7/25/2019 Module 7 - Flame Safeguard Principles
1/181
Module 7. Flame SafeguardPrinciples
Prepared and Presented By :
Youdhiyan [email protected]
+62-811886021
POWER PLANT WORKSHOP PLN PuslitbangBogor, 5-8 May 2014
5/5/2014 Flame Safeguard - Principles 2
Flame Safeguard ?
Consists of a Flame scanning device and Amplifiersystem to monitor the Burner flame in acombustion chamber to assure safe and reliableoperation
FLAME
SCANNER
BMS
SCANNER
CABLE
FLAME
AMPLIFIER
CUSTOMER
INTERFACE
POWER
mailto:[email protected]:[email protected]7/25/2019 Module 7 - Flame Safeguard Principles
2/182
5/5/2014 Flame Safeguard - Principles 3
What is a Burner ?A device to convert fossil fuel into usableheat energy
5/5/2014 Flame Safeguard - Principles 4
What is combustion ?Combustion, or burning, is the combinationof Oxygen with Fuel, resulting in the releaseof Heat
7/25/2019 Module 7 - Flame Safeguard Principles
3/183
5/5/2014 Flame Safeguard - Principles 5
What is a Flame ?
Flame FrontCombustion reaction occurs at a ratethe produces visible radiation, fuel-air
mixture and combustion process.
Flame EnvelopeContour along which the combustionstarts, dividing line between the fuel-air mixture and the combustionprocess.
5/5/2014 Flame Safeguard - Principles 6
Principles used for Flame Detection
Temperature of gases in the flame
Visible Light radiation
Infrared Light radiation
Ultra-violet Light radiation
Ionized gas molecules in the flame
= Ability to conduct current
Flame Flicker frequency
7/25/2019 Module 7 - Flame Safeguard Principles
4/184
5/5/2014 Flame Safeguard - Principles 7
Flame Radiation
Detection of flame radiation is the mostwidely used method for flame detection
Flames emit radiation along a wide bandof the electromagnetic spectrum, calledthe Flame Spectrum
The Flame Spectrum is made up of ultra-violet, visible, and infra-red radiation
5/5/2014 Flame Safeguard - Principles 8
What is Flame Safeguarding System ????
A single input for a BMS!
Fireye Flame Detector
Detector Signal
Output to BMS
Flame Radiation
7/25/2019 Module 7 - Flame Safeguard Principles
5/185
5/5/2014 Flame Safeguard - Principles 9
Flame Safeguarding Definition
A system which is detects thepresence or absence of a flame in
burner in order to preventuncontrolled combustion .
Every Burner
Needs A Detector!!!
5/5/2014 Flame Safeguard - Principles 10
What is the Characteristics ofa Flame ??
Its HOT
It expands the gases
It makes By-Products There is Ionization in
and around it
It emits radiation Visible light
Infrared
Ultraviolet
D.Shunn
7/25/2019 Module 7 - Flame Safeguard Principles
6/186
5/5/2014 Flame Safeguard - Principles 11
Types of Radiation in Combustion
UV = least available(1%) 1st third of flame:Blue for gas
Visible = 10% of flameBlue /orange /yellow for gas
Bright yellow for oil.
Infrared = 90% of flame2/3 of flame = Red
5/5/2014 Flame Safeguard - Principles 12
What is UV and IR signal ?
A bundle of energy focused at a specific wavelength
7/25/2019 Module 7 - Flame Safeguard Principles
7/187
5/5/2014 Flame Safeguard - Principles 13
Relation between Fuels and Radiant Energy
Fuel Infrared Visible UV
Oil (Pressure) High High Medium
Oil (Steam) High High Low
Gas (Air Premix) Low Low High
Gas (No Premix) Medium Medium Medium
Pulverized Coal High Medium Low
5/5/2014 Flame Safeguard - Principles 14
Methods of FlameDetection
Visible Light. . . . . . . . . . . .Photocells
Infrared (IR) . . . . . . . . . . . LeadSulfide (typically) (InGa As)
Ultraviolet (UV) . . . . . . . . . UVTube (gas filled) UV Cell (solidstate: Super Blue Silicon)
Flame Rod . . . . . . . . . . . . .KANTHAL Rod
7/25/2019 Module 7 - Flame Safeguard Principles
8/188
5/5/2014 Flame Safeguard - Principles 15
What is Flame Amplifiers ??
Scanner outputElectrical pulses
Fireye Scanner
Output to System
400 Threshold on
Operating Range300 Pre-Alarm250 Threshold off
-----
5/5/2014 Flame Safeguard - Principles 16
Conventional Ultraviolet Flame Detectors:
UV Tube ( Optical ) Vacuum Tube Method
Two tungsten ormolybdenumelectrodes in a gas-
backfilled quartzvacuum tube
850 to 950 volts ACapplied from step-uptransformer in thescanner
Gas Discharge DeviceConducts in presenceof UV radiation
7/25/2019 Module 7 - Flame Safeguard Principles
9/189
5/5/2014 Flame Safeguard - Principles 17
Ultraviolet Flame Detection- UV Tube
Vacuum Tube Method (continued) UV radiation passes through the quartz and
strikes the electrodes
A small current flows between electrodes,ionizing the gas, resulting in characteristic blue
glow
The current flow (or avalanche) will be in smallbursts at a rate from 0 to 2,000 pulses persecond
5/5/2014 Flame Safeguard - Principles 18
UV Tube Operation
7/25/2019 Module 7 - Flame Safeguard Principles
10/1810
5/5/2014 Flame Safeguard - Principles 19
Why you need a Self Checking Scanner ?
An Electro-mechanical shutter means ofblocking the flames radiation to thedetectorssensor.
This blocking action detects and alarms afaulty sensor.
Undetected faulty sensors can inadvertentlyhold in a fuel valve, although a flame is notpresent.
5/5/2014 Flame Safeguard - Principles 20
Disadvantages of UV Tube Detectors
Requires high AC Voltage
Limited Life Time
Signal Deteriorates with time
Can fire continuously
Electro-Mechanical Shutter Failures leading to spurious shutdown of Boilers
UV Radiation absorbed by moisture (steam)
Low Discrimination capabilities in a Multi Burner Environment.
Respond to non-flame sources
Spark Ignition
Welding Arcs
Halogen light
X-Ray exposure
7/25/2019 Module 7 - Flame Safeguard Principles
11/1811
5/5/2014 Flame Safeguard - Principles 21
UV Tube Flame Scanner
Disadvantages
Low DiscriminationCapabilities
Precautions / UV Blockers Water vapor (FGR)
Atomizing steam Unburned fuel
Some process gases (H2S, NH3)
5/5/2014 Flame Safeguard - Principles 22
Today's conditions present a challenge , a good scanner mustnot only able to detect the absence or presence of targeted
flame BUT also Flame DISCRIMINATION .
Whatis Flame Discrimination ???
4
7/25/2019 Module 7 - Flame Safeguard Principles
12/1812
5/5/2014 Flame Safeguard - Principles 23
Flame Discrimination Defined
Detector
DISCRIMINATION :
The ability to distinguish the target flame from allother flames in the furnace and the Background
Background Flame
Target Flame
Field ofView
5/5/2014 Flame Safeguard - Principles 24
Conventional DiscriminationMethods
1. Scanner mounting and aiming
2. Controlling the optical field of view 3. Adjustments within the scanner
4. Adjustments within the amplifier
7/25/2019 Module 7 - Flame Safeguard Principles
13/1813
5/5/2014 Flame Safeguard - Principles 25
Discrimination Methods
1. Scanner mounting and aiming
5/5/2014 Flame Safeguard - Principles 26
Discrimination MethodsScanner Mounting and Aiming
Flame must be in front of the Scanner
7/25/2019 Module 7 - Flame Safeguard Principles
14/1814
5/5/2014 Flame Safeguard - Principles 27
Discrimination Methods
Scanner Mounting and Aiming
Target flame must fill the scanners field ofview
5/5/2014 Flame Safeguard - Principles 28
Discrimination Methods
2. Controlling the optical field of view
Installing orifices (field stops) or extendingscanner sight pipe
7/25/2019 Module 7 - Flame Safeguard Principles
15/1815
5/5/2014 Flame Safeguard - Principles 29
Discrimination Methods
3. Adjustments within the scanner UV tube position
Scanner GAIN
Flame flicker target frequency
5/5/2014 Flame Safeguard - Principles 30
Discrimination Methods
4. Adjustments within the amplifier
Adjustable sensitivity (fixed flame relay threshold)
Adjustable flame relay threshold (fixed sensitivity)
7/25/2019 Module 7 - Flame Safeguard Principles
16/1816
5/5/2014 Flame Safeguard - Principles 31
Optical Flame Scanners -
Discrimination capabilities -Flicker Flame
5/5/2014 Flame Safeguard - Principles 32
What is Flame Flicker ?
A Flame is a combination of small controlled explosionswhen Fuel and Air Mixes.
The PULSATING behaviour of the explosions is FlameFlicker
Each Fuel, in combination with a Burner design has itsown Bandwidth of Flicker Frequency
The Flicker Frequencies in Flames can be found from
5 Hz to well over 200 Hz
The heavier the fuel, the lower the Flicker Frequency
7/25/2019 Module 7 - Flame Safeguard Principles
17/1817
5/5/2014 Flame Safeguard - Principles 33
Flame Flicker Frequency :
Characteristics
The Flicker Frequency varies with differentregions of the Flame .
Theoretically, the first 1/3 of the Flameproduces the highest Flicker Frequencies (atlikely the lowest Amplitude)
The final 2/3 of the Flame produces theLowest Flicker Frequencies (and the highestAmplitude)
5/5/2014 Flame Safeguard - Principles 34
Flicker Frequency
Line of Sight
40 Hz
120 Hz40 Hz
Background
TargetFlame
FlickeringFlame
Flame Signal FlickerFrequency
High Amplitude-Low Frequency
Low Amplitude-High Frequency
7/25/2019 Module 7 - Flame Safeguard Principles
18/18
5/5/2014 Flame Safeguard - Principles 35
Bandpass Filters
Allows you to tune into the frequency of the flame
FFT
Background Signal
Target Flame Signal
Bandpass Filter
5/5/2014 Flame Safeguard - Principles 36
Top Related