Chapter 9 Fire Pump Theory Flashcards
With centrifugal pumps, the impeller transmits energy in the form of _____ to the water. The ______ houses the impeller assembly, collects the water and confines it in order to convert the _____ to ______.
Velocity
Pump casing
Velocity to pressure
A centrifugal pump is based on the principle that a rapidly revolving desk tends to what?
Throw water introduced at its center toward the outer edges of the disk
Which type of pump may be used to remove the air and allow atmospheric pressure to force water into the pump?
A rotary vane pump
Spiral divergent chamber that increases in size as it nears the discharge. This is where the velocity of the water is turned into pressure.
Volute
3 main factors that influence a centrifugal pumps discharge pressure
Amount of water being discharged
Speed at which the impeller is turning
Pressure of water when it enters the pump from a pressurized source
Two basic types of centrifugal pumps used by fire
Which one has a phenomenon of cavitation due to recirculation?
Single and multi stage
Single does
Why do single stage centrifugal pumps have that name?
Because they have a single impeller
Single stage centrifugal pumps can provide flow capacities up to
2,250 gpm
What is used to minimize the large lateral thrust of water entering the eye of the impeller?
What minimizes the radial thrust?
A double suction impeller that takes in water from both sides , each side side is equal so it cancels out the thrust.
Having the volutes shoot water in opposite directions.
What allows you to switch A multi stage pump from parallel to series or vice versa?
The transfer valve
When in parallel mode you are in what?
Volume mode
If a two stage pump is rated at 1000 GPM at 150 psi, each of the impellers supplies how many GPM to the pump discharge manifold? This is in parallel mode.
500 gpm each
When pumping in the series position you are in what mode?
Pressure mode
Switching the transfer valve between each mode on a centrifugal pump is sometimes referred to as what?
Changeover
In parallel mode the pump will be capable of supplying 100% of its rated capacity at blank psi, at blank feet of left with blank feet of suction hose while drafting.
150 psi
10 feet
20 feet
What is the spacing between the pump casing and the hub of the impeller?
.01 inch or less
What is the name of the parts used to maintain the preferred spacing between the hub of the impeller and the pump casing?
Wear rings
If all your discharges are shot in the water inside the impeller is allowed to churn for a long period of time what might happen?
The water in the pump might get hot and the metal parts of the pump may expand. If the where rings and impellers expand too much they may come in contact with each other in the friction of the two surfaces rubbing will create additional heat and may result in serious damage to the pump.
What do some newer model centrifugal pumps have that prevents water to get too hot within the pump?
A thermal relief valve
It allows overheated water to circulate between the pump and the main water tank or into the atmosphere
What kind of pumps are powered by gasoline or diesel engines that are independent of the vehicle drive engine?
Auxiliary engine driven pumps
Mechanism that allows a vehicle inch into power equipment such as a pump winch our portable tool.
is typically attached to the what?
Power take off drive
PTO
If a engine with a power take off has the ability for pump and roll than where might the PTO be connected to?
The engines flywheel
Where is a front mount pump usually located and what is it powered off of?
It is usually located in front of the radiator and powered off the crankshaft
How is power supplied to midship pumps?
Power is supplied to these pumps through the use of a split shift gear case or transfer case which is located in the driveline between the transmission and the rear axle
What if there is a malfunction of the transfer case and you cannot put a pump into gear?
The driver operator should know how to manually shift the pump into gear in the event of a malfunction with the transfer case
With the engine idling and the pump engaged most pedometers will indicate between blank to blank miles per hour?
10 to 15 mph
Engaging the pump on a fire engine involves transferring the power from what to what?
From the rear axle to the pump drive gears
The piping system and the fire pump itself must be capable of withstanding a hydrostatic test of how much psi before being placed into service?
500 psi
According to NFPA 1901 pumpers with a capacity of 500 GPM tanks or less should have pipe in capable of flowing how much GPM?
250 GPM
Pumpers with a capacity greater than 500 GPM tanks should be able to flow at least how much GPM?
500 GPM
How is the amount of flow obtained determined? This is for intakes
The amount of flow that can be obtained as determined by the diameter of the pipe from the intake valve to the pump inlet and the straightness of the pipe routing
As a minimum of fire apparatus with a rated pump capacity of 750 GPM or greater must be equipped with at least how many 2 1/2 inch discharges?
What about for pumps rated less than 750 GPM?
2
1
Discharges are usually equipped with a locking ball valve that can be operated in and locked in any position all valves should be designed and maintain so that they are easily operable at pressures of up to how much psi?
250 psi
According to NFPA 1901 apparatus equipped with tanks of less than 1000 gallons must have a tank fill line of at least how many inches in diameter?
Thanks greater than 1000 gallons must be provided with at least how many inches for the tank fill line
1 inch diameter
NFPA 1901 requires that all intakes or discharges that are 3 inches or greater be equipped with slow acting valve controls. This feature prevents the valve movement from open to close in less than how many seconds? This minimizes the risk of damage caused by water hammer when large volumes of water are being moved
3 seconds
Talk about two of the main types of pump trains on an engine pump
There are drain valves on the hose line side of the control valve and please allow an operator to drain a hose line without having to open the nozzle on the line and the discharge valve is closed.
Bleeder valves on gated intakes serve another purpose they are located on the outside of the gated valve to the intake so that you can push the air out of the supply hose through the bleeder without having to open your intake
Name 2 basic concepts for pressure relief calves
Those that relieve excess pressure on the discharge side and those that relieve pressure on the intake side
What type of valve does the most common relief valve use?
A spring controlled pilot valve
The pressure governor is designed to regulate the blank to match the pump discharge requirements
Engine speed
The electronic governor features cavitation protection by returning the engine to idle when the intake pressure drops below?
30 psi
What do modern centrifugal pumps need in order to create a lower pressure in the pump/intake hose than what exists in the atmosphere for drafting?
A priming device
Which instrument displays the engine speed in rpm?
Tachometer
Where is the rpm required to pump the rates capacity located?
On an identification plate on the pump panel
What does a gradual increase in the amount of rpm required to pump the rates capacity mean?
It indicates wear in the pump and possible need for repair
Which gauge displays the temperature of the coolant in the engine that powers the pump?
Pumping engine coolant temperature indicator
Which instrument shows if an adequate supply of oil is being delivered to the critical areas of the engine that powers the fire pump?
Pumping engine oil pressure indicator
What instrument indicates battery condition?
Which one indicates the status of the alternator and charging system?
Voltmeter
Ammeter
Before the engine is started, with the batteries turned on, the voltmeter indicates the ….
Top voltage available when the battery is fully charged , and measure the drop in voltage as electrical accessories are used
