Chapter 10 Fire Pump Theory Flashcards
The centrifugal pump does not use positive action to force water from the pump; rather, it depends on __________ produced by centrifugal force to provide the necessary pump discharge pressure
velocity of water
Positive displacement pumps are still necessary because they pump _____ and are used as priming devices.
air
What are the two basic types of positive displacement pumps?
piston
rotary
Piston pumps are still in service for ________ fire fighting and can provide pressures up to ______ psi
high-pressure steam
1000 psi
From a standpoint of design, what type pumps are the simplest of all fire apparatus pumps?
Rotary-type
What is the most common types of pumps used to prime centrifugal pumps?
rotary-vane
What feature makes the rotary-vane pump much more efficient at pumping air than a standard rotary gear pump?
the self adjusting ability of automatically maintaining a tight fit
What type of pump is used by nearly all modern fire apparatus as their major pump?
centrifugal
What are the two fundamental part of the centrifugal pump?
impeller and casing
What are the 3 main factors that influence a centrifugal fire pump’s discharge pressure?
- Amount of water
- Speed of impeller
- Pressure of water when it enters the pump
Concerning centrifugal pumps, the greater the volume of water being flowed, the __________ the discharge pressure.
lower
Concerning centrifugal pumps, the greater the speed of the impeller, the pressure developed is _______
greater
Doubling the speed of the centrifugal pump’s impeller results in how many times more pressure?
4
What is the capacity of a single intake impeller?
2000 gpm
What kind of impeller was designed to minimize lateral thrust?
double suction impeller
What gives multi-stage pumps their versatility and efficiency?
the capability of connecting the stages in:
series for max pressure
parallel for max volume
What valve is used to switch between series or parallel stages in a multi-stage pump?
transfer valve
Multi-stage pumps may remain in the pressure system until it is necessary to flow more than how much of the rated volume capacity?
2/3rds
What is the maximum net pump discharge pressure at which the transfer valve should be operated?
50 psi
Many power-operated transfer valves operate at pressures as high as how much?
200 psi
What is the first indication that the wear in a centrifugal pump is becoming a problem?
when increased engine rpm is required to pump the rated capacity in pump tests
How can the driver/operator check the pump temp?
by placing a hand on the direct pump intake pipe of the pump
What is the most common type of packing used on centrifugal pumps?
rope fibers impregnated with graphite or lead
Is it ok for a small amount of water to leak around the packing? Why or why not?
Yes. helps prevent excessive heat buildup
When is it ok for water to drip from the packing glands?
when the pump is operating under pressure
When are mechanical pump seals especially problematic?
when they freeze
What type of pumps offer the maximum amount of flexibility?
auxiliary engine-driven
What is the pumping capacity of an auxiliary engine-driven pump that might be mounted on a skid and placed on the back of a small attack fire apparatus?
500 gpm
What is the pumping capacity of an aux engine-driven pump used on ARFF apparatus or trailer mounted?
up to 4000 gpm
Does the PTO pump permit pump-and-roll operation?
Yes
Full Torque PTOs permit the installation of pumps up to how many gpm?
1250 gpm
What are some disadvantages of a front mount pump?
more susceptible to freezing in cold weather
obstruct air flow through radiator
vulnerable in event of front collision
Does the front mount pump permit pump-and-roll?
yes
Where are most front-mount pumps engaged and controlled at?
front the pump itself
How is power supplied to the pump of a midship pump?
transfer case
What gpm can two-stage centrifugal pumps popular in the fire service be rated at?
from 500 GPM to 1500 GPM
With the engine idling and the pump engaged, what does most speedos read?
10-15 mph
How are hydrostatic pumps driven?
A shaft off the front of the engine turns a hydraulic pump that drives a midship or rear-mounted centrifugal pump
Can hydrostatic pumps be used for pump-and-roll operations?
yes
The piping system and pump must be able to withstand a hydrostatic test of how much?
500 psi
NFPA 1901 states that piping size of pumps with a capacity of 500 gpm or less should be sized so that they can flow how much from their booster tank?
250 gpm
The piping size of pumpers with capacities greater than 500 gpm should be sized so that they can flow how much water per minute out of their booster tank?
500 gpm
In respect to height, where are all intake lines of a centrifugal pump located?
below the eye
Pumps that have a capacity of _______ may require more than one large intake connection at each location
1500 gpm or greater
NFPA 1901 requires enough ________ discharge outlets to flow the rated capacity of the fire pump
enough 2 ½” or larger
At a minimum, how many 2 ½” discharges must all fire apparatus with a rated pump capacity of 750 gpm have?
2
Pumps that are rated less than 750 gpm are required to have how many 2 ½” discharges
1
1 ½”, 1 3/4”, 2” hand lines must be supplied with what size piping?
at least 2”
All valves should be designed so that they are easily operable at what pressures?
up to 250 psi
NFPA requires apparatus with a water tank less than 1000 gallons to have a tank fill line of what size?
at least 1”
NFPA requires apparatus with a water tank of 1000 gallons ore more to have a tank fill line of what size?
at least 2”
NFPA 1901 requires slow acting valve controls on what size lines?
3” or greater
Most connections to the pump are equipped with drain valves located on what side of the control valve? Why?
line side.
Provide a way for the driver to drain pressure off the line
How soon must the pressure control device operate after the discharge pressure rises?
within 3-10 seconds
Pressure control devices must not allow the pressure to exceed how much psi above the set level?
30 psi
Are intake pressure relief valves required on pumps that are equipped with electronic governors?
yes
What are two purposes that the oil/fluid serve in a primer pump?
seals the gap between the gears and the case as the pump wears
acts as a preservative and helps prevent corrosion
What should engine speed be when priming?
1000-1200 rpm
Creating a vacuum by using exhaust requires what?
high engine speed
What is the simplest type of primer?
vacuum
At what engine speed does vacuum primers work the best?
low engine speed
NFPA 1901 requires the following controls and instruments to be located on the pump panel:
- Master pump intake pressure
- Master pump discharge pressure
- Engine Tachometer
- Engine Coolant Temp
- Engine oil pressure
- Voltmeter
- Engine Throttle
- Primer control
- Tank to pump valve
- Tank fill valve
- Water level indicator
The master intake gauge is sometimes called what? Why?
vacuum or compound gauge
It is capable of reading vacuum
The master intake gauge is usually calibrated how?
from 0-600 psi positive
from 0-30 inches of mercury on the neg side
When watching the master intake gauge, how do you know that the pump is near its maximum capacity and not able to supply any more lines?
the vacuum reading approaches 20 inches of mercury
The master discharge pressure gauge must be calibrated to what? How about on pumpers equipped to supply high-pressure fog streams?
600 psi
1000 psi
What is a vernier?
Throttle knob
NFPA 1901 allows flowmeter readouts to substitute for __________ gauges. However, even if a flowmeter system is used, the apparatus is still required to have the ______ and ______ gauges.
individual discharge gauges
master intake and pressure gauges
What are the two types of auxiliary coolers?
Marine type
immersion
When should the radiator fill valve be used?
only in emergency situations
