* Hydraulics (pt 2)

Question 1

When multiple lines are connected to an FDC or Siamese…

Answer 1

1. I only use FL from the line with highest FL
2. And I divide the GPM by all available lines. [So for 2 - 2 1/2 supplying 265gpm to standpipe I divide the GPM in half and then figure the FL for one of my 2 1/2]

Question 2

How much water is in the three different hose lines?

Answer 2

1. 5 inch: 1 gallon / foot
2. 2 1/2: 25 gallons / 100 feet
3. 1 3/4: 12.5 gallons / 100 feet

Question 3

Can our centrifugal pumps expel air?

Answer 3

1. Not when it is full of air.
2. But if there is a mixture it can expel it through a discharge.
3. So when drafting the rigid does not have to be completely free of air before I begin to open a discharge

Question 4

When pumping a wet/dry ladder what are the appliance values for the forward pumper?

Answer 4

1. 20psi if going through a wet ladder pump intake
2. 80psi if going through a wet ladder rear intake
3. 80psi if dry ladder [the extra 20psi is to account for the water going through the pump; dry ladder’s don’t have a pump; wet ladders do have a connection in the rear which goes straight to the stick and bypasses the pump and would not need the 20 appliance value, but would need everything else]

Question 5

If I am an engine pumping a wet ladder what calculations do I need to account for? What about a dry/rear intake of a wet?

Answer 5

1. I only need to account for the friction loss in supply hose and 20psi appliance value for forward pumper
2. unless I am going in the rear intake, then I need to account for all the factors: friction loss + NP + Elevation P + 80psi AL]

Question 6

Do I add the appliance value for ladder trucks (50/80) if pumping less than 350gpm?

Answer 6

No

Question 7

Why do I add the 20psi AL for forward pumpers?

Answer 7

To keep the residual pressure above 20psi (we will always add this AP)

Question 8

What is a major shortfall of the tank to pump?

Answer 8

1. Only supplies about 500gpm.

2. The tank fill line may be large enough that I may start to cavitate if I’m pumping 1 3/4 and esp 2 1/2

Question 9

If I am a wet ladder pumping myself, do I add my appliance loss?

Answer 9

I’m not if over 350gpm

Question 10

What is the AP for a 2 1/2 that is being used in the middle of a hose connection? Last time I didn’t even factor this number in.

What about a 1 3/4 nozzle?

Answer 10

(I am actually starting to doubt this. I need to test it out) 30psi regardless of the flow

Too much for practical purposes

Question 11

What is the maximum distance for 1 3/4?

What is GPM and psi for it?

What if I increase the pressure?

Answer 11

1. 400’
2. 140psi
3. 160gpm

Increasing beyond this develops a lot for nozzle reaction without much beneficial increase in GPM because of critical velocity (the practical limit of pressure in hose/pipe. Would need to increase diameter or number of hose lines if supplying another pumper)