Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
11~8929
~ac~ground of the Invention:
This invention relates to a one-piece agitator, pre-
ferably enameled, for use in closed enameled vessels having
manhole openings therein.
There are three general types of enameled vessels.
In one type, frequently referred to as a two piece or clamp
top vessel~ the entire top head of the vessel can be remov-
ed. This facilitates installation of internal components
such as agitators and baffles. However, this type of
construction increases construction costs and-magnifies -
sealing problems, particularly since adj`ustments of the
seals may be necessary because of distortions of the vessel
flanges during enameling of the vessel.
~nother typa of vessel, sometimes referred to as a
one piece vessel ~ith an assembly opening, uses a top head
- formed integrally with the body of the vessel, but with
a relatively large openin~ in the head through which agita-
tors and the like can be installed. Thus, relatively large
container openings are still necessary, with the attendant
production costs and sealing problems.
The third type of vessel, frequently referred to as
a one piece or closed vessel, features an integral top head
with relatively small openings such as pipe connections,
openings for agitator and/or baffle shafts~ and manhole
openings. The largest opening in a vessel of this type
is usually the manhole, which is ty~ically much too s~all
to admit a conventional one piece agitator of the si2e
that would be desirable for many applications. Yhus,
.,:, .. .
although this type o~ reactor minimi~es the construction
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costs and sealin~ problems preserltccl by tlle clamp top
vessel and the one piece vessel with the large asse~bly
opening, it limits the type of agitator that can be install-
ed in the vessel.
Separable enameled agitators--with individual ele~ents
ehat can be introduced tllrougll a relatively snall opening
such as a manhole and assembled inside the vessel--avoid
the foregoing problems. UnEortunately, since the seals
on these separable agitators are rela~ively inaccessible
10 and difficult to e~amine, and since these agitators are
frequently exposed to highly corrosive conditions, it
is difficult and expensive to provide reliable seals for
these separable enameled agitators. ~loreover, even in
the case of very expensive sealing constructions, the
15 connection points on the agitators form weak points where
brea~downs can occur.
Sumr~ary of the Invention:
It is an object of this invention to provide a one
piece agitator that may be completely enameled and then
20 inserted through an opening in a closed vessel, such as
a manhole, which is considerably smaller than the diameter
of the agitator impeller and which provides agitation
comparable to other enamelled agitators.
These objects are achieved by using an agitator with
25 an impeller that can be wound or threaded through the
manhole opening. In a preferred embodiment, a plurality
of agitator blades are mounted on a ring segmellt which
in turn is connected directly to the agitator shaft,
preferably through an offset portion at the lower cnd
30 of the sha~t. Since this impeller can be threaded through
a relatively small opening, such as a manhole, it can have
an outer or circumferential diameter several times larger
than thc greatest cross-section dimension of the manhole,
and still be inserted through a conventional rlanhole in
35 a closed vessel. ~urtl-er advantages of this onc piece
. ~ ,,,
agitator construction, whicll can be completely enamelecl,
are that the impeller blades can be curvcd to form a
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retreat curve impeller and can bc posltioned near the
bottoM of the ves~el, and that, particularly ~ith highly
viscous products, an additional mixing affect is obtained
through the offset formation of the agitator shaft.
Drawings:
Figure 1 is a schematic sectional elevation view
of a vessel containing an embodiment of this invention,
with the agitator shown in perspective.
. ` Figure 2 is a schematic plan view of the vessel and
. 10 agitator shown in Fi~ure 1.
Fi~ures 3-6 are schematic elevation views of other
embodiments of this invention.
Detailed Description:
Figures 1 and 2 illustrate a preferred embodiment
of this invention, with a one piece, completely enameled
agitator mounted inside a typical closed enameled vessel
11. A manhole 17 and ail agitator mounting noz~le 8 are-
provided in the top head of the vessel 11. An agitator
. shaft 1 extends through the agitator nozzle ~. The -.
lower portion 2 of the agitator shaft is offset, and the
agitator impeller is attached to the lo-wer end of the
o~fset shaft connection 2. The impeller comprises a ring
~ ` shaped segment 3 and three agitator blades 4, 5 and 6 ex-
: . tending from the ring segment.3. The agitator blades and
~; 25 the ring shaped segment 3 may all lie in a plane perpen-
dicular to the axis of the agitator shaft 1, as illustrated
in Figure 1. However, the agitator blades 4, S and 6 may
also be inclined slightly upwards to conform to the gener-
ally conical shape of the bottom.of the vessel 11 if it
is desirable to position the agitator as close to tl~e
bottom as possible.
As may be seen from Figures 1 and 2, there is an
opening in the ring segment 3 which allows the ring segment
- to be threaded through the manhole 11. With the illustra- -
. 35 ted three blade impeller, the cut out section may be
approximately 120. The agi~ator blades may be symmetric-
ally arranged on the ring segment 3 with respect to rota-
.
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tion, however, it r~lay be desirablc to dlsplace some of
the agitator blades s.lightly from a symmetrical arrangement
to help balance moments on the agitator, as will be
e~plained in greater detail belo~.
Of course, more than three agitator blades may also
be used. Generally, the agitator blades will be provided
in the number and form desired for various mixing processes.
A preferred form has three blades, flattened to increase
the heighth o the blades, with the~tips curved a~7ay from
10 the direction of rotation of the impeller. This type
of construction, frequently referred to as a retreat curve
. impeller, helps to circulate the material being mixed
throughout the vessel. I~ith three flattened retreat curve
agitator blades mounted on a ring segment such as the
15 one illustrated in Figures 1 and ~, the nixing efectobtained is comparable to that obtained with a conventional
retreat curve i~peller,
The maximum length of.the agitator blade can be chosen
equal to the greatest diameter of the manhole 17, less
20 the necessary space for insertion o approximately 30 to
50~m. In order to provide an optimal assembly, a portion
of the agitator shaft fastened to the ring se~ment 3 may
- .- first run or a certain distance parallel to the agitator
axis, as illustrated in Figure 1. T~?is type of agitator
25 can be directly mounted through an ordinary.manhole open-
- ing 17 of a one piece container. Thus, insertion and
mounting of the agitator does not require any openings
larger than the manhole opening that is usually present,
An agitator drive mechanism (not shown) is generall~
30 attached to the agltator above the agitator mounting nozxle
.8. Also, a conventional finger shaped, ~-shaped or paddle
~hapcd bafle 9 is typically used with the agitators of
this invention. The baffle 9, which can also be inserted
through the manhole opening 17, is mounted in a conventional
35 baffle mounting no~zle or opening 10.
Pecause of the special construction of the agitators
~ of this invention, ~oments are produccd at the point ~hcre
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the agitator is supported in no~zle 8, arising both frol~
the Eorces of flow and also from centrifugal force~. These
moments should be compensated for or balanced to insurc
satisfactory functioning of the shaft sealing, and to avoia
S the need to oversize the agitator shaft and/or drive unit
to prevent overloading in case greater drive po~ers are
required.
The flow forces on the offset portion 2 of the agita-
tor shaft generate moments on the agitator in different
planes perpendicular to the axis o rotation. The mo~ents
on the,agitator shaft and/or the agitator mounts and seals
arising therefrom can be compensated for by slightly
varying the height of one or more of the agitator blades
4, S and 6 relative to the other blades or, as is shown
in Figure 2, by mounting some of the agitator blades in
a position that deviates from a symmetrical arrangement
by a small angle, for example 5. Either of these measures
cause a resulting force ln the area of the agitator blades,
which can compensate for the moment on the agitator shaft
arising from the forces on the offset shaft connection
2. The remaining uncompensated transverse forces do not
affect the functioning of the agitator.
In a similar way, the imbalances arising from the
lack of symmetry o the impeller can be compensated for
by varying the thic~ness of one or more of the agitator
blades 4> 5, 6 or the thickness of the ring shaped segment
3. The weight of certain parts of the impeller may also
be ~aried by other means, as for example, mounting addition-
al masses on one or more agitator blades, so that no
undesired moment influences the a~,itator shaft.
The moment arising at the point of connection between
the ring shaped segment 3 and the shaft connection 2 may
be controlled without special difficulties. A partial
compensation for the moment at this location, which is
produced by flow forces and centrifugal forces, is obtained
by arranging the ring sllaped segment 3 so that it follows
, j
the shaft connection 2 in the direction of rotation 7.
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~ith this arrangement, the resultants of the forces of
flow and the centrifugal forces act in opposite directions,
whicl~ reduces the moment at the p`oint where the ring
segment joins the shaft connection 2.
An agitator of this sort can be completely enameled,
because of its construction fsvorable to enameling techni-
que, wlthout fear oi chipping, which could be caused
through excessive stresses generated in the enameling
process or in the operation of the agitator. This produces
significant advantages in the economy of using a vessel
according to this invention, because it is desirable,
particularly in highly corrosive chemical applications `
at high te~peratùres under high pressures J to avoid the
seals ~nd weak points which were characteristic disadvan-
tages of ~nown segmented enamel agitators.
Figures 3-6 show other versions of this invention
which may also be threaded through a conventional sized
manhole 17 in a closed vessel 11. In each of these
agitators, the impeller is constructed o alternating
sections running at least approximately horizontally and
,
sections running at least approximately vertically. In the`
agitator represented in Fi&ure 3, the i~peller-is essen- -
~` tially made S-shaped in that the agitator blades 14, 15,
- 16 are arranged horizontally and superimposed abo~e one
another, and are connected with each other by vertical
connecting ar~s 12, 13 which are offset from the axis
of the agitator shaft 1. The impeller of the agitator - -
shown in Figure 4 could be considered as a partial S-shape
or as a C-shape with an additional agitator blade attached
essentially vertically at the lowex end o the impeller.
Further advantages of the agitator shown in Figures
3 and 4, in comparison with the agitator illustraeed in
Figures 1 and 2, are the control of higller viscosities
and non-Newtonian substances in mixing, as well as more
; 35 uniform shearing of products which are susceptible to
shearing. The reason for this is the greater leading surface
of the agitator and the surface distrlbution in the whole
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apparatus.
Figures S and 6 illustrate additional exan~ples of
impellers constructed of alternating vertical and at least
approximately horizontal sections. In Figure S, one
` S vertical section is connected to an offset portion of
the agitator shaft, and the first vertical section is
in turn connected to a second vertically extending agitator
blade by a connection which extends approximately horizon-
tally. In Figure 6 the agitator shaft attaches directly
to the approximately~horizontal connecting piece, and
one vertically extending agitator blade is attached at
each end of the connecting piece. These a~itators are
easier to enamel and less espensive than the version shown
in Figures 1 and 2.
Thus, it may be seen that this invention provides
a variety of one piece agitators with impellers that may
be threaded through relative small openings, such as man-
J holes, in closed enameled vessels. All of these agitators
can be completely covered with an enamel coatin~, which
makes them less susceptible to corrosive attack than
- separable blade agitators. Moreover, since there are
no ~oints which can loosen, they are sturdier than separa-
: .
Ble blade agitators. Those skilled in the art will appre-
- ciate that a variety of other agitators of this sort can
be constructed within the scope of this invention, which
is defined by the following claims.
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