when is cavitation created?
when air cavities are created in the pump or bubbles pass through the pump
what is the benefit of a fout-way hydrant valve
a second pumper can connect and boost pressure and not interrupt the flow of water
what is static pressure
pressure on the master intake gauge when connected to a water source but not flowing water
what is the general discharge psi for a standpipe (SBC number also)
150psi
what is the max lift an engine can do when in good working order?
25’
what is the benefit of the reverse lay?
it is the most direct method of supplementing hydrant pressure or doing drafting operations
what can happen to the pump if discharge pressure increases too much and the supply can’t keep up
cavitation could occur to the pump and or the supply system
what is medium diameter hose?
2.5-3” hose
what can occur if dirt or sand is taken into the pump?
it can act as an abrasive and can get into the pump packing and reduce its ability to seal
what is the distance the pump should be rated to lift when operating at its capacity
10’
what is cavitation?
in theory, water being discharged faster than it is coming into the pump
which type of hydrant is the “worst” option to be aware of?
A dead end main hydrant
what is the unit of measure for each foot of lift when drafting?
should be 1” mercury for each 1’ of lift
what is the best hose lay for a drafting operation?
a reverse lay
what is the unit of measurement on the intake gauge when drafting?
inches of mercury (since changes in pressure are so minute)
what should be done after nonpotable water is pumped through the apparatus?
the tank should be flushed
how much FL is found per floor on a multistory building?
5psi
what should be done when attempting to flow from a drafted source?
as the throttle is increased, open the discharge valve slowly (to maintain a prime) until the discharge pressure is achieved.
what are 3 ways to reduce pump from overheating when assisting in a relay operation or having to support a long lay
- establish a continuous minimum flow
- pull the booster line a distance and flow
- partially open tank-fill or tank-to-pump valve
in a severe case, what noise may be heard in the pump?
sound of gravel passing through the pump
what is an easy way to establish prime if the pump primer fails?
open the tank to pump to fill the tank and intake hose (assuming tank to pump valve is able to close)
what prevents water from backing from a standpipe at the FDC
clapper valves
how is a static water pressure reading obtained when connected to an external water source
when the tank is full and there isn’t any flowing water - read the master intake guage
why are dead end main hydrants the “worst” option to be aware of?
there is higher amounts of sediment & deterioration and are served by smaller mains from only one direction
what is the procedure when charging a hydrant thats connected to our intake line?
while keeping the intake valve closed, open the drain valve to bleed off air from the charged line
how much water is needed to encompass the strainer when attempting to draft
24” in all directions is preferrable
what is the typical pressure loss from using a standpipe (SBC number also)
25psi
which valve should be closed after establishing an external water source
close the tank-to-pump valve
what is the surest indication of cavitation ?
the lack of reaction on the pressure gauge to increase in the throttle
what is residual pressure
pressure on the intake gauge when flowing water (connected to a water source)
what is a pressure differential?
creating a partial vacuum (via pump primer)
when would the transfer valve be placed into parallel (volume) setting?
when supplying a relay operation or master stream (when needing to supply large amounts of water)
In general, what can (and ususally does) happen with your supply when your discharge pressure is increased significantly
the supply source may drop due to friction loss
what are some signs cavitation is occurring?
- pressure on the gauge will fluctuate
2. hose streams may pulse
how is the vacuum measured on the pump?
it is measured from the surface of the water to the eye of the pump’s impeller
at what PSI should your intake pressure never go below when pumping from a pressurized supply source?
<20psi
what should you do if the master intake gauge drops below 20psi
either reduce or not INCREASE the throttle to prevent cavitation
as far as drafting goes, how much friction loss is lost per 1000’
0.5psi or 1” of mercury
to create an effective fire stream, what is the max lift recommended?
20’
what is a means of ensuring you dont lose prime when drafting?
use the booster line to flow water back into the static source during the entire draft operation
the amount of friction loss in the intake hose depends on…
diameter of the house and the length
longer/smaller hose increases FL
