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Flow Monitoring Equations And Conversions

Most systems are engineered to operate at fluid velocities lower than 15 feet/second or 4.5 meters/second. This fact, along with the following set of equations, can assist with the correct selection of a flow monitor's measuring range. Also, keep in mind that the most accurate part of a Lake flow meter's measuring range is within the center third of the full range. (i.e. If the nominal flow rate in a system is 10 GPM, do not purchase a flow monitor that has a full-scale flow rate of 10 GPM – order the next higher full scale range.)


Known:         Pipe I.D. (inches), Fluid Velocity (feet/second)
Unknowns:  Liquid Flow Rate (GPM)
Flow Rate (GPM) = 2.447994 x (pipe I.D.)2 x Fluid Velocity

Known:         Pipe I.D. (mm), Fluid Velocity (meters/second)
Unknowns:  Liquid Flow Rate (LPM)
Flow Rate (LPM) = 0.0471189 x (pipe I.D.)2 x Fluid Velocity


Known:         Liquid Flow Rate (GPM), Pipe I.D. (inches)
Unknowns:  Fluid Velocity (feet/second)
Fluid Velocity (ft./sec.) = (0.408498 x Flow Rate/(pipe I.D.)2


Known:         Liquid Flow Rate (LPM), Pipe I.D. (mm)
Unknowns:  Fluid Velocity (meter/second)
Fluid Velocity (m./sec.) = (21.22291 x Flow Rate/(Pipe I.D.)2


Known:         Pressure (PSIG), Flow Rate (GPM)
Unknowns:  Hydraulic Horsepower Development
Hydraulic Horse Power = (Pressure x Flow Rate)/1714


Known:         RPM, Pump Displacement (Cubic Inches/Revolution)
Unknowns:  Flow Rate (GPM)
Flow Rate (GPM) = (RPM x Pump Displacement)/231


Flow Rate Related Formulas

Flow Rate Related Formulas


Volume and Capacity Equivalents

Units

Cubic
Inches

Cubic
Feet

Cubic
Meters

Liters

U.S.
Gallons

Imperial
Gallons

 Cubic Inches

1

0.0005787

0.00001638

0.016384

0.004329

0.003607

 Cubic Feet

1728

1

0.028317

28.317

7.48052

6.23210

 Cubic Meters

61,023.4

35.3145

1

1000

264.17

220.083

 Liters

61.0234

0.0353145

0.001

1

0.264170

0.220083

 U.S. Gallons

231

0.133681

0.003875

3.78543

1

0.833111

 Imperial Gallons

277.274

0.160459

0.0045437

4.54374

1.20032

1

 Pounds of Water

27.6798

0.016018

0.00045359

0.453592

0.119825

0.099828


Example of How To Use This Chart:

Question:

Determine the number of U.S. Gallons in a cubic meter.

Answer:

Using the column labeled U.S. Gallons and the row labeled Cubic meters, the conversion is 264.2 gallons/cubic meter


Pressure and Head Equivalents

Units

psi

Ft of Water

Atmospheres

kg/Cm2

Bar

kPa

psi

1

2.3039

0.06805

0.07031

0.06895

6.89465

Feet of Water

0.4331

1

0.02947

0.03045

0.029926

2.99267

Atmospheres

14.696

33.931

1

1.0332

1.01319

101.319

kg/Cm2

14.2234

32.840

0.96784

1

0.98062

98.062

Bar

14.5038

33.4153

0.9869

1.01976

1

100

kPa

0.14504

0.33415

0.00987

0.010198

0.01

1


Example of How To Use This Chart:

Question:

Determine the psi equivalent to 10 bar of pressure.

Answer:

Using the column labeled psi and the row labeled bar, the conversion factor is 14.5038 psi/bar. The equivalent pressure to 10 bar would equal 10 x 14.5038 = 145.033 psi


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Phone: 262-884-9800 | Toll Free: 800-850-6110
Fax: 262-884-9810

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