Brake Continuity Test:
Brake continuity test is one of the most important tests of air brake system. This test is done to check the continuity of the brake pipe through-out the train. It ensures that the brake pipe pressure gets released/ created, during the brake application/released, simultaneously in brake pipes of all wagons throughout the length of the train.
The underline principle of the test is that first the brake pressure is created from the locomotive. The pressure so created in brake pipe is then destroyed from the brake van/last vehicle and in doing so, the brake pipe pressure in locomotive should also become zero.
The brake pipe pressure is once again created from the locomotive and the build-up of brake pipe pressure is checked from the brake van/last vehicle.
In case of any discontinuity, and/or blockage in the brake pipe the rise/fall of brake pipe pressure in loco shall not cause rise/fall of brake pipe pressure in brake van and vice versa.
The brake continuity test must be carried out on the train in the following circumstances without exception as prescribed by RDSO.
- Fresh locomotive or additional locomotive is attached to the front of the train.
- Fresh locomotive or additional locomotive is attached to the rear of a fully fitted train.
- The vehicle is attached at any position in the fitted portion of the train.
- Vehicles in the fitted portion of the train are detached from other than the extreme rear end.
- After any brake defect or irregularity which has affected the continuity of the brake system has been rectified.
Who shall carry out:
The drivers and guards together must carry out this test as soon as possible after the locomotive is coupled or re-coupled strictly following the detailed procedure laid down by RDSO as given herein:
Step-1: The driver must move the automatic brake valve handle to Run in the leading driving compartment and check that approx. 5.0 kg/cm2 is registered on the brake pipe pressure gauge.
Step-2: The driver must move the automatic brake valve handle to HANDLE OFF/NEUTRAL without a pause and retain initially at least 4.0 kg/cm2 on the brake pipe pressure gauge. In the case of A9 automatic brake valve which does not have “HANDLE OFF//NEUTRAL” position, the following procedure shall be followed after the brake pipe pressure has stabilized close the brake pipe isolating cock provided between additional C2 relay valve and brake pipe of the locomotive.
The guard must then without delay carry out the following:
- If a brake van is a rear vehicle, open the guards‟s emergency Brake Valve until all air is exhausted reducing the pressure to zero. The valve must then be closed.
- If a brake van is not the rear vehicle, open the Brake Pipe cut off angle cock on the rear end of the last vehicle un till all air is exhausted. The Cock must then be closed.
- In the case of the parts fitted train, the Cock must be opened on the rear end of the rear vehicle in the fitted portion all the air is exhausted.
- Before carrying out this part of the test, the guard must have a clear understanding with the driver as to what is to be done to ensure that the train is not moved during the test.
- If locomotive in the rear of the last wagon in addition to the driving locomotive in the front of the train, is used and this locomotive is the last vehicle on the train, then the guard must instruct the driver of the rearmost locomotive to perform the duties of the guard in carrying out the brake continuity test.
- Then the driver must move the Automatic Brake Valve to emergency un till the Brake Pipe Pressure falls to zero. He must then move the Automatic Brake Valve Handle to OFF/NEUTRAL and observe that the brake Pipe pressure does not immediately rise.
- In case of A9 Automatic Brake Valve which does not have HANDLE OFF/NEUTRAL position, the isolating Cock provided between additional C2 relay Valve and Brake Pipe of locomotive must be closed and must observe that the Brake Pipe pressure does not immediately rise.The Guard must obtain an assurance from the driver of the rearmost locomotive that this has been done.
Step-4: The driver of the driving locomotive must observe that the brake pipe pressure has dropped to zero in the leading driving compartment and does not commence to rise again. If the Brake Pipe pressure does not fall, this can be due to Brake Pipe Cut Off angle Cock being closed.If the brake Pipe pressure does not fall to zero, check if a locomotive Automatic Brake Valve or brake controller in another cab/control stand is not in the HANDLE OFF/NEUTRAL position. In the case of A-9 Automatic Brake Valve which does not have HANDLE OFF/NEUTRAL position, check whether the isolating C2 relay Valve and brake pipe of the locomotive are not in closed position.
Step-5: After correction of any fault a further brake continuity test commencing at STEP 3 must be carried out.
Step-6: The driver must move the Automatic Brake Valve to Run position and check that 5.0 kg/cm2 is registered in the locomotive cab and maximum level in the last vehicle as stipulated in the operating rules. In case of A9 brake valve which does not have HANDLE OFF/ NEUTRAL position, after the Cut-out cock between C2 Relay valve and Brake pipe is opened the brake pipe pressure should again build up to 5 Kg/cm2 in the locomotive and to a maximum pressure in the last vehicle as stipulated in the operating rules.