FIELD OF INVENTION
The present invention relates to a testing and calibration apparatus for coal / oil
/ gas flame detection by digital signal processing. More particularly, the invention
relates to an apparatus for testing and calibrating a Flame Scanner head
assembly electronics adaptable to boilers.
BACKGROUND OF THE INVENTION
Boilers are employed to thermal power plants including other industries which
require steam and / or other type of power source for its operation. The boilers
are designed to burn different types of fuels like coal / oil / gas either separately
or in combination. The fuels are admitted to the boiler furnace through the
burners disposed at different locations in the furnace walls. In some types of
boilers, the burners are located in the four corners of the furnace at different
levels (known as corner fired boiler furnaces). In other type of boilers, the
burners are located in the front wall or rear walls of the furnace at different
levels (known as wall fired boiler furnaces).
Generally, any furnace burning fuel is susceptible to explosion in case of
improper combustion. It is observed that most of the furnace explosions occur
during the start up. Some of the probable causes are
- Improper purging of the furnace, including that of the gas and air paths.
- Adapting incorrect or inadequate ignition procedure.
- Maintaining the fuel supply for too long a period without establishing
combustion.
- Relighting the fuel too soon after previous flame out, with improper
purging.
- Introduction of the main fuel without ensuring adequate ignition energy.
Hence it is essential to ensure that certain safe conditions are established and
provided in the furnace before the light up can be resorted to. In the event of a
flame failure during operation of the boiler, the fuel supply is to be immediately
discontinued, the furnace including the gas and air paths are to be purged before
any effort is made to re-introduce the fuel. For prevention of furnace explosions,
the absence of any flame while fuel is being admitted is by the furnace safeguard
supervisory system. Flame monitoring system must be reliable, sensitive enough
to discern even the minimum flame envelope and must have fail safe
characteristic to avoid unnecessary trips.
The prior art flame monitoring (detector) apparatus basically comprises a
plurality of flame scanner head assembly and a plurality of flame scanner
amplifier unit. One each flame scanner head assembly is located in the four
corners of the furnace at different levels in corner fired boiler furnaces,
and one each flame scanner head assembly is disposed near to each of the
burners located in the front wall or rear walls of the furnace at different levels in
the wall fired boiler furnaces.
Each flame scanner head assembly comprises a detector head housing with a
detector head, and a fiber optic cable assembly. The detector head housing
contains an electronics module which converts the light signals transmitted from
the furnace flame via a fiber optic light guide, to an electric current signal. The
electric current signal is further taken to the micro controller based amplifier unit
and processed. Input from each of the flame detector is divided into two
components for example, one signal representing the intensity, and the other
signal representing the flicker frequency. Both the signals are processed digitally
in the micro controller based unit to compute intensity and flicker frequency
parameters of the flame. The electronic module of the flame scanner head
assembly contains an electronic card which requires calibration after assembly,
before commissioning and also at periodic intervals during regular operation.
In the prior art testing and calibration method, a device comprising an exclusive
power supply, resistors, selector switches are employed which is hooked up with
the scanner head electronic card to calibrate the scanner for off-set and gain
adjustment.
Such a testing and calibration device is quite cumbersome, difficult to arrange at
remote locations, and time consuming. Further, the functional aspect of the
scanner head electronics can not be checked due to limitations in arranging
means frequency for modulation including the light source.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention to propose an apparatus to test and
calibrate the flame scanner head assembly of a flame detector system in a boiler.
Another object of the invention is to propose an apparatus to test and calibrate
the flame scanner head assembly of a flame detector system in a boiler at job
site.
SUMMARY OF THE INVENTION
The invention proposes an apparatus, to test and calibrate a flame scanner
assembly within the manufacturing unit including at remote construction sites.
The apparatus consists of an electronic module, a halogen lamp with a reflector,
a condenser lens a quartz window and a test port, all of these components being
mounted inside a metallic box. A VEE block is provided to support the front end
of the flame scanner head assembly. The frequency and intensity of light beam
from the halogen lamp can be varied to simulate the conditions in a boiler
furnace, to test and tune the electronic module of the flame scanner assembly
which is under test.
Accordingly, there is provided an apparatus for testing and calibrating a flame
scanner head assembly electronics adaptable to a flame scanner device in
boilers, the apparatus comprising an electronic module receiving an externally
input power supply and providing a regulated power supply to an auto-halogen
lamp, the electronic module being enabled to internally generate a reference DC-
supply for calibration including a pulsed D.C voltage with variable frequency and
DC-offset/intensity; one each frequency counter and voltmeter to respectively
measure the flickering frequency output of the pulse generator, and to measure
the output voltage signal, the calibration signal output being derived from the
reference source through a mode selection via a SPDT-switch; and one each
condenser lens and quartz window to generate an effective light beam out of
the light source concentrated towards a test port, the flame scanner head
assembly supported by a VEE block being insertable into the test port for testing
and calibration.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l - shows the embodiment of the apparatus according to the invention
Fig.2 - shows the VEE block used for mounting scanner head assembly while
testing
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The Fig.l and Fig.2 illustrate the details of the apparatus. The apparatus
comprises with an electronic module (1). Which provides the power supply to a
Halogen lamp with suitable reflector (2). On energization, the light from the
Halogen lamp (2) passes through a condenser lens (3) and a Quartz window (5)
to make the light beam more effective to concentrate at the aperture (test
window) as shown. A test port (4) is provided to insert the front end of a flame
scanner head assembly. A VEE block (7) is provided to support the front end of
the flame scanner head assembly.
The electronic module (1), lamp with reflector (2), condenser lens (3), quartz
window (5) test port (4) are mounted inside a metallic box (8). The front side of
the metallic box (8) is provided with a Digital Voltmeter (9) to measure the
output voltage variations, a frequency counter (10) to measure the flickering
frequency, an analog instrument (11) to measure the flame intensity, a selector
switch (12) and at least two connectors (13) to take output to the flame scanner
amplifier unit. Power input of 230V AC / 115VAC is given to the test apparatus
via a fused power inlet (6). This power is controlled by an illuminated rocker-arm
switch.
The apparatus is adaptable to test and calibrate the flame scanners employed in
boilers located in power plant or other industries.
The apparatus according to the invention comprises a regulated power supply
unit for receiving 230V & 115V AC, +/- 10%, 50Hz, input power supply routed
through an illuminated isolation switch and providing +15 V, -15 V regulated
power supply with an output voltage tolerance of +/-1%, line / load regulation
including an output current of corresponding rating. The apparatus is enables to
internally generate +1.0 V Reference DC supply with maximum current loading of
5 mA for calibration purposes. Additionally the apparatus comprises means for
internally generating pulsed DC voltage (12V max.) with variable frequency (0 to
120 Hz) and DC offset / Intensity (0 to +10V) to excite the auto halogen lamp (2)
rated for 12 V or 24 V with corresponding wattage rating. A counter is provided
(LED version) to measure the frequency of output from the pulse generator. A
compact voltmeter (LED version) is provided to measure the output voltage signal.
1 micro amp and 1 milli amp calibration signal output derived from +1.000 V
reference source is inputted with a mode selection through a SPDT switch.
The invention eliminates the use of external components and power sources.
The apparatus is configured to calibrate and test a flame scanner head assembly
electronics including a complete flame scanner system comprising the scanner
head assembly and the amplifier. The apparatus is portable. The apparatus can
further be operated by the conventional power source. (230V AC, 1 Phase/110V
AC, 1 phase).
The apparatus is adapted test and calibrate the electronic module called flame
scanner head card.
The flame scanner head assembly along with amplifier chassis can also be tested
for proper setting and operational requirements by simulating the intensity and
frequency variations using the inventive flame scanner test apparatus. This test
apparatus generates concentrated light beam by the halogen bulb of 12V,
25W rating focusing at test port to receive the focused light. The flame scanner
electronic module (head card) can be placed at the test port available in the test
apparatus to receive the focused light. The frequency and intensity of light beam
can be varied to the required level to test and tune the electronic module which
is under test.
The following features are available in the test apparatus:
a. The scanner head electronic module alone can be exclusively fitted to an
attachment means provided in the test apparatus, which makes the light
source to get aligned with the centre of sensor unit.
b. The complete scanner head assembly can be tested by placing a
collimator assembly over a VEE block, so that the self aligned of the light
source get aligned with the center of the sensor unit.
Adjustable focusing means is available to focus the light source onto
the sensor.
c. In order to simulate intensity variations (between dark furnace to bright
furnace conditions), a halogen lamp (2) is used as a light source.
d. An electronic circuit (1) is designed to control the lamp source. This circuit
(1) controls the intensity of light emission by varying the applied voltage.
A variable set point generator is provided for this purpose. In order to
generate the pulsating phenomena of the light source, the intensity is
being modulated by changing the On/Off time of the pulsation as set by
an external set point generator.
e. To calibrate the scanner head electronics without sensor by feeding
current, a precision current source is available, which can be selected for
1 micro ampere and 1 milli ampere by a switch (12).
f. To measure the output voltage variations, a 3 Vi digital display (14) is
also available.
g. Provision is available to check the scanner head electronics alone. This
facility is available to change the intensity and pulsating rate. Same thing
can be viewed in the analog and display meters (11, 14) for intensity and
frequency respectively.
h. There are two connectors (13). One is compatible to connect with scanner
head to check the function independently. Another is to connect and
check the scanner amplifier. The connector function can be selected with
a toggle switch to suit the above purpose.
i. A special type of pig-tail cable with banana connector and crocodile dip to
make the connection faster and easier.
j. The test apparatus can be powered up from a 230 / 115 V AC supply. This
test apparatus is portable.
k. Cooling fans are fitted to use this device continuously, so that overheating
will not happen.
Salient features / advantages of the apparatus / method are:
? Ensures proper tuning of flame scanner electronic card (head card) before
commissioning and also whenever retuning is required for varied fuel
firing conditions.
? Enhances reliable flame sensing due to proper tuning, resulting in safety
to plant equipments and personnel and thereby enhances boiler reliability
and availability.
? Offer operating personnel a flexible tool for tuning of flame sensing
devices at job site.
WE CLAIM
1. An apparatus for testing and calibrating a flame scanner head assembly
electronics adaptable to a flame scanner device in boilers, the apparatus
comprising:
- an electronic module (1) receiving an externally input power supply and
providing a regulated power supply to an auto-halogen lamp (2), the
electronic module (1) being enabled to internally generate a reference DC-
supply for calibration including a pulsed D.C voltage with variable
frequency and DC-offset/intensity;
- one each frequency counter (10) and voltmeter (9) to respectively
measure the flickering frequency output of the pulse generator, and to
measure the output voltage signal, the calibration signal output being
derived from the reference source through a mode selection via a SPDT-
switch (12); and
- one each condenser lens (3) and quartz window (5) to generate an
effective light beam out of the light source (2) concentrated towards a
test port (4), the flame scanner head assembly supported by a VEE block
(7) being insertable into the test port (4) for testing and calibration.
2. The apparatus as claimed in claim 1, comprising an analog instrument
(11) to measure the flame intensity.
3. The apparatus as claimed in claim 1 or 2, comprising a fused power inlet
(6) through which the power is inputted from external source to the
electronic module (1).
4. The apparatus as claimed in any of claims 1 to 3, wherein a pair of
connection (13) is provided enabling the output from the apparatus to be
inputted to the amplifier unit of the flame scanner.
5. An apparatus for testing and calibrating a flame scanner head assembly
electronics adaptable to a flame scanner device in boilers as substantially
described and illustrated herein with reference to the accompanying
drawings.

The invention relates to an apparatus for testing and calibrating a flame scanner
head assembly electronics adaptable to a flame scanner device in boilers, the
apparatus comprising an electronic module (1) receiving an externally input
power supply and providing a regulated power supply to an auto-halogen lamp
(2), the electronic module (1) being enabled to internally generate a reference
DC-supply for calibration including a pulsed D.C voltage with variable frequency
and DC-offset/intensity; one each frequency counter (10) and voltmeter (9) to
respectively measure the flickering frequency output of the pulse generator, and
to measure the output voltage signal, the calibration signal output being derived
from the reference source through a mode selection via a SPDT-switch (12); and
one each condenser lens (3) and quartz window (5) to generate an effective light
beam out of the light source (2) concentrated towards a test port (4), the flame
scanner head assembly supported by a VEE block (7) being insertable into the
test port (4) for testing and calibration.