we can detect whether the bearings are hot, and using vibration analysis we may determine why they are hot. Thermography allows quick imaging of machinery to determine its thermal condition. It can be used to identify and analyse thermal anomalies for condition monitoring. Thermal energy is present during the operation of all machines due to friction losses, energy losses, or any combination thereof. The temperature is a key parameter for monitoring the performance and the condition of machines and to diagnose machine problems. The magnitude and distribution of the temperature are indicators of departure from acceptable performance. Infrared thermal imaging or infrared thermography finds extensive applications in a variety of fields of industry (4-11) . The versatility of IRT for condition monitoring is lucidly discussed in some of the earlier publications (15) . IRT is an ideal technology to investigate thermal anomalies in machines because it provides complete thermal images of a machine, or a machine component, with no physical attachments (ie non-intrusive), requires little set-up and provides the results in a short time. In this paper, we discuss the applications of thermal imaging for condition management of blower bearings, shaft and the motors in ventilation systems in a radioactive plant. 2. Thermal imaging – principle Infrared thermography is a method of mapping the temperature proile of the surface of an object. It makes use of the infrared spectral band of the electromagnetic spectrum emitted by the object. All infrared measurements are normally made in the wavelength band of 0.75 μm-25 μm. The fundamental equations that link the absolute temperature of the object with the intensity and wavelength of emitted radiation are given by Planck’s, Stefan Boltzmann and the Wein’s Displacement Law (12) . The energy emitted and the temperatures are related by Stefan- Boltzmann Law: W = !" T 4 ........................................(1) where W is the radiant lux density, ε is the emissivity, σ is the Stefan-Boltzmann constant and T is the absolute temperature. Condition monitoring of exhaust system blowers using infrared thermography S Bagavathiappan, T Saravanan, N P George, John Philip, T Jayakumar and Baldev Raj Electrical and mechanical machines are integral parts of engineering plants. Machine failures can occur due to many reasons. Thermal energy produced during the operation of all machines can be in the form of friction losses within machines, energy losses within machines, as a characteristic of the process media, or any combination thereof. Infrared thermography (IRT) is an ideal Non-Destructive Testing (NDT) technique to investigate abnormal temperature distribution on machine surfaces, because it provides thermal images of a machine or component remotely. In this paper, we discuss an important application of thermal imaging for condition monitoring of blower bearings, shaft and the motors in ventilation systems used in nuclear plant areas. Sources of abnormal temperatures are detected at the bearings and shaft at the impeller end of the blower of an exhaust system. Also, abnormal temperature distribution is detected in one of the belts of the pulley drive system due to over-tightening. IRT was effectively utilised to pinpoint the sources of excessive heat in the blower and to carry out necessary corrections. We demonstrate the usefulness of IRT to detect the sources of abnormal temperatures in various components of the blower at an early stage of impending malfunction failure that could prevent major breakdowns. Keywords: IRT, passive, blower, bearings, motor, shaft, belt. Dr Baldev Raj is the Distinguished Scientist and Director of Indira Gandhi Centre for Atomic Research, Kalpakkam. He is an Hon Member of ICNDT, Hon Fellow of the Indian Society for NDT, Hon Fellow of The British Institute of NDT and Founder Member of the Board of Directors, World Federation of NDE Centres, USA. Dr T Jayakumar is the Head, Non-Destructive Evaluation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India. Corresponding author: Dr John Philip is the Head, SMART Section, Non- Destructive Evaluation Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603 102, Tamil Nadu, India. Tel: 91-044-2748 0232; Fax: 91-044-2748 0356; E-mail: philip@ igcar.gov.in Shri N P George is an Engineer in Charge of Ventilation Systems, Post Irradiation Examination Division, Indira Gandhi Centre for Atomic Research, Kalpakkam. Dr T Saravanan is a Scientist in the Non-Destructive Evaluation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam. Shri S Bagavathiappan is a Scientiic Assistant in the Non-Destructive Evaluation Division, Indira Gandhi Centre for Atomic Research, Kalpakkam. Paper submitted 05 May 2008 Accepted 15 July 2008