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Fox Gas Mass Flow Meters are used in light and heavy industrial, process heating and commercial facilities, upstream, midstream and downstream Oil & Gas and Wastewater operations. Fox meters measure gas flow rates in mass (Kg/Hr, Lb/Hr) or standardized volumetric units (MSCFD, SCFM). Fox meters can measure virtually any gas flow in a wide variety of applications. Today, almost any facility will have one or more combustion processes such as a boiler, process heater or flare. Measurement of gases to these processes can be used to improve combustion efficiencies, utilities accounting and regulator reporting.

Another common application for Fox meters is monitoring factory compressed air lines for losses. It is safe to say that there will always be leaks in a compressed air system; the question is just how severe the losses will be (many companies report losses in the hundreds of thousands of dollars annually). Ideally, a Fox Flow Meter should be installed on each compressor upon commissioning. This allows the factory manager to establish a baseline air usage for a given level of activity. Any deviation from this baseline -- without any corresponding change in the work load -- suggests a system leak.

Other Fox applications include emissions monitoring, process heating, vent gases, flare gases, digester gases, aeration in wastewater treatment plants, laboratory gas metering, and biogas flows. Find out more about flow meter applications
Fox meters can be used to measure a wide range of pure gases and gas mixtures. These include:

  • Air/Compressed Air
  • Argon
  • Butane
  • Carbon Dioxide
  • Helium
  • Methane
  • Natural Gas
  • Nitrogen
  • Oxygen
  • Propane
Mixed Gases:
  • Biogas
  • Digester gas
  • Flare gas
  • Flash gas
  • Fuel gas
  • Vent gas
There are two types of Fox meters: insertion and inline. Insertion will work in the vast majority of applications, but when the pipe diameter is less than 1.5 inches (37mm), install an inline version. More details can be found on the Fox website. Because the inline model includes flow conditioners to control the flow profile, less upstream and downstream straight pipe is required. Note that insertion meters require a straight pipe run that is equivalent to 15 pipe diameters in length upstream from the meter -- and 10 diameters downstream. For an inline meter, the corresponding figures are 8 and 4 diameters respectively. Note that Models FT1 & FT4A are not currently available in inline styles.

To ensure that all Fox meters meet specified performance parameters and provide accurate, repeatable measurement, all calibrations are performed to NIST-traceable flow standards. Furthermore, all calibration equipment is subject to a meticulous metrology program that includes the selection, control and maintenance of measurement standards.
To ensure that all Fox meters meet specified performance parameters and provide accurate, repeatable measurements, all calibrations are performed to NIST-traceable flow standards. Furthermore, all calibration equipment is subject to a meticulous metrology program that includes the selection, control and maintenance of measurement standards.

Model FT1 Quick Specs (see FT1 datasheet for details):
Flow Accuracy: Air: ±1% R ±0.5% FS
Other gases: ±1.5% R ±0.5% FS
Flow Repeatability: ±0.2% of full scale
Flow Response Time: 0.8 seconds (one time constant)
Temperature Accuracy: ±1°F (±0.6°C) Minimum velocity 15 SFPM
Models FT2A and FT3 Quick Specs (see the FT2A datasheet and/or the FT3 datasheet for more details):
Flow Accuracy: ±1% R ±0.2% FS
Flow Repeatability: ±0.2% FS
Flow Response Time: 0.9 seconds (one time constant)
Temperature Accuracy: ±1.8°F (±1.0°C) over the range -40 to 250°F (-40 to 121°C);
±3.6°F (±2.0°C) over the range -250 to 650°F (121 to 343°C);
Minimum velocity 50 SFPM
Model FT4A Quick Specs (see the FT4A datasheet for details):
Flow Accuracy: Air: ±1% R ±0.2% FS
Other gases: ±1.5% R ±0.5% FS
Flow Repeatability: ±0.2% of full scale
Flow Response Time: 0.8 seconds (one time constant)
Temperature Accuracy: ±1°F (±0.6°C) Minimum velocity 15 SFPM
The FT1 meter is FM & FMc, ATEX, IECEx for Class I, Division 1/Zone 1 areas, and CE approved.

The FT2A meter is FM and FMc approved for Class I, II, III, Division 2, Groups A, B, C, D, E, F, G, T4A hazardous locations.

The Fox FT3 meter is FM & FMc, ATEX, IECEx for Class I, Division 1/Zone 1 areas and, CE approved.

The FT4A meter is FM & FMc, ATEX, IECEx for Class I, Division 1 areas and, CE approved.

See the specific product datasheet for detailed agency approval information.
The standard probe is made of 316 stainless steel. For extremely corrosive environments, Hastelloy C-276 is the preferred option (available on Models FT2A and FT3).
Minimum and maximum flow rates are 15 - 60,000 SFPM (FT2A, FT3 & FT4A) and 15 - 15,000 SFPM (FT1).
One quarter inch (6.5mm) is the smallest Fox inline meter and can measure as low as 0.035 SCFM (0.055 NM3/H). Special length probes are available for measuring exhaust gases in large ducts.
A remote unit separates the sensor from the meter electronics. One advantage is that the electronics enclosure can be mounted such that the display is easy to read and the configuration buttons are easy to operate. Additionally, the probe junction box can be mounted in an area where the ambient temperature is in a range of -40 to 212°F (-40 to 100°C). Remote options are available for Models FT2A and FT3.
The Fox Power Pro™ Sensor, available on Models FT2A and FT3, offers higher accuracy and a wide turndown ratio of 1000:1 (100:1 typical). It can operate in velocities up to 60,000 SFPM – almost twice that of competitors units – while still performing accurately in very low flow applications, as well.

The Fox DDC-Sensor™, available on Models FT1 and FT4A, is a Direct Digitally Controlled sensor that interfaces directly with the microprocessor to allow more speed and programmability. It also provides a technology platform for calculating accurate gas correlations.

The Gas-SelectX® gas selection menu available on Model FT1, with an expanded selection available on the FT4A, uses a correlation algorithm from one calibration to allow the meter to measure multiple pure gases and gas mixtures.

Models FT1, FT3 and FT4A offer an in-situ Calibration Validation feature. This feature allows the operator to confirm that the meter is running accurately in the field, without the need to send the meter back for annual factory calibrations. Calibration Validation Certificates can be printed if the free FT View software is used to initiate the tests. This feature is of particular value in environmental monitoring applications such as flare and vents where periodic calibration validation is mandated.
No. Fox meters operate in all types of gases, but a thermal mass flow meter is not designed to measure liquid or steam flows. The gas can be “wet” -- so long as it is non-condensing. Droplets forming on the sensor element will affect its reading and may cause the meter to display an error code.

To lessen the chance of moisture forming on the tip, the meter can be installed from underneath the pipe. This allows any moisture to flow downwards, away from the tip, due to gravity.
In the case of monitoring emissions for EPA regulation requirements, the EPA states that calibration for Thermal Mass Flow Meters must be performed per manufacturer specifications.

If using the Calibration Validation, it is recommended that this test be performed annually.
Yes. Many users will move the meter around the plant when conducting compressed air surveys or energy audits.
Yes. A 4-20mA, pulse output, and a USB port are standard on all Fox models.
  • Communication options available:
  • Model FT1 - RS485 Modbus RTU and BACnet MS/TP (pulse output is not available when communication option has been ordered); HART communication option
  • Model FT2A - RS485 Modbus RTU, BACnet MS/TP, Profibus-DP, DeviceNet and Ethernet Modbus TCP
  • Model FT3 - RS485 Modbus RTU and HART
  • Model FT4A - RS485 Modbus RTU (pulse output is not available when communication option has been ordered); HART communication option
Yes. All Fox meters are EPA compliant for emissions monitoring applications.

In addition, the Model FT3 and FT4A in-situ Calibration Validation feature is of particular value in environmental applications such as flare and vents where periodic calibration validation is mandated. The test allows operators to validate the calibration and accuracy of the meter in the field without the need to send the meter back for annual factory calibrations. These tests also allow the operator to print out Calibration Validation Certificates for each of the tests if the free FT View software is used to initiate the tests. These tests can be performed as often as needed to comply with local, regional, or national emissions reporting requirements.
Yes. With a 0.8 - 0.9 second response time, the Fox meter can quickly react to fluctuations in the gas stream.
Yes. The 2nd generation DDC-Sensor™ used in the FT1 and FT4A is especially robust becuase of its non-cantilevered design. The sensor elements are welded to the probe at both ends making it significantly tolerant to vibration and particles in the flow stream.

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