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FIELD OF INVENTION:
The present invention relates to Flow Isolator apparatuses (FIA) adapted in the
ducts and pipelines carrying fluids like air, flue gas or fuel gas. More particularly,
the invention relates to a sealing device for flow isolator apparatus.
BACKGROUND OF THE INVENTION:
Swing type flaps, rotating type flaps, sliding gate plates are examples of Flow
Isolator Apparatus (FIA). Applications of the flow isolator apparatus (FIA) are
plenty in ducts and pipelines carrying fluids like air, flue gas or fuel gas. Steam
generators in thermal power stations, flue gas desulphurization systems and
Integrated Gasification and Combined Cycle (IGCC) plants are a few applications.
Maintenance of downstream equipment or hazard prevention or wastage
avoidance requires high degree of isolation between the gas/air/fluid pressure
upstream of the FIA and it's downstream. For flow isolation, the FIA has the
flowing components:
i) Isolator element; (IE) and
ii) Sealing element (SE)
In the open position, the isolator element (IE) and Sealing Element (SE) are
away from one another in their extreme position, while at the closed position the

IE and SE are in their closest contact position. The IE acts like a main dam for
the flow, while the SE tightens the gaps in the parts of the IE making the
apparatus more and more leak-tight. The SE plays thus, an important role in
ensuring the degree of leak-tightness.
The SE should have characteristics of springness or rigidity modulus at hot fluid
temperature, should not erode away by fluid flow with or without particles in it
and should not work-harden and crack by fatigue.
In the case of a plate gate type flow isolator, the sealing element (SE) bears
against the IE's border surfaces near the edges on all the fours sides on either
side, viz. upstream and downstream. The higher the pressure of bearing
surfaces, the greater is the sealing. In the case of a flap type of isolator the SE
bears against the mating surface along the edge of the next flap; here also, the
pressure of contact surfaces of SE and IE decide the sealing efficiency, given the
material of SE and the differential pressure of the flow medium across the
isolator.
The prior art discloses a sealing system based on double sealing of stainless steel
material 316L for flap type dampers. Here, the gate plate of the gate is
functionally substituted by the flap; the double sealing on either side of the gate
plate is reproduced by two separate sealing elements in tandem on the moving
flaps and flexing against strips, which bear from the frame side. The flexure is
caused by flap pressing against this strip member all around.

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Sealing device in the prior art is designed basically on the principle of keeping
the sealing element inside an envelope such as a pipe or duct or, in general, a
conduit, and then actuating the SE to press against the IE, principally by means
of the motion of the IE.
US 6588768 B discloses a sealing device having seal elements inside the flow
conduit and actuated for sealing by the movement of the isolator element, viz.
damper Flap or gate plate. The Gates have a gate plate piercing the gap below
two stacks of seals of flexural materials like thin strips of stainless steel and
spring steel. This gives two sealing surfaces, on either side of the gate plate; the
sealing pressure purely depends on the deflection forced on the seals by the
difference between the initial gap and the gate plate thickness. The present
materials give the springiness for effecting the sealing but no special property for
consistency of springiness over operating cycles of the gate is specified.
However, the prior art has a limitation for example, the actuation is to be inside
the conduit and sealing enhancement is requiring a seal air plenum chamber.
OBJECTS OF INVENTION
It is therefore an object of the invention is to propose a sealing device for flow
isolator apparatuses which eliminatas the disadvantages of the prior art.
Another object of the invention is to propose a sealing device for flow isolator
apparatuses, in which the sealing element is actuated by external actuators in
opposed to in-conduit actuation.

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A still another object of the invention is to propose a sealing device for flow
isolator apparatuses, in which the sealing element is formed in such a way that
spring characteristics of the elements remains substantially unaffected at hot
fluid temperature.
Yet another object of the invention is to propose a sealing device for flow isolator
apparatuses, which ensures the sealing effectiveness interialia leak-profness by
the sonic signal of the flow medium.
A further object of the invention is to propose a sealing device for flow isolator
apparatuses which is compact in size, reliable and cost-effective.
SUMMARY OF INVENTION:
Accordingly, there is provided a sealing device for flow isolator apparatuses
adaptable in steam generator, Integrated gasification and combined cycle plants,
and ducts or pipelines carrying fluids, comprising a conduit having a plate gate
isolator interposed therein; a movable gate plate insertable in or withdrawable
from the conduit, a seal element being configured as a part of an actuator
mechanism, the seal element on actuation traverses towards the gate plate and
contacts the plate surface to achieve a first level of sealing; a cam pressing
behind the seal element to achieve a second level of sealing, a sonic probe feed
arrangement transmitting sound wave representing the noise of the liquid
medium via the shaft of the actuator causing the actuator to rotate
correspondingly to achieve a final level of sealing of the apparatus.

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Thus, the invention ensures that the SE is actuated by external actuation; the
function of actuation from motor to the SE is achieved by a penetrating shaft
from the motor outside to the SE inside the duct/pipeline. To make the
penetration possible without the communication of the medium from extreme
ambient air, there is a bellow, which is seal welded to the shaft all around on one
end and seal welded on the conduit surface on the other end.
The prior art problem of internal actuation is further solved by a second
embodiment of the device of the invention in which a cam is provided which is
driven by an actuating device, electrical, pneumatic or any other prime mover
which can work with an embedded control. This is made possible by avoiding
the forced penetration of the gate plate through the gap between the stack of
seal leaves and having the conduit at the shaft entry by a flexible bellows, which
allows linear and partial torsional relative motion without giving a possibility of
connecting the upstream or downstream of the isolator with the outside ambient.
The spring element of the SE is made of haste alloy strip tested and proven for
consistency of springiness over tens of thousands of cycles. The leak tightness
problem of prior art is improved by taking a feed back from the sonic noise
generated at the sealing surfaces by the medium and operating the servo
actuator further till the predetermined level of signal is realized.
In the present invention, the seals are not stationary on the frame as in a plate
gate; The seal element does not move with the flap member as in a flap damper.
It is a timed-operation seal, which moves after the gate plate, or flap reaches a
final position of closure. Once in this position, the gate plate or flap triggers a

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position-based action for the seals to be activated by external actuator. Actuation
is all around and presses the seals to the required seal tightness and is achieved
by a plurality of actuators of much smaller capacity compared to that required for
the main actuator moving the gate plate. A sonic pick up mounted on the seal
element assembly or on the frame assembly captures the small leak signals and
gives feedback for the seal bearing actuator to act on further, till probe certifies
there is nil or no adverse leakage past the gate plate or damper flap. Thus,
good leak tightness is possible without the aid of seal air between flap edges as
air chambers.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 - shows a sealing device in a plate gate isolator according to the
invention.
Figure 2 - shows a sealing device in a flap damper isolator according to the
invention.
Figure 3 - shows as to how the sealing device of the invention is implementated
in a plate gate isolator.
Figure 4 - shows the bellows of the sealing device of the invention implementing
the leak- proof sealing in a flow isolator apparatus.
Figure - 5 shows a seal element of the sealing device of the invention providing
seal-coverage on the corner of the joining components of the apparatus.

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DETAIL DESCRIPTION OF INVENTION
Figures 1 to 5 illustrate the invention in further details. Fig 1 shows the plate
gate isolator called hereinabove as the Flow Isolating Apparatus (FIA) in a duct
which is one of the forms of an envelope for the medium. This duct or in
general, an envelope is named here as a conduit (1). The conduit (1) as shown
in one of the many positions, that is, in horizontal position and can be equally
applicable to any other position in space. The seal elements (not shown) are
inside the conduit (1) and are actuated to bear against the gate plate (2) and are
made to engage all around by being pressed against the plate (2) with a seal
actuator mechanism (4). The gate plate (2) is capable of inserting in or
withdrawing out of the conduit (1) consequent upon a sealing between
atmosphere and the flow medium inside the conduit (1) being provided by a
gland (3). It may be seen in the figure 1 that the gate plate (2) engages and
located by a vee-block (4A) at the bottom to enable the forces to be taken by
the seal pressing against the gate plate (2).
Here, the seal element being a part of the seal actuator mechanism (4), is
traversed towards the plate (2) and then presses the seals against the plate
surface (2); first it contacts the plate surface and because of the pre-bent edge,
it bent and rises parallel to the plate surface to achieve the first level of leak
tightness; further level of leak tightness is obtained by a cam pressing behind
the seal leaf against the plate; the second level is supplemented by a sonic probe
feed back arrangement; the sonic probe, which 'listens' to the leaking noise at
the seal by the medium and transmitted through the shaft of the actuating

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mechanism (4) or the body of the conduit (1). This keeps the actuator (4)
turning till the pre-determined level of tightness is achieved. The pre-determined
level of leak-tightness is known through a calibration of 'leak versus sonic signal'
done prior to the operation either on site or in the shop test lab.
Fig.2 shows a sealing device in a flap damper type isolator applications. This is a
flap damper, where a sealing element (7) is typically placed on a stationary
frame of the conduit (1) and atleast one flap (5). The sealing element (7) is pre-
bent taking the near about final position of the flap (5). A damper shaft (6) turns
and closes the flaps (5) till the contact is reached with the seal element (7). At
this point the first level of leak tightness is realized. Further tightness is achieved
by the actuation of a cam (8) by an external actuator which takes the signal from
the position indication probe. The turning of the cam (8) is controlled by a sonic
probe (not shown) which works, as explained before, on the principle of leaky
medium's noise past the seal element (7). Here, the sealing element (7) is a strip
or a plurality of strips to provide cyclic life over tens of thousands of flexure
operations. The material is haste alloy strip and type-tested in laboratory rig for
its suitability for many cycles as demanded by the applications in the present
industrial situation..
Movement of the SE (7) towards the IE, including rotation of the shaft (6) till the
noise becomes nil or negligible, is achieved through an embedded system of
electronic control using an algorithm evolved for the effective leak tightness as
well as smooth operation of the isolator.

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Fig.3 shows a close up view of the device of fig.l, depicting as to how the SE (7)
is getting pressed against the gate plate (2) in a typical location. When the gate
plate (2) reaches a closed position, it engages a position switch which triggers
action of the actuator (4) to turn a shaft (6) pulling a lever (9) through the cam
(8) mounted on the shaft (6). The seal (7) is mounted on a frame (not shown)
which is pushed by the movement of the lever (9) in a guide (10). The pre-
bending of the seal edge at the gate plate (2) helps to bend it uniformly against
the gate plate (2) and rise to a vertical position thereby giving the first level of
leak tightness. Further level of leak tightness is achieved by further turning of
the cam (8) which, by its predetermined profile, makes no more movement of
the seal (7) but presses the seal (7) against the gate plate (2). This is aided by
the coordination of the rotation of the cam (8) by a feed back mechanism from
the sonic probe taking signal from the leaky noise of the medium as described
earlier.
Fig.4 shows the bellows (11) at the extreme of the shaft penetration of the
conduit (1) to avoid leakages to outside or inside from atmosphere. Bellows (11)
at the penetration at the end permit axial and rotational movements. The force
of pressing is decided by sonic probe mounted at the shaft end to act on the
mechanically transmitted signal of the leak through the shaft and actuates the
rotation accordingly.
Fig.5 shows typical seal element (7) coverage at the corners of the gate plate
(2). The seal element (7) is a single or a plurality of seal leaves of specified
material with lab tested haste alloy for cyclic life over tens of thousands of

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cycles. The figure shows the corner in detail as to how the seal strips (7) are
arranged without leaving the corner to become a point of junction but an area of
coverage.
BENEFITS OF THE INVENTION:
The invention is based on the concepts of separating the movement of the
isolator element from the seal element through an external actuation, bringing
forth several advantages; for example:
i) The engagement of SE with the gate plate throughout its movement
from open to closed position and vice versa, in the prior art, causes
rubbing and friction necessitating actuator power to overcome this
resistance. In the present invention, there is no contact till the final
position is reached when the actuator of the IE stops and the
operation of the SE starts. This SE actuation is more a matter of
precision and low power requirement as few grams of SE only are
moved and pressed, instead of movement of the isolator element
having to pierce or face friction with the seal element, as in the prior
art.
ii) The sealing effectiveness is ensured by the sonic signal of the leaking
medium itself and hence, the tightness is achieved to the limit of the
preset leak tightness including zero leakage.

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Hi) Since pressing the SE (leaves) is done by external actuator, the
number of seal leaves gets reduced. Fewer seal leaves are used
against a stack of seals in the prior art.
iv) Damage to seal element leaves is costly as the springy material has to
be having thinness and springy characteristic and fatigue strength. In
the prior art, there is likelihood of the seal elements getting crushed or
damaged as they are always in contact during the opening or closing
operation in the case of plate gates.
v) Since the SE leaves are dimensionally smaller compared against bulb
type of the prior art, the material content of the SE is reduced.
vi) The haste alloy material strip of pre-tested quality ensures high
reliability and maintainability in operation.

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WE CLAIM
1. A sealing device for flow isolator apparatuses adaptable in steam
generator, Integrated gasification and combined cycle plants, and ducts or
pipelines carrying fluids, comprising:
- a conduit (1) having a plate gate isolator interposed therein;
- a movable gate plate (2) insertable in or witdrawble from the
conduit (1);
- a seal element (7) being configured as a part of an actuator
mechanism (4), the seal element on actuation traverse towards the
gate plate (2) and contacts the plate surface to achieve a first level
of sealing;
- a cam (8) pressing behind the seal element (7) to achieve a second
level of sealing,
- a sonic probe/ arrangement transmitting sound wave representing
the noise of the liquid medium via the shaft (6) of the actuator (4)
causing the actuator (4) to rotate correspondingly to achieve a final
level of sealing of the apparatus.

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2. The device as claimed in claim 1 comprising flexible bellows (11) on the
conduit (1) at the entry point of the shaft of the actuator (4) which allow
a linear and partial tensional relative motion.
3. A sealing device for flow isolator apparatus adaptable in steam generator,
Integrated gasification and combined cycle plants, and ducts or pipelines
carrying fluids, comprising:

- a sealing element (7) placed on a stationary frame supported in a
conduit (1) and a flap (5) of the isolator, the sealing element (7)
being pre-bent and disposed near about a final position of the flap
(5);
- a damper shaft (6) on rotation turns and closes the flap (5) till a
first level of sealing is obtained between the flap (5) and the
sealing element (7); and
- a cam (8) actuatable by an external actuator in correspondence
with the sound signal transmitted by a sonic probe to cause the
cam (8) to achieve the final level of sealing.
4. The device as claimed in claim 1 or 2, wherein the sealing element (7)
comprises a plurality of strips made of haste alloy.

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5. The device as claimed in claim 1, comprising a position switch which
triggers the actuator (4) when the gate plate reaches a closed position
and engages the position switch, and wherein, the actuator (4) turns the
shaft (6) pulling a lever (9) though the cam (8) mounted on the shaft (6).
6. The device as claimed in claim 1 or 4, wherein the sealing element (7)
mounted on a frame is pushed by the movement of the lever (9) to shift
the sealing element inside a guide (10).
7. A sealing device for flow isolator apparatuses adaptable in steam
generator, integrated gasification and combined cycle plants, and ducts or
pipelines carrying fluids as substantially described and illustrated herein
with reference to the accompanying drawings.
8. A sealing device for flow isolator apparatus adaptable in steam generator,
Integrated gasification and combined cycle plants, and ducts or pipelines
carrying fluids as substantially described and illustrated herein with
reference to the accompanying drawings.

The invention relates to a sealing device for flow isolator apparatuses adaptable
in steam generator, Integrated gasification and combined cycle plants, and ducts
or pipelines carrying fluids, comprising a conduit (1) having a plate gate isolator
interposed therein; a movable gate plate (2) insertable in or witdrawble from
the conduit (1); a seal element (7) being configured as a part of an actuator
mechanism (4), the seal element on actuation traverse towards the gate plate
(2) and contacts the plate surface to achieve a first level of sealing; a cam (8)
pressing behind the seal element (7) to achieve a second level of sealing, a sonic
probe/ arrangement transmitting sound wave representing the noise of the liquid
medium via the shaft (6) of the actuator (4) causing the actuator (4) to rotate
correspondingly to achieve a final level of sealing of the apparatus.