Month 12; Hydraulics Section 2 (Field Formulas)

Question 0

When extending a preconnect

• 1 3/4”
• 2 1/2”

Answer 0

• 1 3/4” @ 125 gpm add 10 PSI per 50’ section.

- 2 1/2” @ 250 gpm add 5 PSI per 50’ section.

Question 1

Friction Loss for 2 1/2” Hose (Field Formula)

Drop the Zero

Answer 1

1. Start with the GPM flow through the hose Ex. 350 GPM
2. Drop the last digit (Drop Zero) 350 = 35
3. When flowing less than 450 GPM reduce the value by ten
   Ex. 35 = 25psi FL/100
4. When flowing more than 450 GPM or more only drop the zero
   Ex. 450 GPM = 45 psi FL/100
5. This method produces a friction loss value in PSI per 100’ of hose.

Question 2

Relay Pumping

Minimum intake Pressure
Maximum intake Pressure

Answer 2

• Do not exceed the rated pressure on the hose or capacity of the pump.
• Minimum intake pressure on the receiving pump is 20 PSI.
• Maximum intake pressure on the receiving pump is 90PSI.

Question 3

Supplying on the Aerial

• How much friction loss for aerial?
• How much friction loss for the monitor?
• What about elevation loss?
• What should the standard operating PSI be?
• What is the max PSI?

Answer 3

• Do not exceed the rated pressure of the hose or capacity of the pump.
• Add 10 PSI friction loss for the aerial waterway.
• Add 25 PSI friction loss for the monitor.
• Add in the estimated elevation loss (+/-)
• The flow meter can be used to determine GPM flow.
• Standard operating pressure should be 200 PSI or less.
• A max of 250 PSI is allowed but a relief valve for the tower will be spilling water.

Question 4

Elevation Loss (+/-)

Answer 4

-Add 5 PSI per floor not counting the 1st Floor.

Question 5

Intake Relief Valves

Answer 5

Set by Dept Mechanics to 120-150 PSI

Question 6

Relief Valves

Answer 6

Set by driver to 10-20psi above the anticipated operating pressure.

Question 7

Pressure Governors

Answer 7

Automatically adjust engine RPM to maintain the desired engine pressure. Set by driver to the desired operating pressure.

Question 8

Hand Held Solid Bore

• Tip Pressure
• 1/2”
• 1”
• 1 1/8”
• 1 1/4”

Answer 8

• Tip Pressure = 50 PSI
• 1/2” = 50 GPM
• 1” = 200 GPM
• 1 1/8” = 250 GPM
• 1 1/4” = 300 GPM

Question 9

Master Stream Sold Bore

Tip Pressure
1 3/8
1 1/2
1 3/4
2

Answer 9

• Tip Pressure = 80psi
• 1 3/8 = 500 GPM
• 1 1/2 = 600 GPM
• 1 3/4 = 800 GPM
• 2 = 1000 GPM

Question 10

Combination Nozzles

Nozzle Reaction

Answer 10

NR = GPM/2

Ex. House set-up at 125 GPM

NR = 125/2 = 62.5lbs

Question 11

Solid Bore Nozzles

Nozzle Reaction

Answer 11

NR = GPM/3

Ex. 1 1/4” hand-held solid bore tip, flowing 50psi at tip
NR= 300/3
NR = 100lbs

Ex. 1 3/4” master stream tip, flowing 80 psi at tip.
NR= 800/3
NR = 266.6lbs