Handheld instruments M
anufacturing and production processes consistently face challenges in ensuring the longevity and efficient functioning of their
equipment, especially as they age. Just like any entity subjected to time, equipment breaks down due to friction, corrosion, thermal and mechanical cycling, vibration, and other forces. The inevitable progression of these factors results in reduced performance, and ultimately, equipment failure. The crux, then, is to determine when this will occur so preventive maintenance can be performed at an optimal time to prevent failure at lowest possible cost, without significantly impacting production.
IDENTIFYING FAILURES BEFORE THEY HAPPEN: THE PF CURVE
Those entrenched in condition monitoring are no strangers to the PF curve, developed by Nowlan and Heap. It illustrates the different stages of a component’s lifecycle, illustrating when an inspection method might shed light on equipment’s health, right from the proactive stage to when a fault is discerned.
As you can see on the PF curve, temperature analysis is one condition monitoring technique used in the predictive domain. Enter: Thermography. As an essential condition monitoring technique, thermography serves as an earlywarning system, indicating when machinery or assets are showing signs of wear, even before a discernible fault emerges.
Measuring Temperature
At its core, thermography involves capturing temperature readings of an asset. A singular temperature reading can offer insights, yet its standalone value might be some what limited. Consider an electrical motor in a factory running at 73°C. Without additional data, is this concerning? To ascertain this, one might need to delve into the specifics of the motor, examining its standard operating temperature range. Yet even that might not offer a complete picture.
For instance, if the standard range of the motor is from 50°C to 80°C, at 73°C the motor currently runs at the higher end of this range. However, how frequently should it be inspected? What’s the current condition? When is maintenance required? Will it fail? These questions remain unanswered, and we have no ability to predict the future condition of this motor.
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THE IMPORTANCE OF TREND ANALYSIS Understanding a machine’s health goes beyond a single measurement. External and internal factors, such as load variations, cooling efficiency, and environmental conditions, can influence the operating temperature. Tracking these temperatures over time provides condition monitoring specialists with a clearer picture. For example, if we monitor the temperatures of an electric motor installed in January 2019 every month, patterns start emerging. Perhaps the temperature fluctuates between 50°C and 55°C, correlating with the changing seasons. This suggests that the motor operates within a safe range and is not overloaded. Regular checks every two or three months might suffice. However, another motor from the same time may show a consistent rise in temperature, indicating potential issues. What is missing is a trend, baseline, or pattern of the normal operating conditions of this motor.
With such a broad range of standard operating temperatures, it is difficult to know the condition of the motor with a single measurement. Building
THE IMPORTANT ROLE OF THERMAL IMAGING FOR CONDITION MONITORING
Figure 2. Temperature Trends of Electric Motor 2 (Years 2019-2023): Seasonal Variations, Rising Patterns, and the Impact of Maintenance Interventions
a trend of operating temperatures will allow a condition monitoring specialist to accurately assess the condition of the motor.
If an electric motor was installed in January 2019, and monthly temperature readings were taken, then these temperatures could be plotted to identify what the operational norms are for this specific motor, in this location, powering this specific process. A well functioning motor may record temperatures similar to the graph (see figure 1).
Figure 1.Temperature Trends of Electric Motor 1 (Years 2019-2023): Seasonal variability in electric motor indicating stable performance within standard operating ranges
This graph shows an electric motor that has a degree of temperature fluctuations between 50°C and 55°C which track reasonably well with the seasons of the year, getting warmer in the summer and cooler in the winter. So, what can we ascertain from this information? The motor is operating at the lower end of the standard operating temperature range and does not appear to be mechanically overloaded or under an especially high load. A condition monitoring professional may even decide to inspect this motor every two or three months unless temperatures change significantly. This motor shows no obvious signs of concern, and we would expect it to continue working reliably for the foreseeable future.
May 2025 Instrumentation Monthly
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