TM 5-815-1/AFR 19-6
slight flow in the direction of normal filtration
temperature applications.
will greatly reduce the effectiveness of
(3) Reverse flow with bag collapse. Even though
cleaning. For this reason a positive sealing
flexure can be detrimental to the bag, it is
type valve is recommended for baghouse inlet
frequently utilized in order to increase the
and outlet. Shaker baghouses are normally
effectiveness of cleaning in a reverse
used in small capacity systems or systems
baghouse. Filter bags collecting dust on the
with a large number of filtering
inside of the fabric are collapsed by a burst of
compartments.
reverse air which snaps the dust cake from
(2) Reverse flow without bag collapse. This
the cloth surface. The bags do not collapse
cleaning method is used with a dust that
completely but form a cloverleaf type pattern.
releases fairly easily from the fabric. (See
Collapse cleaning uses the same equipment
figure 9-4). A low pressure reversal of flow is
arrangement as reverse flow without bag
all that is necessary to remove deposited dust
collapse. One design sends a short pulse of air
from fabric. To minimize flexure and wear;
down the inside of the bag, along with the
the fabric is supported by a metal grid, mesh,
reverse flow, to produce increased flexure
or rings, sewn into the bag. Any flow that is
and cleaning as is illustrated in figure 9-5.
reversed through the filter must refiltered.
The principal disadvantage of flexural
This results in increased total flow, requiring
cleaning is the increased fabric wear. If the
a greater cloth area, and producing a higher
dust cake fails to be removed completely, the
filtering velocity. This net increase in flow is
bag will stiffen in that area and cause wear in
normally less than 10 percent. Reverse
adjacent areas during cleaning.
pressures range from 125 pounds/square inch
(lb/in2) down to a few inches, water gauge.
(4) Reverse-flow heating. With a reverse flow
cleaning system it may be necessary to have a
The gentle cleaning action of reverse flow
reverse flow heating system. This system
allows the use of glass fabric bags in high-
9-2
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