Module 3 - Hydraulic Calculations

Question 1

Four Principles of Friction Loss

Answer 1

1. Varies directly with the length of the hose (double the length = double the friction loss)
2. Varies with the square of the velocity (flow) – if we double the flow we will have 4x the FL
3. For a given flow, FL varies inversely as the 5th power of the hose diameter
   655 /445 = 7
   - For the same flow a 44mm hose will have 7x more FL than the 65
4. Is dependent on flow and does not change with different pressure

Question 2

Basic Friction Loss Calculation

Answer 2

FL/L = (Q/100)^2 x C

Question 3

FL/L = (Q/100)^2 x C

Answer 3

FL/L = FL per length in 30m lengths

Q = quantity of water flowing in L/M

C = coefficient of friction of a given hose

Question 4

Coefficients

Answer 4

44mm = 6
65mm = 0.8
77mm = 0.4
125mm = 0.03

Question 5

Determining Friction loss

Answer 5

Two ways: actual test and calculations

Question 6

Hydraulic Calculation Pump Discharge Pressure

Answer 6

PDP = NP + TFL + APP +/- ELEV

Question 7

PDP = NP + TFL + APP +/- ELEV

Answer 7

PDP – Pump discharge pressure
NP - nozzle pressure
TFL – total friction loss
APP – appliance pressure loss
ELEV – elevation pressure gain or loss

Question 8

Nozzle Pressure

Answer 8

solid bore handline – 350 kPa
Fog nozzle handline – 700 kPa
Master stream – 550 kPa

Question 9

Total Friction loss – different sized lines

Answer 9

TFL = FLa + FLb

Question 10

Appliance Friction Loss

Answer 10

We consider flow under 1400 lpm to be negligible and consider it to be zero

Flows of 1400 lpm and above simply add 70 kPa to our PDP

Excluding master stream devices

Question 11

Elevation Equation

Answer 11

Pressure in a column of water is calculated at 10 kPa per meter of elevation

When there is a rise in elevation we need to add to our discharge

When there is a drop in elevation we need to subtract from the discharge pressure

Question 12

Elevation Change

Answer 12

Commonly found at high rise events

Every floor is 4m – add 40 kPa/floor above ground

We count from the second floor up to the fire floor because we are level with the first floor when pumping

Residential = 3.5m, commercial = 4m

Question 13

Net Pump Discharge Pressure (NPDP)

Answer 13

Centrifugal pumps can take advantage of incoming water pressure to increase pumping efficiency

If an engine is required to discharge 1000kPa and it has an intake pressure of 350kPa, the pump only needs to add 650kPa more to meet the demand

Question 14

Nozzle Calculations

Answer 14

Not performed on the fire ground

Too low – limits the flow to less than critical application rate

Too high – may result in unreasonable nozzle reaction

Question 15

Nozzle Flow (Solid Bore)

Answer 15

L/Min = 0.067 x D^2 NP

Question 16

Bore Sizes

Answer 16

44mm handline – 24mm
65mm handline – 29mm
Blitzfire solid bore tips – 24mm, 32mm, 38mm

Question 17

Nozzle Reaction

Answer 17

NR = 0.0015 x D^2 x NP

Question 18

Configurations of connecting to Hydrants

Answer 18

Single
Twin
Single relay
Twin relay
Two hydrant supply

Question 19

Single

Answer 19

Question 20

Twin

Answer 20

Question 21

Single relay

Answer 21

Question 22

Twin Relay

Answer 22

Question 23

Two hydrant supply

Answer 23

Question 24

Limiting Factors and Solutions

Answer 24

Available water flow from the hydrant/main

The pressure hydrant has to push the water down the supply hose to the truck

Friction loss created by the hose lay supplying the truck

Question 25

Available water flow from the hydrant/main

Answer 25

Use 125 port as well as a 65 port with a 65 to 125 adapter

Use a second hydrant

Question 26

The pressure hydrant has to push the water down the supply hose to the truck

Answer 26

Relay supply engine helps maximize the water to the attack engine

Question 27

Friction loss created by the hose lay supplying the truck

Answer 27

Can be reduced by twinning the supply lines directly from the hydrant or in a relay

Question 28

*When using a second hydrant, the attack engine compound gauge

Answer 28

must not exceed the original static pressure to prevent pumping back into the water supply*

Question 29

Hydrant Flow depends on: (S.L.I.P)

Answer 29

• Size
• Length
• Internal condition
• Pressure of the water main

Question 30

*City of Calgary water services considers hydrant flow of ___________ as a minimum

Answer 30

5000 lpm as a minimum

Question 31

High rise events

Answer 31

have a standard of 150kpa friction loss and must be added to the calculations

Question 32

relay operations

Answer 32

boost the pressure to a maximum of 1260 kpa from the supply engine

Question 33

Max forward lay

Answer 33

of lengths = (discharge-safety) / FL/L

Question 34

twinning from a single hydrant will increase the flow by

Answer 34

approx. 30%

Question 35

using two hydrants will yield higher flow than twinning from 1 hydrant

Answer 35

approx. double

useful in areas with low flowing hydrants