 MIXER
PLACEMENT
- Bridge-mounted Mixers:
- Cylindrical Tanks
- Baffled: Place mixer dead center.
- Unbaffled: Place mixer 1/6 to 1/4 tank diameter off
center.
- 1/6th will provide strong vortex
- 1/4 will provide very little vortex
- Square or Rectangle Tanks:
- Baffled or Unbaffled: Place mixer dead center.
- Unsure? Contact Admix at 800-466-2369.
- Clamp-mounted mixers: Typically limited to small portable
mixers, clamp-mounts are usually on the side wall of the tank
or a separate bracket attached to the tank or mixing vessel. General
shaft position is at a 10 to 15 degree angle (from a side view,
vertical position) into the tank. Also, for swivel-type clamps,
the option is to angle the shaft at a 10 to 20 degree angle to
the right, as viewed from the top looking down into the mixing tank.
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High Shear
Mixing
- Optimal: One (1) mixing head diameter off bottom
- 1.5 to 2 mixing head diameters minimum coverage
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Low Speed Agitation
- As close as ½ impeller diameter off bottom
- 1.5 to 2 mixing head diameters minimum coverage
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High Shear Mixing
n
Ratio of mixing head diameter (D) to tank diameter (T) should
be 1/10th or greater.
Low Speed Agitation
n
Ratio of impeller diameter to mixing
tank diameter should be 0.25 or better depending upon viscosity.
High viscosity requires
a minimum 0.35 - 0.4 ratio.
ADDING GUMS, HYDROCOLLOIDS, POWDERS OR
THICKENERS
 For
these powders, conventional "sprinkling" into the tank
while mixing is actually detrimental;
the viscosity
builds slowly and the pumpability of the medium decreases. In high
shear/high flow applications, the powder needs to be incorporated
and hydrated quickly, before it gets a chance to build viscosity.
1. Make sure there is a good vortex and high bulk fluid velocity
in tank with the liquid phase
2. Add powder quickly, all at once!
3. You will see that the powder will be incorporated, dispersed,
or hydrated more easily.
 This
chart outlines some of the typical ingredients and mixing
challenges we have encountered
over years of supplying sanitary mixing
equipment. Please take a minute
to look at the list (click image to open PDF). If you have experienced
challenges with any of these and are looking for solutions, contact us at 800-466-2369
or email us at mixing@admix.com.
Admix would like to become your Mixing
Technology Partner
as we continue to share our expertise with customers worldwide.
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Mixing is a key operation for many
processes -- a necessity when two or more ingredients must be blended
together. We are often asked to provide a definition of mixing
versus agitation or blending.
Sounds simple enough, but not so when you add other "mixing"
terms such as dispersing, hydrating, suspending or emulsifying!
In other words, depending upon the ingredients involved, "mixing"
or "blending"
may not properly describe the operation required. The following
are brief descriptions to define each situation:
Mixing:
The generic term for the operation encompassing all the variations
that follow.
Agitating:
Typically defined as a low speed blending operation with turbine
type blades or paddles.
Blending:
Mixing or agitating two or more
miscible liquids of similar viscosity
(or solids only) and density, often done inside a vertical helical
screw blender.
Dissolving:
Where the dissolution of a solid in a liquid is necessary, as with
salt or sugar solutions. Simple agitation techniques are normally
sufficient if time is not a factor, although high shear techniques are required when other
solids (ingredients) may block dissolution of the primary solid
or when faster dissolution would be beneficial.
Dispersing:
The action of scattering immiscible
particles, droplets or gas bubbles in a matrix liquid. The results
can properly be called dispersions,
but more often they are given more specific names:
n Suspension,
when solid particles, usually above colloidal size, are dispersed
n Emulsion, when
droplets are dispersed, such as oil in water or water in oil
n Lyosol, when
air or gas bubbles are dispersed
Homogenizing:
This term is usually applied to a very intense mixing action, but literally
it only means that all components are so thoroughly mixed that they
are "made alike". This term should not be limited to the
action of one particular type of equipment.
Hydrating:
Many ingredients when used as binding or stabilizing agents will
"swell" when activated by high shear and attach themselves
to other molecules. Hydrocolloids such as gums, stabilizers, polymers,
etc., require a high shear device to be thoroughly dispersed for 100% hydration.
More than Mixing
- Size Reduction:
In order to speed up the mixing
process, modern machines introduce
a high degree of kinetic energy. This very often results in a reduction
of particle or droplet size. This can mean
n the break-up
of agglomerations, and can be done in batch or in-line mode, or
n more typical
is the shear action of tearing droplets apart or the crushing
or slicing of solid particles.
If any of these mixing operations
fit your requirements, or if you have been struggling with a low
speed agitator where high shear equipment may be more appropriate,
call us toll free at 800-466-2369
for more information about our sanitary mixing
equipment specifically engineered
for difficult-to-process ingredients.
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