FIELD OF THE INVENTION
The present invention generally relates to an embedded device which displays
the rotor position and controls a sector plate Jactuator mechanism in leakage
control system of Rotary Regenerative Air preheater.
The present invention particularly relates to an innovative display and control
mechanism for the Air preheater to display the leakage gap between the sector
plate and radial seals during operation of the Air preheater.
More particularly, the present invention relates to an Embedded device to display
and control leakage gap between a sector plate and radial seals in Rotary
Regenerative Air Preheaters.
BACKGROUND OF THE INVENTION
Air preheater is used in Thermal power stations/Industrial applications to transfer
the heat from the flue gas leaving boiler/furnace to the entering combustion air
through regenerative heat transfer surface in a rotor which revolves continuously
through the air and gas streams.
A Rotary Regenerative Air preheater transfer heat from the flue gas leaving the
boiler to the entering combustion air through regenerative heat transfer surface
in a rotor which revolves continuously through the gas and air streams. The rotor
is divided into compartments by a number of radially extending plates referred as

diaphragms. These compartments are adapted to hold number of baskets which
contain the mass of heat absorbent material commonly formed of stacked plate-
like heating elements.
In a typical Rotary Regenerative heat exchanger, the hot flue gas and the
combustion air enter the rotor shell from opposite ends and pass in counter flow
directions over the heat exchange material housed within the rotor.
Consequently, the cold air inlet and the cooled gas outlet are at one end of the
heat exchanger, referred to as the cold end, and the hot gas inlet and the heated
air outlet are at the opposite end of the heat exchanger, referred to as the hot
end.
The Air preheater is divided into a flue gas side or sector and one or more
combustion air sides or sectors by sector plates. Flexible radial seals on the rotor,
usually mounted on the top and bottom edges of the diaphragms, are in close
proximity to these sector plates and minimize leakage of air between sectors and
to separate the air and flue gas streams from each other. The radial seals are
fixed in the diaphragm plate radial to the rotor post along with seal holding bar
and is touching the sector plate. Regenerative Air preheater is rotated by the
drive system. During operation of the Air preheater, the rotor gets turns down
axially, due to this the gap between sector plate sealing surface and radial seals
is increased. Through this gap the high pressure air leaks to the low pressure gas
side. In order to measure the leakage gap between sector plate and radial seals,
it is necessary to introduce an innovative rotor position monitoring and control
mechanism.

EP 0933610A1 shows a mechanical sensor which has number of limit switches to
provide input signal to a Programmable Logic Controller (PLC) panel or an
electrical proximity sensor with logical output connected to a PLC. Based on
these input, the PLC panel implements some algorithm and controls a Jactuator
Motor drive panel. The sensing and control operation is done at a definite
interval of time. This PLC based control system does not provide a linear
indication of the rotor position and speed.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose embedded device to display
and control leakage gap between a sector plate and radial seals in Rotary
Regenerative Air Preheaters which continuously monitors and provides a linear
indication of the rotor position and speed in RPM.
Another object of the invention is to propose embedded device to display and
control leakage gap between a sector plate and radial seals in Rotary
Regenerative Air Preheaters which minimizes the gap by deflecting the sector
plate.
Yet another object of the invention is to propose Embedded device to display and
control leakage gap between a sector plate and radial seals in Rotary
Regenerative Air Preheaters which can display information about the rotor
position, such as gap, speed of rotation and alarm in case of stall condition of
the rotor.

SUMMARY OF THE INVENTION
The leakage in Rotary Regenerative Air pre-heater is dependent in terms of the
shift in the rotor position due to rotor turn down during operation. The signal
from a sensor is fed to an embedded device where it is processed to display the
actual gap between the sector plate sealing surface and the radial seals. This
signal is further processed to drive the Jactuator motor to effectively control the
gap between the sealing surface and radial seals. A safety and control logic is
incorporated in an embedded device to set the sector plate sealing gap as
desired by the user. The embedded device also annunciates an alarm during
boiler trip or rotor drive gear failure and brings back the sector plate to the
normal position as it was in cold condition (default location).
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 - shows a block diagram of an embedded device for Automatic Leakage
Control System for APH according to the invention
Figure 2 - shows a flow diagram depicting signal processing according to the
invention.
Figure 3 - shows the internal block diagram of the embedded device of Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A signal from an electronic sensor [2] is processed at the embedded device [1]
to derive information regarding rotor position including a simultaneously display
of the gap (in millimeter) and the speed of the rotor (in RPM). This data is used
as a feedback signal by the embedded device [1] to command a Motor Control
panel [3] to correspondingly position the sector plate with the help of the
Jactuator motor assembly to achieve the leakage or the permitted gap between
the sector plate and the radial seals. The embedded device [1] also annunciates
an Alarm in the Unit control room if there is a fault in the Jactuator motor
assembly [4].
The embedded device [1] is designed to retract the sector plate to the cold
condition (default condition) in event of the air pre heater rotor drive assembly
failure or the boiler trip

WE CLAIM:
1. Embedded device to display and control leakage gap between a sector
plate and radial seals in Rotary Regenerative Air Preheaters, the device
comprising a flash memory based microcontroller to receive an input
signal from an electronic sensor, process the signal in terms of rotor
position, the speed of the rotor, and real time gap between the sector
plate sealing surface and the radial seals; a plurality of buffered output
ports to transmit command to a jactuator motor attached to a motor
control panel having multiple limit switches; a buffered input ports to
receive the feedback from the Limit switches including the input signal
coming from the sensor, wherein the jactuator motor is enabled to re-
position the sealing surface of the sector plate relative to the radial seals
in order to maintain a desired gap.
2. The embedded device as claimed in claim 1, wherein a control logic is
incorporated to process the signals in respect of pre-stored values.
3. The embedded device as claimed in claim 1, wherein the device is enabled
to sound an Alarm if there is a fault in the Jactuator motor assembly.
4. The embedded device as claimed in any of the preceding claims, wherein
the Jactuator Motor Panel is commanded to retract the sector plates to
the cold condition position (default position), in case of emergencies such
as a boiler trip.

5. The embedded device as claimed in any of the preceding claims, wherein
the device transmits a command to the Jactuator Motor Panel to bring
back the sector plate the cold condition in case there is any fault in the
Rotor gear assembly or the RPM goes to zero.
6. The embedded device as claimed in claim 1, wherein the device is
configured to continuously the speed of the rotor of air preheater.

ABSTRACT

The invention relates to an embedded device to display and control leakage gap
between a sector plate and radial seals in Rotary Regenerative Air Preheaters,
the device comprising a flash memory based microcontroller to receive an input
signal from an electronic sensor, process the signal in terms of rotor position, the
speed of the rotor, and real time gap between the sector plate sealing surface
and the radial seals; a plurality of buffered output ports to transmit command to
a jactuator motor attached to a motor control panel having multiple limit
switches; a buffered input ports to receive the feedback from the Limit switches
including the input signal coming from the sensor, wherein the jactuator motor is
enabled to re-position the sealing surface of the sector plate relative to the radial
seals in order to maintain a desired gap.