Overview
Walsn Flame Detection System is the essential equipment for the FSSS of coal-fired, gas-fired and oil-fired boilers. Based on the physical property of flame, the detector detects the combustion condition in real time. Once the flame is off or the combustion conditon is abnormal, the detector gives the signal as the logical judging factor for fault alarm or FSSS. According to the signal, the users can stop supplying the fuel into the boiler timely if the flame is of and prevent the boiler from explosion resulting from some flammable materials which accumulate in the furnace or pipe.
Walsn Flame Detection System includes Walsn FD-100 integrated intelligent flame detector, conduit component, on-site connection box, cable components, flame detector power supply cabinet and cooling air fan system.
Fig.1 Systematical Picture of Walsn Flame Detector
A:On-site connection box B:Power Supplies Cabinet
C:To Walsn computer (comm) D:To DCS system
K1,K2 : Air pressure switch E:Cooling air
C:Air fan control box F:Cooling air system
Walsn Flame Detection System can be widely used in power plants, oil refineries, cement factories, chemical and steel industries, etc.
Combustion Process of Fuel
The combustion process can be divided into several stages, at different stages, there will be different light strength and flicker frequency which is also affected by combustion quality. Take the process of pulverized coal combustion in the furnace for example, there are four stages, including dark zone, primary zone, complete combustion and burn-out zone. In primary combustion zone, the lightness is less than the maximum, but the flicker frequency can reach the peak. The flame detector discerns the combustion state according to the state of the flicker frequency; therefore the primary combustion zone is the best part to detect the flame.
Fig.2 Spectral Distribution Graph of Radiation Intensity from Different Fuel
A:χ ray and γ ray E:Visible Light Zone
B:Relative Intensity F:Thermal Energy
C:Ultra-violet Zone G:Infrared Zone
D:Optical Energy L:Microwave Radiation
a:purple b:blue c : green d:yellow e:orange
f:red H:oil I:coal J:gas
Different fuels produce different light intensity. Therefore, there will be different detecting instruments for different conditions. In general, coal flame can release infrared, visible light and ultra-violet. However, the ultraviolet is easy to get weakened by combustion products and ash particle. Therefore, visible light or infrared flame detector is often used for detecting coal combustion flame. To detect oil flame, it is recommended to use the detecting instruments which are more sensitive to UV, IR and visible light because gas flame releases stronger UV, IR and visible light. To detect gas flame, it is recommended to use UV detectors because gas flamed releases strong UV in the primary combustion zone.
Detection principle
Walsn Company supplies the intelligent flame detector (FD-100) to determine the presence or absence of flame through collecting and amplifying the flame signal but also a series of computing and analysing. FD-100 detects the flame based on the characteristics of fuel flame signal. FD-100 can output the flame quality in real time. FD monitoring and management software can realize remote controlling via the communication of RS-485 and some flame detectors.
Firstly, FD-100 divides flame signal into strength signal and frequency signal. The former represents brightness of flame and the latter represents flame flicker. Meanwhile, frequency signal contains spectrum, bandwidth and peak value, etc. The flame frequency is 1200 Hz; while frequency of coke button and ash content in the furnace is less than 2 Hz. Therefore, analyzing the frequency signal enables users to determine the presence or absence of the flame. Flame detector is applied to measuring the flame quality and determining the presence or absence of the flame through amplifying, filtering, computing and processing the strength signal.
Fig.3 Principle of FD-100
Walsn FD-100 Integrated Intelligent Flame Detector
FD-100 utilizes SMT technology and combines photoelectric converter, microprocessor,Human-Computer Interaction(HCI)and output interface. FD-100 can generate the output signal of fault, the presence or absence of flame, 4-20mA analogy output and RS-485 interface which meets MODBUS standard via quick connector. FD-100 is not only compact but also easy to mount, debug and maintain. FD-100 is applied to oil-fired and coal-fired burners.
A:Detector
B:Furnace wall
C:Burner nozzle
The best results are obtained when the detector is aimed so that the detector's line of sight intersects the burner center at a slight angle (e.g. 5o-10o) and sees a maximum of the primary combustion shown in the figure as above.
Features
High performance photosensitive resistance (spectral response range: 700mm~1700mm)
high light Eight-character LED display
Built-in NC amplifier; widely used in different flame condition
Integrated design, compact structure, easy to install
Independent analog output 4-20MA for showing flame characteristics.
Self-checking and alarm signal output
High self-learning function, can figure out the feature of flame
Remote online adjusting and parameters setting
Technical parameters
Mechanical part
Housing Material: Die-cast aluminum
Housing Weight: 1.8kg
Installation method: Screw joint
Electrical
Power supply: 24VDC±10% DC 0.35A
Electric connection: 12-pin electrical quick disconnect connector
Analog output: 4-20mA
Max. connected load 750Ω(ohms)
Contact output: Flame relay NO
Failure relay NC
Contact capacity: 2A@30V DC 2A@220V AC
Display interface: eight-character alphanumeric LED display
Operation interface: Four(4) pushbutton style keys
Connecting cable: 12-pin, special high temperature, flame-retardant and shielded flexible cable
Max. external diameter: 9mm
Cooling air
Cooling air current: 5 SCFM—15 SCFM
Cooling air pressure: 6 KPa
Cooling air supply: clean, dry, cooling air
Ambient
Ambient temperature: -40℃- 75℃
Humidity: 0% - 95% relative humidity, no condemning
Protection level: NEMA 4X IP66
Storage temperature: -40℃ - 85℃
Conduit Assembly
Walsn FD-100 Flame determines the presence or absence of the flame according to the flame flicker frequency. The detector should be mounted so that the main combustion zone is within the detector's line of sight. FD utilizes optical fiber installation.
Fig.5 Figure of Conduit Assembly
A:Internal Conduit Assembly B:External Conduit Assembly
C:Optical Fiber Assembly D:Furnace Wall Installation Assembly
E:Y-pipe F:Mounting Flange
G:Walsn FD-100 Flame Detector H: Cable Assembly
I:Cooling Air Tube
The conduit assembly contains external conduit, internal conduit, optical fiber and furnace wall installation assembly. The conduit assembly is used to transmit the flame flicker signal out of furnace via optical fiber so that enables the flame detector to determine the flame.
Technical Parameter of Conduit Assembly
Angle……………………coal flame detector 7°- 10°,oil flame detector 5°- 7°
Ambient temperature…………………………………………………-40℃ - +450℃
Spectrum range…………………………………………………300nm - 1800nm (IR)
Light transmittance ……………………………………………………………..＞85%
Optical fiber structure…………………………………………………….fiber bundle
Material……………………………………………………….. Carbon steel /Stainless
On-site Connection Box and Cable Assembly
On-site Connection Box
FD-100 is connected to an on-site connection box through the cable with a quick connector.
Fig. 6 On-site Wiring Diagram
C:Remote communication A D:Remote communication B
E:Remote files selection 1 F:Remote files selection 2
G: flame relay (N.O.) H: flame relay (COM)
I: fault relay (N.C.) J: fault relay (COM)
K: fault relay (N.C.) L: fault relay (COM)
M: flame relay (N.O.) N: flame relay (COM)
P: flame relay (N.C.) Q: flame relay
R: fault relay S: remote communication A
T: remote communication B X: Remote files selection
O1: To prior flame detector
O2: To next flame detector or RS-485 to RS-232 Converter
O3: To Power Supplies Cabinet
O4: To DCS
Installation personnel can handle all the wiring via the on-site connection box. In the connection box, there are two communication wires which must be connected to the other wires of 12-cond. cable independently, and they must be connected to each FD-100 in a way of multi-point (daisy-chain)connection. Meanwhile, the two communication wires must be connected to up-down connection box so that the flame detector can communicate with the computer via the two wires.
Cable Assembly
FD-100 is equipped with special 12-cond. shielded flexible cable. The cable shell is made by polyolefin material which is flame-retardant and Low Smoke Zero Halogen (LSZH). The cable of each detector can reach up to 100m in length.
The standard package of flame detector includes a 12-cond. cable male connector. Walsn Company can also provide a female connector according to the requirements of clients to satisfy the installation needs.
Flame Power Supply Cabinet
The power supply cabinet is equipped with special power, providing reliable power to FD-100.
The cabinet is available for connecting two-loop single-phase 180V -260V,50Hz power supply. In general, one of two-loop power is from uninterrupted power supply (UPS); another loop is from emergency power supply. The cabinet supplies 24V DC to FD-100 after the two-loop power finish auto switch.
Cooling Air Fan System
The cooling air fan system is used to provide the clean air to FD-100 to ensure the lens of FD-100 can keep cleaning and cooling. The system contains two import cooling air fans (one of them for backup), air fan control box, cooling air fan power supply with air duct and air pressure switch, etc.
Cooling Air Fan
The Cooking air fan is used to transmit air and gas which is non-hypergolic, harmless to human and non-corrosive to steel. Any sticky substance is not permitted to exist in the gas. All dust and hard particulate must be less than 150mg/m3, and gas temperature must be lower than 80 ℃
Air fan Control Box
The cooling air system is equipped with special air fan control box.
Once the air fan control box receives a control signal(ON/OFF and Low Air Pressure Interlocking instruction) from DCS system, the box gives a response to DCS system with a signal(ON/OFF and High Air Pressure Alarm). It is recommended to place the control box nearby the cooling air fan. The box is used to control the cooling air fan.
Cooling Air Fan Power
The power for the cooling air fan is 380V AC. There are two loop and independent power supplies, which are for alternative operation. Two loop powers should be supplied in normal operation. The main power should be supplied prior to the emergency power.
Only one loop power will be supplied to the cooling air fan at any time because two loop powers have the alternative and auto-switching function which can protect the native driver of electric machine from overheating.