ch10 Fire Pump Theory Flashcards
blank pumps are used as priming devices to get water into centrifugal pumps during drafting operations
positivie displacement pumps
blank pumps are the simplest of all fire apparatus pumps from the standpoint of design
Rotary-type
The blank pump consists of two gears that rotate in a tightly meshed pattern inside a watertight case
Rotary gear pump
The blank pump is constructed with movable elements that automatically compensate for wear and maintain a tighter fit with closer clearances as the pump is used
rotary vane pump
In this type of pump the rotor is mounted off center inside the housing
Rotary vane pump
The blank pump is classified as a nonpositive displacement pump because it does not pump a definitive amount of water with each revolution. Rather it imparts velocity to the water and converts it to pressure within the pump itself
centrifugal pump
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 edge of the disk
The blank transmits energy in the form of velocity to the water
impeller
the blank collects the water and confines it in order to convert the velocity to pressure
casing
the volume capability of the pump is dependent on the size of the blank of the impeller
eye
the greater the volume of water being flowed, the blank the discharge pressure
lower
doubling the speed of the impeller results in blank times as much pressure if all other factors remain constant
four
To minimize the blank thrust of large quantities of water entering the eye of the impeller, a double suction impeller was designed
lateral
Water being removed at two places and traveling in opposite directions cancels the blank thrust
radial
blank has an impeller for each stage mounted within a single housing
multi-stage centrifugal pump
When the transfer valve is in the pressure position, all the water from the intake manifold is directed into the eye of the blank
first impeller
the process of switching between pressure and volume is sometimes referred to as
changeover
the blank valve are essential in a multi-stage pump
clapper
the blank of the water moving through the impeller prevents most water in the discharge from escaping back into the intake
velocity
The first indication that wear is becoming a problem is when?
Increased engine RPM is required to pump the rated capacity in pump tests
To restore the capacity of the pump without replacing the pump itself, Blank or blank are provided in the pump casing to maintain the desired spacing between the hug of the impeller and the casing
replaceable wear rings, clearance rings
the blank transfers the necessary energy to spin the impellers at a very high rate of speed
gearbox
Proper mounting of these units is essential for dependable and smooth operation
PTO pumps
The PTO unit is powered by an blank in the truck transmission
idler gear
The typical unit is driven through a gear box and a clutch connected by a universal joint shaft to the front of the crankshaft
Front-Mount pumps
Power is supplied to the pump through the use of a split-shaft gear case(transfer case) located in the drive line between the transmission and the rear axle
Midship pumps
These units are driven by a shaft from the front of the vehicle’s engine
hydrostatic pumps
blank pumps may be powered by either a split shaft transmission or by a PTO
rear mount
The majority of all fires are initially fought with the water carried on the fire apparatus blank
tank
The blank valve prevent damage to the tank if the tank to pump valve inadvertently opens when water is being supplied to the pump under pressure, such as during a relay
check
Pumps that have a capacity of blank gpm or greater may require more than one large intake connection at each location
1,500
Discharges to which 1.5, 1.75, and 2 inch handlines are attached must be supplied by atleast blank inch piping
2
A tank fill line should also be provided from the blank side of the pump
discharge
NFPA 1901 requires some type of pressure control devide to be part of any fire apparatus pumping system. The device must operate within 3 to 10 seconds after the discharge pressure rises and must not allow the pressure to exceed blank psi
30
the main feature of a blank is its sensitivity to pressure change and its ability to relieve excessive pressure within the pump discharge
relief valve
Blank are intended to reduce the possibility of damage to the pump and discharge hoselines caused by water hammer when valves/nozzles are closed to quickly
intake pressure relief valves
it is generally recommended that intake relief valves be set to open when the intake pressure rises more than blank psi above the desired operating pressure
10 psi
Most blank are also equipped with a manual shut-off valve that allows the water supply to the pump to be stopped if so desired
Screw on intake pressure relief valves
the main feature of a blank is that it regulates the power output of the engine to match pump discharge requirement
pressure governor
These use a pressure-sensing element(pressure transducer) that is connected to the discharge manifold
electronic governor
