FIELD OF THE INVENTION
The present invention relates to improved isolation devices used in Power and
Industrial Boilers. More particularly the invention relates to an improved damper
Device for isolation of associated equipment in boiler during on-line maintenance
of fans and air pre-heaters.
BACKGROUND OF THE INVENTION
Louver and Biplane dampers are used for isolation of equipments for online
maintenance of Fans and Air Preheaters in Boilers. The drive system of the
Louver Damper and Biplane Damper consists of drive levers, lock levers,
knuckles, adjusting links etc. Drive levers distributes the motive power from a
drive shaft to a slave shaft through the adjusting links. The Drive Lever consists
of a Hub and two Lever arms. In the existing design, the Lever is tangent to the
Hub at the point of connection. Hence the Hub outer diameter is determined
based on the Lever height. This leads to over sized Hub for Drive Lever
application.
In the existing design, the oversized Drive lever puts additional load on the drive
and slave shaft. The additional weight of the drive and lock lever reduces the
overall lifespan of the drive and slave shaft due to fatigue loading.
In the existing design, the lever arm is tangent to the hub, it leads to localized
loading of the hub.

In order to overcome this problem, a novel method of Drive Lever (04) and Lock
Lever design has been developed.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an improved damper
device for isolation of associated equipment in boiler during on-line maintenance
of fans and air pre-heaters which reduces the overall weight of drive lever and
Lock Lever of the damper device without compromising on structural rigidity.
Another object of the present invention is to propose an improved damper device
for isolation of associated equipment in boiler during on-line maintenance of fans
and air pre-heaters which increases the moment of Inertia of the Lever arm
along the major axis to allow a thinner plate thickness for the Drive Lever and/or
Lock Lever
Yet, another object of the present invention is to propose an improved damper
device for isolation of associated equipment in boiler during on-line maintenance
of fans and air pre-heaters which allows rigidity of the device by providing a
number of stiffeners.

A further object of the invention is to propose an improved damper device for
isolation of associated equipment in boiler during on-line maintenance of fans
and air pre-heaters which optimizes the hub size to substantially reduce the
weight of the device.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved damper device for isolation of
associated equipment in boiler during on-line maintenance of fans and air pre-
heaters comprising at least one Lever Boss, and two each lever arms respectively
for Drive Lever and Lock Lever. The purpose of the Drive Lever and Lock lever is
to transmit the power from a drive shaft to slave shafts. In addition, the Lock
Lever provides a mechanism to mechanically lock the damper blades in both
open and close position. According to the invention, the lever arm is having
higher moment of Inertia along the major axis with reduced plate thickness,
hence weight reduction is achieved in comparison to prior art. In this proposed
device, the outer diameter of the lever boss is independent of the height of the
lever arm, thereby achieving substantial reduction in overall size and weight of a
Lever Hub of the damper device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Schematic of prior art Drive Lever of the damper device
Figure 2 Schematic of prior art Lock Lever of the damper device
Figure 3 Schematic of improved Drive Lever according to the invention

Figure 4 Schematic of improved Lock lever according to the invention
Figure 5 Schematic arrangement of a prior art damper device with drive lever
Figure 6 Schematic arrangement of alternative type damper device of prior
art with a drive lever.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Louver damper (09) and Biplane damper (08) (see Figures 5, 6) are used to
isolate the flow of Air or Flue Gas for online maintenance of equipments like Air
Preheaters, Fans used in power and Industrial Boilers. Drive lever (04) and Lock
Lever (05) are part of a drive mechanism of the dampers (Figures 3, 4) which
are used in the Dampers (08, 09) to distribute the power from a drive shaft to
slave shafts and to lock the damper blades. The Drive lever (04) consists of Hub
(01) and Lever arms (02). The two Lever arms (02) are used in the device.
In the prior art drive lever (06) and Lock lever (07) (Figures 1, 2) the lever arm
is tangential to the hub at the outer most connection point. Based on calculations
it was observed that, the hub (01) meets the designed load at a lesser outer
diameter in comparison to the height of the lever arms (02). The hub (01)
diameter is independent of the height of the lever arm (02) at the connection
point. In addition by increasing the height of the lever arm (02) at the hub (01),
the design loads is met with a lever arm (02) formed of thinner plate size.

Additional stiffeners (03) are provided to withstand any transverse load arising
out of misalignment of the Drive levers (04).
In the improved damper device, the lever arm (02) plate is mounted all around
the hub (01), where as in the prior art drive lever (06) and Lock lever (07), the
lever arm is tangent to the hub at the outermost point of connection.

WE CLAIM :
1. An improved damper device for isolation of associated equipment in
boiler during on-line maintenance of fans and air pre-heaters, the
improvement is characterized in that the device having a drive mechanism
comprising at least one lever boss, a drive and/or a lock lever, the drive
and/or lock lever provided with at least two lever arms and having a hub,
the lever allowing distribution of power from a drive shaft to multiple slave
shafts including locking of damper blades, and in that the height of the
two lever arms along the major axis is extended using thinner plate
member such that the lever arms are wrapped around the hub resulting
in increased moment of inertia of the lever including a more uniform
distribution of power.
2. The device as claimed in claim 1, wherein number of stiffeners are
provided on the hub to withstand transverse load if generated due to
misalignment of the drive and/or lock lever.

ABSTRACT

The invention relates to an improved damper device for isolation of associated
equipment in boiler during on-line maintenance of fans and air pre-heaters, the
improvement is characterized in that the device having a drive mechanism
comprising at least one lever boss, a drive and/or a lock lever, the drive and/or
lock lever provided with at least two lever arms and having a hub, the lever
allowing distribution of power from a drive shaft to multiple slave shafts including
locking of damper blades, and in that the height of the two lever arms along the
major axis is extended using thinner plate member such that the lever arms are
wrapped around the hub resulting in increased moment of inertia of the lever
including a more uniform distribution of power.