ME | July/Aug 2009 | 11

CertifiCAtion– how to achieve results using Infrared Thermography

New GeNeratioN IR CaMERas

Thermal Imaging or Thermography is a very versatile maintenance tool. In the hands of a skilled operator it instantly shows anomalies in mechanical, civil and electrical engineering components. With lower cost cameras now available and the potential for increased use

for energy efficiency surveys, there has never been a more exciting time for thermography. But there are dangers; untrained or inexperienced operators may show faults where none exist and miss potential problems. The future of thermography lies in a greater understanding of the science and technology behind the technique.

How does thermography work?All objects, even cold ones, All objects, even cold ones, emit infrared radiation. The

amouAll objects, even cold ones, emit infrared (IR) radiation. The amount depends on temperature, so an IR detector can be used to measure temperature - the principle used in IR thermometers. IR radiation is part of the electromagnetic spectrum with a wavelength slightly longer than that of light, so it behaves rather like light and can be reflected or absorbed. Only a very few materials are transparent to infrared.

IR thermometers and cameras work on the same principles. They all detect IR radiation, but the IR camera has an array of thousands of elements that detect infrared from different parts of the field of view to make a picture. Not all thermal imaging cameras are calibrated to measure temperature; for some applications like security it is not necessary. It is important to remember that the detectors measure IR radiation, but they can only show an accurate temperature if the correct environmental conditions have been set into the camera’s computer.

Common misconceptionsThe IR radiation picked up by a detector depends on the emittance or emissivity of

the surfaces in front of it. A surface with a low emittance emits only a small fraction of the IR radiation emitted by an object at the same temperature with a high emittance. A low emittance surface, such as a new copper busbar, reflects a high proportion of the IR radiation that falls on it – the copper busbar is like a mirror and most of the infrared from it is reflected from the surroundings. It is almost impossible to measure its temperature.

Since real objects have emittance somewhere between zero and one, the IR radiation will come partly from the object’s own temperature and partly from reflections of everything facing the object. IR cameras usually include settings to compensate for this, but setting the wrong reflected temperature can give an error of several degrees in the temperature display. Reflections of other hot objects can often give misleading results and many inexperienced thermographers have reported ‘hot spots’ on busbars when what they are really seeing is a reflection of their own body.

IR radiation will not go through steel, aluminium, brick, concrete, most plastics or glass. Faulty connections cannot be seen through switchgear covers, although if serious overheating occurs the cover will get hot too. You cannot measure temperature accurately through a mesh, unless both the mesh and the object are properly focused and the correct reflected ambient temperature has been set in the camera.

On the following pages we consider the question of certification and review the new generation of IR cameras.

12 | July/Aug 2009 | ME

T h e R m O g R A p h Y

The author, from a background as a full time infrared thermographer in industry, understands the benefits of running an in-house programme,

and acknowledges that success was due to the experimental exposure gained over many years working with infrared technology to the exclusion of any other duties, plus the support of senior management which allowed time to conquer a steep learning curve. It is easy to buy equipment, but quite another matter to find an effective person able to provide quality data that will enhance a maintenance programme. As with many condition monitoring techniques, infrared thermography

is a skilled art form that requires technician and engineeers to be educated in infrared physics, have a thorough understanding of applications and be able to develop their knowledge with continual field experience.

Over the years many individuals have joined courses ‘just to get a certificate’. In reality, most technicians and engineers are shocked to learn that the methods they have employed in the past do not provide accurate temperature

measurements. The infrared camera is a scientific instrument and is designed to give a data output based on a known condition, in this case it is usually set to measure objects which have a 100% efficiency to emit infrared radiation. In reality, this is theoretical as no such object exists. This is where the skilled technician excels; their awareness will lead them to alter the instrument to the correct parameters. Both emissivity and reflectivity have to be inputted correctly, as one of the initial stages

to correct the instrument’s mathematical calculation with the aim of achieving quantitative analysis. Several other factors are required in order to achieve correct temperature measurements. When introducing an in-house programme, product training on cameras only covers the basic operation of the instrument and often fails to convey the complexity of using infrared instruments in the field.

historically, infrared thermography certification was usually based on ASNT SNT TC 1A, the American standard which provides a guide or outline of the course content. This is a second party certification scheme usually operated by training providers who deliver a course and end of course examination, often requiring field work from the students to complete the process. The certificate is given to the student by the training provider on behalf of the company that employs the individual.

Where is the fluid level in the vessel? Analysing the data in conjunction with the process information would allow the technician to understand the thermal patterns on this vessel.

Continued on page 14 •

Certification– how to achieve results using

Infrared Thermography

On a recent trip to conduct a series of Infrared Thermography training courses, it was very evident that the technology has been embraced universally by industry. Many organisations have been motivated to terminate their existing contract agreements with specialised thermography consultancy firms in favour of piloting their own in-house infrared programmes, and the appearance of lower cost instruments and media exposure has contributed to these decisions. The many benefits include: the instrument being available 24/7, reduced consultancy fees and company employees having in-depth knowledge of company assets. On one level this would seem a favourable way forward whilst reducing costs, however, it will only work if the replacement programme is successful — and that often fails to happen.

austin Dunne, european Training manager

Institute of Infrared Thermography (IIT)

Above: This hot gas pipe is operating at a uniform

temperature. A technician must understand how to measure the temperature accurately, but the

image displays many different energy levels.

In europe, some countries provide certification based on a third party principle, the training being delivered by a provider and the certification conducted by a separate organisation based on standards like eN473 or the Scandinavian equivalent. Third party examinations, being independent, provide a recognised competence level as the training organisation has no access to the examination questions, thus ensuring uniformity of minimum competences. Although considered to be superior to second party schemes, the process is fragmented and only operates in certain areas of the world and is not seen as a solution across continents.

Over recent years, the BINDT (British Institute of Non Destructive Testing) has taken the outline from an international standards group and used it as a platform for producing a certification scheme based on ISO 18436. They have developed this third party certification scheme using pCN (a well established accreditation body) to deliver a high quality process for qualifications in a range of condition monitoring techniques, including Infrared Thermography, Vibration Analysis, Acoustic emission, Ultra-sound, etc. Industry should be seen to embrace a scheme designed to ensure the fundamentals are understood in each technology,

Take the Fluke challenge: request a FREE test-drive today!

Get your hands on a powerful Fluke thermal imager and test-drive it at your own site. If you take up our challenge to submit your best workplace image, you could win one of the 30 test tools we’re giving

away in 2009, including a Fluke Ti25.

Do more, save moreFor industrial maintenance professionals, Fluke’s easy-to-use thermal imagers are the best tools around to identify problem areas accurately and precisely, across a whole range of applications.

• Innovative: IR-Fusion® saves time and money• Powerful: image quality boosts confidence• Rugged: survives a 2-meter drop test

Get your hands on the Fluke Ti25 with IR-Fusion®. No time for a test-drive? Play the Fluke Challenge game on-line.

0207 942 0700

Take the Fluke challenge and request

a FREE test-drive today:www.fluke.co.uk/challenge

www.fluke.co.uk/ti

Fluke. Keeping your world up and running.®

Be a winnerGet your hands on the

best thermal imager

14 | July/Aug 2009 | ME

T h e R m O g R A p h Y

specialist thermoraphers due to cost and complexity of use. This market-led demand has resulted in a new generation of cameras that combine thermal imagery with digital photography. They are ideally suited for close up inspection work on items such as window frames, doors and identification of insulation gaps, rather than the more panoramic images to be obtained from those with higher resolution.

manufacturers, including Irisys, have developed a variety of models that offer digital and thermal images. Naturally they all vary, and in some cases the two images can be superimposed to give the operator a precise location for the interpretation of the ‘hot spot’ identified by the thermography process.

Voice annotation has also been built in, enabling operators to make verbal notes of each image taken, thereby enhancing reports generated later on a pc by positive identification of all aspects of the images. The audio facility has been combined with an alarm regime that offers engineers the opportunity to pre set the camera to give audio as well as on-screen visual warning when temperatures outside the defined parameters are identified. This will be a significant asset to plant engineers undertaking routine checks on large numbers of electrical control panels, wiring or fuses, as a pre-determined temperature limit can be set to trigger the alarm to alert the user that there are areas that require closer inspection. engineers involved with mechanical equipment incorporating bearings will be equally delighted with the new cameras as they will give early warnings of bearings that are overheating and therefore likely to fail because they have begun to disintegrate. And we all know how much more expensive it is to replace equipment that has been damaged by a failed bearing than pre-emptive bearing replacement.

Some of the new cameras on the market meet Ip54 requirements for outdoor use, where extreme temperatures, dust and the like could be a problem while others incorporate two cursors which enable the display of Delta T temperature differences without the need to capture two images. Through built in hot and cold tracking the cursors will also automatically identify hottest and coldest points, or both.

The mix of thermal and digital technology contained in an easy to use package that takes the guess work out of thermal imaging for less than £2,000 must offer the most economical and efficient way forward.

• Continued from page 12

Three years ago the markets were hit by the first low cost, high resolution cameras that have revolutionised the use of thermography and

vastly enhanced the appreciation of the benefits of the technology. They have been responsible for bringing thermography to the attention of a wider public through thought provoking images of large, well recognised buildings that have been published in media worldwide

seeking to illustrate energy conservation issues. They have revealed previously unknown heat loss through roofs, windows and doors, in

buildings ranging from local housing developments to the most prestigious of national edifices. At the same time they have been used increasingly to identify ‘hot spots’ in plant and machinery, giving maintenance engineers the opportunity to take corrective measures before a heat problem becomes a disaster.

The demand for this equipment will undoubtedly continue, but many users – particularly plant engineers and the increasing number of new energy surveyors – have been calling for affordable and user-friendly cameras which previously had only been available to

and which promotes a minimum time requirement for practical experience prior to certification, whilst providing an independent assessment of each student. This scheme could grow rapidly and will ultimately be recognised as a world standard for training and certification in condition monitoring activities.

Legislation on the use of infrared thermography is quite sketchy at the moment and it is not unusual to see a complete novice purchase these scientific instruments and offer services without any in-depth training or experience. This obviously allows a reduction in their charge-out rate and compromises consultants who compete in the field with high quality equipment, expert training and many years of practical experience. As more insurance companies now demand infrared inspections prior to the issue of their insurance certificates, it is essential that the survey is carried out by competent individuals. Industry must set standards

to ensure consultants and practitioners obtain the required skills, training and experience to ensure the quality of data collected.

FootnoteThe IIT is an Accredited Training Organisation for

the BINDT and provides independent education, training and support to industry. Trainers are experienced thermographers who convey both the theoretical and practical aspects of the technology, and certification conforms to ISO 18436 and ASNT SNT TC 1A. The emphasis is to raise the awareness of thermography and develop skills in all industry sectors. Courses are offered in over 50 countries with training manuals in over 10 languages. IIT staff are always available to answer general enquires and questions on the certification processes.

alan.thomson@irisys.co.uk

Alan Thomson of IRISYS says that thermal imaging is playing an increasingly important role in all aspects of energy conservation and plant maintenance — a role that is going to increase substantially with the arrival of the latest generation of cameras.

New Generation IR Cameras

info@infraredinstitute.co.uk