The axle boxes are used to transmit the pressure of the car, which it creates by acting on the necks of the wheelsets, as well as to limit the longitudinal and transverse sections of this pair.
Node device
If we talk about the arrangement of the axle box unit, it is important to immediately note that it is the most important component of the wheelset of a car. The installation or dismantling of this element also takes place in conjunction with the installation or replacement of the wheelset. In addition to what has been described above, the assembly is also intended to establish a strong connection between a pair of wheels and a trolley frame. The engagement is via over-spring spring suspensions. Another task for which the axle box of the car is intended was the storage of lubricant for roller bearings. In other words, this part is a kind of capacity. This element also limits the unnecessary movement of a pair of wheels relative to the frame of the trolley and transfers the load of the mass of the car to the neck of the axle.
Component Parts
The box unit of a freight car consists of a large number of parts.
The first part is a tidal hull designed for spring suspension.
The second element of the node is a labyrinth ring. The location of this part is the rear cover of the axle box body. It is pressed onto the pre-approachable part of the axis.
The next element is the roller bearings. This unit element consists of an inner ring, has a separator with cylindrical rollers and has an outer ring.
Further, a small part called a thrust ring is located between the roller bearings.
Another device that is designed to install an outer bearing is a snap ring.
A plate washer or a castellated nut is necessary in order to carry out end fastening.
The axle box also has a fastening cover, felt and rubber gaskets between the parts and an inspection cover.
All these elements are connected in a single node, which was called the axlebox.
Connection method
Currently, there are two types of attachment of the unit to the trolley. They are called maxillary and maxillary.
If we talk about the second embodiment, then in this case the node assembly, for example from a passenger car, will have two brackets that are designed to carry out such a node installation procedure as over-spring spring suspension. The attachment parts of the assembly have holes through which they are attached to the frame of the trolley with the help of such a part as spintons. In such cases, the installation of the labyrinth part of the axle box is cast together with its body and forms a solid structure.
It is very important to monitor the temperature of the axle box heating during movement, and therefore the upper part of the body has a through hole, which is designed specifically for mounting SKNB. The abbreviation SKNB stands for bucket heating control signaling device. It is worth adding that during installation in this way the labyrinth ring is pressed and installed only with preliminary heating of this part to a temperature of 125-150 degrees Celsius.
What malfunctions of the axle box assembly may occur?
Since this element has many components, as well as parts that move, their wear, abrasion and failure are quite logical. And due to the fact that passenger or freight cars carry a large number of people or valuable material, the failure of the unit will entail almost a catastrophe.
Faults include the following:
- Bearing failure. Most often it happens because the roller is jammed and it stops making a rotational movement.
- A problem such as a violation of the end fastening may occur. Most often it happens because the nut comes off the neck of the axis or the bolt heads break off.
- Such a malfunction as turning the inner ring of the bearing or kink of the journal axis is possible.
- A malfunction is also considered the moment at which the heating temperature of the axle box assembly exceeds 70 degrees Celsius.
Symptoms of a node failure
There are a number of signs by which it can be determined that the operability of this element of the car is impaired and inspection and repair are required. Such signs include rattle or tapping, which periodically becomes audible during the movement of the composition.
Since the bearings inside the axlebox are metal, the sound of how these objects are poured during movement is also a sign of a knot breakdown. Incidents such as leakage of grease from the labyrinth ring, scale or discolouration on the axle box, the presence of smoke from the unit or its smell after the car is stopped, are also signs that the axle box is faulty and needs repair. Faults in the axle box assembly also include too high a temperature in the upper part of the element. It is this symptom that is easier to notice than the others, since this parameter is controlled, an automatic alarm is triggered.
Traffic safety
The safety of the entire train depends heavily on the proper operation of this unit. Due to the fact that the composition develops a rather high speed, the heating temperature of the axle box can increase at a very high speed - up to 20 degrees Celsius per minute. Due to severe overheating, the chance of a breakdown such as turning the ring or jamming the entire part increases. The occurrence of one of these two malfunctions of the axle box assembly will entail the wagon coming off the rail.
Axle box
Repair work must be carried out either within the time period established by the technical documentation, or in the event of a breakdown. There are practically no differences between the designs of this element of a freight wagon or an electric locomotive, and therefore, an example of repair of an axle box assembly can be considered on such a model of an electric locomotive as VL80.
The analysis of the unit begins with the fact that the nut is turned away, and then the bolt is knocked out. It is very important to check its thread. It is worth noting that the washing of all parts of the axlebox is also an important part of the repair, since pollution will cause the bearings to stop rotating. But here it is necessary to take into account the fact that after washing, before disassembling the element, more than 6 hours should not pass. This is argued by the fact that a longer presence of moisture on the parts will lead to too rapid corrosion.
What to check during repair
Very thorough inspection is necessary to expose the axle box bearings and eyeliner. Those eyeliners that are deemed suitable for further use must be sent for magnetic flaw detection. Those that are considered more unsuitable for operation are dismantled and transferred to the place of inspection, assembly and formation of eyeliners.
Roller bearings are thoroughly cleaned. First, they are washed with a soapy emulsion, then washed again in gasoline, after which you need to wipe them dry with napkins. After they also undergo such procedures as inspection, measurement and flaw detection.
When examining these elements, it is very important to pay attention to the presence of defects such as traces of overheating, cracks that most often occur on rings, separators or rollers. It is worth noting that almost 37% of all failures of axlebox units arise due to the fact that fatigue failure or wear of the centering surface of the separator occurs.