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Positive Dispacement Pump definition
Delivers a measured amount of water on each stroke or cycle of the pump.
Positive Displacement Slippage
No slippage. If discharge is stopped, pump will break.
Types of Positive Displacemnt Pumps
2. Rotary Gear
3. Rotary Vane
Rotary Gear and Vane uses
Driven by starter motor. Used as primer pump to exhaust air in a centrifugal pump.
Centrifugal Pump advantage/disadvantage
100% slippage (can run without discharge)
Can not exhaust air
Centrifugal Pump Nomentclature
Volute- housing around impeller
Impeller- spinning part that creates flow
Eye- takes in water to center of impeller
Diffuser Vane -water thrown out of impeller here
Wear rings- take bulk of wear in spinning impeller
Freedom pump- Mechanical seal replaced packing gland for cooling the shaft
Pump Rated Capacity PSI
Rated at 150 psi net pump pressure. Above this output is diminished.
Net Pump Pressure
100% at 150 psi
70% at 200 psi
50% at 250 psi
Occurs when impeller tries to thow more water than intake can provide.
Rapidly creates steam in pump and causes damage
Sounds like rocks in the pump
Possible causes of cavitation
Throttle too high
Positive Displacement pump lowers atmospheric pressure in the volute forcing water into the eye of the pump.
Anti Siphon Hole
Top of priming system
Size of a broom straw .04"
Small intake to release suction on oil tank when priming is done
Two Stage centrifugal pump
Has two impellers
independate (parallel or volume)
one feeds the other (series or pressure)
Used in two stage pump to change from parallel to series
Lower pressure to 50 psi before changing from volume to pressure, because pressure will double
When to use parallel or volume
When ever you pump more than 1/2 your rated capacity
Intake relief or Dump Valve
Takes excessive intak water pressure and dumps it on the ground.
Tank to Pump
Opens tank water to gravity feed into the pump.
Tank to pump notes
500 gallons per minute
NFPA requires 80%
3- 31/2 inch line
Tank Fill valve
Fill the tank from the pump
Helps to cool the pump
3/8 inch discharge line to cool the engine
Used on older engines to relieve excessive back pressure created by closing a discharge
Feeds water and pressure back to intake side of pump
PSG (Pressure Sensor Governor)
Electronic control to maintain Master Gauge pressure when there are changes in the the hose lines
Used in stead of relief valve
Changes the fuel to the engine
Fire pump components
pump components and nomenclature