How to Select Gas Flow Meters
Image Credit: OMEGA Engineering Inc., Aalborg Instruments, Clark Solutions
Gas flow meters are used for measuring the flow or quantity of a moving gas. Measuring the flow of fluids is a critical need in many industrial plants. The ability to conduct accurate flow measurements allows process operators to properly monitor and control flow. In some cases, inaccurate flow measurements or failure to take measurements can cause serious (or even disastrous) results.
The basis of good flow meter selection is a clear understanding of the parameters surrounding a particular application. These may include gas type, gas viscosity, possible contaminants or corrosive elements, pipe or system size, etc. Gas flow meters can be classified based on type, performance specifications, and features.
Types of Gas Flow Meters
There is a vast array of different types of flow meters, but most can be classified by the means in which it measures flow.
- Differential pressure flow meters rely on Bernoulli's principle, measuring pressure drop over an obstruction inserted in the flow to correlate to gas flow.
- Velocity flow meters measure the velocity at one or more points of flow and integrate the flow velocity (v) over the area (A) to calculate flow (Q), using the relationship:
Q = v x A
- Positive Displacement flow meters measure gas flow by precision-fitted rotors in which rotation is proportional to the volume of the displaced fluid.
- Mass flow meters use various means such as heat to measure mass flow rate.
The GlobalSpec SpecSearch Database provides industrial buyers the ability to select gas flow meters based on performance specifications. These include the flow rate range, operating temperature, and operating pressure.
- Flow rate range is the range of fluid flow that the device is designed to measure. Mass, velocity, or volumetric flow rates above or below the specified values may not be measurable by the device and could damage the instrument or its calibration.
- Operating temperature is the accepted range of temperatures in which the device can properly operate. Handling media outside this range could damage the instrument.
- Operating pressure is the accepted range of pressures in which the device can properly operate. Pressures below this range may not be measurable and those exceeding this range could cause device failure.
Gas flow meters can include a number of additions to make the device compatible with the system. These include mounting types, various end fittings, interface options, and electrical outputs. They may also include a number of different features to offer additional measuring capabilities such as temperature or density.
ReferencesRead user Insights about Gas Flow Meters
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Liquid Flow Meters
Liquid flow meters are used to measure the volumetric flow rate or amount of a moving liquid.
Mass Flow Meters and Controllers
Mass flow meters and controllers measure flow rate in units of mass or volume per units of time (e.g., pounds per minute). They are designed for use with gases, liquids, steams, or slurries.
Mass Flow Switches
Mass liquid flow switches and mass gas flow switches are devices used for measuring the flow or quantity of a moving liquid or gas in terms of a unit of mass per unit time, such as pounds per minute. These devices may be sensors with electrical output or may be stand-alone instruments with local displays and controls.
Ultrasonic Flow Meters
Ultrasonic flow meters use sound waves to determine flow rates. They can be either Doppler Effect meters or Time-of-Flight meters.
Velocity Flow Switches
Gas flow switches and liquid flow switches, velocity, are used to measure the flow or quantity of a moving fluid in terms of velocity, such as feet per minute.
Volumetric Gas Flow Switches
Volumetric gas flow switches are devices with a switch output used for measuring the flow or quantity of a moving gas in terms of a unit of volume per unit time, such as cubic feet per minute.
Volumetric Liquid Flow Switches
Volumetric liquid flow switches measure the flow or quantity of a moving fluid in terms of a unit of volume per time, such as liters per minute. These flow sensing devices have a switch output.
- Analog Current
- Analog Voltage
- Audible or Visual Alarms
- Averaging / Multi-Insertion
- Cone Type
- Controller Functions
- Coriolis Meter
- Electromagnetic Meter
- Flow Nozzle
- Insertion Type
- Laminar Flow
- Measures Density
- Measures Level
- Measures Temperature
- Network / Fieldbus
- Orifice Plate
- End Fittings:Other
- Interface Options:Other
- Pitot Tube
- Plain End
- Recorder / Totalizer Functions