Train inspection system
A train inspection system is one of various systems of inspection which are essential to maintain the safe running of rail transport.
Because safety is of high importance when train cars move across the rails, there must be inspections. The cars are heavy and have moving parts that can break or become defective. Worn or broken parts can drag, pound, and generally destroy the cars and the track structure they run on. Parts and loads must not extend outside the limits of the car, and there should be no leaking of the cars' contents.
Quality inspections are needed not just before a train is moved, but also as it travels to its destination.
Overview
There are several levels of inspection on railroad equipment. Inspections are continuous, starting when the car is being built and repeated at regular intervals.Before the train begins its journey, the locomotives and the cars are checked. This is done by mechanical department workers, sometimes cameras and scanners are also used. Some of the items certified good to go are things like the braking system including hand-brake release, brake application, condition of the air valves, piping and hoses, communication equipment, and many more. Very much like the checklist an airline might use. When the pretrip work is done, the train is considered safe to move.
Once the movement begins, the train is continuously watched by employees, scanners and monitors. These are sometimes called "in motion defect detectors" or defect detectors.
Technologies
As the railroad has evolved from block stations and control towers to a centralized dispatching system, they have also moved to more advanced inspection tools. The technologies in use today vary from a simplistic paddle and switch to infrared thermography, laser scanning, and even ultrasonic audio analysis. These devices are used to inspect engines, cars and the loads on them.The systems used on North American and other railways fall into a dozen or so major groups, some are listed below.
Wheel impact load detector (WILD)
High impact wheels have some defect where it does not roll smoothly along the track. A flaw in a wheel causes vibrations or banging. This is very destructive to the track structure and the rolling stock.Weigh in motion (WIM)
Checks for overloads or shifted loads that can be dangerous.Truck hunting
Looks for hunting oscillation of the trucks or wheelset; a lateral movement in the gauge of the track, like drifting back and forth in a lane of traffic. This action can increase above a certain speed to the point the wheel flanges impact the rails, potentially causing damage to both. There is also force absorbed by this action that will affect the energy consumption of train operations.Truck performance
Is stiff or poorly steering or axle sets that don't follow the path of the track correctly. Presents itself like 'dog tracking" where the trucks are biased to run against the flange on one side or the other. Truck performance defects include tracking position and angle of attack on a per-axle basis, as well as rotation, shift, inter-axle misalignment, and tracking error on a per-bogie basis. Truck performance detectors can provide early detection of bogie defects, and early warning of derailment risks through flange climb or rail break.Acoustic bearing detectors
Listens with special microphones for internal bearing defects as the equipment moves across the detector. These are very sensitive and can detect problems before the bearing fails.High wheel temperature detectors
Look for hot wheels, which are generally caused by braking equipment failures. This equipment may be combined with bearing temperature detectors.Bearing temperature scanners ("hot box" detectors)
This type of defect detector uses ultra sensitive infrared cameras called pyrometers. These devices take the temperature of each bearing as it passes by the scanner. This data is then compared to preset "Alarm limits". If the whole consist is without problems, the train is passed. If however there is overheating in one or more of the bearings, an alarm is given.These messages can be by radio to the train crew or might be sent to the dispatch center for handling. The data is also used to detect a trend over several locations that might predict a future failure. If an alarm is sent, the train is stopped, and either the defect is corrected or the offending car is removed for repair. Many derailments are avoided by these devices which is why thousands of them are in use on rail systems across the world.