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Practical guide: Thermography in preventive maintenance

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When it comes to maintaining buildings and technical systems, thermography has proved to be an indispensable aid. With the help of invisible infrared radiation, it is not only the function and condition of electrical and mechanical systems that can be monitored reliably. Weak spots and wear can also be detected at an early stage and non-destructively and thus remedied in good time. Furthermore, thermography provides excellent services for quality control and fill level measurement in production plants. In facility management, for example, it enables optimum control of heating systems as well as simple and safe testing of electrical systems.

No wonder then that the use of thermography is required in various standards and guidelines and that some insurance companies require their customers to regularly assess the insured equipment and facilities thermographically. Companies that refrain from regular thermographic inspections will therefore be subject to considerable financial and legal risks in the event of personal injury and property damage.

This practical guide will introduce you to the most important fields of application of thermography and demonstrate how you can significantly improve your maintenance processes and system availability with the aid of thermal imagers.

Thermography for more safety and efficiency in facility management

Plant operation and safety, operating costs, and energy consumption – facility managers not only have to keep an eye on a number of factors, but also have to improve the efficiency of systems and processes at the same time.

Inspecting electrical systems

Overheated connections in a control cabinet indicate potential or actual defects. A thermal imager can detect anomalies such as these without contact and during operation, before downtimes can even occur.

Discover the energy-saving potential

A thermal imager allows concealed weak spots, thermal bridges, mould or faulty installation to be detected in a building. Especially in existing buildings, a thermal imager can be used to uncover large potential energy-savings fast and easily.

Fig. 1: A thermal imager can detect anomalies such as overheated connections in a control cabinet.

Detecting damage on and in the building

If water damage occurs in a building, this is usually due to potential leaks in the floor or walls. This results in the extremely time-consuming and laborious task of trying to identify the location of the leak, as large areas of the floors or walls often have to be opened up. On the other hand, a thermal imager means the leaks can be specifically accessed and rectified cost-effectively.

Checking radiators

Contamination in a heating system has adverse effects on its efficiency, as large amounts of energy is wasted. To ensure that a heating system is working efficiently it’s a good idea to analyse the function of the radiator with a thermal imager before pressure flushing to reveal uneven heating. After flushing, the thermal imager can be used to quickly check that the radiator is working properly and efficiently.

Thermography makes preventive maintenance easier

Unscheduled costly system downtimes can be prevented to a large extent by regularly checking electrical installations, control cabinets and mechanical components. Carrying out thermographic inspection a second time reduces a system’s rate of failure by around 80 percent and provides an added safeguard against fire.

Defining the scope of inspection

Before beginning the inspection tour, the thermographer or plant manager needs to define a few aspects to include: How extensive does the inspection need to be? At what intervals are the tours to take place? And which thermal imager meets the requirements?

Defining prioriy criteria

Identifying the risk doesn’t mean it is automatically eliminated. When and how a problem is remedied – immediately, as fast as possible, at the next opportunity – is decided by the thermographer or plant manager. On the one hand, rectifying all identified thermal anomalies immediately would be too inefficient and costly. On the other hand, a component’s temperature limit also depends on its function. It’s therefore advisable to classify the inspection results, for example, into three priority classes:

  • Class A (red): A severe problem that requires immediate action.
  • Class B (orange): A serious problem that needs to be remedied within a week.
  • Class C (yellow): A problem that needs to be remedied the next time the system is scheduled to be shut down.

The applicable standard regulations, type of system, and previous experiences are primarily referred to in determining these priority levels. The aim has to be the efficient operation of a system with as little interruption as possible while ensuring the greatest level of work, equipment and environmental safety.

Challenges faced in maintenance

It’s not only countless measuring points that require inspection during technical maintenance. Depending on the size of the particular measurement object, up to three thermal images are required to evaluate it; this means that often hundreds of images are generated by the thermal imager in one inspection tour. This gives rise to the following challenges:

  • How can the thermal images be assigned to the respective measurement object?
  • How expensive and time-consuming are the evaluation and reporting processes?
  • Can the temperature development of a component be identified over the course of time, and can the necessary measures be derived from this?

The solution: Automatic site recognition

Testo SiteRecognition can be used to create a measurement site archive in the Testo IRSoft analysis software, which serves as a database for all thermal images. For every measuring location stored in the archive, markers (small symbols similar to QR codes) can be created and attached on site. During the subsequent inspection, this marker is simply recorded using the camera’s wizard; the measuring location, along with its corresponding information, is then automatically stored with the thermal image and sorted into the measuring location archive with the software. On the basis of the description of a measurement object or a date, the images can located quickly and easily in the archive. This makes it possible, for example, to simply and directly call up comparative images from previous periods; this allows temperature developments over a certain time period to be assessed and, if necessary, the right action to be taken. Time-consuming, error-prone management and manual archiving become unnecessary.

Site recognition in three steps:

  • One-off creation of the measurement objects:  First, the measurement objects have to be saved once in the software and then assigned to the measuring locations. The database created during this process is transferred once via USB interface to the thermal imager, and stored there for the inspection tours. In this step, a marker is created for every object being measured, printed on self-adhesive labels, and attached to the object.
  • Inspection: During the tour of inspection, the respective marker is scanned using the digital camera of the thermal imager. This activates the object being measured and measuring location and all thermal images saved afterwards will be assigned to these.
  • Archiving and analysis: At the end of the inspection tour, the thermal imager is connected to a PC that has the software installed on it. With the aid of the import wizard, the thermal images are automatically assigned to the measuring locations and stored. After the automatic importing process, the respective thermal image can be opened and analysed, or compared with a reference image that has preferably been created during the commissioning or review of a machine. Critical temperature differences can thus be easily identified and appropriate measures initiated quickly.

Contact Testo, Tel 011 380-8060,


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