Brake System
There are 5 types of brakes available on this loco.
1. Automatic Train Brake (Pn)
2. Direct Brake (Pn)
3. Parking Brake (Spring Loaded)
4. Anti Spin Brake.(Pn)
5-Regeneration Brakes.(Elect)
Note: All the brake system functions are monitored by brake electronics and if there is any wrong configuration, the brake electronics do protective action along with P-1 message on screen. One circuit breaker is also provided in SB-2 for this brake electronics. In case of failure of brake electronics, crew should check this MCB.
Automatic Train Brake (A-9)- In both the cabs one Drivers Brake Controller (DBC) is provided which is the electrical switching equipment.
The function of the driver’s brake controller is to generate a variable voltage code in accordance with the position of the controller handle and to perform a number of ancillary electrical functions. A pneumatic valve is incorporated to provide a pneumatic emergency brake function in addition to the electronically controlled emergency brake.
This brake is utilized for charging and discharging the B.P. Pressure to apply/release train brake and also loco brakes in conjunction working.
This A-9 is remaining active in active cab only. Once the BL key is rotate from D to OFF, this handle will not functions, but its emergency position will act. This valve has following 6 positions
Handle position Pressure (kg/cm2 )
Release 5.4 ± 0.05 (LPO)
Running 5 ± 0.05
Initial Application 4.60 ± 0.05
Variable Full Service 3.35 ± 0.10
Emergency 0
Neutral 0 P
B. P. Charging system Running
Running
When the handle of the brake controller is placed in the ‘Running’ position, the ‘Running’ E.P. valve energized the E-70 valve and allow the 5 kg / cm2 pressure to go in brake pipe via cock no.70.
As such A-9 gives electrical command to valve E-70 and E-70 allows 5 Kg / cm2 pressure to enter in BP. The system for charging the brake pipe is fully self-maintaining.
Note:
coc 70 performs the function of A-8 (L&T) coc as in WAG-5/7 locos). This coc is provided with electrical switch due to which its position is monitored by brake electronics and if there is wrong configuration of coc, concerned P-1 message appears on the screen.
Braking:
When the handle of the brake controller is placed in a apply position the control circuits will produce the pressure to give the relevant brake pipe pressure.
The brake signal from the brake controller causes the control pressure to fall to the level demanded by the particular brake code which in turn causes the Air from the brake pipe now flows past to atmosphere through E-70 valve. The brake pipe pressure is then held constant at a reduced level, which corresponds to the particular braking requirement, against any normal leakage by the self maintaining feature.
Emergency:
When the handle of the brake controller is placed in the EMERGENCY’ position one of the cam operated switches within the controller opens to cut off the power supply to all E.P. valves of E-70, except the ‘Isolate’ E.P. valve which is already de-energized. At the same time the pilot valve in the driver’s brake controller opens venting the operating air from above the piston in the emergency exhaust valve located in the driver’s cab. This valve then opens to vent the brake pipe direct to atmosphere at the emergency rate.
In addition to direct exhaust as all the electrical supply switched off the ‘Release’ and ‘Application’ E.P. valves are de-energized causing the valve E-70 lifts and therefore vents the brake pipe to atmosphere. In emergency, brake of 2.5 kg/cm2 is applied through C3W valve.
Neutral:
When the handle of the brake controller is in the ‘Neutral’ position the cam operated switches within the controller cut off the power supply to all the E.P. valves (except ‘Isolate’ E.P. valve which is already deenergized) as for the ‘Emergency’ position.
Release:
When the handle of the brake controller is held in the spring loaded ‘Release’ position, the ‘Full Bore’ and ‘Running’ E.P. valves (of E-70) are energized. In this condition the system operates as described for the ‘Running’ condition, except that the ‘Full Bore’ E.P, valve is energized. This valve allows a low-pressure overcharge in BP pipe.
Low pressure over charge is achieved by raising the normal brake pipe pressure of 5 kg/cm2 to a pressure of 5.4 kg/cm2 and holding this for a limited period after which the overcharge is arranged to bleed down at a prescribed rate.
The pressure of 5.4 kg/cm2 in the brake pipe is held for a short period by an electronic timing device on the low-pressure overcharge circuit board. At the end of this period the ‘Low Pressure Overcharge’ release E.P. valve is de-energies in a controlled manner which thus reduces the pressure in the control reservoir and hence the brake pipe at a predetermined rate towards a level of 5 kg/cm2 . Even overcharging up to 5.4 kg/cm2 for short time and normalized with restricted rate, there will be no brake binding in load as overcharging feature of DV will prevent DV to overcharge.
Note: The handle of A-9 can be remove and insert in neutral position and can be locked by locking device. If the electronic brake control system fails, a priority-1 message display on the screen and an emergency brake is triggered.
Direct Brake (SA-9): To apply loco brakes, Drivers Direct air Brake Valve (SA-9) is provided in both the cabs. The operation of this system is near about same as in case of WAG-5/7. But unlike WAG-5/7 there are no cocks on inlet as well as outlet pipes of Drivers Direct air Brake Valve (SA9). Instead of cock the EP valves (pilot valves) are provided which keep the Drivers Direct air Brake Valve (SA-9) in service only in active cab automatically.
As a preventive measure, the handle of Drivers Direct air Brake Valve in rear cab should be kept in release position.
Unlike WAG-5/7, separate relay valves are provided for loco brakes through Drivers Direct air Brake Valve and loco brakes through conjunction working. So possibility of total brake failure due to relay valve failure is eliminated.
The Drivers Direct air Brake Valve has two positions; APPLY and RELEASE
Apply:-
When the driver’s control handle is moved to the ‘brake on’ position, air from the main reservoir admits in the out let pipe which (3.5 kg/cm2 max) is further connected to braking relay valve 58. This pressure operates the relay valve so relay valve again allow the MR pressure waiting at its port to the brake cylinders through 2 nos of DCVs and bogie isolating coc. Brake cylinder pressure can be seen in the gauges provided in both the cabs.
Release: When the driver’s control handle is moved towards the ‘release’ position, it isolates the main reservoir pressure from the relay valve. Simultaneously, allows the pressure from the relay valve to escape to atmosphere through its exhaust port. As the pressure from relay valve get exhausted, relay valve further disconnect the pressure flow from MR to brake cylinder and simultaneously the pressure of brake cylinder get exhausted to atmosphere through exhaust of relay valve.
Any desired releasing stage for the brake cylinder pressure may be obtained according to the position of the driver’s control handle. The direct brakes are used to apply loco brakes. In WAP5 direct brake apply on wheel disk with the pressure of 5 kg/cm2 whereas in WAG-9/WAP-7 it apply on wheel tyre as conventional loco with the pressure of 3.5 kg/cm2 . The brake handle remains active only in active driver Cab.
Start/running interlock (i.e. regression of TE / BE) is initiated when the speed of loco is above 10 KMPH and BC pressure share in gauge by 0.6 kg/cm2 and above.
For isolation of brakes of particular bogie, bogie coc are provided. COC for bogie -1 is provided below machine room -1 above MCP-1 where as COC for bogie -2 is provided below machine room -2 above MCP-2 .
Brake cylinder gets supply from following:
From SA-9 through C-2 (58) relay valve (3.5 kg/cm2 )
From C3W DV in conj. Working through C-2(57) relay valve(2.5 kg/cm2 ) From Anti spin device (Wheel slip) (0.6 kg/cm2 to 1.0 kg/cm2 )
From blending valve (DBR cut off) : in proportion To separate these different pressure paths different DCVs are provided in the path.
Diagram Of Loco Brake system
