Rail defects and their classification. Rail defect designation structure

There are a fairly large number of a wide variety of rail defects. All of them arise for various reasons. In total, four main types of deficiency are distinguished, due to which a breakdown occurs. Poor track manufacturing and welding technology is the first cause of wear. The second reason is that the content of the path is too low. The material has such a parameter as contact fatigue strength, and if this parameter is not high enough, then the rails also become unusable. The last reason for the failure of these objects is the impact of rolling stock moving along them.

Reasons for Failure

During operation, rail defects and their likely occurrence are calculated based on several facts. Firstly, an important factor is the amount of tonnage that has passed along a segment of the track. Secondly, the load on the axis of the rolling stock plays a role. The speed of trains is also able to affect the condition of the rails. Practice and observations show that in the warm season, that is, in the spring and summer, the number of failed paths decreases. In autumn, this indicator increases slightly, and in winter it rises by 2-3 times, compared with the warm season. There is an explanation for this and it consists in the fact that at low temperatures the metal is characterized by increased fragility. In other words, its toughness is reduced to a minimum. The largest percentage of track failure due to rail defects occurs in March, if we talk about the European part of the country, and also in April, if it concerns the eastern and Siberian regions.

Flaw detectors are used to identify such problems. 96.5% of all identified problems can be determined using removable or portable devices. Another 2% are detected using car flaw detectors and another 1% using other models of this device. It is very important to note that there is a classification of rail defects and their description using numbers. This is done in order to be able to conduct a static accounting of rails.

Classification

Any damage, kinks or defects in track sections are identified using a unified number system. The first two numbers are primary, and the third auxiliary. The first number indicates the type of defect or damage to the rail. In addition, it also indicates the location of the problem on the railway section. The second digit describes the type of defect or describes the damage, taking into account the reason for which it appeared. The third auxiliary digit indicates the location of the defect or damage along the length of the rail. In more detail, rail defects and their classification are described by numbers from 1 to 9 for the first sign.

• If the first number is 1, then this means that there was spalling and delamination of the metal on the rolling surface of the rail head.
• If the value is 2, then this means that transverse cracks in the rail head were found on a segment of the track.
• The number 3 also indicates the presence of cracks in the rail head, but of a longitudinal type.
• The number 4 indicates that plastic changes have occurred, that is, wrinkling, vertical, lateral or uneven wear of the head.
• At number 5 there are injuries and defects of the rail affecting the neck.
• 6 is a failure or damage to the sole of the rails.
• 7 - this is a fairly strong deformation, as this figure indicates the occurrence of kinks over the entire cross section of the railway.
• If kinks occur in the vertical and horizontal plane, then the number 8 is assigned to the first place.
• All other rail defects, damage, etc., which do not fall into any of the above categories, are indicated by the number 9.

Determining the meaning of numbers

The second of the main digits for the rail defect code also has many meanings, and more precisely, from 0 to 9.

• If the second digit is 0, then this means that the defect arose due to the deviation from production technology when creating this section of the railway.
• The number 1 indicates that the metallurgical quality of the steel used to manufacture the rails was insufficient. It is also possible that the strength of the steel was lower than necessary for normal operation.
• 2 - indicates that during the processing of the ends, errors were made, due to which the section of the path failed. In addition, this also includes some of the disadvantages that arise when processing rail profiles.
• 3 - these are rail track defects that arose due to the fact that the requirements of the instructions for the current maintenance of the facility were violated. It also includes damage caused by the fact that the principles of processing bolt holes at a metallurgical plant were violated.
• If the second is the number 4, then this means that the problems with the rails arose due to the specific impact on them from the rolling stock, for example, due to slipping. This also includes damage that occurs due to the fact that the rolling stock does not pass a proper check or driving conditions are violated.
• The number 5 includes all damage that is caused by any mechanical influences from the side, for example, an impact with a tool, an impact of a rail on a rail, etc.
• Rail welding defects that are caused by irregularities in the operation of the welding machine are quite common . They arise in welded joints and are numbered by the number 6.
• 7 - problems associated with the operation of rails at the joints.
• 8 - these are flaws that arise due to surfacing of rails, as well as due to improper welding of rail joints.
• All problems caused by corrosion are numbered 9.

It is worth noting that the failure of a section of the track due to breakage of the rails is a consequence of several factors simultaneously. Most often, it turns out that a lack of care for the railway greatly accelerates the development of those flaws that were made during the assembly or welding of the structure. Because of this, it becomes difficult to determine the cause, since it is necessary to find the main source of failure. Rail track rail defects, or rather their numbering, also has a third digit.

• 0 indicates that the problem is present along the entire length of the rail.
• 1 means that the problem is in the junction, in several places. The bolt joint, which is located at a distance of at least 750 mm from the end of the rail, may be broken. If we are talking about a welded joint, then at a distance of 200 mm symmetrically 100 mm to each side of the axis of the weld.
• 2 indicates that the problems are somewhere outside the junction. If we are talking about a bolted connection, then you need to look at a distance of 440 mm symmetrically 220 mm on each side of the axis of the weld at the bottom of the rail.

Rail welding defects and other damages are also divided into four categories, depending on their degree of development. There is a degree of DP, D1, D2 and D3. The most dangerous are DP. This designation indicates that damage has reached critical values ​​or dimensions. Such sites should be replaced first. Defects that are classified as D1 and D2 will be eliminated in accordance with the established procedure, which takes into account the intensity of the development of the problem. Rails with flaws belonging to category D3 are replaced only if the head of the track distance decides so. The decision is made on the basis of the data transmitted by the team leader after a scheduled inspection and taking into account the degree of development of the defect. As a result, it turns out that the rail defect codes consist of three digits, as well as the designation of the degree of their development on the site.

Flaw detection

Flaw detection is a procedure for identifying flaws in the structure of a railway using special flaw detection devices. It is worth noting that the rails go through this procedure several times. The first flaw detection is carried out at the rolling mill, when it is necessary to assess the quality of the finished work. The next verification process takes place under operational conditions, that is, on the road. Additionally, verification is carried out in rail welding workshops, where the welding process is carried out not only new, but also repair or welding of old structures.

The flaw detection procedure is intended primarily to identify those dangerous rail defects that are inside the structure, that is, that have no flaws on the outside. This makes it possible to timely replace a damaged structure.

Types of problems

Currently, all types of defects, methods for their elimination, causes of their occurrence, means for their determination, etc. are presented in the "Normative and Technical Documentation NTD / CPU 2002". In addition, it is worth noting that there is also experimental documentation, as well as a classification of NTD / CPU 1-93 rail defects, according to which all problem sections of the railway are divided into acute defective (OD) and defective (D). It is the category of flaws D with the help of NTD / CPU 2002 that is divided into a large number of species, depending on the cause of occurrence, degree of distribution, and location on the track.

To defective rails are those that pose a direct threat to the movement of the train, because due to the influence of a flaw, they can collapse directly under the wheels of the train or cause the rolling stock to go out of the way. If such a site is found, it must be immediately replaced with either a new or an old one from the kilometer-by-kilo stock. If new defects of railway rails were discovered before the warranty period for their use expired or less tonnage was passed through them than indicated in the documentation, then a complaint is made to the metallurgical plant where they were manufactured. If the defect was identified at the welded joint also earlier than the due date, then the complaint is presented to the rail welding plant.

To the defective rails belong those sections of the track that, due to the long service life, began to become unusable. The formation of flaws in such areas is expected. However, they still must ensure the safe passage of rolling stock. Although in some cases, a speed limit is introduced when passing such a segment of the path. The new edition of rail defects and their classification is presented in the normative and technical document NTD / CPU 2002. The code values ​​of possible problems were presented above.

Division into acute defective and defective areas

The documentation indicates the speed with which the train is allowed to move along a particular section of the track. If the degree of development of the defect belongs to the DP group, then the speed of movement is not more than 40 km / h until eliminated. Category D1 allows a speed of not more than 70 km / h, D2 - not more than 100 km / h. Defects belonging to group D3 do not create a limit on the speed of movement of rolling stock.

In addition, there are deadlines for replacing each group of defective rails. If no replacement occurs within the specified time period, the category is replaced with a higher one. In other words, DP3 goes to D2, D2 to D1, D1 to DP. Naturally, with each transition, the replacement periods are toughened up more severely, and also the restriction on the speed of movement increases, in accordance with the established norms.

Rail defects and their new NTD / CPU classification also determine problems that place a track section into a state of acute defective or simply defective tracks. To OD belong such problems as:

• The occurrence of transverse, longitudinal or lateral cracks in the rail head. Most often, breakdowns belong to the second and third groups, and their codes are 20, 21, 24, 25.
• Cracks in bolt holes with code 53, as well as cracks in the neck of the rail, regardless of size, as well as with codes 50, 55, 59 and 56.1.
• Corrosion or local wear of the rail with code 69 cracks that occurred due to corrosion fatigue, punctures of the sole of the rail with code 60, 64, 65, 66, as well as transverse fractures of the rail.

The occurrence of any of these new defects leads to the fact that even a new section of the railway enters the state of OD and must be urgently replaced. There are several signs by which defective rails are identified in the pick-and-drop tracks. This may include:

• excess of the normalized reduced code 41 + 44, side code 44, or vertical wear of the rail head;
• metal chipping, if the depth does not exceed 3 mm, and the length is 25 mm;
• the presence of slippage from the wheels of rolling stock, wave-like wear.

It is also worth adding that the largest percentage of the transition of normal rails to the defective category is due to the fact that there is a lack of contact fatigue strength of the material. Such problems of defects in rails and turnout elements, which are also installed on rails, are classified as codes 11 and 21. Also quite often the cause is problem 44, which means severe lateral wear of the rail head. Quite often there is corrosion of the sole of the rails - 69.

Particularly dangerous defects and causes

First of all, when checking the rail, it is necessary to pay attention to those breakdowns that are caused by the "fatigue" of the metal. They are considered the most dangerous. If we consider in more detail, it looks like this. The composition wheel is in contact with the rail in a fairly small area during movement. It is through this small platform that the enormous amount of tension that a moving train creates is transmitted. It is these contact stresses, especially if they arise in the immediate vicinity of the rail head, cause its chipping, or lead to chipping of the metal. The more wheels pass through this section, the stronger the metal “gets tired”. It is because of this that defects 11.1-2 are caused by such a problem as the low contact strength of the material. To avoid this problem, or at least to make the rails withstand more movements, it is necessary to increase the strength of the raw material.

The separation or chipping of the metal can also be caused by the presence of hairs, sunsets or captures, which may appear on the surface of the rails during rolling.

Such groups of rail defects as 20.1-2 and 21.1-2 are considered very dangerous. As for the second group of flaws, they often appear in the form of internal cracks in the head or external cracks that appear in the fillet area in the head. If such a problem arises, then a rail may break later under the weight of a moving train into many small pieces. Naturally, this will lead to an accident and, most likely, the departure of the train. As for problems with the code 20.1-2, they arise in the head itself, and the main reason for their appearance is the shortcomings in the manufacturing technology.

Railroad defects due to poor inspection

It is worth noting that on October 23, 2014, the classification of rail defects 2499 NTD / CPU was approved. This document entered into force on September 1, 2015, and the document itself contains 140 pages. In addition, a new instruction on the maintenance of paths 2288 was also adopted. This document entered into force on 01.03.2017.

Such flaws as 11.1-2 and 21.1-2 also quite often arise precisely due to the fact that road foremen poorly monitor the condition of the rails. If in the first period of operation an incorrect rail tilt occurs, the main voltage will shift from the center of the section to the edge where the head is located, which, of course, will lead to its rapid wear. The frequency of occurrence of defects increases significantly even if a violation of the smoothness of rail threads occurs. Further, it is important to note that the growth process of the appearance of these problems is strongly associated not only with inadequate care of the tracks, but also with violations in the care of the moving part of the train itself. If jagged, sliders and other flaws appear on the wheels of the car, this greatly affects the fatigue strength of the metal and its development.

In addition to the head, quite often there are problems in the neck of the rails - cracks in the area of ​​bolt holes, the main problem. Most often, a crack originates in the contour of a bolted connection, and then leaves at a slope of 45 degrees to the horizon. An effective means of dealing with such cracks is the quality of the joints. In other words, it is necessary to tighten the bolts as tightly as possible, to prevent sagging of the rails or their subsidence. , . – .

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Definition of railway defects

To date, the only method that can detect new rail rail defects at an early stage and prevent it is the ultrasonic method.

This non-destructive testing method allows you to detect damage in metal rails using ultrasonic pulses. This method is used in many industries where there is work with metal, however, it is most popular at railway stations where it is most important to monitor the quality of tracks. Ultrasonic flaw detection allows workers to quickly and accurately identify hidden damage, without affecting or destroying the object of study.

This method of detecting rail defects has several undeniable advantages.

First, and most importantly, the absence of any damage or any other traces left on the test sample, that is, new defects. Secondly, the cost of such equipment is quite low, and the reliability of the data obtained as a result of its use is very high. In addition, it is important enough that such a device allows you to search for new rail defects at any time of the year, which is especially important.

The ultrasonic method for detecting defects allows you to find even the slightest damage in any metal products and joints. For this reason, they are also actively used to inspect turnouts and welded joints of a structure. Using ultrasound equipment, the following damage can be determined: occurrence of disturbances in the uniformity of the structure; check places damaged by corrosion; check whether or not the chemical composition of the rail is as stated in the documents.