Temperature Capabilitites

High temperatures in wheel ends can result from damaged bearings, brake issues, prolonged braking, tire anomalies, and environmental factors. This article aims to explain how the TraX device measures, and broadcasts temperature data. It applies to devices operating with firmware version BSS10 and later.

The SKF TraX Technical Specification - Connected Version document provides the authoritative guide to the device's behavior.

Measuring and Broadcasting Temperature Data

With rising temperatures, the frequency of temperature measurement sampling and broadcasting intensifies. The device has a temperature measurement accuracy of +-3 °C.

The device broadcasts three temperature measurements:

• Maximum Temperature: Highest recorded temperature since commissioning or reset.
• Minimum Temperature: Lowest recorded temperature since commissioning or reset.
• Current Temperature: Most recent temperature reading, updated every five minutes.

Only the "Current Temperature" value is expected to change regularly. However, if the current temperature exceeds any previously recorded high or low (since commissioning or reset), it will also update the "Maximum Temperature" or "Minimum Temperature" values accordingly.

Behavior According to Temperature Ranges

The table below summarizes how the device behaves in three different temperature ranges.

Temperature range	Sampling frequency	Temperature in Celcius	Temperature in Fahrenheit	Data Broadcast: Vehicle at a Standstill	Data broadcast: Vehicle is  moving
Normal	Every 5 minutes	-40¹ to 69	-40¹ to 149	None	Every 30 minutes
Heightened	Every 10 seconds	70 to 99	150 to 211	Every 1 minute
Extreme ²	Every 5 seconds	100 and above	212 and above	Every 10 seconds

¹	The minimum acceptable limit to use the product.
²	Should the temperature surpass 105 °C (221 °F), the sensor will still measure and relay data, but its precision may not be assured. It is advisable to replace the sensor if such temperatures have been reached.

A complementary description of the temperature ranges is detailed in the table above:

• In normal operating conditions: Where temperatures are at or below 70°C (150°F), the vehicle must sustain a speed of at least 60 km/h (40 mph) for at least 30 minutes for the device to broadcast data. Therefore, if temperatures are within this "normal" range and the vehicle doesn't meet the required speed and duration, such as when it is stationary or moving too slowly, the device does not broadcast data.
• In heightened operating conditions: Should the temperature rise above 70 °C (150 °F), whether the vehicle is stationary or moving, the sampling frequency will escalate, and the device will broadcast data every minute.
• In extreme operating conditions: In extreme events, when the temperature is above 100 °C (212 °F), the sampling frequency increases even further, and broadcasts are transmitted every 10 seconds.

Temperature Alarms

The device is designed for long-term monitoring rather than immediate alerts. It will activate a temperature alarm if the measured temperature exceeds 95 °C (203 °F) for more than 30 minutes.

Enhancing Thermal Event Detection

To expand on the device´s temperature measurement capabilities, the TSP can implement controls into its platform to generate alerts for rapid thermal events.

Rapid thermal events can be identified by analyzing sensor data, collected during brief temperature spikes. As previously mentioned, the device escalates its broadcasting frequency with fresh temperature readings as the temperature rises, depending on the temperature range. Therefore, it is essential that the TSP can capture and process all device data broadcasts, not just those triggering an alarm.

The TSP can also compare the temperature values from all the TraX devices mounted on the vehicle to detect unexpected thermal events better.

The table below outlines general guidelines for three severity levels of rapid thermal event alarms: Caution, Warning, and Critical. It may be necessary to adjust the temperature thresholds for each fleet according to its tolerance for false alarms, as the risk of false alarms increases with lower threshold settings.

Alarm Severity	Alarm Rule	Duration	Temperature Threshold in Celcius	Temperature Threshold in Fahrenheit
Caution	Crosses temperature threshold once	n/a	95	203
Warning	Crosses temperature threshold three times	5 minutes	95	203
Critical	Temperature is above the threshold	30 minutes	95	203

To clarify, the temperature thresholds in the table above serve as guidelines if the TSP chooses to implement support for capturing rapid thermal events in their platform.

The device will flag a Temperature Warning when the temperature remains above 95 °C (203 °F) for more than 30 minutes, which corresponds to the "Critical" Alarm Severity in the table. The device will not flag Temperature Warning for any other Alarm Severity listed in the table.