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Hydraulics > Chapter 12 Principles of Fire Service Pressure Loss Calculations > Flashcards

Chapter 12 Principles of Fire Service Pressure Loss Calculations Flashcards

1
Q

Test conducted in the 1970s revealed that wetting additives could reduce friction loss as much as __. What are these test often referred to as?

A

40%

wet water test

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2
Q

To date no mathematical models exist for calculating friction loss with wetting additives. The best recommendation is to ___

A

reduce the final answer by 25%, to provide a safe margin of error

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3
Q

Name of the first hydraulic formulas available to the fire service

A

underwriters formulas

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4
Q

What are the two reasons it’s not advisable to use the underwriters formulas anymore

A
  1. based on hose technologies in the 30s and 40s with significantly higher friction loss
  2. different formulas based upon the amount of water being flowed
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5
Q

What were the two types of hose-lines being used when the underwriter’s formula was developed?

A

3/4” or 1” booster hose

2.5” rubber lined firehose

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6
Q

what are the two premises of the underwriters formula?

A

based on 2.5” hose

based on 100ft sections of hose

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7
Q

When was the usefulness of the underwriters for more called into question? What was the workaround?

A

when hose other than 2.5” started being used

calculating the friction loss of 2 1/2” hose then converting the flow rate into the actual hose used

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8
Q

FL= CQ ²+L name of each component

A

FL- friction loss
C- coefficient
Q ²- flow rate and hundreds of GPM
L- hose length and hundreds of ft

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9
Q

what are the three options fire personnel have at the discharge end of parallel lines

A
  1. connect lines into multiple inlet master stream
  2. connect lines into a Siamese appliance that in turn discharges a single hose
  3. connected lines into being intake of one or more fire apparatus equipped with pumps
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10
Q

test showed that when two hoselines of equal length are siamesed to supply a fire stream, friction loss is approximately___ of a single hose line at that same flow and nozzle pressure…. when running trips its ___

A

25%

10%

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11
Q

coefficients represent averages, in real life the coefficient number will vary with a number of factors including: (5)

A
  1. age of the hose
  2. manufacture
  3. design
  4. how well it’s been maintained
  5. number of bends, cracks and creases
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12
Q

departments wishing to know exact coefficients can get the information two ways:

A
  1. request information from the manufacturer

2. test their own hose

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13
Q

what equipment is required to determine friction loss coefficients (5)

A
  1. pitot or flowmeter
  2. to in-line gauges
  3. test hose
  4. smoothbore nozzle (pitot)/ any nozzle (flowmeter)
  5. worksheet
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14
Q

what are the steps you must perform to determine your own friction loss coefficient

A

step 1. lay 300ft of hose in lengths of 50ft
step 2. connect to discharge, and nozzle
step 3. 50’, gauge, 200’, gauge, 50ft, nozzle
step 4. flow, complete worksheet

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15
Q

if water exerts a pressure of .433 psi per foot, or 2.31 ft of water… what does this equates to in terms of pressure loss?

A

you lose .5 PSI per foot of water or

EP= .5 H

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16
Q

In hose assemblies flowing over 350 GPM an appliance loss of 10psi is factored into calculations. what appliances garner this friction loss?

A 
Wyes
 Siameses
 reducers and increasers
 manifolds
 FDC/ standpipe (possibly)
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17
Q

What are the two premises of the underwriters formula?

A

based on 2.5” hose

based on 100ft sections of hose

18
Q

Coefficients represent averages, in real life the coefficient number will vary with a number of factors including: (5)

A
  1. age of the hose
  2. manufacture
  3. design
  4. how well it’s been maintained
  5. number of bends, cracks and creases
19
Q

Appliance friction loss generally is considered significant only in cases where the total flow through an appliance is at least_____, what is the frictional loss?

A

350 GPM

10 psi

20
Q

Master streams, aerial waterways, and standpipe systems assume a friction loss of __

A

25psi

21
Q

When determining the friction loss equal length, equal diameter, multiple lines… the operator can____

A

perform calculations for one line because the other lines will have approximately the same friction loss

22
Q

Determining friction loss in a wyed hose line of equal length and diameter is easy, when the nozzle pressure hose length and diameter of both the hose lines are the same then…

A

Wyed appliance equally splits the water flow, So you only have to consider one of the wyed hose lines to compute the total pressure loss

23
Q

In situations where one half of the wyed lines is at a higher elevation, how should you figure the pressure loss

A

calculate on a worst-case basis, meaning the elevated pressure loss should be factored in

24
Q

To calculate friction loss in hoselines of varying size and lengths you must do what?

A

calculate each line individually, then determine which part of the hose lay has the greatest amount of pressure loss. Pump discharge pressure will be set for the line with the highest friction loss, other lines will be gated down

25
Q

The underwriter’s formula was found to be in accurate for flows less than__

A

100 GPM

26
Q

when wyed lines have unequal lenghths or diameters how is friction loss calculated?

A

Determine friction for each unequal length/ diameter, then use the line with the greater pressure loss in final calculation

27
Q

was the primary difference between calculating friction loss for master stream hose arrangement and hand lines

A

volume of water that master streams flow

28
Q

most master streams used by municipal fire departments are capable of flows up to 1000 GPM. They can be supplied by ___MDH hose or____ LDH hose

A

3 MDH

1 LDH

29
Q

if hose line supplying the master stream device are and are being pumped from the same pumper, to ease calculation of friction loss what should you do

A

use the average of the hose length, for calculation

30
Q

what are the methods for determining pressure loss and required pump discharge pressure (6)

A 
flowmeters
 hydraulic calculations
 pump charts
 hand method
 condensed Q formula
 GPM flowing
31
Q

what is the ultimate purpose of all fireground hydraulic calculations?

A

to discharge an appropriate amount of water from the nozzle to be used for fire attack

32
Q

why are flowmeters particularly advantageous when supplying master streams with automatic nozzles

A

driver may be supplying insufficient discharge pressure that looks acceptable but is producing an ineffective stream

33
Q

NFPA 1901 allows the use of flowmeters instead of pressure gauges on discharges of what size

A

1.5-3”

34
Q

flowmeters must provide a readout that his increments no larger than

A

10 GPM

35
Q

If an increase in pressure does not produce an increase in flow ( flowmeter) what may be the cause

A

hoses kinked
midline valve closed
vehicle tire on hose

36
Q

what are the three basic types of hydraulic calculations available to the fire service?

A

manual
mechanical
electronic

37
Q

explain the hand or counting finger method

2.5” hose

A

left hand, finger tips are assigned 2, 4, 6, 8, 10… the spaces between the fingers represent the odd numbers. the base of the fingers represent flow 100, 200, 300, 400, 500… with the spaces between being 150-450. to determine friction loss start with required flow and multiply the corresponding fingertip number by the first number at that finger base

38
Q

explain the finger counting method

1 3/4” hose

A

left hand, fingertips are assigned 1-5, thumb base is assigned 12 all other finger bases are 9 and knuckles are assigned 100-200gpm. go to the flow knuckle and multiply the tip number by base number for friction loss

39
Q

what is the condensed to formula used for?

A

To determine friction loss in 3”, 4” and 5” hose

40
Q

how does the condensed Q formula compare with

FL=CQ ² L

A

the condensed Q formula is less accurate, friction loss is 20% greater

41
Q

What is the primary determinant of friction loss?

A

volume of water flowing per minute, taking into account the length and diameter of the hose-line

Hydraulics (15 decks)

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