A flaw detector car is a type of rolling stock of railways intended for continuous high-speed control of rails laid in a way and detection of external and hidden defects in them.
General characteristics
Flaw detectors are produced on the basis of four-axle passenger cars moved by a locomotive , with ultrasonic and magnetic search devices.
Principle of Operation
In an ultrasonic flaw detector car, echo is mainly used (a sign of defect detection is the received reflected signal from it) and mirror-shadow methods (a sign of defect detection is a change in the intensity of ultrasonic signals reflected by the rail sole). ( more about methods )
In Russia, until recently, flaw detectors with magnetic finders were the most widespread. The principle of operation of a magnetic finder is based on the use of a magnetodynamic field arising in a rail when it is magnetized by a moving permanent magnet. The defect is detected by a change in the density of eddy currents and the direction of motion of the magnetic flux flowing around the crack in the rail. During the movement of the flaw detector car, each rail thread is magnetized by an electromagnet, an EMF is induced in the search coil in the form of single pulses of various values, durations and shapes. After amplification, they are recorded on film or paper tape. Control by this method reveals internal transverse cracks that affect up to 35% of the cross section of the rail head at a depth of more than 5-6 millimeters, and longitudinal cracks at a depth of 4-5 millimeters. The working speed of a magnetic flaw detector car reaches 70 kilometers per hour.
In the 2000s, there is a gradual replacement of magnetic and ultrasonic cars with combined ones that combine the advantages of both methods: the magnetic method identifies defects at shallow depths and does not require direct contact with the rail, and the ultrasonic one - defects of deep and medium occurrence.
Development Prospects
Improving the quality of control is facilitated by an increase in the sensitivity of the measuring and recording systems and the identification of defects at a deeper depth at an early stage, as well as automation of the signal decryption process.
Flaw detectors in the subway
In the Moscow Metro, a flaw detector car appeared in 1975. It was a subway car of type "A" No. 1031 of 1935 of construction. In his salon there were several rooms. One of them was a control room. One trolley was flaw detector, the second main. Until 1999, it was operated at the Krasnaya Presnya depot. From 1999 to 2012, flaw detector No. 9425 was used in the same depot, which was converted from the 81-714 wagon. In the Vladykino depot there were two defectoscope cars 81-717 No. 9267 and No. 9279. Car No. 9267 was decommissioned in 1996, car No. 9279 was transferred to the Kaluga depot in 2015. There is also a flaw detector car in the St. Petersburg metro . This is an Em-type car No. 3875, which, after being converted into a flaw detector, received number No. 003. It was operated at the PM-1 Avtovo depot. Now it is inoperative.
See also
- Travel meter
- Travel trolley
- Flaw detector
- Unbrakable control
- Ultrasonic testing
Literature
- Rail transport: Encyclopedia / Ch. ed. N. S. Konarev . - M .: Big Russian Encyclopedia , 1994. - P. 50. - ISBN 5-85270-115-7 .