Note: Descriptions are shown in the official language in which they were submitted.
lO9Z525
This invention relates to industrial baghouses and,
more particularly, to an improved cage, bag and diffuser
assembly for a baghouse to facilitate maintenance.
Continuous emphasis on environmental quality has
resulted in increasingly strenuous regulatory controls on
industrial emissions. One technique which has proven highly
efficient in controlling air pollution has been the separation
of undesirable particulate matter from a gas stream by fabric
filtration.
Such filtration is carried out in dust collection
apparatus known in the trade as a "baghouse" which operates on
the same general principle as an ordinary household vacuum
cleaner, except on a much larger scale. Basically, the
baghouse is a sheet metal housing divided into two chambers,
referred to as plenums, by one or more tube sheets. Disposed
within openings communicating with the plenums are fabric ;~
filters. A particle-laden gas stream, induced by the action of
a fan, blows into one chamber (dirty air plenum) wherein dust
accumulates on the fabric filter as the gas passes through the
fabric into the other chamber (clean air plenum) and out the
exhaust.
Although all baghouses are designed in accordance ;~
with the foregoing general principles, there are numerous
operational and structural distinctions. The present invention -~
relates to a baghouse wherein the dirty and clean air plenums - ~
are separated by a tube sheet having a plurality of vertically ---
suspended filter bags in which cylindrical wire cages are
inserted for skeletal support. Filtration of the process gas
occurs from outside to inside of the bags. As a result,
baghouses constructed in this manner are normally referred to
as outside bag collectors.
During continuous operation of the baghouse the
... ,.;~, :
.i - - - - , : - - -
~092s25
bags must be periodically cleaned to remove the filter cake
which is deposited on the fabric. One of two clenaing methods
are typically employed in an outside bag collector. In
pulsing-plenum cleaning, high pressure air is introduced to a
compartment in the clean air plenum and the dust cake is
simultaneously dislodged from all filter bags in that
compartment~ With pulse jet cleaning, on the other hand, the ~ ~-
upper end of the cage is equipped with a diffuser, venturi or
nozzle directed interiorly of the cage and a short blast of -
high pressure air or a discharge of low pressure, high volume - `~
air is individually introduced through each nozzle. This pulse
of air travels through the filter sleeve to dislodge the dust
cake. ;
It is of course inevitable that, in service, bags
within the baghouse will develop leaks or ruptures which impair
the efficiency in removing particulate matter from contaminated
gas. However, in order to stay within industrial emissions
standards and operate at peak efficiency, it is imperative that ~ ;~
defective bags be identified and replaced. Proper baghouse
maintenance is therefore of crucial importance.
The replacement of defective bags has traditionally
been a time-consuming and costly maintenance operation -
requiring at least two workmen. With the top access door of
the clean air plenum removed, the bag to be replaced is first
.,
located. Next the venturi or nozzle, such as venturi 40 in
FIG. S of U. S. Patent No. 3,876,402, is removed and laid aside
for installation later. The clamping band, such as band 60 of
Patent 3,876,402, is then removed from around the tube sheet ~ ~
collar, such as collar 31(b) of the foregoing patent. The cage ~; :
and bag, such as cage 41 and bag 42 of Patent 3,876,402, is
then lifted from the tube sheet and one workman lowers the bag
and cage assembly to a second workman on the ground. The ~-
~''''~"` ' ~ - '
,,-:, ,, :.. -: - :
l~9Z5ZS
filter sleeve is then stripped off of the cage. At this phase
of the maintenance operation it is common to encounter bags
which are fused to the cage and require additional stripping
time. Once the bag is removed, however, the cage is thoroughly
inspected for corrosion and sharp edges that may tear or weaken
the filter fabric. Such areas must be filed or brushed to
present a smooth surface once again. Cages in bad condition
must be replaced altogether. A new filter sleeve is then
carefully fitted over the reconditioned or replaced cage and
the assembly is again raised to the top of the baghouse. The
assembly is carefully lowered into the appropriate opening in
the tube sheet and the fabric filter is folded over the tube
sheet collar and encircled with a clamping band. Finally, the
venturi or nozzle is replaced and should be carefully aligned
in the opening to the cage-bag assembly. Any misalignment of ~-
the nozzle will naturally misdirect the cleaning pulse during
subsequent cleanings and can result in premature bag failure -
and inefficient cleaning.
As apparent from the foregoing description, the
prior art maintenance procedure is not only costly and time-
consuming but, when properly done, requires exceptional care.
Accordingly, there is a long felt need in this industry for ;~
improvements in bag, cage and nozzle assemblies to alleviate ---
the many maintenance difficulties which have been encountered
in the past. The,primary goal of this invention is to meet
this need.
More specifically, an object of this invention is
to provide an improved cage, bag and nozzle assembly to
decrease maintenance time and costs heretofore associated with
baghouse operations. Also, the improved assembly achieves the
added advantage of prolonging bag life which, in turn, results
in a less rigorous maintenance schedule. These advantages are
~; 3-
.. . . . -
:
iO92525
achieved by provision of a unitary and preassembled filter
cartridge which replaces the three separate components
comprising the bag, cage and diffuser in a conventional outside
bag collector and which may be discarded entirely when it is
necessary to replace the filter.
Another object of the invention is to provide an
integrally joined cage and nozzle construction which rigidly
maintains alignment of the nozzle with respect to the cage to ~
insure proper jet pulse cleaning after installation. As an ~ -
adjunct to this object, the improved construction eliminates
the requirement of a separate collar to be spot welded on the ~ ~
upper cage assembly for tensioning the bag as has been ~;
practiced by this industry.
Another object of the invention is to provide an
improved cage fabricated of wire mesh chosen to optimally
support a filter bag yet still permit unrestricted flow through
the filter. High speed photography tests reveal that the wire
cage can actually block air flow through the filter and thus
impair efficiency of the baghouse in both filter and cleaning
operations. To minimize this effect, it has been determined -~
that a wire mesh cage is best fabricated from wire 1/2" to 1"
to 2" in the range of 14 to 16 gauge wire.
An additional object of this invention is to
provide a filter cartridge of the character described which is ~ !
self-sealing upon installation in the tube sheet. Thus, the ~ -~
prior time-consuming methods of carefully folding the bag
itself over the tube sheet collar or the even more undesirable
situation of re~uiring a sealing material separate of the bag
are outmoded by this filter cartridge. The preassembled
cartridge is simply inserted in the tube sheet and press fitted
to the collar of the tube sheet to achieve an effective seal
thereagainst.
4-
- ~o9z~
A further object of the invention is to provide an
improved bag construction for an outside bag collector to
permit utilization of a filter sleeve of cylindrical
construction having two open ends. Outside bag collectors have
traditionally employed a cylindrical bag having a sewn in
bottom. Naturally this feature requires a separate
manufacturing operation during the bag fabrication. Inasmuch
as all of the process gas in a baghouse must necessarily flow
past the bottoms of the bags, the bottom is a point of high
wear and acts as a baffle within the dirty air plenum. In one
embodiment of this invention, the bag is constructed from a
cylindrical sleeve having a specially designed reinforced cuff
which seals against the bottom pan or end closure secured to
the bottom of the cage.
Yet another object of the invention is to provide -~ -
an improved end cap for a cage assembly to be used with filter
sleeves having an open bottom. When an open bottom filter
sleeve has been used in this industry, it is necessary that the
bottom of the cage be fitted with an end cap. The end cap may
be welded to the bottom of the cage and the filter sleeve is
secured thereto by means of an adjustable clamping band such as
a conventional hose clamp. The construction of this invention
provides for an end cap which may be crimped onto the cage
without splitting or otherwise rupturing the end cap as has
been encountered in crimping operations.
Other and further objects of the invention,
together with the features of novelty appurtenant thereto, will
appear in the course of the following description of the
drawings.
Thus, the present invention provides a filter
cartridge for installation in an outside bag collector, said
cartridge comprising: a cylindrical cage having open upper and
.. .
- 10925Z~
lower ends; a circular cap secured to the lower end of said
cage, said cap including an outer cylindrical clamping surface .
and a peripheral ridge projecting outwardly from said clamping
surface: a filter sleeve encasing said cage and having an open .~.
bottom; a cuff formed in the bottom of said filter sleeve :
adjacent said circular cap; and a continuous band disposed
within said cuff to encircle said clamping surface of said cap ~-
and thereby seal the bottom of said filter sleeve against said
cap.
The accompanying drawings, which form a part of the . .
specification and are to be read in conjunction therewith, and :
in which like reference numerals are employed to indicate like
parts in the various views~
FIG. 1 is a perspective view of an outside bag --
collector typical of the type for which the filter cartridge
herein is designed; ~ :
FIG, 2 is a side elevational, partly sectional, ~`
view of a disposable filter cartridge constructed in accordance ~^
with a preferred embodiment of the invention, the break lines .
indicating continuous length of the filter bag; :-:
FIG. 3, located on page 3 of the drawings, is a top ~-
plan view of the cage-bag assembly taken along line 3-3 of FIG.
2 in the direction of the arrows; ~ - `
FIG. 4 is a top plan view of a first alternative -
construction of an improved filter bag;
FIG. 5 is a side elevational view of the filter bag ~:
taken along line 5-5 of FIG. 4 in the direction of the arrows
with a fragmentary portion of the diffuser and cage assembly
being slightly withdrawn from the bag for purposes of clarity; ~ :
FIG. 6 is a top plan view of a second alternative
construction of an improved filter bag;
FIG. 7 is a side elevational view.of the bag taken
--6--
~' '.
,:: . -, . . . .
~9Z525
along line 7-7 of FIG. 6 in the direction of the arrows, the
fragmentary portion of the diffuser and cage assembly being
slightly withdrawn from the bag for purposes of clarity; ~
FIG. 8 is a top plan view of a third alternative :
construction of an improved filter bag;
FIG. 9 is a side elevational view of the bag taken
along line 9-9 of FIG. 8 in the direction of the arrows;
FIG. 10 is a bottom plan view of an end cap
constructed in accordance with another embodiment of the
invention;
FIG. 11 is an inverted, side elevational view of :~
the end cap taken along line 11-11 of FIG. 10 in the direction
of the arrows and illustrating the cap prior to the crimping -
thereof onto the cylindrical cage;
FIG. 12 is an inverted, side elevational view of ~-
the end cap shown in FIG. 11, but illustrating the end cap
ully crimped and positioned in a crimping jig with a crimping
force indicated by the arrows; :.
FIG. 13, located on page 1 of the drawings, is a
20 side elevational, partly sectional, view of the bottom portion .-
of an open ended filter bag constructed in accordance with
. .
another embodiment of the invention.
Referring to FIG. 1 in more detail, the baghouse "- :-
basically comprises a sheet metal housing 20 equipped with an
inlet duct 21 to the dirty air plenum 22 and an outlet duct 23 .;.
from the clean air plenum 24. Process gas is pulled through
the baghouse by means of a fan 25.
Interiorly of the housing 20, the dirty and clean -~
air plenums 22 and 24 are separated by a horizontal tube sheet
30 26 from which are suspended a plurality of filter cartridges -~
27. For replacement maintenance, access to the filters 27 is ~:-
provided through the clean air plenum 24 by one or more doors `
~. .
~: -7_
~;
iO9Z~5Z5
19 in the roof of the housing.
Particular attention is now directed to the filter
cartridge 27 illustrated in FIGS. 2 and 3. The cage of the
cartridge comprises a cylindrical wire mesh cage 28 having a
wire mesh bottom 28a and open at the upper end thereof. The
cage is preferably fabricated from wire mesh in the range f ~2
by 1 inch or 1 to 2 inches in either 14 to 16 gauge. A ~2 by 1 ~ -
~nch size in 14 gauge is best for use with felted fabric
filters and a 1 by 2 inch size in 16 gauge is desirable for use -
with woven fabric filters.
Rigidly attached to the upper end of the
cylindrical cage 28 is a diffuser member 29. The diffuser
member 29 includes a central diffuser portion 29a, frusto-
conical in shape, which extends interiorly of the upper opening
of the cage 28. Integrally formed with the upper edge of the
diffuser portion 29a is a cylindrical channel defined by
vertical opposed walls 29b and 29c which receive the upper edge ;
of the cage 28 therebetween. The interior wall 29b may be
crimped against the cage 28 and the outer wall 29c to rigidly
join the diffuser member 29 with the cage 28 and maintain
alignment therewith. Integrally joined to the lower edge of -~: `
the outer wall 29c is a horizontally disposed shelf 29d adapted
to overlie the upstanding collar 26a of the tube sheet 26 when
the filter cartridge 27 is installed thereon. A plurality of
downwardly extending flexible fingers 29e are integrally joined
to the outer edge of the shelf portion 29d, being adapted to
encircle the upstanding collar 26a on the tube sheet when the
filter cartridge 27 is installed. Several of the flexible
fingers 29e around the periphery of the diffuser member 29 are
equipped with outwardly projecting bosses 29f formed in the
upper surfaces of the fingers.
~ : - - ,
;~ ' " ' ~
1(~9~525
FIG. 2 illustrates use of the diffuser-cage
assembly 28 and 29 with a conventional filter bag 30 having a
sewn in bottom 30a and the upper end 30b thereof folded over
the upstanding collar of the tube sheet as is required prior to
full insertion of the cage assembly. To complete installation,
a clamping band 31, such as a conventional hose clamp,
encircles the flexible fingers 29e of the diffuser member and
is disposed with its upper edge beneath the bosses 29f in order
to prevent the band 31 from slipping upwardly. Tightening of
the band 31 causes the flexible fingers 29e to seal the upper
portion 30b of the bag against the upstanding collar 26a of the
tube sheet.
It should be noted that with the foregoing cage
construction, proper alignment is maintained between the cage
28 and diffuser 29 by virtue of the rigid attachment of the
diffuser to the cage. Since the diffuser is rigidly atached ` ~-
and has a low profile it may be walked on by maintenance ~ :
workers in the clean air plenum without displacing the diffuser
relative to the cage or the cage relative to the tube sheet. ~
20 This of course speeds replacement and normal maintenance of the --
baghouse.
In order to achieve a self-sealing feature for use
in conjunction with the foregoing cage assembly, FIGS. 4
through 9 disclose three alternative constructions of an `~ -
improved filter bag. With reference first to FIGS. 4 and 5,
the bag includes a cylindrical sleeve 32a having an inside
diameter substantially equal to the outside diameter of the
cage 28. Attached to the upper edge of the sleeve 32a is a
circular annulus 32b having a width at least as great as the
width of the shelf 29d plus the vertical length of the flexible
fingers 29e on the diffuser member 29. Furthermore, it is
important to this invention that the outer diameter of the
_g_
:~ ~ , . . - - :
lO9ZSZS
annulus 32b be larger than the diameter of the diffuser member
29 defined by the flexible fingers 29e. The particular bag
illustrated in FIGS. 4 and 5 is fabricated of felted material
and, thus, it is unnecessary to provide a hem at the upper end .-
of the bag and the annulus 32b may be stitched directly to the
upper edge of the sleeve 32a. If, on the other hand, a woven
fabric is employed as the filter media, it is typical to
provide a hem at the upper edge of the sleeve 32a in order to
prevent unraveling of the material. In such event, the inside
diameter of the annulus 32b would be stitched to the upper edge
of the hem.
FIGS. 6 and 7 illustrate a second alternative bag
construction. Again, the bag includes a cylindrical sleeve 33a
which encases the cage. Inasmuch as the fabric illustrated is
a woven material, the bag is provided with a hem 33b and
extending upwardly therefrom is a frusto-conical flare 33c
having an inside diameter at the upper edge thereof greater
than the diameter of the diffuser member defined by the
flexible fingers 29e. The flare 33c is furthermore of
sufficient length to at least equal the width of the shelf
portion 29d plus the vertical length of the flexible fingers
29e of the diffuser.
In the event the bag is fabricated of felted
material, the hem illustrated in FIG. 7 may be eliminated and
the lower portion of the flare 33c may be stitched directly to ~-
the upper end of the bag itself.
FIGS. 8 and 9 illustrate a third alternative bag
construction. The bag includes a cylindrical sleeve 34a which
encases the cage 28. Inasmuch as the fabric illustrated is a
woven material, the bag is provided with a hem 34b at the upper
edge thereof. Attached to the hem 34b and extending upwardly
therefrom is a cylindrical skirt 34c which extends above the
--10--
1~ ~
, ~.i, . . - , - - - - , - . . . .
... .
-- ~09Z525
upper edge of the hem 34b a distance at least as great as the
- length of the shelf 29d plus the vertical length of the
flexible fingers 29e on the diffuser member. As will be noted
in FIG. 9 with respect to the third bag construction, the skirt
34c in the condition illustrated when it is initially slipped
onto the cage 28 does not have a diameter larger than the
outside diameter of the diffuser member as defined by the
flexible fingers 29e. Accordingly, it is imperative that the
skirt 34c be fabricated of a stretchingly deformable material,
such as a deformable felt, which may be hand stretched and
deformed to provide an opening at the upper end thereof larger ;
than the diameter of the diffuser member 29. In other words, ~-;
the seal illustrated in FIG. 9 is easily stretched to a
position such as that shown in FIG. 7.
In FIGS. 5, 7 and 9, the cage 28 and diffuser 29
are illustrated slightly withdrawn from the bag for purposes of
clarity. Prior to installation in the tube sheet 26, however, ;~
the lower edges of the flexible fingers 29e of the diffuser
engage the seal itself. That is, in FIG. 5 the fingers 29e
contact the upper surface of the annulus 32b, in FIG. 7 the
fingers 29e contact and are received slightly within the flare ~ -~
33c, and in FIG. 9, with the material stretched out to a ~ -
position such as shown in FIG. 7, the fingers 29e likewise
engage the skirt 34c and are received slightly within the upper
opening thereof.
During installation, the cage and bag cartridge 27
is inserted through an opening in the tube sheet 26 and lowered
until the upstanding collar 26a of the tube sheet engages the `
back or exterior surface of the seal apron (i.e., annulus 32b,
flare 33c, or stretchable skirt 34c depending upon which bag
construction is employed). Thereafter, downward pressure is ~ -
applied to the diffuser 29 and the cage 28 is fully inserted
-11-
, .~
lO~Z~Z5
into the bag and seated against the upstanding collar 26a of
tube sheet as shown in FIG 2. Since the outermost diameter of
the seal apron (i.e., annulus 32b, flare 33c or skirt 34c) is
larger than the diameter of the flexible fingers, the seal is
automatically folded over the upstanding collar 26a of the tube
sheet as a downward force is applied to the diffuser 29. In
other words, it is not necessary to separately fold the seal
over the upstanding collar prior to full seating of the
diffuser. Also, when the diffuser is properly seated on the ^
tube sheet collar, proper alignment of the filter cartridge 27
within the dirty air plenum 22 is insured. Proper alignment of
the nozzle portion 29a with respect to the cage 28 is of course
insured by virtue of the crimping seal between the cage 28 and
- diffuser 29.
; With the cartridge 27 fully seated on the tube
sheet collar 26a, a clamping band 31 is fitted to encircle the
flexible fingers 29e and be disposed beneath the bosses 29f
thereon. Tightening of the clamping band 31 causes the
flexible fingers 29e to reduce in diameter and bias the seal
32b, 33c or 34c against the tube sheet collar 26a, thus
insuring a leak-free seal and completing the installation of ~
the cartridge 27. When it is desirable to again replace the ~ ~-
filter, it is necessary only to remove the clamping band 31 and
to discard the used cartridge 27 in its entirety including the
bag, cage and diffuser. A new cartridge 27 may then be
inserted in the tube sheet as described and the entire
maintenance can be accomplished by one man and with only one
trip to the top of the baghouse.
All of the foregoing bag constructions may employ a
cage 28 having a wire bottom and a bag having a sewn in fabric
bottom. For use with any of the previous bags, however, there
is provided (as shown in FIGS. 10-13) a cage end cap 35 to
-12-
109Z525
permit use of the bags having an open bottom. With particular
reference to FIGS. 10 and 11, the cap 35 includes exterior and
interior walls 35a and 35b integrally joined to define a
channel therebetween which receives the wire cage 28. The
lower end of the inner wall 35b is integrally joined to a
circumferential groove 35e defined by the lower portion of the
inner vertical wall, a substantially horizontal bottom portion
35d and an inclined or sloping side wall 35e. Integrally
joined to the side wall 35e of the circumferential groove and
closing the center portion of the cap is a circular plate
35f. Completing the construction of the end cap, a peripheral
ridge 35g is formed in the outer vertical wall 35a of the cap. ~ -
The circular groove 35c adjacent the interior ~ ~ -
vertical wall 35b of the end cap forms an important feature of
the cap 35. Of critical importance is the depth of the groove ;~
35c. The depth of the groove is defined as the vertical -~
distance from the plane of the circular center plate 35f to the ~ -~
bottom portion 35d of the groove. Tracing along the lateral
surface of the groove 35c in FIG. 11, the distance from the
20 outer edge o~ the circular center plate 35f along the sloping -
side wall 35e and across the bottom portion 35d of the groove
and up the inner wall 35b to a point of intersection with the
imaginary, extended plane of the circular plate 35f must be
equal to or greater than the horizontal distance between the ~ -;
outer edge of the circular center plate 35f to a point in the
; imaginary plane of the center plate 35f just touching the
vertical wires of the cage 28.
With the cap 35 inserted over the end of the cage
28 as shown in FIG. 11, the assembly is placed in a crimping
jig as illustrated in FIG. 12. The circular jig 36 is
substantially the same diameter as the outer wall 35a of the ~
cap and a crimping force, as schematically illustrated by the ~ ~-
13
. ^ . - . , - - .
lOg2525
arrow 37, forces the inner vertical wall 35b toward the outer
~ertical wall 35a to crimp the cage 28 therebetween. As can be
appreciated by comparing FIG. 11 with FIG. 12, during the
cr~mping operation, the depth of the annular groove 35c
decreases to facilitate crin~ping without rupturing the end cap.
With the end cap 35 50 installed on the bottom of
the cage 28, an open bottom filter sleeve may be fitted around
the cage and an adjustable clamping band may be tightened
around the filter to bias the fabric to the outer wall 35a of
the cap. During tensioning of the bag along the cage, the
ridge 35g of the cap assists in preventing slippage of the
clamping band or filter.
Alternatively, and as a part of this invention,
there is provided a modification of the lower end of the bag to
facilitate installation of the bag on the cage. This
modification is illustrated in FIG. 13. A continuous metal
ring 38 is disposed within a sewn cuff 39a in the bottom end of
the filter bag 39. The ring 38 is so si~ed as to have an
inside diameter equal to or slightly larger than the outside
diameter of the vertical outer wall 35a of the cap, but a
o
smaller diameter than the outside diameter of the ridge 35g
formed in the cap 35.
So constructed, the cage assembly is inserted into
the bag 39 and the ring 38 and cuff 39a at the lower end of the
bag are easily pushed onto the end cap 35 to encircle the outer
wall thereof as illustrated in FIG. 13. The peripheral ridge
35g prevents the upward displacement of the ring 38 relative to
the cage.
From the foregoing it will be seen that this
invention is one well adapted to attain all ends and objects
hereinabove set forth together with the other advantages which
are obvious and which are inherent to the structure.
-14-
..
iO92525
It will be understood that certain features and
subcombinations are of utility and may be employed without
reference to other features and subcombinations. This is
contemplated by and is within the scope of the claims. -~
Since many possible embodiments may be made of the
invention without departing from the scope thereof, it is to be
understood that all matter herein set forth or shown in the
accompanying drawings is to be interpreted as illustrative and ~ ;
not in a limiting sense.
'~
:~` ~
,.
.
'' '.''.' .'~
.' ,' ~
''', -. ~'
."'' ~.',,,
,." ~
~ - ~
."', . .. .
~': ,
, --
,
-15-
,~.~'~. :;,
