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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
| 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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