A large mine in the Southwest was having trouble getting accurate temperature measurements of the ball bearings involved in crushing giant boulders to extract copper. During the grinding, the pressure of the heavy ore and the vibrations caused by the grinding process caused the bearings to overheat. The bearings were cooled by turning inside an oil tray that lubricated the bearings and helped prevent friction.

The mine first used noncontact infrared temperature sensors, but they could not be located close enough to the bearings. Instead of accurately reporting the bearings’ temperature, the noncontact sensors were primarily measuring ambient temperatures around the bearings. The inaccurate readings meant that bearings would burn up before the dangerous rise in temperature was detected.

Moore Industries, North Hills, Calif., solved the problem with a custom installation of its Worm flexible temperature sensor with a specially designed copper head. The flexible sensor rides on the bearings to make temperature readings in close proximity to the bearings. When the sensor detects the bearings have reached a critical temperature, an advance warning alarm sounds, alerting workers to add oil to the bearing tray to avoid burn out. Copper was used because it is particularly effective as a heat sink, pulling heat from the bearings to get more accurate measurements.

The company has published a case study on this application on www.miinet.com.