Preventing Failure: Thermal Imaging for Low-Voltage Panels
Preventative Maintenance Evolution: Why Thermal Imaging is Critical for Control Circuits
The recent NTSB report on the Francis Scott Key Bridge collapse serves as a powerful reminder of how a seemingly minor electrical issue in a control circuit can escalate into a catastrophic failure. The report delivers a clear mandate: thermal imaging must be applied routinely to low-voltage control wiring and components.
The Hidden Danger in Low-Current Circuits
Current industry practice often prioritizes thermal inspection on high-load components, such as main power feeds, motor loads, and transformers. This focus is logical, as these components generate the most heat. However, the NTSB report highlighted a key vulnerability in the signal and control circuits of the Dali vessel:
Recommendation B: "The benefits of infrared imaging as part of preventative maintenance programs for routine monitoring of electrical components to detect inadequate signal wire connections."
Control circuits, though carrying minimal current compared to power circuits, are responsible for initiating critical actions, such as shutting down a system or, in this case, maintaining power supply stability. A poor connection in these circuits—caused by a loose screw, a manufacturing flaw, or contamination—creates localized high resistance.
How Thermal Imaging Provides an Early Warning
This high resistance results in localized heating, often long before the problem causes a visible arc or a complete system failure.
Sensitivity is Key: While the overall cabinet temperature might remain acceptable, a thermal camera is sensitive enough to detect the temperature differential between a healthy wire/terminal and a failing one.
The Problem Demonstration: As demonstrated in the accompanying video, even a single strand of wire carrying a load can quickly show a significant temperature increase compared to its neighbors. This temperature rise, even if it's only 10 or 20 F above ambient, is a clear sign of impending failure
.Preventing Cascading Failures: A thermal scan allows maintenance teams to identify and repair a loose connection during routine maintenance, preventing the eventual burnout or arcing that could trip a circuit breaker, cause unexpected shutdowns, or lead to a cascading failure of critical systems.
Actionable Steps for Maintenance Programs
To integrate this crucial finding into your maintenance program, consider the following:
Expand Scope: Include dedicated thermal inspections for all control panels, terminal blocks, relays, power supply connections, and circuit board components, not just the main power distribution sections.
Focus on Contrast: Look for hot spots—a rapid and visible change in color or temperature reading compared to adjacent components—rather than focusing solely on absolute temperature limits.
Documentation: Record thermal images of panels to establish a baseline for healthy systems, allowing future inspections to easily spot deviations.4
By shifting focus to include the thermal inspection of control circuits, organizations can proactively eliminate low-current, high-risk failures, ultimately enhancing system resilience and safety.
Press release showing detail of the terminal block connection https://controls.tw/qyba7
NTSB report: https://controls.tw/37wre