What Is a Bearing Temperature Sensor?
A bearing temperature sensor is a temperature sensor used to measure the temperature of bearings and detect abnormalities.
Bearings typically increase in temperature after the start of operation, reaching a steady state at a temperature 10 to 40°C higher than the ambient temperature after a certain period. If the bearing temperature does not stabilize and continues to rise abnormally, it indicates a malfunction that needs to be addressed. Bearing temperature sensors are used to detect such malfunctions early. Particularly critical bearings often use temperature sensors to prevent damage like seizure, which can lead to equipment downtime.
Uses of Bearing Temperature Sensors
Overview
Bearing temperature sensors are used to monitor the temperature of bearings in various machines. By measuring the internal temperature of bearings, they help quickly detect abnormal temperature rises, enabling rapid detection of malfunctions and prevention of accidents.
Uses of Bearings
Bearings are mechanical components used to support rotating bodies such as shafts smoothly and accurately. They are also known as bushings. Bearings are widely used in industrial machinery, automobiles, aircraft, railway vehicles, household appliances, and other industrial products.
In particular, in piston engines like diesel engines, bearings support the crankshaft at the correct position, allowing it to rotate within the engine block (main bearing). Diesel engines are used in various applications, including ships, power generation, and industrial uses.
Principle of Bearing Temperature Sensors
Causes of Abnormal Temperature Rise in Bearings
Bearings start to gradually increase in temperature as soon as they begin to operate, typically reaching a steady state after 1-2 hours. The normal temperature of bearings depends on the machine’s heat capacity, heat dissipation, speed, and load. If there is a malfunction, the bearing temperature will rise rapidly and become abnormally high. Common causes of abnormal temperature rise include:
- Extreme shortage or excess of lubricant, or inappropriate lubricant
- Improper installation of the bearing
- Insufficient internal clearance of the bearing or excessive load
- Excessive friction in the sealing device
- Creep on the fitting surface
Mechanism of Bearing Temperature Sensors
Bearing temperature sensors can estimate the internal temperature of the bearing by measuring the temperature outside the bearing chamber or directly measure the outer ring temperature of the bearing using oil holes. Some products can be directly screwed into the grease nipple mounting hole of the bearing.
The sensor mechanism for detecting temperature includes thermocouples and resistance temperature detectors (RTDs). A thermocouple is a temperature sensor that uses the electromotive force generated by the temperature difference between two connected metals. Thermistors and RTDs measure temperature by correlating material resistance with temperature. Thermistors are characterized by their ability to measure within a narrow temperature range with high sensitivity and small size. RTDs, on the other hand, can cover a wide temperature range with good linearity but are less sensitive than thermistors.
Types of Bearing Temperature Sensors
Various bearing temperature sensors are available on the market, with different operating temperature ranges, such as -40 to 105°C, -15 to 60°C, and up to 1200°C. Some products can sound an alarm at a specified temperature.
For diesel engines, bearing temperature sensors can be paired with lubricant oil sensors that measure the temperature of the oil rising to the piston crown, allowing for comprehensive temperature monitoring. Some products offer complete wireless capabilities through wireless communication and self-powering systems, and others are powered by lithium batteries.
Additionally, there are sensors that can simultaneously measure vibration speed, acceleration envelope, and temperature, as well as sensors that can communicate with tablets, smartphones, or smartwatches via Bluetooth. Many products are also equipped for cloud integration. Given their use in harsh industrial conditions, many sensors meet standards for waterproofing, dustproofing, fire resistance, and explosion proofing.