Pneumatic Fundamentals Flashcards
What components do air compressors typically have on or near them? (6)
- Filters to clean air
- Air coolers, to cool compressed air
- Air dryers to remove moisture
- Pressure switches to automatically start/stop compression
- Safety valves in case of defects
- Isolating/delivery cocks
What unit is compressed air measured in?
kPa (Kilopascals)
What is the role of a compressor governor?
To monitor air pressure in main reservoir system, and control operations and ensure consistent pressure
What will happen to air compressor system in case of Compressor Governor failure?
It will run continuously.
What are the three types of compressed air reservoirs?
Main, auxiliary and/or supplementary reservoirs
What is the function of a main air reservoir safety valve?
To prevent the main reservoir from being overcharged should the air compressor fail to stop
What is the function of an Air Dryer?
What is a driver’s responsibility to the air dryer in their train preparations?
To remove water particles, oil and solid particles from compressed air.
Driver is only required to check external physical condition of dryer
What is the primary purpose of the pneumatic EMU systems?
To provide friction breaking
Train equipment that employ pneumatics include: (7)
- Friction brakes
- Air suspension systems (not X’Trap)
- Sanding equipment
- Whistles
- Pantograph raising (Comeng, HCMT)
- Saloon doors opening and closing (Comeng)
- Spring park brakes
What is a simple valve and a complex valve?
Simple valve = used to turn flow on or off
Complex valve = distributes flow depending on other parameters
What can isolating cocks be used for?
Turn equipment on or off, or can redirect compressed air into different pathways
What will happen if the Main Reservoir systems cannot reach its minimum level?
The train will stop due to compromised safety
How does the Electro-Pneumatic brake system work?
It uses compressed air to apply a brake block or disc pad onto wheel
When is the Electro-Pneumatic (EP) brake system applied?
Automatically, once the train’s speed reduces to a point where the Electro-Dynamic brake system becomes less effective
What will happen to an EMU if there is a loss of electrical brakes?
Friction brakes will take over
What is the third breaking system unique to Comeng and what type of brake is it?
Automatic Air Brake, friction brake
What is the air in the auxiliary reservoirs used for?
Friction breaking
What damage can occur if a friction brake system develops faults or leaks? (eg. sticking brakes)
Damage to tracks or wheels
What braking system will prevent the train from rolling away if there is not enough air within the train?
Spring park brake
What reservoir does the Spring Park Break use?
Main reservoir
How does a pneumatic spring park break work?
Once main reservoir has been depleted, the spring is released and will apply mechanical force friction brakes to prevent train from rolling
When will the sanding equipment on a Siemens and HCMT be deployed?
Automatically, once the train recognises wheel slip
How does the sanding equipment decrease wheel slip?
The sand enables increased grip between wheel and railhead. Air is used to assist gravitational discharge
Where can the initial supply of compressed air required to raise the pantograph on a Comeng be obtained? (3)
- Main reservoir
- Storage reservoir
- battery-powered compressor
How are X’Trap and Siemens pantographs raised?
via electric motor
What must a driver be mindful of when raising pantograph?
Train components will become live
Pantographs on HCMT are raised pneumatically using either: (2)
- Main Reservoir pressure
- Battery-powered auxiliary compressor on DMp cars, should main res pressure be insufficient
