In metro system with less equipment and less weight the proven system to be used , in brake system at present in India Twin pipe architecture is mainly used.
To overcome weight, cost and maintenance less Single pipe architecture brake system can be introduced.
In Railway Application, two main types of Brakes control architecture are available:
- Bake Pipe (BP) Control.
- Electro-Pneumatic(EP) Brake control
|BP Control||The brake pipe control concept is mainly defined in UIC standards and is standard in freight or regional trains application where the brake is little used and with low deceleration level. Driven by a locomotive . Main line EMU BP is mainly used in rescue application .|
|EP brake control||In metro (EMU) operation, brake application are very frequent ,high level of decelerations and good accuracy in stopping distance are required. To satisfy these requirement the optimized use of ED brake and capacity to manage degraded modes become key issue|
Standard specification of Brake system used in Indian Metro system
Brake System Over view:
The brake system includes:
- Compressed air supply by an oil free piston type air compressor and air dryer unit
- An electro-pneumatic, microprocessor controlled direct service brake which performs the blending function depending on the brake demand signal and the dynamic brake performance.
- An automatic indirect brake which is applied for back-up mode and for an emergency brake application in the event of failure of the direct service brake.
- Possibility of towing mode operation based on brake pipe (indirect brake).
The brake system is microprocessor controlled and provides an extensive brake management that controls, manages and diagnoses equipment (excluding Parking Brake equipment, monitored by the vehicle control) that is involved in the braking process and communicates with the train management system to provide train wide safety, reliability and availability
The service brake (direct) is controlled by the brake management via microprocessor based electronic control units. The brake system is based on the „fail safe” principle during emergency brake, controlled by the emergency brake loop.
In order to achieve redundancy during service and emergency brake an indirect brake – hardware based – is provided, fully independent from the service brake circuit.
The brake management controls the following brake systems all over the train:
- Pneumatic Service Brake (with ED-Brake Brake priority)
- Wheel Slide Protection
For the service brake the ED-Brake is prioritized in order to minimize the wear of the friction brake.
The friction brake equipment performs the following functions:
- Service Brake Service Brake with (at times also partial)
- ED-Brake Brake failure
- Emergency Brake Emergency Brake (released by driver’s emergency push button)
- Parking Brake Stopping Brake
- Holding Brake
Types of Brakes:-
1. Service Brake – ( Full Service Brake ) Electric Regenerative brake and Electro – Pneumatic friction brake blending, Load weighed and
2. Emergency Brake – EP Friction Brake, Load weighed
The Train is equipped with EB Loop Wire ,The EB brake Loop is connected to Emergency Brake
Magnet Valve ,which is opened when de-energized and closed when energized (Fail Safe
System) So in case emergency brake magnet valve is de-energized by interrupting EB Loop, the
emergency brake will be applied automatically
3. Holding Brake – The Holding brake is provided to prevent the train from rolling backwards on the rising gradient.
VVVF have control on Roll Back application and release, The Holding Brake is 70% of Full service
4. Parking Brake – Spring Applied Pneumatic release system
5. BP-Back Up Brake – Brake Pipe (BP) controlled back-up brake system is provided in order to take over the brake
control function in case of failure of individual electronic or electrical control elements
Traction and brake Logic Block Diagram with Driver and with System
Wheel Slide Protection
Single –Pipe Architecture
In single-pipe architecture, only EP (electro pneumatic ) brake control along hard wire with train line is used
In twin-Pipe architecture BP control provided in addition to single-pipe architecture
The presence of Back up Brake Pipe
- Doesn’t improve the general availability of the train
- Additional equipment mean more weight
- Additional maintenance
- Can impact the general availability of the train ( if there is a leakage in brake pipe the train have to be withdrawn )
- Intrinsic reliability of brake system is decreased
- During recuse of dead train with healthy train – brake is controlled by BP back up system in Twin pipe architecture.
- During recuse of dead train with healthy train- brake is controlled by direct brake with 100% braking and motoring by driver TBC ( Traction and brake control) handle
Advantage of Single Pipe architecture. :
- Reduce weight.
- Less maintenance.
- Easy trouble shooting.
Conclusion of Brake system: The Single Pipe architecture brake system has a proven track record on conventional trains. This integrated mechatronic system comprising pneumatic, electronic and software elements allows all necessary functions such as load dependent braking, service braking, emergency braking, wheel slide protection and remote release to be individually controlled, in a decentralized fashion for each bogie. With this revised and defined brake system, the performance of the system is optimized with increased maintainability.