compressor — temperature (infrared-spot-bearing)
Physics
Section titled “Physics”A compressor’s motor or airend bearing generates frictional heat continuously while running; a developing defect (lubrication loss, race pitting, misalignment) raises the bearing housing’s steady-state surface temperature above its healthy baseline, and a sudden lubrication failure produces a fast rate-of-rise rather than a slow drift. A fixed non-contact infrared (IR) spot sensor aimed at the bearing housing surface measures the housing’s emitted infrared radiance and converts it to a surface temperature reading, without needing physical contact or a drilled/tapped mounting point, which matters on a housing where adding a contact probe boss is impractical or where the surface moves slightly under thermal expansion. Bearing housing thermal mass gives surface temperature a time constant on the order of minutes, so there is no benefit to sampling faster than that physics allows; sampling the IR sensor’s analog output at 1 Hz resolves the fastest realistic rate-of-rise for a developing bearing failure (well under 1 degree C/second) with large margin, keeping data volume to the historian small.
Sensor
Section titled “Sensor”- Spec: fixed-mount infrared spot temperature sensor, 4-20 mA or digital output, small spot size at short standoff distance
- Signal: scalar (Cel), range n/a
Example parts
Section titled “Example parts”- Omega Engineering OS-MINI-IR series fixed infrared temperature sensor (4-20 mA output)
- Micro-Epsilon thermoMETER CSmicro series fixed IR temperature sensor
- Teledyne FLIR AX8 fixed-mount thermal imaging/spot sensor (analog + digital output)
Mounting
Section titled “Mounting”Mount the IR sensor on a rigid bracket off the compressor frame, aimed perpendicular at the bearing housing surface at the manufacturer’s rated standoff distance so the sensor’s spot size stays within the housing surface and does not pick up background (ambient enclosure wall, adjacent hot piping) in its field of view. Verify the target surface is not highly reflective bare metal, which gives an inaccurate low reading from a fixed-emissivity sensor; apply a small patch of high-emissivity tape or paint to the spot if needed and set the sensor’s emissivity setting accordingly.
Wiring
Section titled “Wiring”4-20 mA (or digital, per the chosen part) output cable from the sensor to an analog/ digital input on the edge box’s I/O module, routed away from the compressor motor starter and any VFD cabling to avoid electrical noise pickup.
Validation
Section titled “Validation”run the compressor through a normal duty cycle and compare the detector’s logged bearing housing temperature against a handheld calibrated infrared thermometer reading taken at the same spot at the start, middle, and end of the run
Expected: detector reading within +/-3 degC of the handheld reference at each spot check, accounting for the same emissivity setting, with no missed rise above high_c
Safety notes
Section titled “Safety notes”- de-energize and lock out the compressor and motor starter circuit (LOTO) before installing the mounting bracket near the bearing housing
- compressors store pressurized air/gas in the system even after motor lockout; verify the discharge line and receiver are isolated or vented per the site’s energy-isolation procedure before working near the airend
- the bearing housing is a hot-surface burn hazard during and immediately after running; even though the sensor itself is non-contact, installers positioning or adjusting the bracket can still contact the hot housing
120–450 USD, difficulty 2/5, ~25 min install downtime.