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