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Flashcards in ME..How it works Deck (28):
1

Describe how the parking brakes work and how to apply them.

Parking brake works by an additional brake chamber (can) connected to the service brake on the rear brakes. Air pressure holds back a spring inside additional can. When air is removed or drops below 40 psi – spring activates and causes service brake to be applied. Apply them by pulling maxi knob out.

2

What other type of pump is also used by the fire service and what is its main use?

Positive displacement – used for priming the centrifugal pump

3

what are the two main pressure control devices used by the fire service and what is the difference?

Relief valve – opens a bypass between the suction and discharge side of the pump

Governor – adjusts engine rpm to decrease pressure and maintains highest pressure

4

Describe the auxiliary braking system and how it works.

Retarder – trans fluid goes into retarder housing that has opposing spinning vanes – energy is absorbed and slows down drive shaft. Heat is dissipated through trans cooler and radiator.

5

What warnings and at what temperatures will you get when the transmission cooling system capacity is exceeded?

The tranny will decrease retardation output but after temps are too high. Warning light and alarm sounds when it exceeds 330 degrees or sump pressure over 2500. Secondary warning light will illuminate and sound if above 3300.

6

Define nozzle reaction and how Newton’s third law affects firefighters

Force exerted against nozzle man. For every action there is an equal and opposite reaction

7

What are some methods for preventing the pump from overheating?

Flow water, use recirculating valve, take out of pump when not using, supply line

8

When drafting from a static water source, how does water get into the pump?

Atmospheric pressure pushes it up the intake after air is removed from the line from the priming pump. Pressure in the line is less that outside air pressure.

9

At what rate will the pressure increase/decrease when the throttle switch is engaged?

4 psi

10

What is a slack adjuster and what does it do?

Mechanical device that automatically adjusts the clearance between brake linings and brake drum/rotor, it senses the length of stroke of the air chamber push rod.

11

How does a pressure governor differ from a relief valve?

A pressure governor controls throttle speed based off pressure readings on intake and discharge pressure. A relief valve operates by pre-loading a spring that will release pressure that exceeds its spring setting releasing excess pressure in to the suction side of the pump.

12

What is the procedure to take a vehicle out of service for an “immediate need” and give 3 examples of reasons.

The Company Officer contacts dispatch to remove the unit from service. Dispatch then notifies the B/C. Examples are 1) Mechanical Failure 2) Accident that renders the vehicle out of service, 3) inadequate staffing.

13

Describe how the parking brakes work and how to apply them.

Parking brake works by an additional brake chamber (can) connected to the service brake on the rear brakes. Air pressure holds back a spring inside additional can. When air is removed or drops below 40 psi – spring activates and causes service brake to be applied. Apply them by pulling maxi knob out.

14

What other type of pump is also used by the fire service and what is its main use?

Positive displacement – used for priming the centrifugal pump

15

what are the two main pressure control devices used by the fire service and what is the difference?

Relief valve – opens a bypass between the suction and discharge side of the pump

Governor – adjusts engine rpm to decrease pressure and maintains highest pressure

16

Describe the auxiliary braking system and how it works.

Retarder – trans fluid goes into retarder housing that has opposing spinning vanes – energy is absorbed and slows down drive shaft. Heat is dissipated through trans cooler and radiator.

17

What warnings and at what temperatures will you get when the transmission cooling system capacity is exceeded?

The tranny will decrease retardation output but after temps are too high. Warning light and alarm sounds when it exceeds 330 degrees or sump pressure over 2500. Secondary warning light will illuminate and sound if above 3300.

18

Define nozzle reaction and how Newton’s third law affects firefighters

Force exerted against nozzle man. For every action there is an equal and opposite reaction

19

What are some methods for preventing the pump from overheating?

Flow water, use recirculating valve, take out of pump when not using, supply line

20

When drafting from a static water source, how does water get into the pump?

Atmospheric pressure pushes it up the intake after air is removed from the line from the priming pump. Pressure in the line is less that outside air pressure.

21

At what rate will the pressure increase/decrease when the throttle switch is engaged?

4 psi

22

What is a slack adjuster and what does it do?

Mechanical device that automatically adjusts the clearance between brake linings and brake drum/rotor, it senses the length of stroke of the air chamber push rod.

23

How does a pressure governor differ from a relief valve?

A pressure governor controls throttle speed based off pressure readings on intake and discharge pressure. A relief valve operates by pre-loading a spring that will release pressure that exceeds its spring setting releasing excess pressure in to the suction side of the pump.

24

What is the procedure to take a vehicle out of service for an “immediate need” and give 3 examples of reasons.

The Company Officer contacts dispatch to remove the unit from service. Dispatch then notifies the B/C. Examples are 1) Mechanical Failure 2) Accident that renders the vehicle out of service, 3) inadequate staffing.

25

. How does the jake brake work?

The exhaust brake consists of a flapper valve installed in the exhaust pipe between the engine and the muffler. When activated, the flapper restricts the passage of the exhaust gases and increases the back pressure in the cylinders during the exhaust stroke. This increases the natural retardation effect of the engine. Braking torque will vary depending on the transmission range selected.

26

. how does water governor reduce ep once excess pressure is detected?

It is pressure activated to adjust the engine throttle. The speed of the impeller determines the pressure and the engine speed determines the speed of the impeller. When excessive pressure builds up, a tube from the discharge side of the pump transmits the resulting pressure rise to a governing device, which then cuts back the throttle.

27

Jake brake/ exhaust brake

The exhaust brake consists of a flapper valve installed in the exhaust pipe between the engine and the muffler. When activated, the flapper restricts the passage of the exhaust gases and increases the back pressure in the cylinders during the exhaust stroke. This increases the natural retardation effect of the engine. Braking torque will vary depending on the transmission range selected.

28

clearance rings on pump?

A very close tolerance must be maintained between the pump casing and the hub on the impeller .01 inch or less. Any increase in the opening lessens the pumps effectiveness.
As the gap increases from impurities, sediment, dirt and sand, the gap increases and greater amounts of water are allowed to slip back into the intake and thus are not available at the discharge. Eventually the pump is not able to pump its rated capacity, first indication being when increased engine rpm is required to pump the rated capacity in pump tests.