FIELD OF THE INVENTION
The present invention generally relates to an improved bunker shutoff gate of a
coal feeding system. More particularly, the present invention relates to an
improved device for effective isolation of a bunker from the raw coal feeding
system of thermal power plants.
BACKGROUND OF THE INVENTION
In a typical thermal power plant, boilers are generally operated using coal as
primary source of input energy. Coal conveyors are employed to transport the
coal from coal yard to coal bunkers. Coal bunkers are used as storage devices.
There is a gate valve provided at bunker outlet to isolate or regulate the flow of
coal from the bunker to coal feeders. Such a valve includes a gate moving across
an opening to regulate or isolate the flow. The operation of the gate valve is vital
as the isolation of the bunker is essentially warranted during operation of the
thermal power plant to protect the coal feeders in case of a bunker fire, or while
the feeders being isolated for maintenance.
The conventional gate valves used to feed coal frequently develop defects
making them difficult to operate, if not impossible, against the standing coal
column of the bunker. To overcome the difficulties, rod gates were introduced in
between the bottom of the coal bunker and the gate valves. A rod gate
essentially consists of a plurality of steel rods with sharp ends to penetrate
through the standing coal column of the bunker. The rods are arranged in a
staged manner on both sides of the rod gate body to hold the coal column of the
bunker. Then the coal gate is operated to isolate the bunker.
The prior art systems of providing rod gates in the coal feeding system over and
above the gate valve, is redundant and poses difficulty for a manufacturer to
accommodate both the rod gate and the gate valve from the layout
considerations.
US Patent No. 4,253,283 dated May 03, 1981 discloses a movable gate damper
which comprises a damper having an opening there through, an aperture
defining a blade member movable between a first position, in which the aperture
is aligned with the opening to permit the flow of fluid to the damper, and a
second position, in which the blade damper substantially blocks the flow of fluid
through the damper opening.
This prior art is related to the dampers applicable for controlling the flow of fluids
such as hot gases through a duct.
US patent No. 2,792,150 dated May 14, 1957 discloses a bulk material valve
which comprises a rack and pinion, and a bulk material valve or gate valve. This
valve describes a valve structure with a gate plate which moves across an
opening to regulate the bulk material there through.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an improved device
for effective isolation of a bunker from the raw coal feeding system of thermal
plants, which eliminates the disadvantages of prior art.
Another object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which the bunker is provided with a gate valve to isolate the flow of
coal from the bunker to the coal feeder.
Yet another object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which a plurality of spikes are provided with wedge at bottom and top
to substantially penetrate against standing coal column of the coal bunker so as
to generate a higher shearing force.
A further object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which width to depth ratio of the spikes is optimized for applying
higher shear force to ensure uniform plate penetration across the coal column.
A still further object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which the gate plate is configured with a deep curve enabling the
spikes to travel across the opening and accommodated within the rear side of
the gate body.
Yet further object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which the thickness of the gate plate is selected to allow from maintain
of top and bottom wedge shaped spikes at the front end to enable a higher
penetration of the standing coal column.
Another object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which the gate is formed of a wear resistant stainless steel to maintain
sharpness of the spike throughout the service and to withstand the erosion due
to moisture of the coal.
A still another object of the present invention to propose an improved device for
effective isolation of a bunker from the raw coal feeding system of thermal
plants, in which the gate plate operable by the gate valve is provided with the
spikes which are enabled to produce on penetration, a shearing force which
moves the gate efficiently.
SUMMARY OF THE INVENTION
According to the invention, the improved device comprises a gate plate with
spikes which provides a higher shearing forces to penetrate through the standing
coal column of the bunker. The spikes are wedge shaped at top and bottom and
are equally spaced in front of the gate plate.
The gate plate is configured to allow the spikes to penetrate the coal column
progressively, when the gate plate is moved from the front to rear to isolate the
coal flow. The gate plate is operable both manually and electrically.
At the end of the travel, the gate plate moves to the rear end of the gate body
through an opening in the gate body and housed in the gate body away from the
coal column to ensure isolation of the coal flow.
The gate plate is selected at an optimum thickness to have the wedges
configured at top and bottom of the spikes, and made of wear resistant stainless
steel to maintain a configuration to withstand erosion due to moisture of the coal
in the bunker.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure-1 - Shows an improved device gate valve with the gate plate with spikes
according to the invention.
Figure-2 - Shows the improved device with the gate plate in fully closed
position.
Figure-3 - Shows the detail configuration of the spike of the gate plate in the
improved device according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Figure 1 shows an improved device with gate valve, in which the gate plate (02)
is provided with spikes configured in the front and is housed in the gate valve
body (01). The spikes (03) provide a shearing forces necessary to penetrate a
standing coal column. The gate plate (02) is moved from front to rear end of the
valve body by operating an electrical motor or by manual operation. The gate
plate (02) is configured such that the spikes are enabled to move progressively
from the front to rear within the opening so as to penetrate the standing coal
column. Figure 2 shows the improved device with the gate plate in closed
position. The gate plate is configured to be completely accommodated within the
gate body. Figure 3 shows a configuration of the spike in detail. The spike is
configured to maintain a width(b) to depth (d) ratio of about 4:6, and the spike
is configured as wedges from top and bottom.
WE CLAIM
1. An improved device for effective isolation of a bunker from a coal
feeding system, the device comprising at least one gate valve and one
gate plate (01), wherein the gate plate is provided with spikes (3) at
the front of the gate plate, the spikes being formed with wedge shape
from top to bottom to allow penetration against a standing coal
column, wherein the spikes are disposed at regular intervals, and
configured with a width to depth ratio of 4:6, to obtain an uniform
distribution of force of a coal column in the bunker to the gate plate
and spike during movement of the gate plate in an opening of gate
body.
2. The device as claimed in claim 1, wherein the gate plate is configured
to allow the spikes to advance progressively so as to penetrate a
standing coal column during the movement of the gate plate and close
the opening.
3. The device as claimed in claim 2 where the gate plate with spikes is
housed in a housing during closing of the opening to ensure a
complete isolation of the coal flow from the bunker.
4. An improved device for effective isolation of a bunker from a coal
feeding system as substantially described and illustrated herein with
reference to the accompanying drawings.
Dated this 17th day MARCH 2010.

The invention relates to an improved device for effective isolation of a banker
from a coal feeding system, the device comprising at last one gate valve and
one gate plate (01), wherein the gate plate is provided with spikes (3) at the
front of the gate plate, the spikes being formed with wedge shape from top
to bottom to allow penetration against a standing coal column, wherein the
spikes are disposed at regular intervals, and configured with a width to depth
ratio of 4:6, to obtain an uniform distribution of force of a coal column in the
bunker to the gate plate and spike during movement of the gate plate in an
opening of gate body.