Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] Air Damper For A Fire Tube
FIELD
[0002] There is described an air damper which controls combustion air to a
burner
positioned in a fire tube.
BACKGROUND
[0003] United States Patent 4,702,692 (Burns et al) entitled "Air
Reduction Controls for
Oil-Treating Vessels", describes an air damper that has become a standard in
the oil industry.
This air damper consists of a fixed plate having a plurality of air flow
openings and a rotatable
plate having a plurality of air flow openings. By rotating the rotatable
plate, the air flow
openings in the rotatable plate can either be brought into register with the
air flow openings in
the fixed plate or the air flow openings in the fixed plate can be at least
partially blocked by
the rotatable plate. The air damper of Burns et al was welded in a duct that
extended radially
from a fire tube.
SUMMARY
[0004] There is provided an air damper for a fire tube which includes an
air damper body
with a fixed plate having a plurality of air flow openings and a rotatable
plate having a
plurality of air flow openings. The air damper body has an air inlet face, an
air outlet face,
and an outer circumference. A central burner passage is provided through the
air damper
body. This central burner passage is adapted to receive a burner body. A
deformable
circumferential seal is provided around the outer circumference of the air
damper body. This
circumferential seal is adapted to engage an inner circumference of a fire
tube solely by
friction.
[0005] As will hereinafter be further described, the use of
circumferential seal has a
dramatic beneficial effect on performance, when compared to the same assembly
without a
circumferential seal.
[0006] It is preferred that the rotatable plate is positioned at the
inlet face of the air
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damper body and the fixed plate is positioned at the outlet face of the air
damper body. With
this configuration, the rotatable plate is more readily accessed for the
purpose of making
adjustments.
[0007] It is preferred that the outlet face of the air damper body has
outwardly projecting
air deflectors overlying the air flow openings of the fixed plate. This
configuration imparts a
helical flow to air flowing through the air damper body.
[0008] It is preferred that a handle is provided on the rotatable plate.
This enables a
manual force to be exerted via the handle to rotate the rotatable plate
thereby adjusting the
position of the air flow openings of the rotatable plate relative to the air
flow openings of the
fixed plate.
[0009] It is preferred that an ignitor passage extend through the air
damper body in
parallel spaced relation to the central burner passage. This configuration
enables an ignitor to
be positioned to ignite combustion gas flowing through the burner body.
BRIEF DESCRIPTION OF 'THE DRAWINGS
[0010] These and other features will become more apparent from the
following
description in which reference is made to the appended drawings, the drawings
are for the
purpose of illustration only and are not intended to be in any way limiting,
wherein:
[0011] FIG. 1 is a front elevation view of an air damper for a fire tube.
[0012] FIG. 2 is a front perspective view of the air damper illustrated
in FIG. 1.
[0013] FIG. 3 is a rear elevation view of the air damper illustrated in
FIG. 1.
[0014] FIG. 4 is a rear perspective view of the air damper illustrated in
FIG. 1.
[0015] FIG. 5 is a top plan view of the air damper illustrated in FIG. 1.
[0016] FIG 6 is a rear perspective view of the air damper illustrated in
FIG. 1, positioned
in a fire tube.
[0017] FIG. 7 is a front perspective view of the air damper illustrated
in FIG. 1,
positioned in a fire tube.
[0018] FIG. 8 is a side elevation view, in section, of the air damper
illustrated in FIG. 1,
positioned in a fire tube.
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[0019] FIG. 9 is a detailed side elevation view, in section, of the air
damper illustrated in
FIG. 1 positioned in a fire tube.
DETAILED DESCRIPTION
[0020] An air damper, generally identified by reference numeral 10, will
now be
described with reference to FIG. 1 through FIG. 9.
Structure and Relationship of Parts:
[0021] Referring to FIG. 5, air damper 10 includes an air damper body 12
with a fixed
plate 14 and a rotatable plate 16. Referring to FIG. 1 and FIG. 2 fixed plate
14 has a plurality
of air flow openings 18. Referring to FIG. 3 and FIG. 4, rotatable plate 16
also has a plurality
of air flow openings 20. Referring to FIG. 5, air damper body 12 has an air
inlet face 22, an
air outlet face 24, and an outer circumference 26. Air, indicated by arrows
28, enters air
damper body 12 through air inlet face 22 and exits air damper body 12 through
air outlet face
24. Referring to FIG. 2, FIG. 4 and FIG. 5, a central burner passage 30 is
provided through
air damper body 12. Referring to FIG. 8, central burner passage 30 is adapted
to receive a
burner body 100, as will hereinafter be further described. Referring to FIG. 1
through FIG. 4,
a circumferential seal 32 is provided around outer circumference 26 of air
damper body 12.
Referring to FIG. 8, circumferential seal 32 is adapted to engage an inner
circumference 102
of a fire tube 104 solely by friction.
[0022] Referring to FIG. 2, FIG. 4 and FIG. 5, it is preferred that
rotatable plate 16 is
positioned at inlet face 22 of air damper body 12 and that fixed plate 14 is
positioned at outlet
face 24 of air damper body 12. With this configuration, the rotatable plate is
more readily
accessed for the purpose of making adjustments.
[0023] Referring to FIG. 2 and FIG. 5, it is preferred that outlet face
24 of air damper
body 12 has outwardly projecting air deflectors 34 overlying air flow openings
18 of fixed
plate 14. This configuration imparts a helical flow to air flowing through air
damper body 12.
[0024] Referring to FIG. 4 and FIG. 5, it is preferred that a handle 36
is provided on
rotatable plate 16. This enables a manual force to be exerted via handle 36 to
rotate rotatable
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plate 16 thereby adjusting the position of air flow openings 20 of rotatable
plate 16 relative to
air flow openings 18 of fixed plate 14.
[0025] Referring
to FIG. 4 and FIG. 5, in order to prevent air flow from circumventing air
damper body 12, fixed plate 14 and rotatable plate 16 are loosely clamped
together. The term
"loosely is used, as the mode of clamping must not impede rotation of
rotatable plate 16. The
mode of clamping illustrated are nuts 40 and bolts 42. Bolts 42 extend through
fixed plate 14.
However, to facilitate rotation of rotatable plate 16, bolts 42 extend through
slots 44 in
rotatable plate 16.
[0026] Referring
to FIG. 2, FIG. 4 and FIG. 5, It is preferred that an ignitor passage 46
extend through air damper body 12 in parallel spaced relation to central
burner passage 30.
This configuration enables an ignitor 106 to be positioned to ignite
combustion gas flowing
through burner body 100.
Operation:
[0027] Referring
to FIG. 6 through FIG. 8, burner body 100 has a nozzle end 108 and a
fuel gas source attachment end 110. In preparation for installation, burner
body 100 is
inserted into central burner passage 30 of air damper body 12 With nozzle end
108 protruding
passed air outlet face 24 of air damper body 12 and fuel gas source attachment
end 110
protruding passed air inlet face 22 of air damper body 12. Air damper 12 is
then inserted into
fire tube 104. When air damper 12 is inserted into fire tube 104,
circumferential seal 32
engages inner circumference 102 of fire tube 104 solely by friction. Referring
to FIG. 9, it
can be seen that circumferential seal 32 deforms to create an air seal.
Beneficial results have
been obtained when circumferential seal 32 is made of a flexible, high
temperature rated
material, such as silicone. Referring to FIG. 8, either before or after
insertion of air damper
body 12 into fire tube 104 ignitor 106 extended through ignitor passage 46 and
positioned
relative to nozzle end 108 to ignite combustion gas flowing through burner
body 100 to
nozzle end 108.
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[0028] Tests
were conducted to determine the relative efficiency of air damper 10, with
and without circumferential seal 32. It was determined that air damper 10 with
circumferential seal 32 outperformed air damper 10 without circumferential
seal 32. The
increase in efficiency depended upon the turn down rate of the combustion
system. For
5 example, when the combustion system firing rate was reduced to 40% of the
maximum
possible firing rate and rotatable plate 14 was rotated relative to fixed
plate 14 to reduce the
air flow through air damper body 12 to 40% of capacity (60% turn down), air
damper 10 with
circumferential seal 32 transferred up to 43% more heat into the process for
the same quantity
of gas consumed, as compared to combustion assemblies having air dampers
without
circumferential seal 32.
[0029] The gap
about the periphery of the damper had never previously been considered a
problem, because the air damper was never used to completely shut off the flow
of air
anyway. A peripheral seal was added, forcing all the air flow to pass through
the damper.
The effect on efficiency was then measured. Marginal increases in efficiency
were measured
at lower turn down rates. However, as the turn down rates became higher,
unexpected
increases in efficiency were measured. As set forth above, with a 60% turn
down rate, up to
43% more heat is transferred.
[0030] In this
patent document, the word "comprising" is used in its non-limiting sense to
mean that items following the word are included, but items not specifically
mentioned are not
excluded. A reference to an element by the indefinite article "a" does not
exclude the
possibility that more than one of the element is present, unless the context
clearly requires that
there be one and only one of the elements.
[0031] The scope of the claims should not be limited by the illustrated
embodiments set
forth as examples, but should be given the broadest interpretation consistent
with a purposive
construction of the claims in view of the description as a whole.
