MEASURING LIQUID FLOWABILITY (VISCOSITY)
In order to achieve consistent results in generating aerosols with a mass median
diameter (MMD) in the sub 20-micron range, several variables must be kept under
control at the same time. The ability of an aerosol generator to consistently break up
a liquid into appropriate sized droplets depends on (3) key elements:
1.
The available energy flow (air flow) through the nozzle is governed by the
blower speed. As the air mass and its velocity through the nozzle decreases,
the droplet size (MMD) will increase assuming that the liquids viscosity and
flow rate remains constant.
2.
The flow rate of the liquid governed by the speed of the liquid pump.
3.
The viscosity of the liquid.
Various liquids have different viscosities. Viscosity is defined as a fluids resistance to
flow commonly measured in units of a centipoise (CP). Generally, the thicker the
liquid, the greater the viscosity and the higher the CP number. Examples of some
liquid viscosities are:
LIQUID VISCOSITY
(CP)
WATER
1
DIBROM
3-4
DOW
MFC
3-4
PYRETHRIN, RESMETHRIN
6-7
DURSBAN 1.5 ULV
12-14
TECHNICAL MALATHION
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By measuring the flowability of a liquid, adjusting the engine speed to produce the
desired nozzle boom pressure, and by setting the flow rate, accurate particle size can
be achieved.
To measure the relative flowability (viscosity) of your formulation:
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1.
Place a sample of the formulation liquid to
be dispensed in the relative flowability
meter provided with the machine such that
the liquid level is above the top line.
2.
Hold the meter vertical and allow the liquid
to flow through the brass orifice at the
outlet end of the meter into an appropriate
container.