What Does a Train Brakeman Do?

Train braking is to artificially stop the train's movements, including decelerating it without accelerating or stopping it. To relieve or reduce the braking effect of a braked train or locomotive is called "mitigation". A set of equipment installed on a train for braking and mitigation, collectively referred to as a train "braking device". "Brake" and "braking device" are commonly known as "brakes". The implementation of braking is often referred to as "up brake" or "down brake", and the implementation of relief is referred to as "release brake".

Train brake

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Before introducing the braking device, let's talk about the braking method of the train:

Train brakes can be divided into "common brakes" and "emergency brakes" in terms of operation. Under normal circumstances, the brakes applied to adjust or control the speed of the train, including pit stops, are called "common brakes", which are characterized by a relatively mild effect and adjustable braking force. In emergency situations, the brake applied to stop the train as soon as possible is called "emergency braking" (also called "very braking"). It is characterized by its rapid action and the full use of train braking capacity. .

The distance traveled by the train from the moment the brake is applied to the moment the train speed drops to zero is called

Manpower is used as the braking motive force, and the steering direction of the handwheel and the magnitude of the hand force are used for manipulation and control. Simple in construction and low in cost, it is the oldest and most tenacious brake in railway history. In the early stage of railway development, there were only such brakes on locomotive vehicles. Each car or several cars was equipped with a brake officer, and operated in accordance with the driver's whistle command. Due to the weak braking force and slow movement, it was not convenient for the driver to directly manipulate it. It was soon replaced by non-human brakes, and hand brakes became auxiliary backup brakes.

The pressure air is used as the braking motive force to control the pressure by changing the pressure of the pressure air. The braking force is large, and the control is sensitive and convenient. China s railways use pressure air for short as wind

Automatic

Is electronically controlled

There is also a vacuum brake, which is characterized by using the atmosphere as the driving force to change the "vacuum degree" to operate and control. When the brake valve handle is placed in the relief position, the vacuum pump is in communication with the train tube, the air in the train tube and the brake cylinder is drawn away, and the upper and lower sides of the train tube and the brake cylinder are maintained at a high vacuum, and the piston falls due to its own weight. , The piston rod protrudes outward. When the brake valve handle is placed in the braking position, the train tube communicates with the atmosphere, and the atmosphere enters the train tube and the brake cylinder piston. Because the ball check valve has been dropped and closed when the air extraction is completed, the atmospheric pressure can only hold it down and cannot open the valve port, so the atmosphere cannot enter above the piston. The pressure difference between the top and bottom of the piston pushes the piston up, and the piston rod retracts into the cylinder to cause braking. Vacuum brakes are simpler to construct in non-manual brakes, cheaper, and easier to maintain. However, due to the limited atmospheric pressure itself, it is difficult to achieve "absolute vacuum". Moreover, larger brake cylinders and thicker train tubes are required. Therefore, some railways that use vacuum brakes, with the traction weight and operation The increase in speed has been or is being transitioned to air braking.

The so-called "locomotive air pressure" and "tail air pressure" are actually the air pressure of the master air cylinder of the locomotive and the air cylinder of the vehicle. Generally, the wind pressure of a passenger car is 600Kpa, which is equivalent to supporting the braking device with a wind pressure of 600Kpa, and maintaining a gap between the brake shoe and the tread of the wheel so that the train can move forward. When braking is needed, the driver presses the brakes, and the reduction of 40Kpa is the deceleration of the train. When the brake is reduced by 160Kpa, the brake shoes tightly hold the wheel tread, that is, the vehicle stops. In general: after the train starts to pass the exit signal or the train stops and restarts in the section, and when the wind pressure at the tail is abnormal, the running captain should actively call the train driver. The running length: ×× secondary tail pressure ×× Kpa. Train driver: ×× secondary tail pressure ×× Kpa, the driver understands. Before the train enters the growing downhill ramp or after the train braking test is performed, the train driver should actively call the operating captain. Train driver: ×× time commander, locomotive wind pressure ×× Kpa. Operating vehicle length: ×× secondary tail wind pressure ×× Kpa. Train driver: ×× secondary tail pressure ×× Kpa, the driver understands.