AW Gear Meters GEAR METERS - Manual (Page 6)

Positive Displacement Flow Meters
Operation and Installation Manual
5
Product Description and Principle of Operation
AW Gear Meters positive displacement gear flow meters are similar in design to the gear pump.
However, the principle of operation is reversed: instead of the gears driving the medium, the medium
drives the gears. A non-intrusive sensor detects the movement of the gear. As each tooth passes the
sensor, the sensor produces a square-wave pulse and measures a discrete volume of liquid. The
resulting pulse train is proportional to the actual flow rate, providing a highly accurate representation of
the fluid flow. All flow meters are designed with highly wear-resistant moving parts to provide
exceptionally long service life. The materials of construction are:

stainless steel or high-strength aluminum housing

stainless steel gears

either tungsten carbide sleeve bushings or stainless steel ball bearings (depending on model)
The fluids you are metering should be compatible with these materials.
Filtration
Filtration depends on the model. Make sure to follow proper filtration requirements for your specific
model. Because the internal assembly has very small clearances, small filter sizes are required, especially
for ball-bearing flowmeter versions.
Filters are meant to filter out impurities in the fluid stream. If you are measuring fluids with fillers, even if
the fillers are smaller than the maximum recommended filter size, please consult the factory for correct
meter selection.
Installation
Preferred Flow Direction
The preferred flow direction is marked with an arrow on the meter showing the flow direction in which
the flow meter was calibrated (see figure 2). However, the flow meters have bi-directional flow
capabilities and are often used for bi-directional flow applications. Since the meters indicate flow in both
directions, if reverse flow detection is not desired, install a check valve up-stream of the flowmeter.
Preferred Orientation
The preferred orientation for mounting gear meters, especially in low flow and/or low viscosity
applications, is so that the internal shaft/gear assembly is in a horizontal orientation (housing bolts
facing sideways, not up/down). This allows for the least amount of internal drag due to mass of gears.
Notice