Pumps and Hydraulics Flashcards
Hydraulics
The study of physical characteristics exhibited by fluids at rest and in motion.
Hydrostatics
Fluids at rest
Hydrokinetics
Fluids in motion
Friction Loss
That part of the total pressure that is lost while forcing water through pipes, fittings, hose and adaptors
Engine Pressure
Pressure that must be developed at the apparatus to overcome friction loss, elevation, and provide correct nozzle pressure
Net Engine Pressure
Engine pressure less any intake pressure
Nozzle pressure
Pressure that must be delivered to the nozzle in order for the nozzle to function properly and flow the correct amount of water.
Water Hammer
Force transmitted through a fluid when an obstruction is placed quickly in the path flow
Cavitation
Bubbles of vapor created in the pump that pass from negative to positive pressure then collapse or implode.
Physical characteristics of water
a. 1 gallon of fresh water weighs 8.35lbs
b. 1 gallon of water = 231 cubic inches
c. 1 cuft = 1728 cuin of water
d. 1 cuft = 7.418 gal
e. 1 cuft = 62.5lbs
NFPA 1901
Standard on Fire pumps
Class A pumpers
c. Pumpers will have one 2.5in outlet for every 250GPM (i.e., TFD engines have 5)
d. UL test plate on pump panel has rated capacities of pump
e. TFD’s pumper’s capacity is 1250
f. Used to boost pressure
Rated capacity of TFD pumpers
i. TFD engines rated capacity is 1250GPM
ii. 100% of rated capacity @ 150psi
iii. 70% of rated capacity @ 200psi
Five times pumps are tested
a. By manufacturer
b. By 3rd party representative (UL or FM)((Underwriters Laboratory or Factory Mutual))
c. Upon delivery (acceptance test)
d. Annually (done by field units)
e. After extensive maintenance (to pump)
Types of pumps
Positive displacement (can move air)
Non-positive displacement
(cannot move air)
Positive displacement pumps
i. Pump and displace air
ii. Moves a given amount of water with each stroke or rotation
iii. Two types
1. Piston – works with vacuum created by a moving piston, as well as with one way valves that restrict water flow
2. Rotary – comes in two types
a. Rotary gear
b. Rotary vane
Non-positive displacement pumps
i. Centrifugal pumps
ii. Based on the principle of centrifugal force
iii. Most common type used in fire service
iv. Does not pump a definite amount of water with each revolution
v. Capable of utilizing incoming pressure
Components of a centrifugal pump
- Casing
a. Constructed of fine grain alloy, cast iron
b. Minimum tensile strength of 30,000psi
c. Split into two sections for easy removal of impeller assembly - Impeller
a. High quality bronze construction
b. Stainless steel shaft
c. Eye at the center with vanes curving outward
d. Vanes covered on both sides by shrouds, which confine the water within the vane pockets.
Part of a centrifugal pump to know for diagram…
i. Eye
ii. Hub
iii. Stripping edge
iv. Volute
v. Impeller
vi. Vanes
vii. Shroud
viii. Casing
ix. Discharge
Pump mounting and drive arrangements
a. Auxiliary engine driven (brush truck)
b. Cross mounted engine
c. Power take off (pump and roll)
i. Pump is driven by a crankshaft connected to the PTO on the chassis transmission
ii. Pump pressure changes when the driver changes vehicle speed
iii. Allows pump-and-roll capability
d. Front mount
e. Mid-ship mount (TFD)
Stages of pump
a. Refers to number of impellers
b. Both single and multistage are common
c. All TFD pumpers are Hale, Single Stage, midship mounted pumps.
d. Ladder 1 and Tower/Ladder 17 (Quint17) are Waterous, 2 stage pumps
2 stage pumping patters
volume/parallel
pressure/series
Volume/parallel
i. Each impeller receives ½ the intake volume
ii. Both impellers pump to discharge side of pump
iii. Each impeller is capable of delivering 50% of total capacity
iv. Total GPM equal to the sum of each impeller
v. Transfer valve between impellers closed
vi. Used when you want more than 50% of rated capacity
Pressure/series
i. Water is pumped from first impeller through open transfer valve to second impeller then to discharge
ii. Pump discharge volume remains constant
iii. Second stage impeller doubles pressure
iv. Used when less than 50% of rated capacity is needed
v. Engine doesn’t have to work as hard
Pump accessories
Relief valves and governors Priming devices Discharge and intake valves Instrumentation gauges Auxiliary coolers
Standard relief valves
a. Relieves excess discharge pressure back into the suction side of the pump
2. Separate intake and discharge relief systems
TPM relief system
a. Total Pressure Master
b. Relieves excess pressure from both discharge and intake sides of pump
c. Has a sensing valve on intake side of pump
i. Blinking light = relieving external
ii. Solid light = relieving internal
d. On all TFD pumpers
Pressure governors
a. Use engine speed to control excess discharge pressure
b. Engine speed determines impeller speed
c. Hydraulic line from discharge side of pump transmits pressure rise to governing device which then cuts back the throttle.
What do relief valves and governors do?
a. Use engine speed to control excess discharge pressure
b. Engine speed determines impeller speed
c. Hydraulic line from discharge side of pump transmits pressure rise to governing device which then cuts back the throttle.
Priming devices
i. Necessary because centrifugal pumps are not capable of pumping air
ii. Three categories
1. Positive displacement pump
a. Rotary vane or rotary gear
b. TFD uses rotary vane on all apparatus
c. Electric drive
2. Exhaust pumps
3. Vacuum pumps
Types of gauges
Pressure
Compound (can read below 0)
Controls and instruments at pump panel
- Master pump intake gauge
- Master pump pressure gauge
- Tachometer
- Engine temp gauge
- Engine oil pressure gauge
- Voltmeter
- Discharge valves
- Primer control
- Water tank to pump valve control
- Water tank fill valve control
- Water tank level indicator
Instrument and gauge details
iii. On both types of gauges, pressure is measure by a gauge containing a closed curved tube known as the Bourdon Tube.
iv. As pressure is applied water enters the open end of the tube and it tends to straighten
v. The tube is connected to a gear mechanism that controls the movement of the needle.
vi. Master pump intake gauge must be compound
1. Reads in psi on pressure side
2. Reads in 0-30 inHg on vacuum side
Auxiliary coolers
i. Engine cooler – helps control engine temp during pumping operations. Uses heat exchanger
1. Usually in upper radiator hose
2. New pumpers installed near pump tranny
ii. Recirculating line (pump cooler) – Keeps pump water cool when pump is engaged and no water is flowing. Recirculates water from pump to booster tank.
Pumping problems
i. Water hammer
1. Force transmitted through a fluid when an obstruction is placed quickly in the path of the flow.
2. Can damage equipment and hurt people.
3. Can be prevented by opening and closing valves on hydrants, trucks and nozzles slowly.
ii. Cavitation
1. Bubbles of vapor created in the pump that pass from negative to positive pressure then collapse or implode
2. Sounds like gravel in the pump
3. Damages the pump
4. Caused by running out of water, or water getting too hot.
Engine pressure formula
Engine pressure = Nozzle pressure + Friction Loss +/- Hydrant pressure + appliance loss (EP=NP+FL+/-HP+AL)
Smooth bore formula
iii. GPM formula 29.7D^2√NP
iv. Nozzle reaction = 1.5D^2NP
Fog nozzle formula
v. Fogs have preset GPM settings/ratings
vi. NR=.05GPM√NP
vii. √50=7.07
^^not sure what this last bit is..^^
Friction loss
- All based off of 2.5in hose
- FL/100’ = 2Q^2+Q for over 100GPM
- FL/100’ = 2Q^2+.5Q for less than 100GPM
- If you need to change something, do [formula]*coefficient
a. 1.75in hose coefficient = 5.95
b. 2.5in hose coefficient = 1
c. 5in hose coefficient = .031
d. Red line coefficient = 86
Tandem pumping
i. Two pumpers operating from one hydrant
ii. Hooked up inlet to inlet
iii. Used when a single hydrant has more water available than is being utilized by a single pumper
Relay pumping
i. Used when it is necessary to lay supply lines over long distances
ii. Distance limited by friction loss and elevation
iii. Pumpers set in relay to boost pressure
iv. Attempt to maintain 40lbs residual pressure
v. Hooked up outlet to inlet
THINGS TO KNOW!!!
a. When to use volume/parallel and pressure/series
b. What is NFPA 1901
c. 100% of rated capacity is at 150GPM
d. Know the five times the apparatus pump is tested
e. Gallon of water – 8.35
f. Main advantage of a centrifugal pump is that it can utilize incoming pressure
g. Formulas are based off of 2.5in
h. Know the difference between tandem and relay pumping
i. Q = quantity of water/100
j. Know the nozzle pressure formulas
k. Know friction loss
l. Know definitions
