Pneumatic Fundamentals

Question 1

What components do air compressors typically have on or near them? (6)

Answer 1

1. Filters to clean air
2. Air coolers, to cool compressed air
3. Air dryers to remove moisture
4. Pressure switches to automatically start/stop compression
5. Safety valves in case of defects
6. Isolating/delivery cocks

Question 2

What unit is compressed air measured in?

Answer 2

kPa (Kilopascals)

Question 3

What is the role of a compressor governor?

Answer 3

To monitor air pressure in main reservoir system, and control operations and ensure consistent pressure

Question 4

What will happen to air compressor system in case of Compressor Governor failure?

Answer 4

It will run continuously.

Question 5

What are the three types of compressed air reservoirs?

Answer 5

Main, auxiliary and/or supplementary reservoirs

Question 6

What is the function of a main air reservoir safety valve?

Answer 6

To prevent the main reservoir from being overcharged should the air compressor fail to stop

Question 7

What is the function of an Air Dryer?

What is a driver’s responsibility to the air dryer in their train preparations?

Answer 7

To remove water particles, oil and solid particles from compressed air.

Driver is only required to check external physical condition of dryer

Question 8

What is the primary purpose of the pneumatic EMU systems?

Answer 8

To provide friction breaking

Question 9

Train equipment that employ pneumatics include: (7)

Answer 9

1. Friction brakes
2. Air suspension systems (not X’Trap)
3. Sanding equipment
4. Whistles
5. Pantograph raising (Comeng, HCMT)
6. Saloon doors opening and closing (Comeng)
7. Spring park brakes

Question 10

What is a simple valve and a complex valve?

Answer 10

Simple valve = used to turn flow on or off

Complex valve = distributes flow depending on other parameters

Question 11

What can isolating cocks be used for?

Answer 11

Turn equipment on or off, or can redirect compressed air into different pathways

Question 12

What will happen if the Main Reservoir systems cannot reach its minimum level?

Answer 12

The train will stop due to compromised safety

Question 13

How does the Electro-Pneumatic brake system work?

Answer 13

It uses compressed air to apply a brake block or disc pad onto wheel

Question 14

When is the Electro-Pneumatic (EP) brake system applied?

Answer 14

Automatically, once the train’s speed reduces to a point where the Electro-Dynamic brake system becomes less effective

Question 15

What will happen to an EMU if there is a loss of electrical brakes?

Answer 15

Friction brakes will take over

Question 16

What is the third breaking system unique to Comeng and what type of brake is it?

Answer 16

Automatic Air Brake, friction brake

Question 17

What is the air in the auxiliary reservoirs used for?

Answer 17

Friction breaking

Question 18

What damage can occur if a friction brake system develops faults or leaks? (eg. sticking brakes)

Answer 18

Damage to tracks or wheels

Question 19

What braking system will prevent the train from rolling away if there is not enough air within the train?

Answer 19

Spring park brake

Question 20

What reservoir does the Spring Park Break use?

Answer 20

Main reservoir

Question 21

How does a pneumatic spring park break work?

Answer 21

Once main reservoir has been depleted, the spring is released and will apply mechanical force friction brakes to prevent train from rolling

Question 22

When will the sanding equipment on a Siemens and HCMT be deployed?

Answer 22

Automatically, once the train recognises wheel slip

Question 23

How does the sanding equipment decrease wheel slip?

Answer 23

The sand enables increased grip between wheel and railhead. Air is used to assist gravitational discharge

Question 24

Where can the initial supply of compressed air required to raise the pantograph on a Comeng be obtained? (3)

Answer 24

• Main reservoir
• Storage reservoir
• battery-powered compressor

Question 25

How are X’Trap and Siemens pantographs raised?

Answer 25

via electric motor

Question 26

What must a driver be mindful of when raising pantograph?

Answer 26

Train components will become live

Question 27

Pantographs on HCMT are raised pneumatically using either: (2)

Answer 27

• Main Reservoir pressure
• Battery-powered auxiliary compressor on DMp cars, should main res pressure be insufficient