Chapter 9 - Fire Pump Theory Flashcards
- Self-priming pump that utilizes a piston or interlocking rotors to move a given amount of fluid through the pump chamber with each stroke of the piston or rotation of the rotors. Used for hydraulic pumps on aerial devices’ hydraulic systems and for priming on centrifugal fire pumps.
Positive Displacement Pump
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Modern fire department pumpers are equipped with _____________ pumps as their main pump.
centrifugal
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_________ pumps operate using a piston that moves back and fourth in a cylinder.
Piston pumps
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- Positive-displacement pump using one or more reciprocating pistons to force water from the pump chambers.
Piston Pump
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From the standpoint of design, _________-_______ are the simplest of all fire apparatus pumps.
rotary-type
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_________ _______ pumps consist of two gears that rotate in a tightly meshed pattern inside a watertight case.
Rotary gear
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The total amount of water that can be pumped by a rotary gear pump depends on the ?
size of the pockets in the gears and the speed of rotation
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The rotary gear pump is a positive displacement pump because each pocket in the gears contains a ?
definite amount of water, which is forced out of the pump each time the gears turn with a positive action.
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To prevent damage to the casings, most gear pumps feature gears made of __________ or another soft metal, while strong alloy such as _______ _______ is used for the pump casing.
bronze / cast iron
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___________ ______________ pumps are self-priming, deliver a definite volume of water or air, and exhaust air from the pump and deliver water.
Positive displacement pumps
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__________ ________ pumps are constructed with moveable elements that automatically compensate for wear, maintaining a tighter fit with closer clearances as the pump is used.
Rotary vane
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This pump is one of the most common types of pumps used to prime a centrifugal fire pump?
Rotary vane pump
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- Type of positive displacement pump commonly used in hydraulic systems. A rotor with attached vane is mounted off-center inside the pump housing; pressure is imparted on the water as space between the rotor and the pump housing wall decreases.
Rotary Vane Pump
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Rotary Vane Pumps:
The distance between the _________ and the __________ is much greater at the intake than at the discharge.
rotor / housing
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Rotary pumps are prone to failure if not ?
exercised regularly
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Nearly all modern fire apparatus feature a ____________ pump as their main pump.
centrifugal
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- Pump with one or more impellers that rotate and utilize centrifugal force to move the water. Most modern fire pumps are of this type.
Centrifugal Pump
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Centrifugal Pumps:
This pump is classified as a _____________ displacement pump as it does not pump a definite amount of water with each revolution.
nonpositive
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Centrifugal Pumps:
The pump imparts ___________ to the water and converts it to ___________ within the pump itself.
velocity / pressure
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The operation of a centrifugal pump is based on the principle that a rapidly revolving disk tends to throw water introduced at its ?
center toward the outer edges of the disk
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Centrifugal Pumps:
The __________ acts as the disk receiving its water through the ______ in its center.
impeller / eye
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- Vaned circulating member of the centrifugal pump that transmits motion to the water.
Impeller
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- Intake orifice at the center of a centrifugal pump impeller.
Impeller eye
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Centrifugal Pumps:
The _________ of the impeller dictates the amount of pressure that is developed.
speed
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Centrifugal Pumps:
The faster the disk is turned, the harder the water is thrown, giving the water more __________.
velocity
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Centrifugal Pumps:
The volume capacity of the pump is dictated by the size of the ?
impeller
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Centrifugal Pumps:
A larger impeller has a larger eye, allowing greater ?
flow capacity
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Centrifugal Pumps:
The off-center mounting of the impeller within the casing creates a water passage of gradually increasing size as it nears the discharge outlet of the pump. This section of the pump is called the _________.
volute
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- Spiral, divergent chamber of a centrifugal pump in which the velocity energy is given to water by the impeller blades is converted into pressure.
Volute
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Three main factors influence a centrifugal fire pump’s discharge pressure:
- Amount of _________ being discharged
- ________ at which the impeller is turning
- Pressure of water when it enters the pump from a _____________ source
- water
- speed
- pressurized
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Centrifugal Pumps:
For example with all other factors remaining constant, doubling the speed of the impeller will result in _______ times as much pressure.
four
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A centrifugal pump is unable to pump ______ and is not ______-____________.
air / self-priming
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There is a phenomenon of _____________ due to recirculating in single-stage pumps, where excess capacity is not allowed to escape the impeller area. This may lead to pump damage.
cavitation
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Pumps used in the fire service constructed with a single impeller are referred to as ?
single-stage centrifugal pumps
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Single-stage centrifugal pumps:
These may consist of front-mount pumps, power take off, auxiliary engine driven, and midship pumps that use a single intake impeller and a simple casing to provide flow capacities up to _________ gpm.
2,250 gpm
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_____________ centrifugal pumps have an impeller for each stage mounted in a single housing.
Multistage
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Multistage centrifugal pumps:
When the pump transfer valve is in the volume position, each of the impellers takes water from a source and delivers it to the discharge. This is know as pumping in the ?
parallel (volume) position
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Multistage centrifugal pumps:
When the transfer valve is set in the pressure position, all water from the intake manifold is directed into the eye of the first impeller. This is know as pumping in ?
series (pressure) position
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Setting the transfer valve to series greatly increases the maximum ____________ that may be attained; however increasing the ___________ results in a corresponding loss in ___________.
pressure / pressure / volume
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The process of switching between pressure and volume is sometimes referred to as “_______________”.
“changeover”
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Switching from volume to pressure can result in the immediate doubling of the previous ?
discharge pressure
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The maximum net pump discharge pressure at which the _____________ valve may be safely operated varies by manufacturer and age of the pump.
transfer valve
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If there is any question as to the correct position of the transfer valve, it is best to operate in ___________ rather than _________.
parallel (volume) / series (pressure)
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In the parallel mode, the pump will be capable of supplying 100 percent of its rated capacity at ______ psi at _____ feet of lift with _____ feet of suction hose while drafting.
150 psi / 10 feet / 20 feet
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___________ (________) valves are essential to the operation of a multistage pump.
Clapper (check) valves
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- Hinged valve that permits the flow of water in one direction only.
Clapper Valve
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- Automatic valve that permits liquid to flow in only one direction. For example, the inline valve that prevents water from flowing into a foam concentrate container when eduction pressure is disrupted.
Check Valve
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A very close tolerance must be maintained between the pump casting and the hub of the impeller. This opening is usually limited to _____ inch or less. Any increase in the opening lessens the effectiveness of the pump.
.01 inch or less
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To restore the pumping capacity without replacing the entire pump, _______ rings or __________ rings in the pump casing may be replaced to maintain the preferred spacing between the hub of the impeller and the pump casing.
wear rings or clearance rings
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- Replaceable rings that are attached to the impeller and/or the pump casing to allow a small running clearance between the impeller and pump casing without causing wear of the actual impeller or pump casing material.
Wear Rings
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Newer model centrifugal pumps may be equipped with a __________ _________ valve that opens to allow overheated water to circulate between the pump and the main water tank or into the atmosphere.
thermal relief valve
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The driver/operator can check for excessive pump temperature manually by placing a hand on the direct pump intake pipe. If it is warm to the touch, the driver/operator should open a ?
discharge, tank fill, or circulator valve
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When operating a pump not equipped with a thermal relief valve, the best course of action to prevent overheating is to ensure that ?
some water is moving through the pump at all times
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Pump impellers are fastened to a shaft that connects to a ____________ ________. The transmission transfers the required energy to spin the impellers at a very high rate of speed.
transfer case
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_____________ seals are the most common type in use today.
Mechanical
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Pumps powered by gasoline or diesel engines independent of the vehicle-drive engine are examples of ____________ pumps.
auxiliary pumps
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Although used on some structural fire fighting pumpers, the most common applications for auxiliary engine driven pumps are:
- ___________ rescue fire fighting vehicles
- ______________ fire apparatus
- _________ water supply apparatus
- _________ mounted fire pumps
- ___________ fire pumps
- Airport (ARFF)
- Wildland
- Mobile
- Trailer
- Portable
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- Mechanism that allows a vehicle engine to power equipment such as a pump, winch, or portable tool; it is typically attached to the transmission.
Power Take-Off (PTO) System
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- Ability of an apparatus to pump water while the vehicle is in motion.
Pump and Roll
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In the past, conventional PTO units were limited to powering pumps up to approximately ______ gpm. However, some manufacturers now provide full torque power take-offs that allow for the installation of pumps as large as ________ gpm. This type of PTO is commonly used with automatic transmissions where the __________ of the engine drives the PTO unit.
500 gpm / 1250 gpm / flywheel
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Some fire department pumpers feature an extended front bumper with a pump mounted between the __________ and the _________ of the vehicle.
bumper / grill
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- Fire pump mounted in front of the radiator of a vehicle and powered off the crankshaft.
Front-Mount Pump
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One major disadvantage of the front-mount pump is susceptibility of the pump and gauges ?
freezing in cold weather due to their exposed position.
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During warm weather operations, front-mount pumps may obstruct ___________ through the vehicles radiator and may contribute to overheating.
airflow
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Most fire departments operate pumpers that feature the pump mounted laterally across the frame behind ?
These pumps are called ________ pumps.
the engine and transmission / midship
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Midship Pumps:
The gear ratio is arranged so that the impeller turns faster than the engine, usually _____ to _____ times as fast.
1 1/2 to 2 1/2 times as fast
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With the engine idling and the pump engaged, most speedometers will indicate between _____ to _____ mph.
10 to 15 mph
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Apparatus with ______-________ pumps are becoming increasingly popular.
rear-mount
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