Pumping Apparatus Driver/ Operator — Lesson 8 Customary Pumping Apparatus Driver/Operator Handbook, 2 nd Edition Chapter 8 Customary — Theoretical Pressure.

Pumping Apparatus Driver/ Operator — Lesson 8 Customary

Pumping Apparatus Driver/Operator Handbook, 2nd Edition

Chapter 8 Customary — Theoretical Pressure Calculations

Pumping Apparatus Driver/Operator

8 Customary–2

Learning Objectives

1.Answer questions about friction loss, elevation pressure, and total pressure loss (TPL).

2.State the equation for determining friction loss.

3.Calculate friction loss.

4.Select facts about determining your own friction loss coefficients.

(Continued)


8 Customary–3

Learning Objectives

5.Test hose carried on your apparatus to determine friction loss.

6.Answer questions about appliance pressure loss.

7.Select facts about elevation pressure.

8.State the equations for determining elevation pressure. (Continued)


8 Customary–4

Learning Objectives

9.Calculate elevation pressure.

10. Answer questions about hose layouts.

11. Calculate total pressure loss in single hoseline layouts.

12. Calculate total pressure loss for wyed hoselines of equal length. (Continued)


8 Customary–5

Learning Objectives

13. Calculate total pressure loss for siamesed hoselines of equal length.

14. Calculate total pressure loss for standpipe operations.

15. Calculate total pressure loss for multiple hoselines of unequal length.

(Continued)


8 Customary–6

Learning Objectives

16. Calculate total pressure loss for wyed hoselines of unequal length and for manifold hoselines.

17. Calculate total pressure loss for master streams.

18. State the equation for determining pump discharge pressure.

(Continued)


8 Customary–7

Learning Objectives

19. Calculate pump discharge pressure.

20. State the equation for determining net pump discharge pressure (NPDP).

21. Calculate net pump discharge pressure.


8 Customary–8

Friction Loss andElevation Pressure

• To produce effective fire streams, it is necessary to know the amount of friction loss in the fire hose and any pressure loss or gain due to elevation.

• Causes of friction loss– Hose condition– Coupling condition– Kinks– Volume of water flowing per minute (Continued)


8 Customary–9

Friction Loss and Elevation Pressure

• The calculation of friction loss must take into account the length and diameter of the hoseline and any major hose appliances attached to the line. Because the amount of hose used between an engine and the nozzle is not always the same, driver/operators must be capable of determining friction loss in any given length of hose.

(Continued)


8 Customary–10

Friction Loss and Elevation Pressure

• Elevation differences, such as hills, gullies, aerial devices, or multistoried buildings, create a pressure loss or gain known as elevation pressure.

• Together, friction loss and elevation pressure loss are referred to as total pressure loss.


8 Customary–11

Determining Friction Loss

• Equation A

FL = 2Q2+Q

FL = Friction loss in psi

Q = Flow rate in hundreds of gpm (flow/100)L = Hose length in hundreds of feet (length/100)

(Continued)


8 Customary–12

Determining Friction Loss

• Determine the number of hundreds of gallons of water per minute flowing (Q) through the hose by using the equation:

Q = gpm/100

Determine the number of hundreds of feet of hose (L) by using the equation:

L = feet/100(Continued)


8 Customary–13

Determining Your Own Friction Loss Coefficients

• If you wish to calculate more accurate results for the fire hose that is carried on your apparatus, rather than use the results from the standard friction loss coefficients, it is recommended that you test your hose to determine the actual coefficients.

(Continued)


8 Customary–14


• In order to get results indicative of averages that can be expected on the fireground, it is necessary to use the same hose that would be used on the fireground.

• Conduct tests on hose that is in service, not on hose that has been in storage or hose that has never been put into service (unless new hose is about to be placed into service).

(Continued)


8 Customary–15


• Departments should test only one hose type at a time.

• It is important that all measuring devices are in good condition and properly calibrated.

(Continued)


8 Customary–16


• Needed equipment– Pitot tube or flowmeter– Two in-line gauges,

calibrated in increments of 5 psi or less

– Hose to be tested– Smoothbore nozzle (if

using pitot tube)– Any type nozzle (if using

flowmeter) (Continued)


8 Customary–17


• Refer to Skill Sheet 8-1 Customary for detailed instructions.


8 Customary–18

Appliance Pressure Loss

• Appliances on the fireground include reducers, increasers, gates, wyes, manifolds, aerial apparatus, and standpipe systems.

(Continued)


8 Customary–19


• Appliance friction loss is insignificant when the total flow through appliances is less than 350 gpm.

• For this lesson, assume a 0 psi loss for flows less than 350 gpm and a 10 psi loss for each appliance (other than master stream devices) in a hose assembly when flowing 350 gpm or more.

(Continued)


8 Customary–20


• Friction loss caused by handline nozzles is not considered in the calculations in this lesson, as it is generally insignificant in the overall pressure in a hose assembly.

• For this lesson, assume a friction loss of 25 psi in all master stream appliances, regardless of the flow.


8 Customary–21

Elevation Pressure

• Elevation pressure is created by elevation differences between the nozzle and the pump.

(Continued)


8 Customary–22

Elevation Pressure

• Water exerts a pressure of 0.434 psi per foot of elevation.

• When a nozzle is operating at an elevation higher than the apparatus, this pressure is exerted back against the pump.

• To compensate for this pressure “loss,” elevation pressure must be added to friction loss to determine total pressure loss.

(Continued)


8 Customary–23

Elevation Pressure

(Continued)


8 Customary–24

Elevation Pressure

• Operating a nozzle lower than the pump results in pressure pushing against the nozzle.

• This “gain” in pressure is compensated for by subtracting the elevation pressure from the total friction loss.

(Continued)


8 Customary–25

Elevation Pressure


8 Customary–26

Determining Elevation Pressure

• Equation B

EP = 0.5H

EP = Elevation pressure in psi

0.5 = A constant

H = Height in feet

(Continued)


8 Customary–27

Determining Elevation Pressure

• It is generally easier to determine elevation pressure in a multistoried building by another method. By counting the number of stories of elevation, use:

• Equation C

EP = 5 psi x (number of stories)


8 Customary–28

Hose Layouts

• The combination of friction loss and elevation pressure is referred to as total pressure loss.

• Pressure changes are possible due to hose friction loss, appliance friction loss (when flows exceed 350 gpm), and any pressure loss or gain due to elevation.

• By adding all the affecting pressure losses, the total pressure loss can be determined for any hose lay.


8 Customary–29

Simple Hose Layouts

• Single hoseline

• Multiple hoselines (equal length)

• Wyed hoselines (equal length)

• Siamesed hoselines (equal length)


8 Customary–30

Single Hoseline

• Is the most commonly used hose lay

• Presents the simplest friction loss calculations


8 Customary–31

Multiple Hoselines (Equal Length)

• When determining the friction loss in equal length multiple lines whose diameters are the same, it is only necessary to perform calculations for one line.

• When the diameters of the hoselines vary, friction loss calculations must be made for each hoseline. The pump discharge pressure is then set for the highest pressure.


8 Customary–32

Wyed Hoselines (Equal Length)

• When using a wye, it is important that the attack lines wyed from the supply line are the same length and diameter in order to avoid two different nozzle pressures and an exceptionally difficult friction loss problem.

(Continued)


8 Customary–33


• When the nozzle pressure, hose length, and diameter are the same on each wyed line, an equal split of the total water flowing occurs at the wye appliance.

• This enables only one of the wyed hoselines to be considered when computing the total pressure lost.

(Continued)


8 Customary–34


• Step 1 — Compute the number of hundreds of gpm flowing in each wyed hoselines by using the equation:

Q = flow rate (gpm)

100

(Continued)


8 Customary–35


• Step 2 — Determine the friction loss in one of the wyed attack lines using the equation:

FL = 2Q2+Q

(Continued)


8 Customary–36


• Step 3 — Compute the total number of hundreds of gpm flowing through the supply line to the wye by using the following equation:

QTotal = (gpm in attack line 1) + (gpm in attack line 2)

100(Continued)


8 Customary–37


• Step 4 — Determine the friction loss in the supply line using.

(Continued)


8 Customary–38


• Step 5 — Add the friction loss from the supply line, one of the attack lines, 10 psi for the wye appliance (if the total flow exceeds 350 gpm) and elevation pressure (if applicable) to determine the total pressure loss.


8 Customary–39

Siamesed Hoselines (Equal Length)

• When calculating friction loss in siamesed lines, however, it is necessary to use a different set of coefficients than for single hoselines.

(Continued)


8 Customary–40


• Step 1 — Compute the total number of hundreds of gpm flowing by using the equation:

Q = gpm flowing

100

(Continued)


8 Customary–41


• Step 2 — Determine the friction loss in the attack line

• Step 3 — Determine the amount of friction loss in the siamesed lines

(Continued)


8 Customary–42


• Step 4 — Add the friction loss from the siamesed lines, attack line, 10 psi for the siamese appliance (if flow is greater than 350 gpm), and elevation pressure (if applicable) to determine the total pressure loss.


8 Customary–43

Complex Hose Layouts

• Standpipe operations

• Multiple hoselines (unequal length)

• Wyed hoselines (unequal length) and manifold hoselines

• Master streams


8 Customary–44

Standpipe Operations

• In most cases, fire departments have predetermined pressures that driver/operators are expected to pump into the fire department connection (FDC) of a standpipe system.

(Continued)


8 Customary–45


• These pressures are contained in the department’s SOPs, in the pre-incident plan for that particular property, or on a faceplate adjacent to the FDC.

(Continued)


8 Customary–46


• In order to be able to determine the required pressure for the standpipe system, it is necessary to determine the total pressure loss.

• Treat the FDC like any other hose appliance.


8 Customary–47

Multiple Hoselines (Unequal Length)

• When unequal length hoselines are used, the amount of friction loss varies in each line.

• For this reason, friction loss must be calculated in each hoseline.


8 Customary–48

Wyed Hoselines (Unequal Length) and Manifold Hoselines

• Remember that when hose lengths are unequal in length and/or diameter, the total pressure loss in the system is based on the highest pressure loss in any of the lines.

(Continued)


8 Customary–49


• Step 1 — Compute the number of hundreds of gpm flowing in each of the wyed hoselines by using the following equation:

Q = discharge gpm

100

• Step 2 — Determine the friction loss in each of the wyed lines.

(Continued)


8 Customary–50


• Step 3 — Compute the total number of hundreds of gpm flowing in the supply line to the wye or manifold by adding the sum of the flows in the attack lines and dividing by 100.

(Continued)


8 Customary–51


• Step 4 — Determine the friction loss in the supply line

(Continued)


8 Customary–52


• Step 5 — Add the friction loss from the supply line, the wye or manifold appliance (if total flow is greater than 350 gpm), elevation loss, and the wyed line with the greatest amount of friction loss to determine the total pressure loss.


8 Customary–53

Master Streams

• Remember to add a 25 psi pressure loss to all calculations involving master stream devices.

(Continued)


8 Customary–54

Master Streams

• Determining friction loss for master streams is essentially the same as those used for other fire streams, unless unequal length or diameter hoselines are used to supply a master stream appliance.

• In this situation, use an average of the hose lengths for ease of calculation.

(Continued)


8 Customary–55

Master Streams

• Aerial devices with piped waterways are treated in the same manner as master stream appliances: using a friction loss of 25 psi to include the intake, internal piping and nozzle.


8 Customary–56

Determining Pump Discharge Pressure

• In order to deliver the necessary water flow to the fire location, the pump discharge pressure at the apparatus must be enough to overcome the sum of all pressure losses.

(Continued)


8 Customary–57


• Equation D

PDP = NP + TPL

PDP = Pump discharge pressure in psi

NP = Nozzle pressure in psi

TPL = Total pressure loss in psi (appliance, friction, and elevation losses)

(Continued)


8 Customary–58


• It is often important that attack lines be supplied with water at somewhere near the required nozzle pressure until the driver/operator has time to calculate the correct pump discharge pressure.

• It is SOP in many departments to initially charge attack lines with fog nozzles at 100 psi and solid stream nozzles at 50 psi while setting up for the pump operation.

(Continued)


8 Customary–59


• Supplying multiple, wyed, or manifold hoselines requires different pump discharge pressures for each attack line.

• Because this is not possible, set the pump discharge pressure for the hoselines with the greatest pressure demand.– Solid stream nozzle (handline) — 50 psi– Solid stream nozzle (master stream) — 80 psi – Standard fog nozzle — 100 psi– Low-pressure fog nozzle — 50 psi or 75 psi


8 Customary–60

Determining Net PumpDischarge Pressure

• Centrifugal pumps are able to take advantage of incoming water pressure into the pump.

• Thus, if a pumper is required to discharge 150 psi, and it has an intake pressure of 50 psi coming into the pump, the pump only needs to add 100 psi more to meet the demand. This concept is called net pump discharge pressure (NPDP). (Continued)


8 Customary–61


• NPDP takes into account all factors that contribute to the amount of work the pump must do to produce a fire stream.

• When a pumper is being supplied by a hydrant or a supply line from another pumper, the NPDP is the difference between the pump discharge pressure and the incoming pressure from the hydrant. (Continued)


8 Customary–62


• Equation E

NPDPPPS = PDP – Intake reading

NPDPPPS = Net pump discharge pressure from a positive pressure sourcePDP = Pump discharge pressure

Note: This equation does not apply to situations where the pumper is operating at a draft.


8 Customary–63

Summary

• To fulfill the primary fireground function of supplying attack crews with an adequate volume of water at pressures that are both safe and effective, driver/operators must be able to make certain hydraulic calculations in the field.

(Continued)


8 Customary–64

Summary

• To do this, they must know how to factor in losses in pressure due to friction, as well as pressure losses or gains because of elevation differences.

• In addition, driver/operators must be able to calculate pump pressure required to supply multiple hoselines of varying diameters, lengths, and configurations.


8 Customary–65

Discussion Questions

1.What four things can cause friction loss?

2.What is total pressure loss (TPL)?

3.What is the equation for determining friction loss?

(Continued)


8 Customary–66


4.What are the equations for determining elevation pressure?

5.What are the four types of simple hose layouts?

6.What are the four types of complex hose layouts?

(Continued)


8 Customary–67


7.What is the equation for determining pump discharge pressure?

8.What is the equation for determining net pump discharge pressure (NPDP)?

Pumping Apparatus Driver/ Operator — Lesson 8 Customary Pumping Apparatus Driver/Operator Handbook, 2 nd Edition Chapter 8 Customary — Theoretical Pressure.

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