Glossary of Terms
Fluids are termed abrasive when they have a tendency to mechanically attack metals and parts made from other materials of construction.
Bernoulli's equation describes the conservation of hydraulic energy across a constriction in a pipe. It states that the sum of the static energy (pressure head), kinetic energy (velocity head), and potential energy (elevation head) upstream and downstream of the constriction are equal.
Coanda Effect flowmeters channel the flow stream in the flowmeter so as to utilize the phenomenon that causes a fluid to attach itself to a surface. Feedback passages are used to alternately attach the fluid to each surface. Oscillating flows through the feedback passages can be related to the flow rate.
The electrical conductivity of a liquid is a measure of the ability of the liquid to conduct electricity (mS/cm). Note that water with few impurities (such as de-ionized water) is not very conductive, whereas water with impurities can be highly conductive.
Fluids are termed corrosive when they have a tendency to chemically attack metals and parts made from other materials of construction.
Fluids are termed cryogenic when they operate at low temperatures, typically below approximately -75°C. Examples of these fluids include liquefied gases, such as oxygen and nitrogen.
Flowmeters applied to custody transfer are used to buy and sell fluids, such as the measurement of natural gas between pipeline companies.
The density of a fluid is its mass per unit volume (lb/ft3; kg/m3; g/cc). Specific gravity is a dimensionless number that represents the density of the liquid relative to water.
The Doppler effect is a phenomenon related to how sound is perceived from objects in motion, such as the horn of a moving car having a higher pitch moving towards a listener than it does when moving away.
A flow nozzle is a constriction consisting of a contoured plate that forms a hole for the flow stream that is sandwiched in the pipe between two flanges.
Hydrocarbons is a general class of chemicals that contain hydrogen and carbon, such as natural gas, fuel oil and gasoline. They are often flammable.
Industrial gases generally refers to pure gases that are commonly used industry, such as oxygen, nitrogen, argon, and helium.
Inferential Flow Measurement
Inferential flowmeters do not measure volume, velocity or mass, but rather measure flow by inferring its value from other measured parameters. Examples of flowmeter technologies that measure inferentially include differential pressure, target and variable area flowmeters.
Laminar Flow Element
A laminar flow element is a constriction consisting of a tube bundle or parallel plates used to measure flows with low Reynolds numbers. The differential pressure across this flowmeter is linear with flow.
Low-Loss Flow Tube
A low-loss flow tube is a constriction that is similar to a Venturi-tube, but with shorter inlet and outlet sections.
Mass Flow Measurement
Mass flowmeters utilize techniques that measure the mass flow of the flowing stream. Examples of flowmeter technologies that measure mass flow include Coriolis mass and thermal flowmeters.
Materials of Construction
Materials of construction are the materials from which the parts of the equipment are fabricated. Parts that are exposed to the operating fluid are termed "wetted" parts.
An orifice plate is a constriction consisting of a flat plate with a hole for the flow stream that is sandwiched in the pipe between two flanges.
Reynolds number is a dimensionless number that is used to describe the flowing characteristics of the fluid. Operating a flowmeter outside of its Reynolds number constraint can degrade accuracy and make some flowmeters turn off.
RD = 3160 · Flow gpm · Specific Gravity / (Viscosity cP · Diameter inch)
Sanitary piping systems and components are used where cleanliness is important, such as in the food and beverage, pharmaceutical and chemical industries.
A segmental wedge is a constriction consisting of a hill-like structure in the flow stream. It is often used for fluids that contain some solids or that are mildly abrasive.
Slurries contain both liquid and solids, and are often used as a means to transport the solids.
A V-cone is a constriction consisting of a cone suspended in the flow stream. It can be used in locations where little space for upstream and downstream piping is available.
Velocity Flow Measurement
Velocity flowmeters utilize techniques that measure the velocity of the flowing stream to determine the volumetric flow. Examples of flowmeter technologies that measure velocity include magnetic, turbine, ultrasonic, and vortex shedding and fluidic flowmeters.
A Venturi tube is a constriction consisting of a streamlined reduction and expansion of the piping containing an inlet section, throat, and outlet section.
The viscosity of a fluid is the ability of the fluid to flow over itself. Water has a viscosity of about 1 cP.
Volumetric Flow Measurement
Volumetric flowmeters directly measure the volume of fluid passing through the flowmeter. The only flowmeter technology that measures volume directly is the positive displacement flowmeter.
Vortex precession flowmeters use inlet vanes to rotate the fluid to form a vortex center (similar to a cyclone) that rotates around the inside of the pipe. The rotation of the vortex can be related to the flow rate.
Vortex shedding flowmeters alternately generate vortices on both sides of a bluff body located in the flow stream. The number of vortices formed can be related to the flow rate.
Water can exhibit different properties depending upon its impurities. Whereas water with many impurities can be very conductive, de-ionized water is a form of pure water that is not very conductive. Boiler feed water often softened or de-mineralized before it is fed into boilers.