Given that biogas composition may change from time to time, and thermal mass flow meters are calibrated to a specific mixture of methane and carbon dioxide, Sage provides correction factors for the user to apply if there are variations from the original calibration.

Biogas Correction Factors

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Sage Metering can calibrate our meters for any digester gas, landfill gas, or biogas mix. However, it may be useful to have correction factors for a typical calibration if the gas composition changes. The following correction factors assume that the initial calibration was set up for 60% methane (CH4) and 40% carbon dioxide (CO2):

    • 65% CH4 and 35% CO2 – Multiply the reading by 0.982 to correct for a new composition
    • 70% CH4 and 30% CO2 – Multiply the reading by 0.965 to adjust for a new composition
      Angling the thermal mass flow sensor in the pipe
      Tilt the enclosure 45 degrees (forward or backward) for applications where condensation may develop inside the pipe’s walls.
    • 55% CH4 and 45% CO2 -Multiply the reading by 1.0185 to correct for a new composition

If there are less significant changes than in the above examples, the corrections are linear in between stated cases.

Water vapor correction is also linear between the following examples:

    • 100% saturated with H2O vapor (non-condensing) – multiply the readings by 1.042
    • 50% saturated with water – multiply the reading by 1.021

Also, mount the sensor 45 degrees to avoid droplets hitting the sensor and causing spikes (see the illustration).

Are you interested in learning more about using a thermal mass flow meter as a biogas flow meter? Read more>

biogas application guide
Biogas Application Guide

How to Overcome 9 Thermal Mass Flow Meter Limitations

Other topics from the Sage Prime Manual you may be interested in are:

How do I clean my thermal mass flow meter sensor?

My Sage flow meter was damaged in shipment

Optional Mounting Hardware for the Insertion Flow Meter

How to Install and Mount my Sage Prime Thermal Mass Flow Meter?

Inline Flow Meter Installation Considerations

Troubleshooting Sage Prime Mass Flow Meters

Flow Profile and Installation Considerations for Insertion Flow Meters

Sage In-Situ Verification Procedure

Sage Mass Flow Meters Warranty

Sage Prime Thermal Mass Flow Meter Features and Benefits

Modbus Protocol and Function Codes

Returning Your Sage Flowmeter via Special Delivery

Sage Metering’s Cancellation and Return Policy

HART Protocol and Access Keys

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