Abstract of Invention
An improved version of the apparatus and method for controlling the flow of fluid along with solid
particles is described. The main claim of this invention is in utilization of rack and pinion mechanism
for converting the rotary motion, initialized by the stepper motor movements based on the signals
received from the sensors into linear motion to a pair of sliding plates for varying the area of opening
of the valve. It is also claimed that the selection of material and construction of the apparatus is made
in such a way that it caters to easy replacement of sliding plates, resistance to erosive environment,
leakproofness of the apparatus, and offers less pressure drop at the down stream of the system.
Field of Invention
The present Invention relates to an improved version of the apparatus for balancing the pulverized
coal material flowing along with the primary air before they reach the boiler. This improved version
of the apparatus helps in adjusting the air to pulverized coal flow mixture ratios passing through each
pipe by varying its area of opening, using externally operated motion control mechanisms.
BACKGROUND OF THE INVENTION
Both adjustable and fixed geometry orifices are being used in most of the pulverized fuel (pf) fired
boilers. Fixed geometry orifices are pre-calibrated and are installed on the respective coal pipes
emerging from coal mill outlets. Over a period they get eroded and become ineffective. Boiler
manufacturers originally supplied riffle devices and further improved the designs by using plates to
divide the flow into alternate directions. Egg boxes are with checkerboard design, which aim in
breaking the coal ropes prior to entry into the riffle device. Of late, ramps have been installed in the
pf pipelines, immediately upstream of trifurcators, to improve pf distribution. The location of the
ramp is adjusted until acceptable pf distribution is achieved. It is claimed that the ramps breakup pf
ropes. However, they may simply divert the ropes to the center of the trifurcator. The performance of
ramps at lower mill end loads is less certain. The problems associated with fixed geometry devices
are addressed to a certain extent by adopting variable geometry devices. Variable geometry devices
include three way splitters with an adjustable pf distributor to reduce mal-distribution, determined by

a pf flow meter. Another way is to use a pf flow balancing dampers with variable construction within
pf pipes. These adjust the dirty air distribution and therefore affect pf distribution. However, the
effectiveness of these devices is not satisfactory as they control pf distribution at the expense of
primary air velocity and static pressure. The effect of the dampers is non-linear with no noticeable
effect until the pipe area is reduced considerably.
The following references describe various US Patents on Adjustable / Variable Orifice devices for
balancing pulverized fuel flow at coal pipes.
1. US 2008 / 0035873 Al to Rickey E Wark describes Variable orifice gate valve.
2. US 7121296 B2 to Rickey E Wark describes Variable orifice valve for air stream containing
particulate coal.
3. US 2006 / 0225629 Al to Edward Kenneth Levy describes on line coal flow control mechanism
for vertical spindle mills.
4. US 6923203 B2 to Rickey E Wark describes Variable orifice valve for air stream containing
particulate coal.
5. US 2006 / 0225629 Al, US 2005 / 0042043 Al to Edward Kenneth Levy describes on line coal
flow control mechanism for vertical spindle mill.
6. US 6,799,525 B2 to Milton George Manos describes the automatic coal damper.
7. US 2004/0173128 Al to Joel Vatsky describes balancing damper.
8. US 6,481,361 Bl to Edmund S Schindler describes the coal balancing damper.
9. US 6,009,899 to John E Polutnik describes variable orifice dual gate valve.
10. US 5,975,141 to Medhat A Higazy describes on line variable orifice for controlling the flow of
pulverized coal and air leading to a coal burner.
11. US 5685240, US 5593131 to Oliver G Briggs Jr; and J Sund describes variable orifice plate for
coal pipes.
It has been observed from above cited references that orifices with both fixed as well as variable
geometry are available. However, most of them adjust the coal flow within the mill or they use either
external spindle or guide vanes, which over a period erode and become ineffective. An example a
Variable Orifice Gate Valve is shown in US Patent No. 2008 / 0035873, wherein the gate valve uses

a plurality of truncated , sector shaped valve elements mounted on the support in circumferentially
contiguous fashion for radial movement between two extreme positions. They are operated manually
using handle mechanisms. Here adjustments are not based on the automation and hence do not cater
to coal flow balancing in all the pipe lines of a mill on continuous basis. Also when these gate
elements erode, there is no mechanism to retain the desired orifice configuration and hence the
system becomes ineffective.
Hence, there is a need to provide a Variable Area Orifice Valve system, which activates and operates
smoothly with the receipt of signals from the coal flow sensors based on the actual coal and air flows
in each pipe. There is a necessity to integrate operation of each variable area orifice valve to move
the sliding plates located within the geometry in backward and forward directions in the steps of less
than a millimeter or so, if it is called for. There is also a necessity to contain the erosion of parts of
operating valve due to high abrasive pf flows and retain the geometry of the orifice intact over
longer periods of operations and also to maintain a desired orifice configuration at any time and in
any of the pipe line. There is also a need for a constant and smooth motion of the sliding plates,
which activate to the change in the orifice area.
Objects of the Invention
An object of this invention is to propose an improved version of the apparatus for balancing the pf
flow in each of the fuel pipe leading to the burner of the boiler.
Another object of this invention is to propose an improved version of the apparatus which
minimizes erosion in the valve during its operation in a highly erosive environment.
Still another object of this invention is to propose an improved version of the apparatus having a
leak-proof enclosure.
Yet another object of this invention is to propose an improved version of the apparatus having a
smooth linear motion of the sliding plates in either directions with out resorting to jamming or
obstructed linear motion.

BRIEF DESCRIPTION OF THE INVENTION:
1. According to this invention there is provided a method for controlling the flow of fluid
transporting the solid particles such as pf coal, comprising the steps of:
i) receiving signals from sensors using microwave systems provided in the online coal flow
measurements system;
ii) translating the signals received from said sensors installed on the fuel pipeline using an
electronic module in to electrical currents in the range of 4-20 mA, based on the quantum
of air and pf flow;
iii) activating the stepper motor controllers using the output signals generated by PLC
modules to direct the stepper motor to run for required step angles;
iv) converting the rotary motion initiated by the stepper motor and further pinions into linear
motion of the sliding plates using rack and pinion mechanism;
v) ensuring the movements of sliding plates to be uniform while motion is in activated
condition;
2. Further according to this invention there is provided a variable area orifice valve for
controlling the flow of fluid along with the solid particles, comprising:
i) a pair of sliding plates having base supports covered with flat plates at both ends and
embedded in a frame,
ii) inlet and outlet nozzles with flanges disposed on the bottom and top plates for further
connecting the apparatus on to the fuel pipeline;
iii) A pair of shims or blocking plates to arrest the leakages due to gaps occurring in between
the inlet and outlet nozzles and interior of the rectangular frame of the valve while the
sliding plates are actively in linear motion,
iv) two pairs of stepper motors with drives and controllers for initiating the linear motions to
their respective sliding plates, using rack and pinion mechanisms, based on the signals
received from the sensors located on the fuel pipelines.

v) a pair of guide blocks for guiding the sliding plates for giving a constraint to achieved an
ensured linear motion, without any wobbling,
vi) A rectangular housing mechanism to keep the internal container mechanism always under
positive pressure by pumping the pressurized air with respect to the coal pipe line
pressures.
Description of invention with reference to the accompanying drawings
Fig. 1. shows variable area orifice valve plan view indicating the position of top plate (1),
Stepper motor drives (4) and sliding plates (3), shims / blocking plates (6),
pinions with shaft (9),and guide blocks (10).
Fig. 2. shows variable area orifice valve elevation view indicating the position of top plate (1) and
bottom plate (2), sliding plates (3), stepper motor drives (4), inlet and outlet nozzles (5),
rectangular housing frame (7), bottom support plates (8), pinions with shaft (9), guide blocks
(10) and motor supports (11).
Fig. 3. shows variable area orifice end view indicating stepper motor drives (04) with
supports (11), top plate (1) and bottom plate (2).
Fig. 4. shows the details of top plate (1) showing the grooves, locations for guide
blocks (10), stepper motor drive (4) and inlet nozzle (5)
Fig. 5. shows the details of bottom plate (2).
Fig. 6. shows the details of sliding plates showing the rack location and wedges (3).
Fig. 7.shows the details of stepper motor drive assembly used to drive the pinion (4).
Fig. 8.shows the details of inlet and outlet nozzles with suitable flanges for connecting to
the fuel pipes (5).
Fig. 9.shows the details of shims / blocking plates to arrest the inward leakage (6).
Fig. 10.shows the details of rectangular housing frame to support both Top and Bottom plates
and arrest the external leakage (7).
Fig. 11.shows the details of Bottom support plates (8).
Fig. 12.shows the details of Pinions (9).
Fig. 13.shows the details of Guide Blocks (10).
Fig. 14.shows the details of Stepper Motor supports (11).

Fig. 15 shows the schematic diagram describing the control system
Fig. 16 shows the sliding plate mechanism with stepper Motors.
Fig. 1 shows the plan view of the variable area orifice valve with the relative positions of stepper
motors (4), sliding plates (3), and the top plate (1). There are two sliding plates (3), which are placed
in an overlapped position. At the tail end of these plates rack teeth are cut on both sides along their
thickness and are driven by a pair of pinions (9), imparting linear motion to the sliding plates (3).
The front end of each of these plates has a semi hexagonal opening cut to match the fuel pipe
opening. Both these plates are guided by a set of guide blocks (10) at their front ends, which are
firmly located to their designated positions. At a distance these sliding plates (3) are provided with
two sets of wedges, which get embedded into the respective dovetail grooves cut on the inner portion
of the top plate (1). Both the sliding plates are properly supported by a set of bottom support plates
(8), located on the top surface of the bottom plate (2). Linear movement to these sliding plates (3) is
imparted by rotation of two pairs of pinions (9) in step angles in such a manner that both these
sliding plates (3) either move inward or outward direction at time and simultaneously to the same
distance. Pinions (9) and sliding plates (3) who adept rack and pinion mechanism. Pinions (9) are
driven by stepper motors (4) which are based on the motor support frames (11) located on the top
surface of the top plate (1).
Fig. 2 shows the variable area orifice valve elevation view to indicate the position of sliding plates
(3), bottom support plates (8), pinions with shafts (9), inlet and outlet nozzles (5) and stepper motors
(4) and their motor support frame (11). Inlet and outlet nozzles (5) with flanges are welded firmly
over the bottom and top plates (2&1) respectively. Inner openings of these inlet and outlet nozzles
(5) are made to match the fuel pipe inner dimensions. Mating edges of these inlet and outlet nozzles
with the bottom and top plates (2&1) are machined in such a way that they do not interfere with the
movements of both the sliding plates (3). Mating surfaces of the outer surface of the outlet nozzle
and the top plate (1) located within the valve is provided with a pair of shims / blocking plates (6) to
arrest any leakage of air or coal fines into the valve. Both the top plate (1) and bottom plate (2) along
with the sliding plates (3), pinions (9), guide blocks (10), bottom support plates (8) are supported
firmly over a rectangular housing frame structure (7) to provide the rigidity to the overall valve
structure. The rectangular housing frame structure (7) also ensures leakproofness of the valve as well
as imparting always a positive pressure within the valve structure when compared to the coal pipe

line pressure. Versatility of this invention lies in the fact that the sliding plates (3) can be changed or
replaced by simply opening the top plate sub assembly and refitting back on to this rectangular
housing frame structure (7) after replacement of the sliding plates (3) is done. Thus, they offer
minimum outage to the power plant. Material for bottom support plates (8) is made in such a way
that it caters for self-lubrication during movements between the mating parts.
Variable area orifice end view of Fig. 3 indicates the stepper motor drives (4) with motor drive
supports (11), top plate (1) and bottom plate (2). The support structure for stepper motors (4) is
firmly positioned over the top plate (1). Stuffing box is provided to each of the pinion shaft coming
out of the valve to ensure the leakproofness of the valve while in operation. The selection of stepper
motors (4) is made in such a way that it takes care of overloading aspects and caters for heavy-duty
operations.
Figure 15 shows the Control mechanism for Stepper Motors using the Microwave technology for
measuring the pf and air mass flow passing through the fuel pipe line. The sensors from the
microwave systems are connected to an electronic module which converts the signal to 4-20 raA
current proportionally. The 4-20 mA signals from all the 4 (four) pipe lines are connected to the PLC
module. The PLC module generates the output digital signal based on the set value of pf coal flow
and the measured value of the pf coal flow. The output digital signal is given to the stepper motor
drive control system to rotate the stepper drive to a desired angle. The rotation angle is translated
into linear motion by Rack & Pinion Mechanism as shown in the Figure 16 of the valve mechanism.
The linear motion of the valve sliding plates controls the openings in the pipe line and hence the area
to be restricted.

WE CLAIM;
1. A method for controlling the flow of fluid transporting the solid particles such as pf coal,
comprising the steps of:
i) receiving signals from sensors using microwave systems provided in the online
coal flow measurements system;
ii) translating the signals received from said sensors installed on the fuel pipeline
using an electronic module in to electrical currents in the range of 4-20 mA, based
on the quantum of air and pf flow;
iii) activating the stepper motor controllers using the output signals generated by PLC
modules to direct the stepper motor to run for required step angles;
iv) converting the rotary motion initiated by the stepper motor and further pinions
into linear motion of the sliding plates using rack and pinion mechanism;
v) ensuring the movements of sliding plates to be uniform while motion is in
activated condition;
2. A method as claimed in claim 1, wherein the motions involving sliding plate movement
comprises:
i) controlling the rotary motion of all the motors either in positive (forward) or negative
(backward) directions from a reference point;
ii) sliding plate movements to ensure that both the sliding plates either move in forward or
backward, but, in opposite directions to each other simultaneously and by the same
distance;
iii) stopping the stepper motor movements after the desired movement is achieved.
3. A method as claimed in claim 1, wherein movement of sliding plates is monitored by:
i) movement of stepper motors in a desired step angles metered and monitored with the help
of absolute / positional encoders installed on them, which furnish the data regarding
overall movement of sliding plates.

ii) motion controllers ensuring the response time is adequate to convert the signals received
from the sensors installed on the fuel pipe lines for translating the effective motion of
sliding plates and also give the feedback once the signal's objective is fulfilled;
iii) motion controllers ensuring that all the stepper motors operate in a desired direction and
exactly same number of step angles;
iv) any loss of signal to any of the stepper motor being amplified to the original value, in
order to get the desired motion at the sliding plate end.
4. A variable area orifice valve for controlling the flow of fluid along with the solid particles,
comprising:
i) a pair of sliding plates having base supports covered with flat plates at both ends
and embedded in a rectangular housing frame,
ii) inlet and outlet nozzles with flanges disposed on the bottom and top plates for
further connecting the apparatus on to the fuel pipeline;
iii) two pairs of stepper motors with drives and controllers for initiating the linear
motions to their respective sliding plates, using rack and pinion mechanisms,
based on the signals received from the sensors located on the fuel pipelines,
iv) a pair of guide blocks and two pairs of wedges for guiding the sliding plates and
giving a constraint to the desired and ensured linear motion, without any
wobbling,
v) A pair of shims / blocking plates.
5. An improved version of the apparatus as claimed in claim 4, wherein the sliding plates
having a coating on both sides for high resistance to erosion.
6. An improved version of the apparatus as claimed in claim 4, wherein the supporting
rectangular housing frame also provides a means to keep the internal environment of the
variable orifice valve always under positive pressure when compared with the internal
environment of the coal pipe line.

7. An improved version of the apparatus as claimed in claim 4, wherein the stepper motors are
placed over the support frame structure, attached to the top plate of the valve, to ensure un-
interrupted operation, irrespective of the position / orientation of the valve.
8. A method for monitoring and controlling the flow of fluid substantially as herein described
and illustrated.
9. A variable are orifice valve substantially as herein described and illustrated.

An improved version of the apparatus and method for controlling the flow of fluid along with solid
particles is described. The main claim of this invention is in utilization of rack and pinion mechanism for converting the rotary motion, initialized by the stepper motor movements based on the signals received from the sensors into linear motion to a pair of sliding plates for varying the area of opening of the valve. It is also claimed that the selection of material and construction of the apparatus is made in such a way that it caters to easy replacement of sliding plates, resistance to erosive environment,
leakproofness of the apparatus, and offers less pressure drop at the down stream of the system.