[0001] The present invention relates to a bearing assembly for shut-off and control dampers
in flue ducts, which assembly includes bearing devices and sealing devices and in
which the bearing devices are arranged in connection with the frame structures of
the dampers in order to shut off and control the said dampers, and in which shaft
members arranged in the damper are fitted to the bearing devices.
[0002] In power plants and other similar applications, the flow of flue gases in massive
flue ducts is regulated by means of large shut-off and control dampers. The shut-off
and control dampers, which hereinafter are referred to by the shorter general term
of dampers, are generally arranged on shafts in their frame structures. Bearings are
arranged on one side of the frame structure and are followed by the operating linkages
and their adaptations, which are connected to operating devices that move them. 'On
side opposite to this operating side, bearing devices, which are intended to ensure
frictionless opening and closing operations, are arranged in the frame structure.
[0003] The temperatures of the gases flowing in the duct are usually hundreds of degrees,
for example, 200 - 400 °C. The flue gases comprise gases containing substances such
as sulphur and soot particles. Such conditions place great demands on the bearings
of the dampers, and particularly on their lubrication and the lubricating substances.
[0004] The state of the art is represented by bearing assemblies, in which the shaft seals
of the bearings are arranged in the frame structure (for example, EP-754 916, EP-937
872). The shaft seal is immediately followed by, for example, a journal or ball bearing,
which is exposed to the flue gases travelling through the damper, and especially to
the solids particles in them. The known bearing assemblies used in dampers are either
permanently lubricated bearings, or bearings requiring further lubrication at intervals,
freedom from maintenance being, however the main criterion of these assemblies. Permanently
lubricated bearings are lubricated, for example, during assembly at the factory. Permanent
lubrication is often the only alternative for the lubrication of bearings in certain
positions, because grease nipples, which permit later lubrication, cannot be arranged
in connection with their bearing shells; instead, they must be arranged to be as tightly
sealed as possible, to prevent heated lubricant from flowing or evaporating out of
the bearings. It is particularly precisely assemblies with ball bearings that generally
require maintenance.
[0005] The soot particles, impurities, and similar that flow with the flue gases cause not
only heat, but also the hardening of lubricants, thus substantially reducing the effective
lubrication of the bearings. This essentially weakens the movability of the dampers
and in the worst cases causes the damper to jam. The hardening of the lubricant can
also potentially block the greasing access, such as a grease nipple. The lubricants
that can be used must be selected according to the process.
[0006] In addition to the above drawbacks, present bearing assemblies become quite large,
because the need for maintenance means that components requiring maintenance must
be placed outside the thermal insulation, where they will be accessible during servicing
operations. This often results in a lack of space around the dampers, thus, for example,
restricting the servicing operations that can be carried out near them. Publication
EP-111576 discloses an example of this, which has operating linkages on both sides
of the frame structure, for adjusting the position of the damper. In this case too,
it is impossible to speak of either freedom from maintenance, or at least of an integrated
bearing construction, or of regulation of the pressure acting on the seal.
[0007] Further, the state of the art is also referred to in the publications US-3,525,328;
US-5,667,311; US-6,139,216; and FI utility model number 3867.
[0008] The present invention is intended to create a new type of more operationally reliable
and integrated bearing assembly for shut-off and control dampers in flue ducts. The
characteristic features of the bearing assembly according to the invention are stated
in Claim 1.
[0009] The integrated bearing assembly according to the invention provides substantially
improved functionality, by creating a proper seal between the flue gases travelling
through the damper and the lubricant lubricating the bearings.
[0010] In addition to the seal, the bearing assembly also reduces the shaft load arising
from the pressure of the flue gases. Further, essentially maintenance-free bearings
become possible for dampers while the small size of the bearing assembly makes it
significantly easier to apply to cramped plant environments.
[0011] Other characteristic features of the bearing assembly according to the invention
will become apparent from the accompanying Claims while other advantages gained with
the aid of the invention are referred to at greater length in the description section.
[0012] Bearing assembly solutions according to the invention, which are in no way restricted
by the embodiments presented in the following, are examined in greater detail with
reference to the accompanying drawings, in which
- Figure 1
- shows a preferred application of the bearing assembly according to the invention,
- Figure 2
- shows a bearing assembly according to the invention in its assembled form,
- Figure 3
- shows an exploded perspective view of the bearing assembly according to the invention,
- Figure 4
- shows a cross-section of the sleeve members of the bearing assembly according to the
invention,
- Figure 5
- shows an exploded perspective view of another bearing assembly according to the invention,
- Figure 6
- shows a top view of another bearing assembly according to the invention,
- Figure 7
- shows a side end view of another bearing assembly according to the invention,
- Figure 8
- shows a side view of another bearing assembly according to the invention, and
- Figure 9
- shows a cross-section of the sleeve members of another bearing assembly according
to the invention.
[0013] Figure 1 shows an example of a preferred application of the bearing assembly according
to the invention. The damper construction shown here is intended, for example, for
shutting off and controlling the flow of gases in the flue ducts of power plants.
[0014] The damper totality comprises a frame structure 11, to which three dampers 10 are
attached by shafts 26. Through-holes for the shafts 26 are arranged in the operating
and maintenance side 27.1, 27.2 of the frame structure 11. At the so-called operating
side end 27.1, the shaft 26 of the damper 10 is mounted in bearing's protruding tube
25 and the end of the shaft 26 is fitted to the damper's 10 operating linkage 12,
through which the dampers 10 are closed and controlled, for example, by a single operating
device (not shown). A bearing assembly 13 according to the invention is fitted to
the operating end 27.1 of each shaft 26.
[0015] At the opposite end 27.2 to the operating side 27.1, through holes and bearings are
arranged for the shafts 26 of the dampers 10 and permit maintenance-free and smooth
shut-off and control operation for the dampers 10, with the aid of the integrated
bearing assembly 13 according to the invention.
[0016] Figures 2 and 3 show a first bearing assembly 13 according to the invention. At one
end of the first sleeve member 15.1 in the bearing assembly 13, there is an internal
collar 15.1' which limits a hole of a diameter arranged so that it forms a tight fit
essentially with the shaft 26 of the damper 10 (Figure 1).
[0017] The internal diameter of the first sleeve member 15.1 is, except for the area of
the internal collar 15.1', adapted to the thicknesses of plaited seal rings 16.1,
16.2 which are fitted to the internal circumference 15.1* of the sleeve member 15.1,
in such a way that the internal circumference of the plaited seals 16.1, 16.2 essentially
corresponds to the outer circumference of the shaft (not shown) running through the
sleeve member 15.1, so that the outer circumference of the plaited seals 16.1, 16.2
forms a tight fit with the internal circumference 15.1* of the sleeve member 15.1
and the shaft.
[0018] Further, the thickness of the material of the plaited seals 16.1, 16.2 is arranged
to essentially cover shy of distance the space arranged for it in the axial direction
of the internal circumference 15.1* of the sleeve member 15.1.
[0019] The plaited seals 16.1, 16.2, of which the bearing assembly 13 according to the invention
includes at least one or several, most commonly 2, are made of a material with the
properties of high resistance to heat, reasonable compressibility, and low friction.
An example of such a material is pure graphite, which is preferably used in the bearing
assembly 13 according to the invention. Pure graphite can resist temperatures of up
to 1000°C, making it suitable for even very demanding bearing applications. The ends
19 of the graphite plaits 16.1, 16.2 are preferably fitted together by bevelling,
so that they also form a tight fit at the ends 19. The thickness of the graphite plaits
16.1, 16.2 can be, for example 8 * 8 mm.
[0020] Cylindrical machining 18 is arranged in the second sleeve member 15.2, with an internal
circumference that is dimensioned to receive both the shaft 26 of the damper 10 shown
in Figure 1 and a bronze journal-bearing sleeve 14, in which the journal-bearing sleeve
14 is arranged, after the assembly has been assembled, to lie between the shaft and
the cylindrical machining 18.
[0021] A protruding collar 14' is arranged at the end of the journal-bearing sleeve 14 and
essentially connects with a protruding collar 15.2' arranged in the second sleeve
member 15.2 (Figure 4). Further, the external diameter of the collar 15.2' arranged
in the first end of the second sleeve member 15.2 is set to correspond to the internal
circumference 15.1* of the cylindrical machining arranged in the first sleeve member
15.1 for the sealing plaits 16.1, 16.2.
[0022] When the bearing assembly 13 according to the invention is being assembled, the connecting
protruding collars 14', 15.2' of the said second sleeve member 15.2 and the journal-bearing
sleeve 14 fit into the space arranged for the sealing plaits 16.1, 16.2 in the first
sleeve member 15.1, so that they lie inside for a distance and are compressed to form
a so-called box seal. The protruding collar 15.2' arranged in the sleeve member 15.2
can also be replaced with a separate ring (not shown), which can be placed freely
in relation to the collar 14' of the journal-bearing sleeve 14. The other operational
components can also comprise several parts.
[0023] Bores 25.1 with internal threads (not shown), are arranged in the first sleeve member
15.1, as well as bores 25.2 in the second sleeve member 15.2, at points corresponding
to the bores 25.1. Screws 17, which carry part of the loading caused by the flue gases
on the dampers 10, and which hold the assembly 13 together, are fitted to the bores
25.1, 25.2. The protruding collar 15.2' arranged in the second sleeve member 15.2
has also the secondary function of carrying the loading caused by the flue gases,
which the securing screws 17 alone may not always necessarily be able to carry.
[0024] Figure 4 shows cross-sections of the first and second sleeve members 15.1, 15.2 used
in the embodiment described. The internal collar 15.1' machined in the first sleeve
member 15.1 is also used to carry the shaft load arising from the damper 10. Additional
collars can be fitted to the internal circumferences 15.1*, 15.2* of the first and
second sleeve members 15.1, 15.2 to carry the shaft load. The sealing plaits 16.1,
16.2 are fitted tightly into the space machined for them in the internal circumference
15.1*. Figure 4 also shows the protruding collar 15.2' arranged in the second sleeve
member 15.2 and the lubricant groove 21 arranged in the journal-bearing sleeve 14.
[0025] In the bearing assembly 13 according to the invention, the loading acting on the
seals 16.1, 16.2 can be adjusted, not only with the assembly screws 17 of the bearing
assembly 13, but also by using, for example, the helical spring member 22 shown in
Figure 4, which is placed in the bottom of the second sleeve member 15.2, between
the end of the shaft of the damper 10 and the bottom of the sleeve member 15.2. The
end of the spring member 22 on the shaft side is shaped so that it forms a very good
fit against the end of the shaft. Altering the stiffness of the spring 22 allows a
suitable level of tightness to be found for the assembly screws 17.
[0026] Figures 5 - 8 show another embodiment of the bearing assembly according to the invention.
The components and principle of this embodiment correspond essentially to the first
embodiment described. In this case, the first and second sleeve members 15.1, 15.2
are square plates. The second sleeve member 15.2 is left open at both ends, allowing
the shaft 26 of the damper 10 shown in Figure 1 to be pushed through it.
[0027] A protruding bearing tube 25 for the shaft 26 running through it is arranged at the
end of the bearing assembly 13 and has devices 24 at its end that are as such known,
for example, for fitting the operating linkage 12 shown in Figure 1 to the end of
the shaft 26. This embodiment is particularly intended for the operating side 27.1
of shut-off and control dampers, in which devices 12 are arranged to shut off and
control the damper 10 (Figure 1).
[0028] A second preferred manner to adjust the load acting on the seals 16.1, 16.2 is shown
in Figure 9, which shows the first and second sleeve members 15.1, 15.2 and a spacer
ring 23 placed between them. By altering the number and thickness of the spacer rings
23 fitted, the pressure acting on the seals 16.1, 16.2 can be easily adjusted using
the protruding collar fitted in connection with the second sleeve member 15.2.
[0029] The integrated bearing assembly according to the invention is preferably permanently
lubricated, so that no lubrication connection at all are shown in it. Lubrication
thus takes place during the assembly stage of the bearing assembly. The bearing assembly
according to the invention is assembled already in the machining stage. It can be
installed in the frame structure 11 of the damper 10 in the application by, for example,
welding the first sleeve member 15.1 to the frame 10.
[0030] It should be understood that the above description and the related figures are only
intended to illustrate the present invention. The invention is thus in no way restricted
to only the embodiments described above or defined in the Claims, instead, many different
variations and adaptations of the invention, which are possible within the scope of
the inventive idea defined in the accompanying Claims, will be obvious to one versed
in the art.
1. A bearing assembly for shut-off and control dampers (10) in flue ducts, which assembly
includes bearing devices (14, 15.1, 15.2) and sealing devices (16.1, 16.2) and in
which the bearing devices (14, 15.1, 15.2) are arranged in connection with the frame
structures (11) of the dampers (10) in order to shut off and control the said dampers
(10) and in which shaft members (26) fitted to the dampers (10) are fitted to the
bearing devices (14. 15.1, 15.2),
characterized in that the bearing assembly is formed as an essentially integrated totality, which includes
- a first sleeve member (15.1), attached to the frame structure (11) of the damper
(10), to which an internal collar (15.1') is fitted at the end next to the frame structure
(11),
- a second sleeve member (15.2), the first sleeve-member (15.1) end of which has a
protruding collar (15.2') fitted around the shaft hole (18), attached with attachment
devices (17) to the first sleeve-member (15.1),
- a journal-bearing sleeve (14), to which a collar (14'), joining the protruding collar
(15.2') fitted in connection with the said second sleeve member (15.1), is fitted,
and
- at least one sealing plait (16.1), which is fitted to the internal circumference
(15.1*) of the said first sleeve member (15.1), in such a way that, when the bearing
assembly is being assembled, it is arranged to be pressed between the internal collar
(15.1') of the first sleeve member (15.1) and at least the protruding collar (15.2')
arranged in connection with the second sleeve member (15.2) to the internal circumference
(15.1*) of the first sleeve member (15.1).
2. An assembly according to Claim 1, characterized in that the said sealing plait (16.1, 16.2) is graphite.
3. An assembly according to Claim 2, characterized in that bevelling (19) is arranged in the ends of the sealing plaits (16.1, 16.2).
4. An assembly according to any of Claims 1 - 3, characterized in that devices (20, 21) are arranged in the assembly for lubricating the bearing (14).
5. An assembly according to any of Claims 1 - 4, characterized in that the ends of the said sleeve member (15.2) are left open.
6. An assembly according to Claims 1 - 4, characterized in that spring-loading member (22) is fitted to the end of the housing of the second sleeve
member (15.2), in order to adjust the pressure.
7. An assembly according to any of Claims 1 - 6, characterized in that at least one spacer member (23) is fitted between the said first and second sleeve
members (15.1, 15.2), in order to adjust the pressure.
8. An assembly according to any of Claims 1 - 7, characterized in that internal collars are fitted to the internal circumferences (15.1*, 15.2*) of the
first and/or the second sleeve members (15.1, 15.2), in order to equalize the shaft
loading.