In the water industry (potable, irrigation, surface water, fountains, etc.) a device that removes particles from a fluid. Openings in the filter allow passage of fluid but not any particle larger than the opening size.
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Irrigation Craft Filter Systems
A pump connected to a fluid source in such a manner that pressure on the fluid at the suction inlet of the pump is equal to or greater than atmospheric pressure at a specified flow rate. This describes a fluid source that when vented to atmosphere, is not only above the pump centerline, but the fluid height above the pump and the intake line friction losses are such that pressure on the fluid as it enters the pump is always equal to or greater than atmospheric pressure.
Vernacular use of the term can describe a pump obtaining liquid from a source whose free surface is above the pump. The implication is that the pump cannot lose prime because the pump does not have to "lift" the fluid from a source located below the pump.
A pump operator must not make the mistake of assuming a pump cannot have suction cavitation if the fluid source is located higher than the pump or the fluid entering the pump is above atmospheric pressure. Pumps experience cavitation whenever the margin of NPSHA over NPSHR is insufficient. Pumps can have NPSHR values greater than atmospheric pressure and would therefore cavitate even if fluid pressure entering the pump were equal to atmospheric pressure.
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There are two types of flow rate measurement, Volumetric and Mass.
Volumetric Flow Rate (Symbol - Q)
The Volume of fluid moving past a point per unit of time, commonly expressed as Gallons per Minute in the U.S., Cubic Meters per Hour in the CGS system.
Because volume is dependent on conditions of pressure and temperature, highest accuracy requires a statement of Q at a given pressure and temperature. When dealing with non-compressible fluids such as water, pressure is not specified.
When expressing or publishing pump performance information, the flow rate data can be given at a specified temperature, pressure, and fluid type, or a standard test procedure is assumed or stated such those standards established by the Hydraulic Institute (HI), or the American Petroleum Institute (API).
The most common measurement of volume flow rate in the United States is Gallons Per Minute, gpm.
1 U.S. GPM = 3.785 Liters Per Minute
1 U.S. GPM = 0.0631 Liters Per Second
1 U.S. GPM = 0.2271 Cubic Meters Per Hour
1 U.S. GPM = 0.8327 Imperial Gallons Per Minute
1 U.S. GPM = 0.0238 Barrels Per Minute
1 U.S. GPM = 34.286 Barrels Per Day
Mass Flow Rate (Symbol
)
Mass Flow is the Mass of the fluid moving past a point per unit of time, commonly expressed as Kilograms per Minute or Hour. Pounds per unit of time could be used so long as the user knows and remembers that pounds are not a true unit of mass but of weight. The National Institute of Standards states that in commerce weight is often considered to be equivalent to mass, but in physics that is not allowed.
A statement of conditions is not always required to attain accuracy in general practice because mass is not related to temperature or pressure. In flow meter specifications flow meter performance may be stated as valid for a specified set of conditions.
Pumps deliver a volume flow rate at a given resistance head, regardless of the mass of the fluid. However the power required to deliver that volume of fluid depends upon the mass flow rate.
The energy required to operate a pump is determined by mass flow not volume flow because the pump consumes more power to pump heavier fluids than light fluids. However in practice Mass Flow is seldom used directly, but instead the Affinity Laws are used to determine Power requirements for a pump.
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A convenient method of analyzing valve performance for Non-Compressible Newtonian fluids. Cv is the American system with the following definition:
The flow rate in gpm, of water @ 600 F., through a valve with 1 psi pressure loss.
The formula for Cv is:
Where:
Cv = Flow Coefficient
Q = Volumetric Flow Rate in Gallons Per Minute (GPM)
∆P = Pressure Differential Across the Valve in Pounds Per Square Inch (PSI)
SG = Specific Gravity @ 600 F. (SG of Water is 1.0)
Therefore the following formulas solve for each unknown value:
If Inlet and Outlet Pressures are known, the Flow Rate is determined as follows:
If Cv and Flow Rate are known, Pressure Drop across the valve is determined as follows:
Cv works for all Non-Compressible Newtonian fluids with viscosities similar to water.
Materials that deform continuously under shear stresses, or put another way, any material that cannot withstand shearing stresses and remain at rest, from the macroscopic viewpoint or scale.
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Glossary - Compressible & Non-Compressible Liquids
Glossary - Newtonian & Non-Newtonian
Type of Impeller found in pumps with specific speed range Ns = 2000 - 4500.
Radial vane impellers impart energy into the fluid primarily by means of centrifugal force as with radial vane impellers, with significant energy transfer by diffusion.
Power characteristic is linear exhibiting an increase in required power as flow increases.
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Glossary - Axial Flow (Impeller / Propeller)
Glossary - Radial Vane (Impeller)
Also called Full Load Current (FLC)
Full Load Amps is the current drawn by a motor when operating at its rated horsepower load, under standard test conditions.
Motors with multiple voltage capability (most common being 208/230/480 volts), have a separate FLA for each voltage listed.
FLA and Voltage ratings are found on the motor nameplate usually found riveted to the side of the motor case.
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Glossary - Service Factor (Motor)
See 2 Pump Graphs - Non-Overloading & Overloading
Non-Overloading Pumps and Motor Life Expectancy
Learn How to Diagnose OVERLOAD problems
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