Serviceable service brakes are like a fire extinguisher, almost no one thinks about them and does not remember once again, however, if, as they say, God forbid that, for example, an accident or emergency braking, we state their malfunction and "all the stones fly into them side". Although, by and large, they themselves are to blame, because at one time they did not pay attention, forgot or "scored" their condition, and therefore their safety, so it seems to me that now we must blame ourselves.
In short, in order not to feel sorry for yourself later and not to slander fate, you need to regularly diagnose the brake system yourself or with the help of specialists, namely: check the brake fluid level, the condition of the brake pads, the tightness of all connections and the integrity of the brake disc.
There are many factors that affect the operation of the brake system, or rather its individual elements, among which overheating of the brake discs is far from the last.
High temperatures are normal for a brake disc
For those who do not quite understand how the brakes are arranged, I will conduct a short digression. The material from which the brake disc is made is subjected to high loads, therefore strength - first of all, strong friction occurs during braking, therefore, in addition to strength, the disc must conduct and give off heat well, be resistant to sudden heating and have low adhesion ability.
It would seem that some kind of "piece of metal" of a round shape, and there are so many requirements for it. I am sure that you did not know that the operating temperature of this "piece of metal" reaches 200-300 degrees Celsius, which is why metals such as cast iron and steel are used in its manufacture. Analogues of steel discs - ceramic brake discs boast the ability to withstand heat equal to 1000 degrees, while they are not able to deform. However, their main drawback is their high cost, which, by the way, is the reason that they are still not used in mass production.
What is the danger of overheating brake discs?
Overheating is fraught with zero efficiency of the brakes, because after that the brake pads begin to interact with the brake disc, as with oil ...
What Causes Brake Discs to Overheat?
Of course, the cause of overheating is friction. So what happens, you ask - stop slowing down altogether? The answer is no, you just need to think about it more often and change your driving style from aggressive to uniform, without jerks and sudden braking. You must understand that heating takes place in a matter of seconds, and cooling takes much longer. Therefore, in order not to have to brake hard, it is necessary to avoid an aggressive driving style. The only place where frequent use of the brakes is justified is driving in city traffic, it is difficult to do anything here, the brake discs, as well as the brake pads, are constantly heated. However, if you continue to "provoke" overheating of the discs by constant acceleration and deceleration, you are guaranteed overheating of the brake discs.
Causes of overheating brake discs:
1. The thickness of the brake pads is below the acceptable level. Often, overheating of the brake discs happens through the fault of the owner, who abuses the number of grooves in the brake discs;
2. The disk is warped;
3. Poor quality brake pads;
4. Rear brakes - drum type. Well, everything is quite simple here, due to the low efficiency of the drum brakes, the main load falls on the front disc brakes, which actually contributes to overheating of the front axle brake discs.
Useful tips for car owners
In the summer, try to avoid washing your car immediately after a long drive. Remember what I said at the beginning, "brake discs heat up very quickly, and cool down much longer", so when you go to the car wash, give the discs, as well as other heated parts, time to cool. This will allow you to get rid of such an unpleasant phenomenon as the deformation of the brake disc, as well as microcracks arising from temperature changes.
Many motorists are faced with such a problem as overheating of the front or rear brake discs. This problem is quite relevant among novice motorists, affecting the safety of the driver and passengers. So what to do if the brake discs are heated? And why is this happening? More about this and will be discussed in our article.
In fact, modern representatives of the automotive industry are powerful devices that are able to reach high speed in a relatively short period of time. Accordingly, the rapid acceleration of a heavy metal object will sooner or later need to be stopped just as quickly. As a result: reliable and fast operation of the brake system affects the safety of the driver when driving.
The design of the automotive braking system is a bit like the shoe brake that most bicycles are equipped with. True, there is a slight difference: on a bicycle, when the brakes are applied, the pads come into friction with the rim, and on cars - with a brake disc (or drum). In addition, bicycle brakes work through a cable, and on a car - using hydraulics. The vehicle stops due to the creation of friction between the brake disc and pad. This process has its consequences, the main of which is the formation of a large amount of heat that needs to be put somewhere. To remove the generated thermal energy, there is a disc brake ventilation that was developed specifically for this purpose.
Disc brakes have repeatedly proved their effectiveness during numerous experiments, which automatically elevates them to the first place among similar analogues. The decrease in the temperature of the working surfaces occurs due to air cooling: when working in the system, there is a constant air circulation.
How the brake system works
The list of advantages of disc brakes should also include "autonomous" cleaning. The fast speed of rotation of the discs removes all dirt and dust accumulated on the surface of the part. Many experts believe that the modern disc brake system is very popular due to its efficiency, the ability to make some adjustments to the system, reliability and long service life. The last point is very relevant, given the current prices for spare parts.
Classification of brake discs
To get a clearer picture, it is worth classifying brake discs. This will improve your knowledge in the field and also help you make a choice if you are still unsure which discs are best for you.
By design
There are two main types of design, according to which the distribution of disks occurs. Namely:
- ventilated;
- non-ventilated.
Ventilated brake discs are made up of two main parts. located at a certain distance from each other. The inner part of the disk is not solid, having screwed up, it is a kind of ventilation system, somewhat reminiscent of turbine blades. When the car is moving, the discs rotate, which allows these blades to create strong air currents, due to which the brake disc is cooled. The air circulation system ensures that hot air is removed from the disc. Thus, cold air enters from one side, and heat leaves from the other.
Design of ventilated discs The introduction of such an ingenious cooling system using radical channels made it possible to significantly improve the braking power of the vehicle by increasing the cooling area.
Non-ventilated brake discs do not have a specific design or shape. This is a common product, which is a solid plate. In some cases, manufacturers apply special slots or notches to the surface of discs. The main difference of this type is its relatively low cost on the market, but at the same time it does not cool down when moving, as happens with a ventilated counterpart.
Non-ventilated discs are a cheaper option According to the material of manufacture
Having more or less familiarized yourself with the type of design, it is worth considering the classification according to the material of manufacture. The production of brake discs is carried out from three main materials:
- metal;
- cermets;
- carbon fiber.
Speaking of the word "metal", it is worth noting that in this case, the discs can be made of steel and cast iron.
Metal brake discs
Cast iron is one of the most common materials for the production of brake discs. It is very durable, cheap, besides, parts made of cast iron have excellent friction properties. It would seem that everything is fine, if not for one big "but". The fact is that such discs, under the influence of high temperature, quickly warp, and if even a small amount of water gets on the heated cast iron during movement, it is destroyed. In addition, the weight of cast-iron discs is very large and they corrode during long-term parking of the vehicle. Therefore, the use of such discs is limited.
Brake discs made of metal: 1 - cast iron; 2 - steel; 3 - stainless steel If we talk about "sports cars" or motorcycles, they are equipped with stainless steel discs. If we compare "stainless steel" with cast iron, then it is slightly inferior in frictional properties, as a result of which such discs are produced somewhat larger and more massive than cast iron counterparts. Many manufacturers also use ordinary steel, but if we are talking only about everyday (folk) cars.
CFRP
Since the mid-70s, sports cars have been equipped with carbon fiber brake discs. This material has practically no drawbacks, with the exception of one - the cost. The only drawback did not allow this material to "go to the masses." But aside from the exorbitant price, using carbon is a great option: good frictional qualities, low weight and, most importantly, resistance to high temperatures.
Brake discs made of carbon fiber Products made of carbon fiber are resistant to corrosion, moreover, they do not warp during operation. But it is worth noting that the exorbitant cost of carbon fiber discs is not the only disadvantage that stands in the way of thousands of motorists. Having bought and installed carbon fiber brake discs, you will also need to take a few lessons on proper braking. If you don’t have any problems with braking on ordinary steel discs (the harder you press the pedal, the more effectively the car slows down), then with carbon discs everything is different. In this case, there are only two positions: move and stop - so harsh carbon brakes.
Ceramics
If we compare ceramic discs with carbon fiber discs, then the former, of course, win in terms of the number of pluses. Ceramic discs do not have such fantastic frictional properties, but they still have a number of advantages, which makes them more suitable for the domestic automotive market.
Advantages of ceramic brake discs:
- high strength;
- corrosion resistance;
- light weight;
- long operating period.
If we compare ceramic discs with cast iron discs, they weigh almost half as much, which increases the life of all car suspension elements. On the new ceramic discs, you can drive more than 300 thousand kilometers.
This is what ceramic brake discs look like Disadvantages of ceramics:
- the efficiency of disks cooled to a certain temperature is inferior to analogues made of iron;
- when braking, ceramic discs can emit a characteristic cutting sound of the driver;
- high cost of the product when compared with metal discs.
Important! If you compare alloy wheels with forged ones, then the cost of the former can be several times lower. In addition, finding the right forged wheels is a real challenge for the driver.
Optimum working temperature of the brake disc
If you do not take into account ceramic discs, which are able to withstand temperatures at around 1000 degrees, then serial brake discs can withstand a maximum temperature of 250-300 degrees. Overcoming this barrier threatens inevitable damage to parts of the brake system.
What requirements should high-quality brake discs meet? Actually, this is about:
- good frictional properties;
- increased strength of the material;
- corrosion resistance;
- high thermal conductivity;
- no deformation at high temperatures.
Temperature measurement of brake discs Based on the aforementioned requirements, one can only guess how rigorously tests brake discs undergo before entering the market. And rightly so, because their overheating worsens the efficiency of the braking system as a whole. In the event of overheating, brake pads, regardless of their price and quality, will not be able to cope with their main task - to adhere to the friction surface of the disc.
What causes overheating?
Initially, I would like to note that the main reason for the heating of brake discs is friction - the main function performed by them. As a result of the friction of the surface of the disc and pad, the temperature instantly rises, but it takes much longer to cool down.
Remember how many traffic lights you meet on the way to work and what is the distance between them. Think for a second, is there enough time between stops for the disc to cool down? Of course not, hence the overheating.
Driving style is a factor that should not be overlooked. Each driver is unique in his own way and this uniqueness is reflected in his driving style. It follows from this that more aggressive and extreme driving leads to the fact that the brake discs will almost always be heated to a high temperature.
Another reason is the failure of any elements of the braking system. For the most part, this reason can be placed on a par with driving style, since the driver directly affects the performance of the system (proper care, timely maintenance, and so on).
The main causes of overheating brake discs Let us consider in more detail the causes of overheating of the brake discs associated with malfunctions of the braking system:
- deformation (change in shape) of the brake disc;
- reduction in the thickness of the friction part of the brake pads or the working surface of the disc;
- poor quality of parts;
- rear drum brakes. The presence of such a mixed system directs the bulk of the load on the front axle, because the drum brake is not able to fully perform its task.
What causes disk overheating?
The consequences of intense heating of the discs are the formation of a certain film that separates the discs and pads. The presence of a film formed as a result of metamorphosis of the properties of the material of the parts worsens the frictional properties of the surfaces of the parts. In other words, the efficiency of the braking system is degraded. And if for some reason you manage to adapt to this style of braking, then you will not be able to avoid boiling the liquid.
What are the consequences of overheating brake discs? An extreme increase in the temperature of the brake discs has a negative effect on the brake pads and calipers, gradually bringing their premature "death" closer.
Important! If replacing the brake pads did not help eliminate the overheating, then the reason most likely lies in the corrosion that has formed around the gum of the clutch master cylinder.
How to prevent overheating?
To prevent such situations, you need to follow some recommendations.
Ways to prevent overheating - Undergoing regular maintenance- this is not another opportunity for reinsurers to rob you, but the recommendations of scientists obtained as a result of numerous studies. Do not ignore the rules, created many years ago for your own safety.
- Aggressive driving- an enemy to your car. Intense sudden braking leads to heating of the metal (the discs heat up much faster than it cools down). As a result, the operation of the braking system is disrupted.
- Brake fluid level in the system- Another factor affecting the performance of the brakes. Check the fluid level regularly.
- Don't Forget to Replace Your Brake Discs. Each manufacturer indicates the mileage on their products, after which it is necessary to carry out a replacement. As an exception, in some cases, pads can occur much earlier (depending on operating conditions).
- The pursuit of savings- this is not the best option. Buying cheap low-quality products, you put yourself in danger. No need to skimp on your own safety.
- Avoid self-medication. Replacement of elements of the braking system is best left to specialists. Only professionals have the right to be responsible for the quality of the work performed.
- Use of car wash services. Try to avoid washing the car immediately after driving, when the elements of the braking system are still hot. In this case, you need to wait a bit until the discs cool down. It would seem a simple rule, but it will save the brake discs from possible damage caused by sudden temperature changes.
Important! Sometimes problems with overheating occur just after replacing the brake pads on your own. In the wrong hands, protective equipment can cause an accident.
Perhaps the problem is novelty?
As mentioned earlier, very often the overheating of the brake discs occurs immediately after replacing the pads. You can find out this only with sudden braking - you should smell an unpleasant burning smell.
To prevent such situations, you need:
- Degrease the friction surface of the discs, thereby getting rid of the remains of conservation grease;
- Clean the hub of possible debris. This does not mean the entire surface of the hub, but only the part to which the disks are attached. Use a hard metal brush for this;
- Inspect all caliper pins for grease. It should be removed and a special lubricant applied instead. If this is not done, then the risk of jamming the caliper structure increases.
Cleaning the surface of the disc and brake caliper pins As a conclusion
Overheating of disks is a serious problem that should never be ignored. Fortunately, you can almost always eliminate this cause yourself. Overheating often happens due to the driver's preference to drive hard and aggressively.
Of course, it is necessary to periodically conduct a visual inspection of the discs and brake pads for various kinds of damage: if necessary, change the pads to new ones, and so on. And remember: your safety and those of your loved ones are at stake!
On the video - Overheating of the brake disc: causes, solutions
Heating is normal. The increase in temperature is due to friction between the brake disc and pads. The average operating temperature of a modern car brake disc is 200 - 300 degrees, however, during aggressive driving with frequent braking, the temperature can reach up to 500 - 700 degrees. Overheating brake discs can be dangerous because the pads do not come into contact with the disc, but literally "slide" over it, reducing braking efficiency.
Causes of overheating brake discs
The most common cause of brake disc overheating is driving style. The more aggressively you drive and the more often you have to brake hard, the more likely it is that the brake discs will overheat.
In addition, brake discs may overheat due to malfunctions or features of the vehicle's brake system:
- brake disc or pads worn out above the permissible norm,
- brake disk warped(replacement required),
- poor quality brake pads,
- drum rear brakes(because this type of brakes are less effective, the front brakes take most of the braking power).
How to prevent brake discs from overheating
Knowing the reasons why the brake disc overheats, it is easy to derive rules that will prevent this from happening.
- First, this moderate driving style no hard braking.
- Secondly, this timely maintenance of the elements of the brake system Regular replacement of pads and discs.
- Thirdly, the use quality components.
In addition, do not wash the car immediately after stopping (especially in summer). Brake discs need time to cool down, so a sudden change in temperature can cause the brake disc to warp.
How to identify overheating brake discs
A complete diagnosis of the brake system (including brake discs) can only be done by a specialist, but you can carry out a visual inspection yourself. You can determine the condition of the brake discs and the temperature to which they are heated by the color of the steel from which the disc is made:
- yellow - temperature 150-280 degrees,
- blue - temperature 300-450 degrees,
- black - temperature 450-500 degrees.
GOST 22235-76
INTERSTATE STANDARD
FREIGHT CARS FOR MAINS
RAILWAYS 1520 mm GAUGE
GENERAL REQUIREMENTS FOR SAFETY
IN THE PRODUCTION OF LOADING AND UNLOADING
AND SHUNTING
IPK STANDARDS PUBLISHING HOUSE
Moscow
INTERSTATE STANDARD
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FREIGHT CARS OF THE MAIN RAILWAYS WITH A GAUGE OF 1520 mm General requirements for ensuring safety in the production of loading and unloading and shunting operations |
GOST |
Introduction date 01.01.78
This standard establishes general requirements for ensuring the safety of freight cars of 1520 mm gauge mainline railways during loading, unloading, compaction, loosening, heating of cargo, as well as during cleaning, shunting and other works.
1. GENERAL REQUIREMENTS FOR SAFETY OF CARS
1.1. Wagons of all types
1.1.1. To ensure the safety of wagons, the requirements of this standard must be met. Charters of railways and regulatory documentation for cars and devices that interact with them.
Damage to a wagon is considered to be a violation of the serviceable condition of the wagon or its components due to the influence of external influences exceeding the levels established in this standard.
Note. - Damage can be significant and be the reason for removing the wagon from service and insignificant, in which the wagon's performance is maintained.
1.1.2. It is only allowed to make changes in the design of wagons, weld doors, hatches, remove platform sides, gondola car doors, removable wagon equipment, etc. with the permission of the state railway authorities.
(Changed edition, Rev. No. 4, 5).
1.1.3. The loads acting on the cars and their elements during loading and unloading * and shunting operations must comply with the "Standards for strength calculations and design of the mechanical part of new and modernized cars of 1520 mm gauge railways of the Ministry of Railways (non-self-propelled)" and regulatory and technical documentation.
* Loading and unloading operations should also be understood as works on the cleaning of wagons, compaction, loosening and heating of goods.
(Changed edition, Rev. No. 2, 4).
1.1.4. Train sets, groups of wagons or individual wagons standing on railway tracks without a locomotive must be securely secured against spontaneous movement (leaving) with brake shoes, hand brakes or other means of securing established by state railway authorities
(New edition, Rev. No. 5).
1.2.10. Bulk cargo should be unloaded from gondola cars through hatches or with the help of car dumpers. Grab unloading of gondola cars, as an exception, is allowed when reloading goods transported by rail and water, provided that the wagons are preserved.
In other cases, unloading with a grab is allowed with the permission of the state railway authority.
(Changed edition, Rev. No. 1, 2, 4).
1.3. Covered wagons
When loading slate, firewood, pipes, plywood, sheet and sectioned non-packaged metal and other similar goods stacked along the car, the end walls of the car at the loading height must be protected by cargo laid across the car (vertically or horizontally), or shields from boards (slabs ) with a thickness of at least 40 mm. Linings should be placed under the outermost stacks of cargo to ensure that the stack is tilted inside the car.
In case of multi-tiered loading, packaged cargoes must be stacked close to each other or secured from possible displacement during transportation.
The stowage of these goods in the space between the doors must be carried out at a distance of at least 25 cm from the surface of the doors and ensure their free opening for unloading from both sides of the car.
The mass of the transport package (the mass of cargo with packaging means) must be such that the load on the floor of the car from the wheels of the loader with the package does not exceed the established p.
The dimensions of packages and block packages should not exceed 1770 mm in length and 1800 mm in height, the dimensions of packaged cargo packages - according to.
Loading and unloading of cargo, except for bulk cargo, through hatches in the roof of the car is not allowed.
Means of securing transport packages - according to GOST 22477.
1.4. Platform cars
1.4.1. Loading and unloading of goods on the folded longitudinal and end sides, as well as with the lowered longitudinal sides with the arrival of caterpillar and wheeled vehicles, should be carried out using transitional bridges and devices that protect the sides and floor of the platform from damage.
It is allowed to pass equipment on a rubber run along the folded end sides of the platforms. In this case, the load concentrated in the middle of the side on the site is 0.25´ 0.25 m, should be no more than 35 kN (3.5 tf). The load applied in the middle of each pair of platform end brackets shall not exceed 50 kN (5.0 tf).
It is not allowed to turn on the floor of the platform of crawler-mounted vehicles without preliminary protection of the floor from damage.
Cargoes transported in bulk, heavy steel ingots, blanks, beams, containers and other cargoes with a mass of individual pieces (places) of more than 500 kg must be laid on the floor of the platform without dropping.
(New edition, Rev. No. 5).
1.4.2. When loading or unloading goods that require the use of walkways, the sides of the platforms when they are fed to high (1100 mm or more) cargo platforms (ramps) must be lowered, and after being removed from the place of loading or unloading, they must be raised and secured.
If the cargo cannot be transported with the sides closed, then the sides of the loaded platform may be left in the lowered position with their appropriate fastening.
Before the loading of large-tonnage containers, the sides must be open (lowered), and after it is completed, they must be raised and secured.
With the sides raised, all wedge locks of the sides must be pushed down to failure. In the open (lowered) position, the sides must be fixed to the rings on the longitudinal beams, and in the absence of rings, tied with wire.
(Changed edition, Rev. No. 2, 3).
Table 1
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(New edition, Rev. No. 5). 2.3. Car dumpers 2.3.1. The gondola car fixing system in the car dumper rotor must ensure the loading of the gondola car bogies throughout the entire unloading cycle. 2.3.2. The total load from the stops (shanks of vibration devices, support beams on the hooks of the clamps), transferred to the top trim of the gondola car, should not exceed the maximum calculated weight of the gondola car and should be distributed evenly on both walls of the gondola car body with a deviation of not more than 10% from the average value. The load transmitted from individual stops must be evenly distributed over the entire width of the gondola top rail over a length of at least 0.8 m and not exceed 98 kN (10 tf) for a 4-axle, 147 kN (15 tf) for a 6-axle, 196 kN (20 tf) for an 8-axle gondola car. The dimensions and placement of stops should ensure the position of each stop above the gondola car rack. The stops must be reinforced with elastic elements. The length of each support element in contact with the upper trim of the gondola car and transmitting vibration loads must be at least 3 m - for machines operating in shock-vibration mode; 2.5 m - for machines operating in vibration mode. The contact surfaces of the supporting elements must be smooth, without protruding seams and overlays. Vibrators should be installed without impacts with overlapping support elements of two racks on each side of the gondola car body in turn above each bogie. The duration of the vibratory machine for one unloading of the gondola car should not exceed 7 minutes. (Changed edition, Rev. No. 2, 3). 2.5.3. Vibratory rippers-unloaders designed for loosening and unloading cargo by vibration of the gondola car body should be used only in conjunction with guide devices that exclude contact of the vibrating parts of the rippers with the elements of the gondola car in the loosening mode. In the loosening mode, the parameters of the machine must comply with the requirements of paragraph. In the unloading mode, the parameters of the machine must comply with the requirements of paragraph. 2.5.4. Vibrating pin rippers, vibrating rippers-unloaders, ripping machines, as well as specialized devices with wedge, knife, bucket (excavator) and other types of scrapers must be equipped with automatic devices (limiters) that provide a gap of at least 0.05 m from the working bodies to the plane end walls (doors), side walls and floor of wagons. This distance must also be ensured both when moving self-propelled units along gondola cars and platforms, and when moving gondola cars and platforms under the units. It is allowed to operate the machines without these automatic devices with the following restrictions on the movement of the working bodies during the operation of the machines: The distance from the axis of the railway track to the outer contour of the extreme working body horizontally - no more than 1.3 m when the axis of the machine is aligned with the axis of the track; The distance from the level of the rail heads to the working body in the lower position is at least 1.5 m; The distance from the plane of the end walls (doors) to the working body is at least 0.05 m. 2.5.5. A resonant vibrating machine with a car rigidly fixed on its bridge must ensure the acceleration of horizontal vibrations of the car at floor level by no more than 12 m/s 2 , and vertical vibrations by no more than 9 m/s 2 . The amplitude of horizontal vibrations of bridge and bridgeless machines should be no more than 110 mm, and vertical vibrations - no more than 25 mm. The angle of the transverse inclination of the rail track on the machine should not be more than 10° (maximum elevation of the upper rail - 0.265 m). The constant force of the longitudinal compression of the devices of the automatic coupling of cars by the mechanisms of the machines in the process of unloading must be at least 196 kN (20 tf) and not more than 980 kN (100 tf). The gaps between the rails on the bridge of the machine and the rails of the railway track on the approaches to the machine should not be more than 0.02 m. In the process of unloading, the wagon must be in a disengaged state, while the braking equipment must be secured with devices that limit the relative movements of the elements of the brake linkage. With unsecured moving doors, unloading of the car on the machine is not allowed. The open door of the car must be secured with a clamp, which excludes its collision with the door stops, and the closed one, if it moves during operation, with additional fastening of the door lock element. The machine must have interlocks that exclude the possibility of the carriage being pushed onto the bridge or its removal until the machine is ready for the corresponding operation, as well as counter rails at the upper line of the track on the bridge of the machine and on the approach to the machine. After unloading, check the tightness of the brake pneumatic network and tighten the fastening of the loose threaded connections of the cars, if necessary, add oil to the axle boxes with plain bearings. (Changed edition, Rev. No. 2, 3). 2.6. Teplyaki 2.6.1. Teplyaks (garages) with a convective method,radiation and combined (radiation with convective)heating of cargo in wagons must be equipped with cooling devices (if operating modes requiring cooling are envisaged), devices for automatic recording of the temperature regime in the heating section and limiting the maximum allowable heating temperature, a set of instrumentation for measuring temperature, devices that protect axle boxes and brake devices from moisture ingress. The temperature should be measured: At the coolant inlet to the section; At least at three points along the length of the greenhouse section - at a distance of 0.20-0.25 m from the walls of the car and at a height of 1.5 m from the level of the rail heads; On the brake cylinder of the car, which is second from the section gate; At the inlet of water used to cool the wagons. With a stable thermal mode of operation of the greenhouse, the temperature measurement on the brake cylinder must be carried out at intervals agreed with the Railway Administration. (Revised edition, Rev. No. 5). 2.6.2. Newly built greenhouses must be tested in accordance with the clause with heating the cargo in the wagons in winter conditions. Based on the test results, the monitoring and control equipment should be adjusted, operating instructions for the greenhouse and regime warm-up charts should be developed. Before the start of seasonal work, the operated greenhouses must be subjected to control tests conducted by a commission with the participation of representatives of enterprises using greenhouses and the state railway authority, and the identified deficiencies are eliminated. (New edition, Rev. No. 5). 2.6.3. The operating mode of the greenhouse should not allow the heating of wagon parts above the level established by p. When heating cargo in tanks, the temperature in the greenhouse, in addition, must be limited in accordance with the requirements of the explosion safety of the cargo. When heating thermal or coking coals in gondola cars, the temperature in the section should not exceed 100 °C. Warming up in the greenhouses of covered wagons loaded with fuels and lubricants is not allowed. 2.6.4. At section temperatures up to 60° Since the time spent by cars in the greenhouse is not limited. At temperatures from 60 to 100° From the time of warming up the cargo in the wagons should not exceed 1 hour, and with a longer warm-up time, cooling devices should be used. The maximum temperature in the section must not exceed 130 °C. 2.6.5. In greenhouses equipped with cooling devices, the lower cooling system is switched on when the temperature of the brake cylinder reaches 55 °C or in the section 100 °C. The cooling system should not be turned off until the end of the cargo heating process. The upper cooling system is switched on when the temperature reaches 100 °C in the section every hour for 3 minutes and 5 minutes before the wagons are taken out of the greenhouse. The water used for cooling should be supplied to the parts and assemblies of the cars evenly along the entire length of the greenhouse and should not be contaminated with mechanical or chemical impurities. The pressure in the network must be at least 0.25 MPa (0.5 kgf / cm 2), and the water temperature should not exceed 25 ° C. (Revised edition, Rev. No. 4). 2.6.6. Before the wagons are fed into the greenhouse, the air from the brake system must be released, the brake line sleeves must be connected. Before entering the wagons into the greenhouse with irrigation devices, the brake devices of the wagons must be installed: Rubber band or clamp on the brake cylinder rod, which does not have a sealing gland; Sealing device at the junction of the front (rod side) cover with the brake cylinder body; Rubber plugs in the atmospheric opening of the air distributor and the moisture outlet in the lower part of the brake cylinder; Protector for auto damper and linkage adjuster; Plugs on sleeves of extreme cars. (Changed edition, Rev. No. 2, 3, 5). 2.6.7. After the wagons are taken out of the greenhouse, it is necessary: Remove the protective devices from the brake devices of the wagons; Check the operation of the braking equipment for braking and release; Lubricate all pivot joints of the linkage and auto-adjusters of the piston stroke of the brake cylinder; Check the condition of the box cars. The malfunctions of the brake equipment and axle boxes of the wagons identified during the inspection must be eliminated by workers specially trained and authorized to perform these works. (New edition, Rev. No. 5). 2.6.8. When operating greenhouses with a top coolant supply and peaked technology for heating frozen cargo in cars, the maximum temperature of the coolant at the inlet to the section should be no more than 160 °C, in the section 90 °C and at the exit from the section 60 °C. With combined heating (side - monotonous and top - according to sharp-peak technology), the temperature limits are set depending on the degree of freezing of the cargo (outside temperature). In case of significant freezing of the load (outside temperature below minus 20 °C), the maximum temperature of the coolant during the first heating cycle is allowed no more than 170 °C, in the section 100 °C and at the outlet of the recirculation (waste coolant) from the section 65 °C. Upon reaching the specified temperatures in the section or recirculation, the heating of the cargo stops. If it is necessary to carry out repeated cycles, the temperature should not exceed 160, 90 and 60 °C, respectively. (New edition, Rev. No. 5). 2.6.9. In greenhouses with radiation and combined (radiation with convective) methods of heating the cargo, the maximum temperature of the coolant at the inlet to the section should be no more than 160 °C, in the section 90 °C and on the brake cylinder 55 °C. (Introduced additionally, Rev. No. 5). 2.7. Hump and shunting devices 2.7.1. The design and operation of marshalling devices at marshalling, freight, district and other stations should ensure the collision of wagons during their sorting at a speed established by the normative and technical documentation (NTD) for wagons. The list of wagons whose passage through the marshalling yard is prohibited is established by the state railway authority in accordance with the requirements of the NTD for wagons. (Changed edition, Rev. No. 3, 4). 2.7.2. Compressor installations of automated and mechanized sorting humps must provide, during the dissolution of trains, the supply of compressed air to the most distant car retarders at a pressure of at least 0.65 MPa (6.5 kgf / cm 2), and in the interval between dissolutions - at least 0.70 MPa (7 kgf / cm 2). (Changed edition, Rev. No. 2, 3). 2.7.3. Carriage retarders must: Meet the requirements, p. (drawing 5); In the inhibited (working) position, ensure the braking of freight cars of all weight categories and axles, which are lowered from the marshalling yards; In the braked (initial) position, allow movement with the locomotive of any rolling stock that is allowed to pass through marshalling yards (refrigerated trains, passenger cars and special rolling stock), at a speed of up to 11.1 m/s (40 km/h); Ensure the interaction of the braking system with one or simultaneously with two wheels of the wagon wheelset. When interacting with one wheel of a wheelset, a counter rail must be installed on the second rail; Have a two-way impact braking system that automatically adjusts to the distance between the wheels and provides the same pressing force on the inner and outer surfaces of the wheel rim; In the process of braking cars, ensure that the pressing force is within the threefold load on the wheel from the mass of the car, but not more than 147 kN (15 tf); To allow the entry speed of cuts from wagons of any weight category to the braked retarder for retarders T-50, RNZ-2, RNZ-2M, PNZ-1 and PGZ up to 6.5 m/s (23.4 km/h); KNP-5 and KB - up to 7 m/s (25.2 km/h); VZPG of all modifications - up to 8 m/s (28.8 km/h); VZP of all modifications - up to 8.5 m/s (30.6 km/h); Provide at an air pressure of 0.65 MPa (6.5 kgf / cm 2) the tire pressing force on the side surfaces of the wheels within: T-50 - (85 ± 5) kN [(8.7 ± 0.5) tf], KNP-5 - (125±5) kN [(12.8±0.5) tf], VZPG and RNZ-2 - no more than 147 kN (15.0 tf). Weight retarders KV-3 must ensure that in the braking position the elevation of the support beam tire above the level of the rail heads is at least 5 mm when the wheels of the car of any weight are on it. The speed of a wagon hitting a brake shoe when lowering wagons from marshalling yards should not exceed 4.5 m/s (16.2 km/h). The speed at which the car enters the parking brake position when the cars are braked with hand shoes, as a rule, should not exceed 3.5 m/s (12.6 km/h). (New edition, Rev. No. 5). 2.7.4. When moving wagons by any means, the traction force must be transmitted through the automatic coupler, rim, wheel axle or wagon pulling bracket. The movement of wagons by directly pushing them with bulldozers, tractors and other vehicles and lifting mechanisms is not allowed. Rope (rope) support on wagon elements is not allowed. The number of loaded wagons simultaneously pulled by the bracket on a straight horizontal section of the track, with an angle between the cable and the longitudinal axis of the track up to 5° should not exceed 14 for 4-axle cars, 10 for 6-axle cars and 8 for 8-axle cars, 10 units for hopper cars. (Changed edition, Rev. No. 2, 3). 2.7.5. The design of undercarriage shunting devices must exclude the formation of dents and notches on the crest, wheel tread and wheel pair axle. 2.8. railway track 2.8.1. Permissible radii of curves of the railway track, on which the movement and coupling of cars is carried out, are given in Table. . table 2
6. The limitation of the validity period was removed according to protocol No. 4-93 of the Interstate Council for Standardization, Metrology and Certification (IUS 4-94) 7. REPUBLICATION (June 1999) with Amendments No. 1, 2, 3, 4, approved in May 1981, October 1984, December 1989, March 1997 (IUS 8-81, 1-85 , 3-90, 6-97) |
When braking, the process of friction between the brake pad and the wheel occurs at the points of their actual contact. The total area of these contacts is insignificant compared to the area covered by the brake shoe. Since heat is released only at the points of actual contact, the heat flux densities and temperature flashes in them can reach large values, causing the friction surface to glow and the metal to go into a plastic state at these points. In this case, the deformation of the metal or its rapid wear occurs, and the place of the temperature flash moves in accordance with the change in contact specific pressures.
The distribution of the heat flux over the entire friction area occurs near the contact surface, and its density decreases sharply compared to the points of actual contact, acquiring a value corresponding to the geometric dimensions of the contacting bodies. Accordingly, the temperature in the surface layers also changes.
It should also be borne in mind that the temperature of any point on the wheel tread surface for each of its revolutions has some fluctuations, which are the result of the fact that when the point under consideration leaves the contact zone, there is a slight decrease in temperature due to heat removal inside the wheel and into the environment; when passing a point in the zone of contact between the wheel and the brake pad, its temperature rises and exceeds the calculated average value. However, when solving thermal problems, this phenomenon can be neglected due to the inertia of the processes and the heat supply over the entire friction surface of the wheel can be considered continuous. Thus, to calculate this temperature Dt at any moment of braking time I, the following expression can be used
The highest temperature during stopping braking on the wheel surface is reached in the middle of this process I = 0.5*v Temperature on the wheel surface at the moment the train stops
Temperature at steady braking (constant speed)
where Of is the coefficient of heat transfer to the environment, kcal/m2s °С; dr - heat flux density, kcal/(m2s); X - coefficient of thermal conductivity, kcal/(ms °С); y - specific gravity, kgf/m3; с - specific heat capacity, kcal/(kg °С); r - braking time to stop, s.
The values of X, y, c are given in Table. 7.1.
Temperature coefficient values Table 7.1
The heat flux density at the initial moment of braking is determined by the formula
where aL - dimensionless heat flux distribution coefficient; Ak is the width of the friction surface of the wheel, m (take equal to 0.09 m).
The heat flux distribution coefficient for the wheel can be determined from the data given in Table. 7.1 (for pads ak=1-al).
The above formulas were obtained for the heating conditions of a semi-infinite body, i.e. when the heat flow has not yet reached the surface that limits the heated body from the side opposite to the heat supply. Such an assumption is acceptable when heating bodies having a sufficiently large thickness. In the majority of actual braking modes for operating conditions, excluding particularly long ones, these formulas can be recommended for calculations. In the latter case, there are special correction factors determined from the graphs.
A preliminary estimate of the heat transfer coefficient depending on the speed (m/s) can be made using the empirical formula (7.3).
Table 7.2
Values of heat flow distribution coefficient
Due to the fact that the braking force changes in the process of filling the brake cylinders and with a change in the speed of movement, the value of At is calculated based on the length of the actual braking distance 5T and the brake preparation time 1p
where (Od is the main specific resistance to the movement of the train (taken equal to 2 N / kN).
In this case, the time I in the expressions for calculating thermal conditions is taken reduced by the preparation time 1l, if 1 > 1.
Based on expressions (7.1), (7.2), we obtain a formula for determining the wheel diameter d, which provides the necessary heat convection to avoid its overheating during emergency braking
When braking, the kinetic energy of the train is converted into heat, heating the brake pads (or discs) and wheels. Considering that with an increase in the speed of movement, for example, the amount of this energy quadruples, the thermal stability of the friction pair becomes of particular importance, the violation of which leads to the loss of frictional qualities and the occurrence of emergencies on the rolling stock.
The permissible value of pressing A", 4 (kN) on a cast-iron brake shoe according to the thermal regime during stopping braking can be found from the expressions where K0 is the initial braking speed, m / s;
tmax is the maximum allowable temperature of the brake pad during stopping braking, °C (for cast iron - 600 °C, for composite - 400 °C);
Od is the coefficient of heat transfer to the environment.
Similarly, the maximum pressure on temperature regimes for composite pads is determined by the expression
Stopping braking time I (s) with a braking distance of 5Т (m) known according to the standards on a given slope from the initial braking speed K0 (m/s) is under the assumption of uniformly slow motion
In the process of braking, a significant heating of the tread surface and the surrounding layers of the wheel occurs. At the same time, for the wheels of traction rolling stock, the tires of which are pressed in in a heated state, there is a threat of its turning and slipping. The criterion for the permissible weakening of the tire tension is its increase in millimeters per 1 m of the wheel diameter ek, which should not exceed 1.2 mm:
for emergency braking
for service braking in long-term mode where 50 is the braking distance, respectively, when following the locomotive with the train and singly, m;
Vts, N - respectively, the thickness and width of the bandage, m;
\U - work during braking for time 1 per wheel, Nm;
Pe is a coefficient that takes into account the share of energy perceived by the dynamic brake.