ftir an advanced ftir for toxic gas analysis digital...ftir: an advanced ftir for toxic gas analysis...

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Fire Tw R E s s Wes ex RH19 2H

FTIR: an AdvancedFTIR for Toxic GasAnalysis(ISO 19702; EN 455452; IMO)

FTIR an Advanced FTIR for Toxic Gas Analysis_digital 15/07/2020 15:21

FIRE TESTING TECHNOLOGY

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Source

Gas Celland

Detector

Moving Mirror

Fixed Mirror

Toxicity analysis of fire effluents isan important aspect for developingmodern materials used in aircrafts,trains and buildings to ensurepublic safety. Analytical techniquesand performance criteria have beenspecified in various fire safetystandards and regulatory codes.FTIR is the technique that has beenchosen by the ISO, EN and IMOstandardisation committees as themost suitable method formeasuring toxic fire effluents. Thecommonly targeted toxic speciesare CO, CO2, HCN, SO2, NOx, HCl,HBr and HF.

Fourier TransformInfraRed (FTIR)SpectroscopyFTIR spectroscopy is a fullspectrumanalytical technique that allows all IRabsorbing species to be detected andmeasured by a single instrument.

The infrared light from the source ismodulated by the interferometer.This device allows for the light to besplit into two different paths andrecombined, producing aninterference wave known as aninterferogram. The light is split via

Classic Michelson Interferometer

an optical device known as a beamsplitter.

The use of a monochromatic orsingle wavelength light source,typically a laser, is used to provide areference signal in theinterferometer. Measurement ofthe interference pattern of thesingle wavelength allows the speedof interferometer’s mirrormovement and alignment to becontrolled precisely.

The light is passed through asample compartment which is oftenreferred to as the sample cell or gascell. Sample cells can be of variousdesigns in order to achieve themost suitable pathlength i.e. totallength that the IR light passesthrough the absorbing medium. Forlong pathlengths (of the order ofmeters) this usually involves theuse of mirror arrangements tobounce the light through thesample medium. As the sample cellcontains the extracted samplemedium, care has to be taken thatthe sample cell is constructed ofsuitable materials and operates atthe required temperature andpressure.

An infrared detector, e.g.deuterated triglycine sulfate (DTGS)detector, and associated electronicsare required to make single pointmeasurements of the infraredsignal as the interferometer scans.

An FTIR analyser does not directlyproduce a spectrum for analysis; aninterferogram is produced. This istimedomain measurement of IRsignal and contains the modulatedwave of the entire broad bandsource. To extract the IR spectrum amathematical manipulation called a


FTIR: AN ADVANCED FTIR FOR TOXIC GAS ANALYSIS

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Fourier Transform must be appliedto the interferogram. Themathematics of this are all handledin software in realtime.

The resulting singlebeam orintensity spectrum is thencompared against a zero orbackground spectrum to producean absorbance spectra. Thisabsorbance spectrum is what weneed to run a spectral analysis,applying Beer’s Law.

Beer’s Law describes the linearrelationship between IR absorbanceand concentration when variablessuch as temperature, pressure andpath length are kept the same.With absorbance spectra collectedand saved, chemometrictechniques can be applied toextract concentration information.FTIR spectroscopy is considered themost suitable analytical techniquefor measuring toxic gas species infire effluents because:– a variety of gases across wide

concentration ranges can bedetermined by a single method;

– monitoring of speciesdevelopment throughout the fireis possible with time resolvedmeasurements;

– toxicants can be identified orreanalysed retrospectively in thestored spectra from previousexperiments.

FTT FTIR SystemFTT has been at the forefront ofsupplying a turnkey solution of FTIRsystem in analysing toxic gases infire effluents. The makeup of thisturnkey solution comprises of anadvanced FTIR analyser, heatedsampling system including all thepneumatics, control/processing

electronics and an industrial PC,which are mounted in a 19" cabinetfor easy accessibility and service.

FTT FTIR is an advanced FTIR gasanalyser used for continuous gasmonitoring in conjunction withFTT’s Cone Calorimeter, SmokeDensity Chamber and SingleBurning Item (SBI) for onlinemeasurements of combustion gasesin fire tests.

Spectroscopic data are oftencomplex, containing large numbersof features which often overlap.The analysis of gases in fireeffluents is especially challengingdue to the great number ofdifferent organic and inorganicchemicals which representativeatmospheres can contain.

FTT FTIR software useschemometrics to resolve data into

meaningful and accurateinformation. It offers users theability to perform chemometricsanalysis on data sets. This softwareis designed so that untrained userscan simply run preloaded models,but will also allow more advancedusers to build and develop models.

FTT’s application specialists haveexperience of developing andimplementing chemometrictechniques on various projects. Wecan provide in depth trainingcourses on chemometrictechniques and data analysis ofspectroscopic measurements,enabling users to fully benefit fromthis powerful software.

As any chemometric technique willonly ever be as good as thecalibration data it is based on, FTTFTIR is calibrated in a purpose built

FTT FTIR (left) and FTTSmoke Density Chamber

(right)



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calibration lab using certifiedtraceable standards.

FTT FTIR is fully configurable tomeet the requirements of EN 455452, ISO 19702 and IMOstandards. In addition, variousprocess monitoring applications arealso possible. Measuredcomponents and calibration rangescan be selected according toapplication.

FTIR Gas AnalyserThe FTIR gas analyser is an integralpart of the system which allowssimultaneous measurement ofmultiple gas compounds.

Typically concentrations of H2O,CO2, CO, SO2, NO, NO2, N2O, HCl, HF,NH3, etc. are continuouslymeasured.

The analyser has a multipass gascell which is heated to 180°C. Thegas cell mirror is gold plated withprotective MgF2 coating whichensures high performance even inhigh water vapour concentrationsor corrosive gases.

The analyser also has an internalsolenoid valve to allow zero gas(usually 99.999% N2) to pass to thegas cell for cell evacuation and zerobackground measurements. This

can be set as a Normally Open (NO)valve which provides a failsafe incase of power failure to ensure thegas cell is purged and gas does notcondense on the optics.

Pressure transducer is installed tomonitor the pressure inside the gascell. Fluctuations in the cellpressure will be corrected for inrealtime by software.

Sampling SystemThe hot extractive sampling systemconsists of a heated sample probe,heated filter, heated sample linesand heated pump unit. The wholesystem is kept at 180°C to avoidcondensation and subsequentwashing of soluble fire gases out ofthe sample. Two stage particlefiltration is used in order to removeparticles from the sample gas. Thesample pump unit includes gasconnections for the FTIR gasanalyser. All sample lines have aPTFE core sample line of 6mm OD,4mm ID, together with a secondaryline for calibration/span gas. End fixtures are stainless steelwhich is robust and provides longlifetimes.

Panel PCThe touchscreen panel PC isrequired to operate the analyser, tocontrol the sampling system, totranslate measured and analysedconcentrations and send alarms tohigher level automation and controlsystems. It is also used forprocessing and storing the samplespectra.

FTT FTIR is supplied with a suite ofthree analytics software.

FTT FTIR SystemInterior (front door

opened)



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i. PASProAnalyser Software for Process(installed on built in touchscreenPC) PASPro is a very simple touse but comprehensive userinterface with setup menus forrunning the FTIR and control ofall system parameters. Itdisplays real time analyticalmeasurements for the selectedgases with an optional “Pass”and “Fail” result qualityindicator next to eachmeasurement. There is an alarmwindow which indicates anyfaults with the system and anevent log updates with each taskthe system has carried out.

ii. PAS Analyser Software(installed on standalone PC)Collected FTIR data (results andspectra) can be downloadedfrom the test station andtransferred to another PC forfurther analysis using PAS whichallows the analysis to bechecked and interfering speciesto be identified. It gives the usercomplete flexibility over the FTIR

Heated filter/valve unit, PTFE filter can be easily replaced from the front

acquisition parameters andallows complex analyticalmodels to be built. Models canbe span corrected to matchreference gas cylinders andlinearity checks can be made forcompliance with performancestandards.

iii. Spectrum Viewer (installed onstandalone PC)It is a standalone application formanipulating spectra andidentifying species that arepresent. It contains no analyticalor collection routines, but is a

valuable tool for the analystworking with spectra, e.g.adding, subtracting, multiplyingand dividing spectra, peakposition locator, baselinecorrection, etc.

PAS – From Spectrum toResultsThe advanced, easy to use PASsoftware provides outstandinganalytical performance. It analysesthe sample spectrum usingsophisticated chemometrics. It iscapable of simultaneous detection,identification and quantification ofmultiple gas species.

Crossinterference effects arecompensated for and analysisaccuracy is maintained even whenanalysing complex gas mixtureswhere there is a possibility ofspectral overlapping. Resolution iscarefully optimised to meetrequirements in fire tests. Thisallows the collection of severalmeasurements every minute whilstretaining high sensitivity. PAS alsoallows for model switching basedon constants or other variables. Forexample, two chemometric modelscan be built over different ranges,one 0100ppm, and one 100



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1000ppm. PAS will automaticallyswitch and use the most suitablemodel for the currentconcentration mix.

PAS software is designed for easyand efficient processing of theresults. Advanced modellingmethods of PLS (Partial LeastSquares) are used for accurate androbust analytical predictions, evenin the presence of unknowninterfering gases. PLS models arebuilt on a component specific basis

Key Features and Benefits• Complete turnkey solution for reliable and accurate analysis of toxic gas species in fire effluents• Time resolved results enabling continuous monitoring of multiple gas speciesdevelopment• Hot extractive sampling; no sample loss or change of composition• Fully automated measurement system with comprehensive safety functions• Fully modular system for maximum flexibility• Fully configurable to meet requirements of ISO 19702, EN 455452 and IMO standards.• Capable of individual analysis of airborne concentrations of CO, CO2, NO, NO2, SO2, HCI, HF,

Phenol, Acrolein, water vapour, etc.• Powerful PAS software suite for different operational and analysis requirements• Span and linearity correct models• Pressure correction, dilution correction, dry/O2 correction of data• Spectra saved with date and time stamped name• Specially configured file contains all chemometric models and analysis information• Final results selection allows best model to be selected for given range• Report concentration results as ppm, mg/m3 or %Vol

and are factor based, constructing amodel with the optimum numberof factors that models the specifiedgas in the full matrix.

There is no limit to the number ofgases that can be measured at onetime with PAS software. Samplespectra are stored as separate fileson the computer, they can be easilyreanalysed with different analysissettings for previously unknowninterfering gases. PLS models arebuilt on a component specific basis

and are factor based, constructing amodel with the optimum numberof factors that models the specifiedgas in the full matrix.

There is no limit to the number ofgases that can be measured at onetime with PAS software. Samplespectra are stored as separate fileson the computer, they can be easilyreanalysed with different analysissettings for previously unknownspecies retrospectively.



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TEST PARAMETERS

General Parameters

Measuring Principle FTIR (Fourier Transform Infrared) Spectroscopy

Performance Unlimited simultaneous analysis of multiple gases, preloaded analysis for 21 gas species

Operating Temperature +5°C to +35°C, noncondensing, dust free ambient air

Storage Temperature 20 +60°C

Response Time (T90) Depending on the gas flow and measurement time

Resolution 4 cm–1 standard. 1 cm–1 optional

Wavenumber Range 399.718 – 5000.088 cm1

Gas Cell Niplated aluminium gas cell of volume 0.3 litresAmbient pressure during normal operation

Gas Cell Temperature 180°C (variable)

Gas Cell Volume 0.3 litres

Gas Cell Path Length 4.2 m (standard, but changeable)

Optics Nonhygroscopic Zinc Selenide beam splitterBarium Fluoride gas cell windows (changeable dependent on application)Diamond turned aluminium gas cell mirrors with protected gold coating

Reference Laser Solid state laser

Source MidIR source, ceramic GlobarWith advanced electronic stabilisation and temperature measurement

Detector DTGS

Sample Gas Noncondensing, particle free

Flow Rate Approximately 4 l/min (variable via external flow orifice)

Sample Gas Pressure Ambient

Dimensions 600 mm (L) × 600 mm (W) × 1400 mm (H) (not incl. castors or plinth)

Net Weight Approx. 125 kg

Measuring Parameters

Zero Point Calibration 24 hours, calibration with Nitrogen (5.0 or higher N2 recommended)

Zero Point Drift < 2% of measuring range per zero point calibration interval

Sensitivity Drift < 2% of measuring range over 24 hours

Linearity Deviation < 2% of measuring range

Temperature Drifts < 2% of measuring range per 10 K temperature change

Detectable Limits Gas dependent, but all <2% measurement range

Pressure Influence 1% per 1% change in sample pressure. Pressure measured and compensated for in gas cell



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Heated Line

Tube Size 4 mm ID/6 mm OD

Core Material PTFE core

Operating Pressure Max. 400 kPa (4 bar)

Temperature 180°C

Fittings 6mm Swagelok

Power Supply 230 VAC or 115 VAC

Power Density 90 Watts/metre

Length Varies for different application requirement. Lengths from 3 metre to 50 metre can be supplied

Electrical Connections

Main Supply 115V or 230V 50/60Hz

Power Consumption The full system including the FTIR Gas Analyser, Touchscreen PC, Heated Filter/Valve Sampling Unit, SamplingProbe and Heated Sampling Lines approximately 2 kW

Gas Species

• H2O • CO2 • CO • NO • NO2 • N2O • SO2

• HCl • HCN • HBr • HF • NH3 • CH4 • C2H6

• C3H8 • C2H4 • C6H14 • HCHO • C6H5OH • C3H4O • COF2

GAS UNIT RANGES

H2O %Vol 030

CO2 %Vol 02 05

CO ppm 03000 010000

NO ppm 0500

NO2 ppm 0500

N2O ppm 0500

SO2 ppm 01000

HCl ppm 0100 05000

HCN ppm 0500

HBr ppm 0100 01000

HF ppm 0100 01000

NH3 ppm 0500

CH4 (Methane) ppm 01000

C2H6 (Ethane) ppm 0100

C3H8 (Propane) ppm 0100

C2H4 (Ethene) ppm 0100

C6H14 (nHexane) ppm 0100

HCHO (Formaldehyde) ppm 020

C6H5OH (Phenol) ppm 0200

C3H4O (Acrolein) ppm 0300

COF2 (Carbonyl Fluoride) ppm 050

Due to the continuous development policy of FTT technical changes could be made without prior notice.



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SERVICES

Power Supply 230 VAC – 50/60 Hz – 13 A

Gas Supplies Purge gas: dry, filtered, oilfree compressed air at 1.0 bar, flow rate approx. 1 ℓ/min, with pressure regulatorZero gas: Nitrogen 5.0 at 1.0 bar, flow rate approx. 3 ℓ/min, with pressure regulatorCheck gas: typically 200 ppm Sulphur Dioxide + 90 ppm Ethylene + balance of Nitrogen at 1.0 bar, flow rate approx. 3 ℓ/min, with pressure regulator

Extraction Exhaust from the analyser flowing at 4 ℓ/min through a 6 mm tube must be vented safely to atmosphere

Operating environment 15⁰C25⁰C, noncondensing atmosphere



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Unrivalled Experience inDesign and ManufacturingFTT’s site in East Grinstead, is home to the largest group of fire scientists andinstrumentation design engineers working on fire testing instrumentation, and is at the heart of our design andmanufacturing. For more than 30 years FTT has provided the highest quality instruments and service for fire testing and research professionals worldwide, directly and through its extensive global sales and support network.

Quality• Worldclass

manufacturing inaccordance withmultiple internationaland national standards,including: EN, ISO &ASTM

• ISO 9001, ISO 14001certified

Integrity• A dedicated team

passionate about firetestinginstrumentation andcontinuous productimprovement

• Delivering reliable,robust and easytouseinstruments for thepast 30 years

Excellence• A worldclass team

made up of qualifiedfire scientists,mechanical, electricaland electronic fireinstrument designengineers andproduction, installationand maintenanceengineers

Global• Worldwide

distribution networkfor global sales,installations, training,maintenance andtechnical support

• Leading global supplierof the ConeCalorimeter, LargeScale Calorimeter, NBSSmoke Chamber andOxygen Index


ftir an advanced ftir for toxic gas analysis digital...ftir: an advanced ftir for toxic gas analysis...

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