Flow Meter Avery Hardoll BM 850

Avery-Hardoll flowmeters are precision made, positive displacement, liquid measuring instruments that maintain accurate metering over long periods of operation. Simplicity of design and construction together with sustained accuracy has led to the widespread use of BM Series meters on aviation refuelling vehicles as well as master meters for use in calibration throughout the world.

Liquid Controls is committed to maintaining the decades long legacy of Avery-Hardoll quality and precision in aviation fueling. Inside their state of the art manufacturing and testing facility in Lake Bluff, Illinois, Avery-Hardoll metering products are manufactured and vigorously 100% flow tested before being put into service.



The BM Series flowmeter directly converts volume to rotational output with minimum scope for error and with minimal disturbance from surrounding conditions, such as turbulence from nearby valves, bends, and other system conditions.

  • Positive displacement measurement
  • 115 to 4000 LPM (30 to 1000 GPM) flow rates
  • Unequalled performance in measurement

The positive displacement principle is the ONLY accurate method of measuring fluid flow.  No other technology can achieve such accuracy because measurement becomes inferred, which is indirect and subject to assumption. The Avery-Hardoll® bulkmeter directly converts volume to rotational output with minimum scope for error and with minimal disturbance from surrounding conditions, eg. turbulence from nearby valves, bends, etc.



  • The product enters the meter through the inlet manifold (1) and causes the rotor (4) to revolve by pressure on the vanes (3).
  • The proximity of the rotor (4) to the body (2) forms an efficient seal, whilst the profile of the casing ensures that the vanes (3) are guided through the measuring crescent (5), where the volume of product is accurately measured.
  • Product at line pressure fills the spaces between the inner (6) and outer (7) end covers providing pressure balanced inner end covers which are therefore protected from distortion due to changes in line pressure.
  • An extension shaft driving through a pressure tight gland in the meter front cover, transmits the rotor revolutions to the calibrating gearing (8) which drives the counter (9).


Viscous Products

Avery-Hardoll bulkmeters can be used on all petroleum products of all viscosities. However there is obviously an increase in pressure drop with more viscous fuels which, under normal circumstances, will limit the maximum flow rate obtainable.

It is recommended that the pressure drop through a bulkmeter should not exceed 15 psi (one bar), above which the load on the bearings will start to cause wear. Consequently when using products with viscosities (at operating conditions) above 100 centistokes, it is necessary to reduce the maximum permitted flowrate. As a guide it is suggested that the pressure drop through the meter should not exceed 10 psi (0.7 bar) for continuous running at maximum speed or 15 psi (one bar) for continuous running at half speed.

Pressure Loss

The low pressure drop for the BM series of Avery-Hardoll bulkmeters is displayed below:


Maximum working pressure: 10.5 bar (150 psi)

Test pressure: 21 bar (300 psi)

Temperature range: -28ºC to 100ºC

Volume per revolution:

  • 2.27 litres (single capsule)
  • 4.54 litres (double capsule)
  • 6.82 litres (triple capsule)

Repeatability (typically): .02%

Calibration :

  • Calibration adjustment is provided to minimize the meter error at any selected flowrate. Adjustment is stepless; no gear changing is necessary; the calibration screw is easily accessible after breaking a seal and removing a sealing screw.
  • All meters are tested to 300 psi (21 bar).
  • All meters are tested before dispatch at a range of flow rates, and test certificates can be supplied if requested.
  • The fluid used for testing is odorless kerosene.
    • Specific gravity at 60/60ºF, 15/15ºC = 0.8
    • Viscosity at 60ºF, 15ºC = 2.4 centistokes.
  • Suggested correction to be made to the calibrating mechanism when used with products with different viscosities as follows:
    • Gasoline + 0.1% + means increase counter readings
    • Kerosene 0.0% – means decrease counter readings
    • Gas Oil – 0.1%
    • Fuel Oil – 0.22%

Specification Product :

  • Meter Series : BM850
  • Pipeline Size : 6” (152mm)
  • Flow Rate : 85 to 1000 Imp. Gal., 387 to 4000 lpm, 23 to 232 M³/h

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