STC SmartScanIS, User Manual

Page: 377 / 391

EUD-2016026-00 Rev.2, SmartScanIS User’s Guide for Union Pacific, 14 January 2021
377
Appendix G
Predictive Gate Scanning
This appendix describes predictive gate scanning of bearings.
G.1 Overview
If a pyrometer is exposed to extreme infrared energy emission, the device itself can be driven
into a saturated state. When this happens, it is blinded to subsequent changes in infrared
energy emission. This blinded state can last up to 1-1/2 seconds.
Under certain circumstances, a pyrometer may be driven into saturation before the opening of
the gate for a given axle. If the open-gate period was the only time during which pyrometer
readings were sampled and processed, the system might miss an overheated bearing due to a
device that was blinded before the opening of the gate. This can happen when a bearing is so
overheated that it gives off infrared energy that can be seen by the pyrometer long before the
bearing enters the pyrometer's field of view.
To compensate for this, the SmartScanIS includes special logic for processing heat seen by
the pyrometers as they scan between the axle gates. The interval between axles has been
divided into two parts.
The first part of this interval is the 20 inches (50.8 centimeters) that immediately precede the
axle as it approaches the bearing scanners. This interval is treated as a "predictive gate"
region in which the actual gate period (the time a bearing is physically in the pyrometer's field
of view) is extended by 20 inches (50.8 centimeters). The remainder of the "between-gate"
interval forms the second part. Heat values read during this second interval are ignored.