Thermal Flowmeters for Compressed Air

Thermal Flow Meters for Compressed Air - featuring a robust technology for compressed air monitoring with ease of adding to existing lines providing transmitted signals and a local LCD display

Learn about Thermal Flowmeters for Compressed Air

CDI 6200 flowmeters make localized metering of air usage a practical way to manage a compressed-air system. Thermal-dispersion mass-flow technology gives the meter sensitivity to low leakage flows, while an innovative mounting design makes it easy to install.

  • NEMA 4 (IP67) enclosure
  • Surge suppression; suitable for distributed DC power
  • Ruggedized version of CDI-5200
  • Suitable for use in wet locations
  • Mass flow measurement via thermal dispersion
  • Built-in LED display
  • Milliamp and pulse outputs
  • CE certified and RoHS compliant
  • No calibration required
  • Separate power supply required

Available for

  • Steel pipe 1/2" through 1.5"
  • Steel pipe DN15 through DN40
  • Copper pipe 3/4" through 1.5"
  • Common metric aluminum sizes
Price: Starting at $495.00
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CDI 5400 flowmeters make localized metering of air usage a practical way to manage a compressed-air system. Thermal-dispersion mass-flow technology gives the meter sensitivity to low leakage flows, while an innovative mounting design makes it easy to install.

  • The original CDI flowmeter
  • Mass flow measurement via thermal dispersion
  • Built-in LED display
  • Wall-plug power supply included
  • Quick, easy wiring and installation
  • Milliamp and pulse outputs
  • CE certified and RoHS compliant
  • No calibration required

Available for:

  • Steel pipe 2" through 8"
  • Steel pipe DN50 through DN200
  • Copper pipe 2" through 4"
  • Common metric aluminum sizes

 

Price: Starting at $645.00
Select Options

CDI 6400 flowmeters make localized metering of air usage a practical way to manage a compressed-air system. Thermal-dispersion mass-flow technology gives the meter sensitivity to low leakage flows, while an innovative mounting design makes it easy to install.

  • NEMA 4 (IP67) enclosure
  • Surge suppression; suitable for distributed DC power
  • Ruggedized version of CDI-5400
  • Suitable for use in wet locations
  • Mass flow measurement via thermal dispersion
  • Built-in LED display
  • Milliamp and pulse outputs
  • CE certified and RoHS compliant
  • No calibration required
  • Separate power supply required

Available for:

  • Steel pipe 2" through 8"
  • Steel pipe DN50 through DN200
  • Copper pipe 2" through 4"
  • Common metric aluminum sizes
Price: Starting at $695.00
Select Options

The CDI 25 is designed for low-cost measurement of air usage at every piece of equipment in an industrial plant.

A minimum-flow alarm indicates leakage by blinking if flow does not drop below a specified level. An average-flow alarm indicates excessive usage. These alarm functions draw attention to waste without requiring central monitoring.

  • Rate, Minimum, Average, and Total display options
  • User-adjustable minimum-flow and average-flow alarms
  • Alarms indicated by blinking LEDs
  • Mass flow measurement via thermal dispersion
  • Built-in LED display
  • CE certified and RoHS compliant
  • No calibration required

Available for:

  • Steel pipe 1/2", 3/4", and 1"
  • Copper pipe 3/4" and 1"
Price: Starting at $295.00
Select Options

Remote display, daily usage display, or an accumulator for all CDI 5200 or 5400 flowmeters.

  • When a meter is mounted where it cannot readily be seen or where it may not be noticed, the remote display repeats the output of the meter at a convenient location, up to 200 feet from the meter.
  • When it is desired to track air usage over time, the display, in its summing mode, shows accumulated usage or, alternatively, total usage during the most recent full day.
  • The display can be programmed to select the desired mode of operation, and labels are furnished to indicate which mode is being used.
Price: Starting at $95.00

Used with CDI 5200 or 5400. Provides a moving average of the flow rate over a user-specified averaging period.

  • When a meter is mounted where it cannot readily be seen or where it may not be noticed, the remote display repeats the output of the meter at a convenient location, up to 200 feet from the meter.
  • When it is desired to track air usage over time, the display, in its summing mode, shows accumulated usage or, alternatively, total usage during the most recent full day.
  • The display can be programmed to select the desired mode of operation, and labels are furnished to indicate which mode is being used.
Price: Starting at $95.00

Remote display, daily usage display, or an accumulator for all CDI 6200 or 6400 flowmeters.

  • When a meter is mounted where it cannot readily be seen or where it may not be noticed, the remote display repeats the output of the meter at a convenient location, up to 200 feet from the meter.
  • When it is desired to track air usage over time, the display, in its summing mode, shows accumulated usage or, alternatively, total usage during the most recent full day.
  • The display can be programmed to select the desired mode of operation, and labels are furnished to indicate which mode is being used.
Price: Starting at $120.00

Used with CDI 6200 or 6400. Provides a moving average of the flow rate over a user-specified averaging period.

  • When a meter is mounted where it cannot readily be seen or where it may not be noticed, the remote display repeats the output of the meter at a convenient location, up to 200 feet from the meter.
  • When it is desired to track air usage over time, the display, in its summing mode, shows accumulated usage or, alternatively, total usage during the most recent full day.
  • The display can be programmed to select the desired mode of operation, and labels are furnished to indicate which mode is being used.
Price: Starting at $120.00
Documents

This universal guide is for use with all CDI-25, 5200 and 6200 meters (pipe sizes 1.5" or less). It includes a 3/16" drill bit, 3/16" and 1/4" hex wrenches, and an aluminum drill guide with two 3/16" drill bushings spaced 2.250" apart. These guides can be attached to the pipe with a band clamp, a C-clamp or a chain clamp.

Price: Starting at $65.00

This universal guide is for use with all CDI-5400 and 6400 meters (pipe sizes 2" or greater). It includes a 3/16" drill bit, 3/16" and 1/4" hex wrenches, and an aluminum drill guide. These guides can be attached to the pipe with a band clamp, a C-clamp, or a chain clamp.

Price: Starting at $95.00

This guide is for use with 2" (50 mm) and 2-1/2" (63 mm) CDI-5400 and 6400 flow meters. It includes a 3/16" drill bit, a 5/16" hex wrench, and an aluminum drill guide and is a cheaper option than the universal guide if you're only working with these specific pipe sizes. These guides can be attached to the pipe with a band clamp, a C-clamp, or a chain clamp.

Price: Starting at $65.00

These half-ring drill guides are for use with specific sizes of CDI-5400 and 6400 meters (3" or larger). They attach to the pipe by bolting into the rear half-ring that comes with the meter. They include a 3/16" drill bit, a 5/16" hex wrench, and a half-ring of the appropriate size to match your meter. When ordering, specify "XXX" to match your meter size (either 30C, 30S, 40C, 40S, 50S, or 60S). Guides for 4" pipe or smaller are $65, for 5" and 6" pipe are $95.

Price: Starting at $65.00

If you ever want to move or remove your CDI flowmeter, these rings plug and cover the holes that are left behind.

Price: Starting at $95.00
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Thermal Flow Meter for Compressed Air

How Thermal Flowmeters Work

Thermal flowmeters use the thermal properties of the fluid to measure the flow of a fluid flowing in a pipe or duct. In a typical thermal flowmeter, a measured amount of heat is applied to the heater of the sensor. Some of this heat is lost to the flowing fluid. As flow increases, more heat is lost. The amount of heat lost is sensed using temperature measurement(s) in the sensor. The transmitter uses the heat input and temperature measurements to determine fluid flow. Most thermal flowmeters are used to measure gas flows. Thermal flowmeters represent 2% of global flowmeter sales.

The amount of heat lost from the sensor is dependent upon the sensor design and the thermal properties of the fluid. The thermal properties of the fluid can and do vary with pressure and temperature, however these variations are typically small in most applications. In these applications where the thermal properties of the fluid are known and relatively constant during actual operation, thermal flowmeters can be used to measure the mass flow of the fluid because the thermal flow measurement is not dependent upon the pressure or temperature of the fluid.

However, in many applications, the thermal properties of the fluid can be dependent upon fluid composition. In these applications, varying composition of the fluid during actual operation can affect the thermal flow measurement. Therefore, it is important for the thermal flowmeter supplier to know the composition of the fluid so that the proper calibration factor can be used to determine the flow rate accurately. Due to this constraint, thermal flowmeters are commonly applied to measure the flow of pure gases. Suppliers can provide appropriate calibration information for other gas mixtures, however the accuracy of the thermal flowmeter is dependent on the actual gas mixture being the same as the gas mixture used for calibration purposes. In other words, the accuracy of a thermal flowmeter calibrated for a given gas mixture will be degraded if the actual flowing gas has a different composition.

Plusses and Minuses

Thermals are middling cost and they are good for low pressure gas. They are well suited for stack flow measurement and emissions monitoring uses. Insertion models are a very good choice for large pipe sizes if used as insertion meters. The best attribute is that if the gas is known, the meter reads true mass flow without needing to include pressure in a calculation. The accuracy is medium only and they are used primarily for gas. Not good for steam flow.

How to Use Thermal Flowmeters

Thermal flowmeters are most commonly used to measure the mass flow of clean gases, such as air, nitrogen, hydrogen, helium, ammonia, argon, and other industrial gases. Mixtures, such as flue stack flow and biogas flow, can be measured when their composition is known. An advantage of this technology is its dependence upon thermal properties that are almost independent of gas density. Be careful when using thermal flowmeters to measure the flow of gases with unknown and/or varying composition, such as hydrogen-bearing off-gases and other mixtures that can disproportionately affect the thermal flowmeter measurement.

Thermal flowmeters can be applied to clean, sanitary, and corrosive gases where the thermal properties of the fluid are known. Thermal flowmeters are most commonly applied to measure pure gases, such as would be used for laboratory experiments, and in semi-conductor production. They can also used in chemical and petrochemical plants when the thermal properties of the gas are known. With proper attention to materials of construction, the flow of corrosive gases, such as hydrogen chloride and hydrogen sulfide can be measured.

Industries Where Used

In order of magnitude, these are used in oil and gas, power, chemical, water and waste, metals and mining, food and beverage, pulp and paper, pharmaceutical and textile industries. Application Cautions for Thermal Flowmeters Thermal flowmeters should not be applied to abrasive fluids because they can damage the sensor. Fluids that coat the sensor can alter the relationship between the thermal properties of the fluid and the measurement and adversely affect the flow measurement. Extensive coating can render the sensor inoperable unless the sensor is routinely cleaned. This can increase maintenance associated with these flowmeters.

Varying the percentage of certain components that have different thermal properties from calibrated values can cause thermal flowmeters to become highly inaccurate. In other words, thermal flowmeters are often not suitable for applications with fluids that have varying composition and unknown components. However, in some applications, thermal flowmeters could measure reasonably accurately when the flow stream contains components with similar thermal properties.

Aerosols and gases with droplets can cause thermal flowmeters to become erratic and/or measure full scale flow. This is because the large amount of thermal energy used to heat the liquid/droplet is interpreted as a high flow signal. Operating a thermal flowmeter above its maximum flow rate will generally not damage the flowmeter but can cause measurement error because its calibration curve can become unpredictable.

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