Defect detector
Encyclopedia
A defect detector is a device used on railroads to detect axle and signal problems in passing train
s. The detectors are normally integrated into the tracks
and often include sensors to detect several different kinds of problems that could occur. Defect detectors were one invention which enabled American railroads to eliminate the caboose
at the rear of the train, as well as various station agent
s stationed along the route to detect unsafe conditions. The use of defect detectors has since spread to other overseas railroads.
n Class I railroad
s began adding radio
transmitter
s and mechanical voices
to their defect detectors; as trains passed detectors, the mechanical or pre-recorded voice would sound out on the railroad's main road radio channel that a train has passed and note any defects that were found. Most often, after a train has passed such an equipped detector, the mechanical voice will report the railroad name, milepost
or location, track number (if applicable), number of axle
s on the train that passed and the phrase "no defects" to indicate that no problems were detected on the train. Sometimes the location's ambient temperature
and train speed are also noted by the mechanical voice. When a problem is detected, the mechanical voice will often start with a long, high pitch alarm tone followed by a description of the problem and the axle position within the train where the problem occurred. Crews can use their touch-tone hand radios to get the detector to repeat error messages. Defect detectors that are equipped with such a mechanical voice are often called talking detectors by railfan
s.
To this day some rail lines, mostly passenger routes with a very high traffic density, maintain centralized readout, non-talking detectors. This is due to the large and confusing volume of radio traffic a talking detector would generate. When an error signal is received a dispatcher or operator will contact the train via radio manually transmitting the error message and required action (like slow down, stop at next station or immediately stop).
Today defect detectors are often incorporated in monitoring platforms that are primarily used by railroads to more closely monitor the status of their trains. In countries where rail transport has been liberalised infrastructure companies use defect detectors to check the quality and status of different train owners. The main concern of the infra owner is protecting their asset and preventing excessive damage. However, studies have been conducted to see whether defect detectors can be used to issue "penalties" track-unfriendly vehicles (or provide discounts to those operators with track-friendly vehicles).
Talking detectors are also used by railfans that are carrying scanners to listen in on the railroad's radio chatter. Railfans are often able to gauge where trains are by listening for the detectors' transmissions; in doing so, the railfans can more precisely predict when a train will pass a specific location to improve their chances of photograph
ing the trains.
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...
s. The detectors are normally integrated into the tracks
Rail tracks
The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast , plus the underlying subgrade...
and often include sensors to detect several different kinds of problems that could occur. Defect detectors were one invention which enabled American railroads to eliminate the caboose
Caboose
A caboose is a manned North American rail transport vehicle coupled at the end of a freight train. Although cabooses were once used on nearly every freight train, their use has declined and they are seldom seen on trains, except on locals and smaller railroads.-Function:The caboose provided the...
at the rear of the train, as well as various station agent
Station agent
In many countries, the station agent is the person in charge of a railway station Variants of station agents can also work at other transit terminals such as airports, ferry terminals, etc....
s stationed along the route to detect unsafe conditions. The use of defect detectors has since spread to other overseas railroads.
History
As early as the 1940s, automatic defect detectors were installed to improve what was normally done with the human eye by railroad workers. The detectors would transmit their data via wired links to remote read-outs in stations, offices or interlocking towers. If a defect was detected, an alarm would sound and the employee on duty would bring the train to a halt using hand or automatic signals.Today
Beginning in the 1980s many North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n Class I railroad
Class I railroad
A Class I railroad in the United States and Mexico, or a Class I rail carrier in Canada, is a large freight railroad company, as classified based on operating revenue.Smaller railroads are classified as Class II and Class III...
s began adding radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
s and mechanical voices
Human voice
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...
to their defect detectors; as trains passed detectors, the mechanical or pre-recorded voice would sound out on the railroad's main road radio channel that a train has passed and note any defects that were found. Most often, after a train has passed such an equipped detector, the mechanical voice will report the railroad name, milepost
Milestone
A milestone is one of a series of numbered markers placed along a road or boundary at intervals of one mile or occasionally, parts of a mile. They are typically located at the side of the road or in a median. They are alternatively known as mile markers, mileposts or mile posts...
or location, track number (if applicable), number of axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
s on the train that passed and the phrase "no defects" to indicate that no problems were detected on the train. Sometimes the location's ambient temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and train speed are also noted by the mechanical voice. When a problem is detected, the mechanical voice will often start with a long, high pitch alarm tone followed by a description of the problem and the axle position within the train where the problem occurred. Crews can use their touch-tone hand radios to get the detector to repeat error messages. Defect detectors that are equipped with such a mechanical voice are often called talking detectors by railfan
Railfan
A railfan or rail buff , railway enthusiast or railway buff , or trainspotter , is a person interested in a recreational capacity in rail transport...
s.
To this day some rail lines, mostly passenger routes with a very high traffic density, maintain centralized readout, non-talking detectors. This is due to the large and confusing volume of radio traffic a talking detector would generate. When an error signal is received a dispatcher or operator will contact the train via radio manually transmitting the error message and required action (like slow down, stop at next station or immediately stop).
Today defect detectors are often incorporated in monitoring platforms that are primarily used by railroads to more closely monitor the status of their trains. In countries where rail transport has been liberalised infrastructure companies use defect detectors to check the quality and status of different train owners. The main concern of the infra owner is protecting their asset and preventing excessive damage. However, studies have been conducted to see whether defect detectors can be used to issue "penalties" track-unfriendly vehicles (or provide discounts to those operators with track-friendly vehicles).
Talking detectors are also used by railfans that are carrying scanners to listen in on the railroad's radio chatter. Railfans are often able to gauge where trains are by listening for the detectors' transmissions; in doing so, the railfans can more precisely predict when a train will pass a specific location to improve their chances of photograph
Photograph
A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...
ing the trains.
Sensors
The sensors installed at defect detector locations can include:- HotboxHot boxA hot box is the term used when an axle bearing overheats on a piece of railway rolling stock. The term is derived from the journal-bearing trucks used before the mid 20th century. The axle bearings were housed in a box that used oil-soaked rags or cotton to reduce the friction of the axle...
detectors - Dragging equipment detectors
- Wheel impact or sliding wheel detectors (often placed at the entrances of delicate high speed track like AmtrakAmtrakThe National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
's Northeast CorridorNortheast CorridorThe Northeast Corridor is a fully electrified railway line owned primarily by Amtrak serving the Northeast megalopolis of the United States from Boston in the north, via New York to Washington, D.C. in the south, with branches serving other cities...
) - High car or shifted load detectors
- Weighing in Motion sensors for axle loads, imbalances or infracharging
- Wide-load detectors
- Structure gaugeStructure gaugeThe structure gauge, also called the minimum clearance outline, is the minimum height and width of tunnels and bridges as well as the minimum height and width of the doors that allow a rail siding access into a warehouse...
& loading gaugeLoading gaugeA loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures...
- Structure gauge
- Hot-Wheel Detection (caused by sticking brake)
External links
- Audio: CONRAIL Talking Detector in Depew, New York (.wav file)
- Audio: CONRAIL Talking Detector in Lancaster, New York (.wav file)
- Photos: 'Wheel Impact Load Detector' at Lara, Australia
- Western New York Railway Historical Society - (more talking detector audio clips)