Flashcards in Chapter 10 Fire Pump Theory Deck (84)
Positive displacement pumps have largely been replaced by ___ for use as the main fire pump on modern fire apparatus.
Positive displacement pumps are used as ___ devices to get water into centrifugal pumps during drafting operations.
The two basic types of positive displacement pumps are:
piston and rotary pumps.
Piston positive displacement pumps may be:
single-acting or double-acting.
The output of the piston positive displacement pump is determined by the size of the cylinder and the:
speed of the piston travel.
The capacity of a piston positive displacement pump is usually determined by the size of the:
Rotary positive displacement pumps are the ___ of all fire apparatus pumps in design.
Rotary positive displacement pumps are now used as:
small-capacity, booster-type pumps, low-volume high pressure pumps, and priming pumps.
The total amount of water that can be pumped by a rotary gear pump depends on the size of the ___ and the speed of rotation.
pockets in the gears
Rotary vane pumps are constructed with moveable elements that automatically compensate for:
The centrifugal pump is classified as a ___ because it does not pump a definite amount of water with each revolution.
nonpositive displacement pump
The centrifugal pump imparts ___ to the water and converts it to pressure within the pump itself.
The ___ of the centrifugal pump transmits energy in the form of velocity to the water.
The ___ of the centrifugal pump collects the water and confines it in order to convert the velocity to pressure.
The ____ of the centrifugal pump is a water passage that gradually increases in cross-sectional area as it nears the pump discharge outlet.
The impeller in a centrifugal pump rotates very rapidly within the casing, generally from ___ rpm.
2,000 to 4,000
The volume capacity of the pump is dependent on the size of the ___ of the impeller: The greater it is, the greater the flow capacity.
Which of the following is NOT a factor that influences a centrifugal fire pump's discharge pressure?
A. Amount of water being discharged
B. Speed at which the impeller is turning
C. Size of the volute and impeller inside the pump*
D. Pressure of water when it enters the pump from a pressurized source
What is changeover?
The process of switching between the pressure and volume position
SOPs in some departments specify that the transfer valve stay in the pressure position until it is necessary to supply more than ___ the rated volume capacity of the pump.
Most manufacturers specify that the pump may remain in the pressure system until it is necessary to flow more than ___ of the rated volume capacity.
Most manufacturers recommend that the transfer valve should be operated at a maximum pressure of:
50 psi (350 kPa).
While the parallel (volume) position may make it difficult to attain the desired pressure, it can supply ___ percent of the rated volume capacity at ___ psi (kPa).
100%, 150 psi (1 000 kPa)
Any increase in the space between the pump casing and the hub of the impeller lessens the pump's effectiveness. This opening is usually limited to ___ or less.
0.01 inch (0.25 mm)
To restore pump capacity without replacing the pump itself, replaceable wear rings (or ___ rings) are provided in the pump casing to maintain the desired spacing.
Packing rings are used to make a seal at the point where the shaft passes through the:
The most common type of packing material is made of rope fibers impregnated with:
graphite or lead.
As packing rings wear with the operation of the shaft, the ___ can be tightened and the leak controlled.
Which of the following are supplied to provide cooling and lubrication between the packing rings and shaft?