IFSTA - Chapter 10 Flashcards
How to prevent pump from overheating during incident
- If water is not flowing for an extended period of time, pump can overheat
- Moving water through the pump must be implemented: booster cooling valve, circulator, or bypass can be set to open and circulate water back into the tank
PG 338
Transitioning to an External water supply
- Connect supply line to appropriate intake of fire pump
- Make connection to intake with closed gate valve
- Open bleeder vale on the gated intake so that air can escape ahead of the water supply; shut the bleeder valve done after a steady stream of water drains from the valve
PG 338
Residual Pressure
- Driver/operators should maintain a residual pressure of at least 20PSI on master intake gauge at all times
PG 340
Choosing a Hydrant
- ## Closest hydrant to the fire may not always be the most prudent choice (due to pumping capability or danger in location)
“Dead End Mains”
Water main that is not looped and in which water can flow in only one direction
- Generally have high amounts of sediment and deterioration
PG 340
Forward Lay
- Method of laying hose from the water supply to the fire scene
- Stop at hydrant, drop end of supply line with FF, proceed to fire location
PG 341
Four-Way Valve Hydrant Operation
- Connect valve to the hydrant
- Connect original supply line, laid by first pumper, to the supply line outlet
- Open the hydrant. The clapper valve has operated to allow water to flow in the supply line
- Connect second pumper to the large diameter pumper intake connection on the four-way vale
- Open pumper intake valve. Open the four-way valve on the hydrant to supply the pump without interfering with the flow through the original supply line
- Connect one of the pumper discharge outlets to the second intake of the hydrant valve
PG 343
Reverse Lay
- Method of laying hose from the fire scene to the water supply
- Apparatus reports to scene before laying a supply line back to the hydrant
- Load the hose with a male coupling to come out of the bed first, using hose with threaded couplings for a reverse lay
PG 344
Master Intake Gauge Pressure Reading
- When pump is full of water and pressure in the system with no water flowing, this reading indicates the static pressure in the water supply system
- This reading is important for estimating the remaining capacity of the hydrant as the water begins to move
- Driver/operator should record the static pressure reading before he/she begins to pump
PG 346
Methods to prevent overheating of the pump
- Establish continual minimum flow during intermittent use of water in fire ground operations to keep the pump from overheating
- Pull a length of booster line or small diameter line and fasten it to a sturdy object
- Open the valve that supplies the booster reel and discharge water in a direction that will not interfere. The booster line may also be directed back into the tank to circulate water continuously
- Open discharge drain valve.
- Partially open the tank fill vale or tank to pump line. Even if the water tank becomes full and overflows, this result is preferable to the pump overheating
PG 347
Residual Pressure
When the pumper is discharging water, the intake gauge displays the residual pressure
PG 347
Static Pressure
When the pumper is not discharging water, the intake gauge displays the static pressure
PG 347
Methods to determine how much more water the hydrant can supply
- Difference between static pressure and residual pressure
1. Percentage method
2. First digit method
3. Squaring the lines method
PG 347
Percentage Method
- First calculate drop in pressure as a percentage:
Percent Drop = (Static-Residual)(100)/Static - Determine how much more water is available based on percentage drop:
0-10% = 3x current amount being delivered
11-15% = 2x current amount being delivered
16-25% = Same amount being delivered
25%+ = More water might be available, but not as much as is currently being delivered
PG 348
First Digit Method
- Quick and easy way to calculate available water using PSI and GPM
1. Find the difference in PSI between static and residual pressures
2. Multiply the first digit of the static pressure by 1, 2, or 3 to determine how many additional lines of equal flow may be added
If PSI drop is equal to or less than the first digit of the static pressure multiplied by 1, three additional lines can be flowed
If PSI drop is equal to or less than the first digit of the static pressure multiplied by 2, two additional lines can be flowed
If PSI drop is equal to or less than the first digit of the static pressure multiplied by 1, one additional line can be flowed
PG 349
Squaring-The-Lines Method
- Note static pressure before any pump discharges are open
- Must also have close idea of the volume of water initially flowed by the pumper.
- Use these numbers to determine the additional amount of water available and square the number of lines currently flowing and multiply this by the original pressure drop
PG 350
Pressure Differential
Effect of altering the atmospheric pressure within a confined space by mechanical means.
- When air is exhausted from within the space, a low pressure environment is created and replacement air will be drawn in
- When air is blown into the space, a high pressure environment is created and air within will move to the outside
Necessary when drafting from static water source that is below the level of the fire pump
PG 352
Cavitation
- Water being discharged faster than it is coming into the pump
- Occurs when air cavities are created in the pump or bubbles pass through the pump
- They move from point of highest vacuum into the pressurized section, where they collapse or fill with water
- This high velocity of water filling these cavities causes a severe shock to the pump
PG 354
Selecting Water Drafting Site
- Amount of water: large quantity available; rapid replenishment (stream)
*Must be at least 24” of water over the strainer - Type or quality of water: pumping “nonpotable water” (untreated water) may be harmful to the pump; saltwater can cause corrosion to pipes; avoid dirt and sand
- Accessibility of water: choose a site with low lift to be able to supply more water
PG 356-357
Connecting Pump for Drafting
- Place apparatus at location from which intake hose will be deployed
- Set parking brake, chock wheels
- Place out traffic control devices
- Do not engage pump until all connections are made and it is ready to be put in operation
- Inspect gaskets for dirt and debris; couple together strainer and intake hose
- Fasten rope to end of strainer to aid in handling of hose and proper positioning of strainer
PG 358
Priming Pump for Drafting
- Must be in parallel (volume) position in two-stage pump
- Set RPMs between 1000-1200RPM
- Operate primer control (typically takes 10-15 seconds for full prime)
- Increase throttle to raise pressure to between 50-100psi
PG 360
Operating Pump for Drafting - Problems
- Air leak on intake side of pump –> recheck intake hose couplings
- Whirlpool allowing air to enter pump –> not enough water above drafting strainer; place floating object above strainer
- Air leakage due to defective pump packing
PG 361