1. Instructor Lee Lautzenheiser
Coralville Fire Department November 2006 Training Basic Fire Pump Theory and Operation
Instructor Lee Lautzenheiser

2. Pump Theory & Operation
Our goal today is to provide you with some basic information regarding fire pumps and friction loss. With this information you should have a better understanding of the way pumps work and how to properly operate the pumps on the apparatus. After this presentation we will go through actual pumping exercises.

3. Pump Theory Centrifugal Pumps Single-Stage (71)
Two-Stage (other pump apparatus)

4. Pump Theory Single-Stage
No Transfer Switch for Pressure and Volume Modes
Limited to 2000gpm
Simpler than Two-Stage Pumps

5. Pump Theory
Single-Stage Diagram

6. Pump Theory
Single-Stage Diagram

7. Pump Theory Two-Stage Two modes: Pressure & Volume
Pump has two impellers vs. single
Larger pump capacities (both volume & pressure) are available

8. Pump Theory
Two-Stage
In volume mode the impellers are in parallel which gives more water volume but require higher RPMs for a given pressure
In pressure mode the impellers are in series which gives higher water pressure at a lower RPM but less total volume is available

9. Pump Theory & Operation
Two-Stage
Switch to volume mode when you are using 50-65% of the pumps rated volume
To transfer between modes the engine RPMs must be less than 1000 and the output pressure under 100psi

10. Pump Theory & Operation
Two Stage
Coordinate transfer with crews as operations will be briefly interrupted
Anticipate pressure changes when changing modes:
Volume Mode will require higher RPMs
Pressure Mode will require lower RPMs

11. Pump Theory
Two-Stage Diagram

12. Pump Theory Centrifugal Pumps
Operates by “slinging” the water out of the pump outlet
Little to no damage occurs when lines are shut down (remember WATER HAMMER)
When no water is being discharged though the pump will heat the water from the friction

13. Pump Theory & Operation
Centrifugal Pumps
Recirculating water is a must to prevent overheating when no water is being flowed
Pumping off the tank – crack open tank fill valve
Pumping off a hydrant –crack open a discharge using a small hose to redirect water to an “out of the way” location
Pumping off a draft – crack open a discharge and flow water back into the water supply

14. Pump Theory & Operation
Centrifugal Pumps
Pressure Relief Valves
Set about 20psi above desired discharge pressure
Do not operate partially opened as it will not suppress the pressure surge
71 does not have a pressure relief valve but computer governor that automatically throttles back when there is a pressure surge

15. Pump Theory & Operation
Centrifugal Pumps
External Pressure Relief Valves
All trucks except 71 have a relief valve on the 5” intake adapter which are set at 100psi
When pumping to other apparatus use a discharge pressure of 60-80psi to mimic hydrant pressure
Expect the discharge pressure to change when going from tank to hydrant or visa versa

16. Pump Theory & Operation
Centrifugal Pumps
Draining Pumps
Open all drains
Open all intakes and discharges except the tank suction

17. Pump Theory & Operation
Centrifugal Pumps
Require priming when drained and this may even be necessary when operating off the tank
Also priming is needed for drafting and water needs to remain flowing to keep the prime
May use another hose or deck gun to flow water into the water supply

18. Pump Theory & Operation
Primer Pumps
Primer pumps are positive displacement
You do not “suck” water but rather the primer pump reduces the pressure in the pump by evacuating the air or water and then the outside air pressure pushes water into the pump

19. Pump Theory & Operation
Centrifugal Pumps
Standpipe Operation
Pump at marked pressure or if not marked then 150psi
Add 5psi for each floor

20. Pump Theory Friction Loss
As water moves through the hose it will encounter friction
Theoretical Formula
FL = CQ2L where C = coefficient for a typical hose of a given size, Q = flow/100, and L = length/100

21. Pump Theory Friction Loss
For our preconnects we have 200 feet of 1¾” hose with a 125gpm at 75psi nozzle…
FL = (15.5)(125/100)2(200/100)
FL = 48.4psi
Total PSI needed is 75psi plus 48.4psi or 123.4psi

22. Pump Theory Friction Loss
For 200 feet of 2½” hose with a 250gpm at 100psi nozzle
FL = (2)(250/100)2(200/100)
FL = 25psi
Total PSI needed is 100psi plus 25psi or 125psi

23. Pump Theory & Operation
Friction Loss
This is why we pump preconnects at 120psi

24. Pump Theory & Operation
A few other pointers…
Add 5psi for each 10 feet of elevation
Typical master stream fog nozzles operate at 80psi, smooth bore nozzles at 50psi and handheld fog nozzles at 100psi
Never let the intake pressure drop below 20psi when operating from a hydrant as damage to the water system may occur

25. Pump Theory & Operations
Remember that if you get hung up to stop and think about what is going on. Start over from the beginning if necessary.
Get out and practice, no need to actually take a truck out as you can verbally go out to the trucks and walk through it

26. Pump Theory & Operations
Questions?