FIELD OF THE INVENTION
The present invention relates to a device in a damper assembly for isolation of
boiler equipments during on-line maintenance.
BACKGROUND OF THE INVENTION
In Boilers, Dampers are used for isolation of equipments for on-line maintenance
of Electrostatic precipitator, Fans, Air Preheaters and flow control for mill inlet
and air-heater Outlet. A Biplane damper (01) is shown in figure 1, Louver
dampers & control louver dampers are engaged for power & industrial boilers to
cater to air and flue gas duct requirement.
According to the prior art, a Gland & Follower plate of dampers are supported by
two Studs. These studs being critical load bearing members, they are pre-heated
and plug welded to the Gland plate. The studs are made of alloy steel, wherein
the Gland plate is made of carbon steel. Plug welding of the stud to the Gland
plate constitutes a critical activity and repeated failure occurs during
manufacturing and assembly of the dampers.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a dismantable studs design
with threaded gland plate and follower plate assembly of dampers used for
isolation of boiler equipments during on-line maintenance.

Another object of the invention is to propose a dismantable studs with threaded
gland plate and follower plate assembly of dampers used for isolation of boiler
equipments during on-line maintenance, in which the contact surface area is
increased to ensure improved load transfer from the screw to the gland plate.
A still further object of the invention is to propose a dismantable studs with
threaded gland plate and follower plate assembly of dampers used for isolation
of boiler equipments during on-line maintenance, which enhances reliability of
the dampers by eliminating plug welding and reduction in damper manufacturing
cycle time.
SUMMARY OF THE INVENTION
Accordingly, there is provided, a device in a damper assembly for isolation of
boiler equipments during on-line maintenance comprising : a gland plate formed
of a first material; a follower plate formed of identical material and shaped
corresponding to that of the gland plate, the follower plate being disposed
spaced apart from the gland plate; the gland plate is provided with one each
threaded holes opposedly constructed and matching with through holes
configured on the follower plate; at least two high strength hexagonal screws
one each being inserted into each of said two through holes and extending to
pass via the threaded holes, wherein one each spring washer and lock nut
reliably holding the screw end on the threaded holes of the gland plate. A screw
is used in place of prior art stud (threaded at one end). The gland plate is tapped
in order to assemble the screw. One extra set of spring washer and lock nut is
used in between the Gland and the follower plates. It eliminates the plug welding
of a stud to the Gland plate.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 depicts a photographic view of a known Biplane Damper Assembly.
Figure 2 illustrates a prior art Damper Frame with Gland plate and welded stud.
Figure 3 shows a prior art Gland plate and welded stud
Figure 4 shows a photographic view of a prior art Gland plate & welded stud
Figure 5 shows schematically shows a threaded Gland Plate and high strength
screws according to the invention.
Figure 6 shows a photographic view of a threaded Gland Plate and high strength
screws for damper assembly according to the invention.
Figure 7 shows the threaded Gland plate of figure 5 with a tapped hole.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Biplane damper (01) is used to isolate the flow of Air or Flue Gas for online
maintenance of downstream equipment. The damper assembly shown is
mounted in the air and flue gas ducts. Ducts carry atmospheric Air/Hot Air/Flue
Gas, to & from different equipment like Air Preheater, Mills, Forced Draft fans,
Induced Draft fans, Primary Air fans, Electrostatic precipitator etc. of thermal
power plant. Similar Gland plate (02) arrangement is also used in Louver
dampers (Isolation duty) and in Control dampers (Regulating duty).
Figure 2 shows a Damper frame with Gland plate (02) and a Stud (03). These
studs (03) are critical load bearing members of the damper.

According to the invention, the assembly of the threaded gland plate (04) and
screw (05) reduces the breakage of the stud (03) by eliminating plug welding.
Figure 4 shows the invented assembly of threaded gland plate (04) and screw
(05). The studs (03) which are used in the prior art arrangement are replaced
with screws (05) in the new assembly.
The prior art Gland plate (02) is normally provided with a through hole without
any thread. In the inventive arrangement, the Gland plate (04) is provided with a
threaded hole to accommodate a screw (05). Each threaded hole of the Gland
plate (04) is assembled with one high strength Screw (05), a spring washer (06)
and a Lock nut (07) as shown in figure 4 No change in mounting arrangement of
Follower plate (08). As an added advantage, with the new assembly, the load
gets distributed over a larger area. Prototype of this modified Gland plate (04)
arrangement has been tested and the results are found satisfactory.
ADVANTAGES OF THE INVENTION
The threaded Gland plate and the Screws eliminate the step of plug welding of
Studs in Dampers used in Power Plants. The above improvement can be carried
out with minimal increase in machining operation. The new assembly increases
the reliability of dampers by eliminating frequent failure of plug welding of the
Stud in Dampers. Further, an increase in load distribution area according to the
invention avoids stress concentration. Due to elimination of plug welding of prior
art, the associated Non-destructive testing (Magnet Particle Inspection) is
avoided, resulting in reduced cycle time.

WE CLAIM :
1. A device in a damper assembly for isolation of boiler equipments during
on-line maintenance, comprising :
a gland plate formed of a first material;
a follower plat e formed of identical material and shaped corresponding to
that of the gland plate, the follower plate being disposed spaced apart
from the gland plate;
the gland plate is provided with one each threaded holes opposedly
constructed and matching with through holes configured on the follower
plate;
at least two high strength hexagonal screws one each being inserted into
each of said two through holes and extending to pass via the threaded
holes,
wherein one each spring washer and lock nut reliably holding the screw
end on the threaded holes of the gland plate.
2. A device in a damper assembly for isolation of boiler equipments during
on-line maintenance as substantially described and illustrated herein with
reference to the accompanying drawings.

ABSTRACT

The invention relates to a device in a damper assembly for isolation of
boiler equipments during on-line maintenance, comprising : a gland plate
formed of a first material; a follower plate formed of identical material and
shaped corresponding to that of the gland plate, the follower plate being
disposed spaced apart from the gland plate; the gland plate is provided
with one each threaded holes opposedly constructed and matching with
through holes configured on the follower plate; at least two high strength
hexagonal screws one each being inserted into each of said two through
holes and extending to pass via the threaded holes, wherein one each
spring washer and lock nut reliably holding the screw end on the threaded
holes of the gland plate.