Air spring is a rubber bellow containing pressurized compressed air with an emergency rubber spring providing various suspensions characteristic to maintain a constant buffer height irrespective of the loaded condition.

The necessity for Introducing Air Spring in Hybrid Coaches:

Due to the Super-Dense Crush Load, the bolster springs become solid, which in-turn damages/breaks the coil spring resulting in discomfort to the passenger. So to overcome the above problem on air suspension (air spring) is introduced in the secondary suspension to maintain a constant buffer height irrespective of the loaded condition by varying the pressure of air inside the air spring.

Working Principle:

With changing loads, air spring reacts initially by changing the distance between air spring support and coach body. then actuating height monitoring valve( leveling valve ), either by taking the compressed air to the air spring or releasing air pressure from it to the atmosphere this process continues until the required height is maintained this mechanism ensures a constant floor height on coaches provided with air springs, irrespective of the load.

The Main Components of Air Spring are as under:
  • Bellows
  • Lateral shock absorbers
  • Level equalizing valve lever
  • Branch pipe 20dia.
  • Inner side emergency spring
  • 150 litres capacity reservoir.
  • 40 litres capacity auxiliary reservoir- 04nos.
  • Non-return valve
  • Isolating cock
  • Duplex check valve
  • Air spring support cradle
  • Air spring releasing valve
  • The required pressure of 7bar is taken from F.P., no extra provision of pressure is required.
    Ride comfort is better than ICF.
  • In ICF bogie coil springs are working on load proportionate deflection system some time which becomes too less (spring become solid) but in air spring a fixed deflection range is maintained having characteristics to vent and receive air as per requirement.
  • Ride quality is the same in empty and loaded.
  • With the use of control or leveling valve, No. extra air is utilized.
  • Constant floor height is maintained resulting in more comfort to passengers.
  • Springs are also able to accept lateral thrust to act as the flexible coil.
  • On typical load (more load) ride quality is same.
  • Improved reliability and reducing maintenance efforts.
  • The choice to set deflection range during manufacturing.
  • Passenger fatigues is reduced the gap between bolster and bogie frame should be maintained 255+5,-0mm during running which provides more deflection range in comparison to coil spring provided on old ICF coaches

If the pressure is reduced more than 1.5kg/cm2 in both bellows, the automatic emergency valve will sense and there will emergency brake application resulted recharging, setting of the audiovisual indicating valve is required en-route also.(RDSO Trials in process)

In rolling examination, the position of leveling valve lever must be ensured to keep in horizontal position
If the lever is in a vertical position, then train should be allowed with the restricted speed of 60kmph or coach should be detached as a decision taken by train examining staff.4. More educated supervisors and staff is required to provide more attention during Rolling in and rolling out examination