Baking & Snack - December 2007 - 69

PROCESSING TECHNOLOGY

KEEP IT MAINTAINED. Sifters are a fairly simple piece
of equipment to maintain. Generally, all they require
is regular lubrication of bearings and inspection of the
sieves and screens.
Nevertheless, inadequate maintenance is a common
problem with sifters, according to Mr. Ricklefs. "If sifters are
not adequately maintained, they can become a liability rather than an asset," he said. "Often the employees used to inspect and maintain the sifters are entry level, and they don't
recognize the functions and importance of this machine."
With good preventive maintenance most issues with sifters will be avoided. "Letting a machine run until it breaks
down is not good maintenance," Mr. Kearns observed.
"Items such as bearings, seals and screens generally give
warning before catastrophic failure."
If bakeries performed weekly inspections as recommended by AIBI and regular maintenance on bearings at appropriate intervals, typically every 30 to 60 days, they shouldn't
experience any major problems, Mr. Ricklefs said.
One of the reasons bakeries may be remiss on addressing
sifter maintenance is because often the sifter is out of sight
and out of mind. Commonly, sifters are located under the
silo, so they are not that easy to access. Baking companies
should provide adequate space for people to work on and
inspect sifters, but they are often shoehorned into an existing facility, according to Mr. Ricklefs. "It should be someplace where people will see it and have access to it," he said.
Another common problem bakeries encounter is that
they do not have the screens tensioned properly, according to Mr. Williams. "If a screen is loose, the product being
screened will puddle up and plug the screen," he said. "A
quick test is to drop a quarter on the screen. If it bounces,
then the screen is ready to sift."
In regard to the screens themselves, a trend that concerns
Mr. Ricklefs is customers requesting magnetic stainless steel
screens rather than more fatigue-resistant synthetic screens.
Although synthetic screens are not detectable by a magnet

ᮣ A power
opener allows
quick and easy
access to all
screens of
this in-line
pressure sifter.
FRED D. PFENING CO.

72 / BAKING & SNACK / December 2007

or metal detector, they generally have a much longer life
because the material is able to flex, he said.
On the other hand, wire screens tend to fatigue, which
can cause pieces to break off. And even with a wire screen,
unless a large enough piece ruptures, a metal detector most
likely will not be able to discover it, Mr. Ricklefs said. "Most
metal detectors are accurate down to a 1 mm sphere, and
with many wire screens, a small segment won't represent
that mass," he explained.
WHOLE DEMAND. The use of whole grains in baked foods
has been a major product trend in the past few years, and it
has led to the use of more sifters, according to Mr. Ricklefs.
Bran flakes in whole-wheat flour require a courser
mesh to pass through than other white flours, according
to Mr. Kearns. "Usually sifter manufacturers will test the
material in a laboratory to determine the optimum mesh
size," he said.
Typically, with whole-grain flours, bakers are not switching back and forth between screens; instead, they are using
separate sifting systems for these products. "Otherwise they
run the risk of forgetting to change the screens and having
too coarse of a screen that won't do any good when the run
regular granulation products," Mr. Ricklefs said. "Also, they
don't want that cross contamination."
Baking companies should be prepared to provide
samples to sifter manufacturers so they can test how well
its sifters work on that particular product. "For a product
such as granulated sugar that we know is going to sift easily,
getting a sample is not as important," Mr. Ricklefs said. "But
some products such as flours we really want to test."
SIFTING OPTIONS. Gravity and in-line sifters are the
two styles of sifters available based on the flow of materials through the screens. In-line sifters are generally used in
conjunction with closed conveying systems that use either
pressure or a vacuum to move materials.
Bakeries also have the option of four basic mechanics
of sifters, based on the motion of the machine: centrifugal, gyratory, gyratory-reciprocal and vibratory. Mr. Kearns
said Fred D. Pfening offers the gyratory sifting action. It "is
preferred by most major bakeries because it is the most effective screening motion and does not rely on rotary paddles
or vibrating springs."
However, not every sifter is going to be right for every product. "Some bakery mixes have fat added to them,
which creates agglomerates, and in that case, our sifter is not
appropriate," said Mr. Ricklefs, whose company also manufactures gyratory sifters. "You need something to disrupt
the agglomerates."
For these products, he pointed out that a centrifugal sifter
would work best because it has beaters. However, a centrifugal sifter does not know the difference between good lumps
and bad lumps, Mr. Ricklefs added, noting that it may not
be best for other products such as flour.

Baking & Snack - December 2007

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