It's time to talk about devices designed to control the brakes. These devices are called "cranes", although a long evolutionary path has taken them far enough from cranes in the familiar everyday sense, turning them into rather complex pneumatic automation devices.
The good old 394 spool valve is still in use on rolling stock
1. Driver's cranes - a brief introductory
A-priory
Train driver crane - a device (or a set of devices) designed to control the magnitude and rate of pressure change in the brake line of the train
Train driver cranes currently in use can be divided into direct control devices and remote control cranes.
Direct control devices are classics of the genre, installed on the vast majority of locomotives, multiple unit trains, as well as special-purpose rolling stock (various road vehicles, railcars, etc.) No. 394 and conv. No. 395. The first of them, depicted on the KDPV, is installed on freight locomotives, the second on passenger locomotives.
In the pneumatic sense, these cranes do not differ from each other in any way. That is absolutely identical. The 395 valve on the top has, molded with it, a tide with two threaded holes, where the “bank” of the electro-pneumatic brake control controller is installed
395th crane driver in natural habitat
These devices are most often painted bright red, which indicates their exceptional importance and special attention, which should be given to them by both the locomotive crew and the technological personnel serving the locomotive. Another reminder that train brakes are everything.
These devices are directly connected to the pipelines of the feed (PM) and brake lines (TM) and, by turning the handle, direct control of the air flow is carried out.
In cranes with remote control, not the crane itself is installed on the driver’s console, but the so-called control controller, which transmits commands via a digital interface to a separate electric pneumatic panel, which is installed in the engine room of the locomotive. On the domestic rolling stock, the long-suffering crane of the driver is used. No. 130, which for a long time made its way to the rolling stock.
Crane controller conv. No. 130 on the control panel of the electric locomotive EP20 (on the right, next to the pressure gauge panel)
Pneumatic panel in the engine room of the electric locomotive EP20
Why is it done this way? In order to have, in addition to manual control of the brakes, a full-time ability to control the automatic, for example, from the automatic train control system. On locomotives equipped with a 394/395 crane, this required the installation of a special attachment on the crane. As planned, the 130th crane is integrated into the train control system via the CAN bus, which is used on domestic rolling stock.
Why did I call this device long-suffering? Because he was a direct witness to his first appearance on the rolling stock. Such devices were installed on the first numbers of new Russian electric locomotives: 2ES5K-001 "Ermak", 2ES4K-001 "Donchak" and EP2K-001.
In 2007, I participated in the certification tests of the electric locomotive 2ES4K-001. It was the 130th crane that was installed on this machine. However, even then there was talk about its low reliability, moreover, this miracle of technology could spontaneously release the brakes. Therefore, the Ermaks, Donchaks and EP2K were abandoned very soon and went into series with 394 and 395 cranes. Progress was delayed until the new device was finalized. This crane returned to Novocherkassk locomotives only with the start of production of the EP20 electric locomotive in 2011. But Ermaki, Donchaki and EP2K did not receive a new version of this crane. EP2K-001, by the way, with the 130th crane, is now rotting at the reserve base, as I recently found out from the video of one railway abandoned fan.
However, railway workers do not have full confidence in such a system, therefore all locomotives equipped with a 130 crane are also equipped with backup control valves, which allow, in a simplified mode, to directly control the pressure in the brake line.
Backup brake control valve in EP20 cab
On locomotives, a second control device is also installed - auxiliary brake valve (KBT), designed to control the brakes of the locomotive, regardless of the train brakes. Here it is, to the left of the train crane
Auxiliary brake valve cond. №254
The photo shows a classic auxiliary brake valve, arb. No. 254. It is installed in many places so far, both on passenger and freight locomotives. Unlike wagon brakes, brake cylinders on a locomotive never are not filled directly from the reserve tank. Although both the reserve tank and the air distributor are installed on the locomotive. In general, the layout of the locomotive brakes is more complex, due to the fact that there are more brake cylinders on the locomotive. Their total volume is significantly higher than 8 liters, so it will not be possible to fill them from the reserve tank to a pressure of 0,4 MPa - it is necessary to increase the volume of the reserve tank, and this will increase its charging time compared to wagon SR.
On the locomotive, TCs are filled from the main tank, either through the auxiliary brake valve, or through the pressure switch, which is acted upon by the air distributor, which is actuated by the train driver's crane.
Crane 254 has the feature that it can itself work as a pressure switch, allowing the release (step!) of the brakes of the locomotive when the train is braked. Such a scheme is called the scheme for switching on the KBT as a repeater and is used on freight locomotives.
The auxiliary brake valve is used for shunting movements of the locomotive, as well as for securing the train after stopping and during parking. Immediately after the train stops, this crane is placed in the very last braking position, and the brakes in the train are released. The brakes of the locomotive are able to keep both the locomotive and the train on a fairly serious slope.
On modern electric locomotives, such as EP20, other KVT are installed, for example, arb. №224
Auxiliary brake valve cond. No. 224 (on the right on a separate panel)
2. The device and principle of operation of the driver's crane conv. №394/395
So, our hero is an old, time-tested and millions of kilometers crane 394 (and 395, but it is similar, so I will talk about one of the devices, keeping in mind the second one). Why is he, and not the modern 130th? First, the 394 crane is more common today. And secondly, the 130th crane, or rather its pneumatic panel, is similar in principle to the old man 394.
Crane driver conv. No. 394: 1 - base of the exhaust valve shank; 2 - body of the lower part; 3 - sealing cuff; 4 - spring; 5 - exhaust valve; 6 - bushing with exhaust valve seat; 7 - balancing piston; 8 - sealing rubber cuff; 9 - sealing brass ring; 10 - body of the middle part; 11 - body of the upper part; 12 - spool; 13 - control handle; 14 - handle lock; 15 - nut; 16 - clamping screw; 17 - rod; 18 - spool spring; 19 - pressure washer; 20 - mounting studs; 21 - pin-lock; 22 - filter; 23 - feed valve spring; 24 - feed valve; 25 - sleeve with a seat of the feed valve; 26 - reducer diaphragm; 30 - adjusting spring of the gearbox; 31 - adjusting glass reducer
How are you? Serious instrument. This device consists of an upper (spool) part, a middle (intermediate) part, a lower (equalizing) part, a stabilizer and a gearbox. The gearbox is shown at the bottom right in the figure, I will show the stabilizer separately
Driver's crane stabilizer conv. No. 394: 1 - cork; 2 - throttle valve spring; 3 - throttle valve; 4 - throttle valve seat; 5 - calibrated hole with a diameter of 0,45 mm; 6 - diaphragm; 7 - stabilizer body; 8 - emphasis; 10 - adjusting spring; 11 - adjusting glass.
The operating mode of the tap is set by turning the handle, which rotates the spool, tightly ground (and thoroughly lubricated!) To the mirror in the middle part of the tap. There are seven positions, they are usually denoted by Roman numerals.
- I - vacation and charging
- II - train
- III - overlap without power leakage in the brake line
- IV - overlap with power leakage from the brake line
- Va - slow deceleration
- V - braking at a service pace
- VI - emergency braking
In the mode of movement in traction, freewheeling and parking, when it is not necessary to actuate the brakes of the train, the crane handle is set to the second, train position.
The spool and spool mirror contain channels and calibrated holes through which, depending on the position of the handle, air flows from one part of the device to another. It looks like a spool and its mirror
In addition, the driver's crane 394 is connected to the so-called surge tank (UR) with a volume of 20 liters. This tank is the pressure gauge in the brake line (TM). The pressure that is set in the surge tank will be maintained by the equalizing part of the driver's valve and in the brake line (except for positions I, III and VI of the handle).
The pressures in the surge tank and the brake line are displayed on the control pressure gauges installed on the dashboard, usually next to the driver's tap. A two-pointer manometer is often used, for example, this one
The red arrow shows the pressure in the brake line, the black arrow shows the pressure in the surge tank
So, when the crane is in the train position, the so-called charging pressure. For multiple unit rolling stock and passenger trains with locomotive traction, its value is usually 0,48 - 0,50 MPa, for freight trains 0,50 - 0,52 MPa. But most often it is 0,50 MPa, the same pressure is used on the Sapsan and Lastochka.
The devices supporting the charging pressure in the UR are the crane reducer and stabilizer, which operate completely independently of each other. What does a stabilizer do? It continuously bleeds air from the surge tank through a calibrated 0,45 mm hole in its body. Constantly, without interrupting this process even for a moment. Air is released through the stabilizer at a strictly constant rate, which is maintained by a throttle valve inside the stabilizer - the lower the pressure in the surge tank, the more the throttle valve opens. This rate is much lower than the service braking rate, and it can be adjusted by turning the adjusting cup on the stabilizer body. This is done to eliminate in the surge tank supercharged (that is, exceeding the charging) pressure.
If the air from the surge tank is constantly leaving through the stabilizer, then sooner or later it will all leave? He would have left, but the gearbox would not give. When the pressure in the UR drops below the charging one, a feed valve opens in the gearbox, connecting the surge tank with the feed line, replenishing the air supply. Thus, in the surge tank, in the second position of the valve handle, a pressure of 0,5 MPa is constantly maintained.
This process is best illustrated by the following diagram.
The action of the driver's crane in the II (train) position: GR - main tank; TM - brake line; UR - surge tank; At - atmosphere
What about the brake line? The pressure in it is maintained equal to the pressure in the surge tank using the equalization part of the valve, which consists of a balancing piston (in the center of the diagram), a supply and exhaust valve driven by a piston. The cavity above the piston communicates with the surge tank (yellow area) and below the piston with the brake line (red area). When the pressure in the HP increases, the piston goes down, communicating the brake line with the supply line, causing an increase in pressure in it, until the pressure in the TM and the pressure in the HP become equal.
When the pressure in the surge tank is reduced, the piston moves up, opening the exhaust valve, through which the air from the brake line escapes into the atmosphere, until, again, when the pressures above and below the piston equalize.
Thus, in the train position, the pressure in the brake line is maintained equal to the charging pressure. At the same time, leaks from it are also fed, since, and I constantly talk about this, it definitely and always has leaks. The same pressure is set in the spare tanks of the cars and the locomotive, also with the draining of leaks.
In order to activate the brakes, the driver puts the crane handle in the V position - braking at a service pace. In this case, air is released from the surge tank through a calibrated hole, providing a pressure drop rate of 0,01 - 0,04 MPa per second. The process is controlled by the driver on the surge tank pressure gauge. While the valve handle is in the V position, the air leaves the surge tank. The equalizing piston is activated, rising up and opening the exhaust valve, relieving pressure from the brake line.
To stop the process of releasing air from the surge tank, the driver puts the valve handle in the shutdown position - III or IV. The process of releasing air from the surge tank, and therefore from the brake line, is stopped. This is how the stage of service braking is performed. If the brakes are not effective enough, another step is performed, for this the driver's crane handle is again transferred to position V.
At regular official braking, the maximum depth of discharge of the brake line should not exceed 0,15 MPa. Why? Firstly, it is pointless to discharge deeper - due to the ratio of the volumes of the reserve tank and the brake cylinder (TC), the pressure on the cars in the TC will not build up pressure more than 0,4 MPa. A discharge of 0,15 MPa just corresponds to a pressure of 0,4 MPa in the brake cylinders. Secondly, it is simply dangerous to discharge deeper - with a low pressure in the brake line, the charging time for spare tanks will increase when the brake is released, because they are charged precisely from the brake line. That is, such actions are fraught with exhaustion of the brake.
An inquisitive reader will ask - what is the difference between overlappings in positions III and IV?
In position IV, the valve spool covers absolutely all holes in the mirror. The reducer does not drain the surge tank and the pressure in it is kept quite stable, because the leakage from the UR is extremely small. At the same time, the equalizing piston continues to work, replenishing leaks from the brake line, maintaining in it the pressure that was established in the equalizing reservoir after the last braking. Therefore, this provision is called "covering with power leakage from the brake line"
In position III, the valve spool communicates between the cavities above and below the equalizing piston, which blocks the work of the equalizing body - the pressures in both cavities fall simultaneously at the rate of leakage. This leakage is not replenished by the equalizing body. Therefore, the III position of the valve is called "overlap without power leakage from the brake line"
Why are there two such provisions and what overlap does the driver use? Both, depending on the situation and the type of locomotive service.
When controlling passenger brakes, according to the instructions, the driver is obliged to put the valve in position III (overlap without power) in the following cases:
- When following a prohibition signal
- When controlling the EPT after the first stage of regulating braking
- When following a steep downhill or dead end
In all these situations, spontaneous release of the brakes is unacceptable. And how can it happen? Yes, it’s very simple - passenger air distributors operate on the difference between two pressures - in the brake line and in the reserve tank. When the pressure in the brake line is increased, the brakes are fully released.
And now imagine that we braked and put in position IV, when the valve feeds leaks from the brake line. And at this time, some idiot in the vestibule slightly opens, and then closes the stop-cock - the bastard is playing around. The driver's valve drains this leak, which leads to an increase in pressure in the brake line, and the passenger air distributor, which is sensitive to this, gives full release.
On trucks, position IV is mainly used - the cargo VR is not so sensitive to pressure increase in the TM and has a harder vacation. In III, the position is set only if there is a suspicion of an unacceptable leak in the brake line.
How are the brakes released? For a complete vacation, the driver's crane handle is placed in position I - vacation and charging. In this case, both the surge tank and the brake line are connected directly to the supply line. Only the filling of the surge tank goes through a calibrated hole, at a fast, but moderate enough pace, allowing you to control the pressure on the pressure gauge. And the filling of the brake line is carried out by a wider channel, so that the pressure there jumps immediately to 0,7 - 0,9 MPa (depending on the length of the train) and remains so until the crane handle is put in the second position. Why is that?
This is done in order to push a large amount of air into the brake line, to sharply increase the pressure in it, which will allow the release wave to reach the last car. This effect is called impulse overcharging. It allows both to speed up the vacation itself, and to ensure faster charging of spare tanks throughout the train.
Filling the surge tank at a predetermined rate allows the tempering process to be controlled. Upon reaching the charge pressure in it (on passenger trains) or with some overestimation, depending on the length of the train (on freight trains), the driver's crane handle is placed in the II train position. The stabilizer eliminates the overcharging of the equalizing reservoir, and the equalizing piston quite quickly makes the pressure in the brake line equal to the pressure in the equalizing reservoir. Here's how the process of fully releasing the brakes to charging pressure looks like from the driver's point of view
Stepped release, in the case of control of the EPT or on freight trains in the mountain mode of operation of the air distributor, is performed by setting the valve handle to the II train position, followed by transfer to the overlap.
How is the electro-pneumatic brake controlled? EPT is controlled from the same driver's crane, only the 395th, which is equipped with an EPT controller. In this “bank”, put on top of the handle shaft, there are contacts that, through the control unit, control the supply of positive or negative, relative to the rail, potential to the EPT wire, and also remove this potential to release the brakes.
When the EPT is on, braking is performed by setting the driver's crane to position Va - braking at a slow pace. In this case, the brake cylinders are filled directly from the electric air distributor at a rate of 0,1 MPa per second. The process is controlled by the pressure gauge in the brake cylinders. In this case, the discharge of the surge tank occurs, but rather slowly.
The release of the EPT can be done both stepwise, by setting the valve to position II, and completely, with setting to position I and overestimating the pressure in the UR by 0,02 MPa above the charge pressure level. This is what it looks like from the driver's point of view
How is emergency braking done? When setting the handle of the driver's crane to the VI position, the valve spool opens a wide channel, directly, the brake line to the atmosphere. The pressure drops from charging to zero in 3-4 seconds. The pressure in the surge tank also decreases, but more slowly. At the same time, emergency braking accelerators are activated on the air distributors - each VR opens the brake line to the atmosphere. Sparks fly from under the wheels, the wheels yuzat, despite the addition of sand under them ...
For each such “throw in the sixth”, the driver is waiting for an analysis in the depot - whether his actions were justified by the instructions of the Instructions for Controlling the Brakes and the Rules for the Technical Operation of the Rolling Stock, as well as a number of local instructions. Not to mention the stress that he experiences, "throwing in the sixth."
Therefore, if you go out onto the rails, slip under the closing barrier to cross the car, remember that for your mistake, stupidity, whim and bravado, a living person, the train driver, is ultimately responsible. And those people who will then have to reel the guts from the axles of the wheel pairs, remove the severed heads from the traction gearboxes ...
I don’t really want to scare anyone, but this is the truth - the truth written in blood and colossal material damage. Therefore, train brakes are not as simple as it might seem.
Сonclusion
I will not consider the operation of the auxiliary brake valve in this article. For two reasons. Firstly, this article is oversaturated with terminology and dry engineering and barely fits into the popular science framework. Secondly, consideration of the operation of the CVT requires the involvement of a description of the nuances of the pneumatic circuit of the locomotive brakes, and this is a topic for a separate discussion.
I hope that with this article I inspired superstitious horror in readers ... no, no, I'm joking of course. Jokes aside, I think it became clear that train brake systems are a whole complex of interconnected and extremely complex devices, the design of which is aimed at the operational and safe control of rolling stock. In addition, I really hope that I discouraged making fun of the locomotive brigade with a stop-crane game. At least someone...
In the comments, they ask me to tell you about Sapsan. There will be "Sapsan", and it will be a separate, good and large article, with very subtle details. This electric train gave me a short but very creative period in my life, so I really want to talk about it, and I will definitely fulfill my promise.
I would like to express my gratitude to the following people and organizations:
- Roman Biryukov (Romych RZHDUZ) for photographic material on the EP20 cockpit
- Site - for schemes taken from their resource
- Once again to Rome Biryukov and Sergey Avdonin for advice on the fine points of the brakes
Until next time, dear friends!
Source: habr.com