influencefloat flow meterThe key factors of actual accuracy
Deviation of medium characteristics

• Density variation:

  • Liquid: When the density change is ≤ 5%, the error can be ignored; If the density change is greater than 10% (such as high and low temperature oil products), recalibration or compensation is required.

  • Gas: Density is strongly correlated with temperature and pressure (ρ∝ P/T), and accuracy needs to be corrected through temperature and pressure compensation.
    example
    Measure natural gas (standard density 1.2 kg/m ³), if the operating pressure is 0.5 MPa and the temperature is 300 K, the actual density is:

When not compensated, density deviation can lead to flow errors of over ± 10%.

• Influence of viscosity:
  High viscosity media (such as lubricating oil) can change the force on the float, causing the lower limit of the range to shift upward (such as flow meters with a range of 0-10 L/min, where the actual minimum measurable flow rate increases to 2 L/min). It is necessary to choose an anti stick float or expand the range.

2. Deviation in installation conditions

• Insufficient straight pipe section:
  When the upstream straight pipe section is less than 5D, turbulence causes the float to shake, and the error may increase to ± 3% -5%.
  Solution: Install a rectifier or choose an anti turbulence flow meter.

• Tilt installation:
  When the vertical installation tilt is greater than 2 °, the friction between the float and the cone tube changes, and the error increases by ± 1% -2%.
  Solution: Use a horizontally installed flow meter or adjust the installation angle.

• Pulsating flow:
  Under pulsating flow conditions such as compressor outlet and pump rear, float vibration causes reading fluctuations with an error of up to ± 5% -10%.
  Solution: Install buffer tanks or dampers, or choose intelligent flow meters with digital filtering function.

3. Environmental and operational factors

• Temperature impact:
  The cone tube and float of the metal tube float flowmeter have different coefficients of thermal expansion. When the temperature changes by more than 50 ℃, the range may shift by ± 1% -2%.
  Solution: Choose a flow meter with temperature compensation or perform regular calibration.

• Pressure shock:
  When high-pressure gas is rapidly released, the float may impact the top of the cone tube due to inertia, resulting in instantaneous readings exceeding the tolerance or damage.
  Solution: Install a voltage regulator valve or current limiting device.

• Human error in reading:
  The glass tube float flowmeter requires manual reading, and visual deviation may result in an error of ± 1% -2%.
  Solution: Choose an intelligent flowmeter with 4-20mA output or install a photoelectric reading device.