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IFSTA Pumping Apparatus, Driver Operator > Chapter 10, Fire Pump Theory > Flashcards

Chapter 10, Fire Pump Theory Flashcards

1
Q

What constitutes a positive displacement pump?

A

It forces all water and air out with each operating cycle (early pumps like rotary or piston pumps).

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2
Q

What kind of pump do most modern fire trucks have?

A

Centrifugal pumps.

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3
Q

Why are positive displacement pumps still a necessary part of the overall pumping system on modern fire trucks?

A

Unlike centrifugal pumps, pos dis pumps can pump air. (priming device for drafting).

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4
Q

What are the 2 types of positive displacement pumps?

A

Piston and rotary.

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5
Q

How does piston pump work?

A
  • piston pump moves up and down
  • as piston moves down, it compresses air in cylinder (creates higher pressure in pump than atmospheric pressure in discharge manifold)
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6
Q

What are the 2 types of piston pumps?

A

Single-acting piston pump and double-acting piston pump.

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7
Q

How does single-acting piston pump work?

A
  • piston moves up and down in a cylinder
  • forward stroke causes water to be discharged
  • return stroke causes pump to fill with water again
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8
Q

How does double-acting piston pump work?

A

On each up and down stroke of the piston, it both receives and discharges water.

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9
Q

What are considered the simplest types of fire apparatus pumps?

A

Rotary Pumps.

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10
Q

What are the 2 types of rotary pumps?

A
  • rotary gear: consists of 2 gears that rotate in a tight mesh pattern
  • rotary vane: moveable elements that automatically compensate for wear, and maintain a tighter fit
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11
Q

What is the most common type of pump used to prime centrifugal pumps?

A

Rotary vane pumps.

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12
Q

Why is the centrifugal pump classified as a non positive displacement pump?

A

It does not pump a definite amount of water with each revolution.

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13
Q

What are the 2 parts that a centrifugal pump fundamentally consist of?

A
  • impeller (transmits energy in the form of velocity to the water)
  • casing (collects the water and confines it to convert the velocity to pressure)
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14
Q

What are the 3 main factors that influence a centrifugal pumps discharge pressure?

A
  • amount of water being discharged
  • speed that the impeller turns
  • water pressure into the pump from a pressurized source (hydrant)
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15
Q

The greater the speed of the impeller on the centrifugal pump, the greater the pressure developed. If the speed of the impeller doubles, how much does the pressure increase?

A

It increases 4 times as much.

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16
Q

What are the 2 basic types of centrifugal pumps?

A
  • single stage (has single impeller)

- two stage (has double suction impeller, takes water from both sides)

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17
Q

What is a multi-stage centrifugal pump?

A

A pump that has an impeller for each stage, mounted within a single housing.

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18
Q

When the transfer valve is set in the “volume” position, how does the pump deliver water to the discharge?

A

Each of the 2 impellers takes water from a source (hydrant) and delivers it to the discharge.

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19
Q

When the transfer valve is set in the “pressure” position, how does the pump deliver water to the discharge?

A

All the water from the intake is directed to eye of the 1st impeller, 2nd impeller increases the pressure and sends water to the discharge.

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20
Q

What is the process of switching between “pressure” and “volume” called?

A

Changeover.

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21
Q

Concerning the transfer valve, why is it better to be in “volume” setting than in “pressure” setting?

A

In volume setting, it can supply 100 percent of rated capacity at 150 psi at draft.

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22
Q

Why are clapper (check) valves essential in a multi-stage pump?

A

When transfer valve is operated, clapper valve allows water to escape back into intake (churns through pump instead of building pressure).

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23
Q

As the pump is used over time, a space between the impeller and the pump casing can be created (due to sediment being forced through while the pump is in higher rpm). Over time, the pump will not be able to supply its rated capacity. How can the pump capacity be restored, with replacing the pump itself?

A

By replacing the replaceable wear rings provided in the pump casing, to maintain the required space between the hub of the impeller and the casing.

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24
Q

What is an auxiliary engine-driven pump?

A

A pump that is powered by a gasoline or diesel engine independent of the engine used to drive the vehicle.

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25
Q

What are the most common applications for auxiliary engine-driven pumps?

A
  • ARFF vehicles
  • Wild land fire apparatus
  • mobile water supply apparatus
  • trailer-mounted fire pump
  • portable fire pump
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26
Q

What is the most unique function of an auxiliary engine-driven pump?

A

With a separate engine, it allows you to conduct mobile attacks (pumping water while in motion).

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27
Q

Where are front-mount pumps mounted?

A

On an extended front bumper, between the bumper and grill.

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28
Q

What are some disadvantages to a front-mount pump?

A
  • susceptible to freezing
  • gauges may suffer damage from freezing temps
  • obstruct airflow through vehicles radiator (overheat)
  • vulnerable position for collision
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29
Q

What is a midship pump?

A

An apparatus with the pump mounted laterally across the frame, behind the engine and transmission (most common).

30
Q

On an apparatus with a midship pump, how is power supplied to the pump?

A

Through the transfer case (engaging “ready to pump” switch in the cab).

31
Q

What is a hydrostatic pump?

A

Pumps driven by a shaft from the front of vehicles engine. Shaft turns a hydraulic pump, that drives a midship or rear mount centrifugal pump, up to 1000gpm (can be used for both stationary and mobile operations).

32
Q

Advantages of rear mount pumps.

A
  • more even weight distribution

- more compartment space on apparatus

33
Q

Disadvantage of rear mount pumps.

A

-more directly exposed to oncoming traffic

34
Q

An integral part of the fire pump system is the piping valves attached to the pump. What are the primary components of the piping system?

A
  • intake piping
  • discharge piping
  • pump drains
  • valves
35
Q

What are the 2 primary ways that water may enter the pump?

A
  • through piping that connects water tank to pump

- through piping that connects pump to external water source

36
Q

Why is it important that piping from tank to pump is large enough to allow for adequate streams to make an effective initial attack?

A

Because majority of all fires are initially fought from tank water.

37
Q

NFPA 1901 states that piping should be sized so that pumpers with a capacity of 500 gpm or less should be capable of flowing how much gpm from their booster tank?

A

250 gpm.

38
Q

NFPA states that piping should be sized so that pumpers with a capacity greater than 500 gpm should be capable of flowing how much gpm from their booster tank?

A

At least 500 gpm.

39
Q

Why does piping, as it nears the pump, typically taper to a square shape?

A

To eliminate the vortex that may occur in water that flows through circular piping.

40
Q

As a minimum, all apparatus with a rated capacity of 750 gpm or greater, must be equipped with at least how many 2 1/2 inch discharges? Less than 750 gpm?

A
  • At least 2.

- only required to have 1.

41
Q

What size piping must be provided for discharges to 1 1/2, 1 3/4, and 2 inch handlines?

A

At least 2 inch piping.

42
Q

A tank fill line should be provided from the discharge side of the pump. Why?

A

It allows the tank to be filled without making any additional connections, when the pump is being supplied from an external supply source.

43
Q

When no lines are flowing, what can be used to circulate water through the pump to prevent overheating?

A

The tank fill line.

44
Q

What controls most of the intake and discharge lines from the pump?

A

Valves (must be air tight).

45
Q

What is the most common type of valve on the apparatus?

A

Ball-type (permits full flow through lines with minimum friction loss).

46
Q

What are the 2 most common actuators for ball-type valves?

A
  • push/pull handles

- quarter-turn handles

47
Q

What type of valves are used on large diameter intakes and discharges?

A

Gate or butterfly valves.

48
Q

NFPA 1901 requires all valves on intakes/discharges that are 3 inches or larger to be equipped with what type of valve controls?

A

Slow acting (prevents opening/closing faster than 3 seconds; minimizes risk of water hammer damage).

49
Q

What is the primary reason the apparatus has pump drains?

A

Provides a way for the driver/operator to relieve pressure from hose line, after discharge valve and nozzle have both been closed.

50
Q

What is the reason for a bleeder valve, on the line side of the intake valve?

A

After the supply line has been connected to the intake, it allows air to be forced out of the supply line, as it fills with water.

51
Q

NFPA 1901 requires some type of pressure control device to be part of any fire apparatus pumping system. How must it operate?

A
  • Must operate within 3 to 10 seconds after discharge pressure rises
  • Must not allow pressure to exceed30 psi.
52
Q

What is the most common type of pressure relief valve?

A

Spring-controlled pilot valve.

53
Q

What are intake pressure relief valves used for?

A

To reduce the possibility of damage to the pump and discharged hose lines caused by water hammer when valves/nozzles are closed too quickly.

54
Q

What is the main feature of a pressure governor?

A

It regulates the power output of the engine to match pump discharge requirements.

55
Q

What is normally the cause of excessive pressure in the pump?

A

Shutting down one or more operating lines.

56
Q

What does a successful draft consist of?

A

The ability to create a lower pressure within the pump and intake hose, than exists in the atmosphere.

57
Q

What is needed for centrifugal pumps (in use today) to create a lower pressure in the pump, than in the atmosphere?

A

A priming device (or primer).

58
Q

What are the 3 types of primers?

A
  • positive displacement
  • exhaust
  • vacuum
59
Q

What are the 2 types of positive displacement primers?

A
  • rotary vane (requires high rpm)

- rotary gear

60
Q

What is considered the simplest type of primer?

A

Vacuum primer.

61
Q

What is the primary gauge used to determine the water pressure entering the pump?

A

Master intake gauge (must be able to measure positive pressure or vacuum).

62
Q

Which gauge on the pump panel shows residual pressure when the pump is receiving water from the hydrant?

A

Master intake gauge.

63
Q

What does the pump discharge pressure gauge register?

A

Pressure as it leaves the pump, but before it reaches the gauges for each discharged line.

64
Q

What does the engine oil pressure indicator read?

A

It shows whether an acceptable amount of oil is being sent to all vital areas of the engine, that are powering the pump (it is NOT a measure of oil level in the crank case).

65
Q

How can the pump overheat?

A

When pump is running for long periods, with no water being discharged (an audible/visual indicator will warn you).

66
Q

What does the voltmeter read?

A

Provides indication of battery condition and alternator output.

67
Q

What is the pumping engine throttle used for?

A

Used to increase/decrease rpm of engine that is powering the pump.

68
Q

What is the most common throttle used on the pump operators panel?

A

Throttle knob (vernier).

69
Q

When the truck will be used for drafting, what is used to operate the priming device?

A

Primer control (pull knob on our truck).

70
Q

What is the primary function of auxiliary coolers?

A

To control the coolant temp in the apparatus during pump ops.

71
Q

What are the 2 types of auxiliary coolers?

A
  • marine type (inserted into one of the hoses in the cooling system, so coolant must travel through it)
  • immersion type (water supplied by pump passes through a coil, immersed in the coolant)

IFSTA Pumping Apparatus, Driver Operator (7 decks)

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