MSA Customer Training Gas Detection Principles.pdf
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Transcript of MSA Customer Training Gas Detection Principles.pdf
© MSA 2007
Gas DetectionGas Detection
© MSA 2007
Measuring, why?Measuring, why?
To take care of workers health and life - prevent dangerous situations
To protect the inventory for damage
To fulfill local / national laws or regulations
© MSA 2007
Measuring, what?Measuring, what?
Ex(Vol%)(%LEL)(%UEG)
Ox(Vol%)
Tox(ppm)
(ml/m3)(mg/m3)
HazardousGases or vapors
© MSA 2007
Combustion
Oxygen
Fuel
Ignition
© MSA 2007
What is Combustion?What is Combustion?
Combustion = reaction between flammable gas and OxygenCombustion without Oxygen = impossibleFor combustion right ratio between combustible gas and Oxygen is neededSufficient ignition-energy will increase the temperature and a reaction will take place
© MSA 2007
DefinitionsDefinitions
Combustible Gases
Ex Explosive (measuring range)Comb CombustibleLEL Lower Explosive LimitUEL Upper Explosive LimitVol% Volume Per cent
© MSA 2007
LEL AND UEL
• Below Lower Explosive Limitnot enough fuel to ignite
• Above Upper Explosive Limitnot enough oxygen
• Between LEL and UEL
Atmosphere is Explosive *VALUES ACCORDING TO NATIONAL ELECTRIC CODE (NEC)
© MSA 2007
METHANE
5 15
LowerFlammableLimit
UpperFlammableLimit
GAS BY VOLUME
© MSA 2007
4 75GAS BY VOLUME
HYDROGEN
© MSA 2007
Acetone 2.5% by volume
Acetylene 2.5% by volume
Benzene 1.2% by volume
Butane 1.9% by volume
Butyl Alcohol (Butanol) 1.4% by volum
Diethyl Ether 1.9% by volume
Ethane 3.0% by volume
Ethyl Alcohol (Ethanol) 3.3% by volume
Ethylene 2.7% by volume
Ethylene Oxide 2.7% by volume
Hexane 1.1% by volume
Hydrogen 4.0% by volume
Isopropyl Alcohol (Isopropanol) 2.0% by volume
Methane 5.0% by volume
Methyl Alcohol (Methanol) 6.0% by volume
Methyl Ethyl Ketone 1.4% by volume
n-Pentane 1.4% by volume
Propane 2.1% by volume
Propylene 2.0% by volume
Styrene 0.9% by volume
Toluene 1.1% by volume
Xylene 1.1% by volume
*VALUES ACCORDING TO NATIONAL ELECTRIC CODE (NEC)
© MSA 2007
Ignition energyIgnition energy
Minimum energy (in mJ) required to ignite a combustible vapor/gas in air
Example:Hydrogen: 0,01 mJMethane: 0,28 mJHexane: 0,24 mJAmmonia: 680,00 mJ
© MSA 2007
Vapor PressureVapor Pressure
The vapor pressure is expressed in mbar at a given temperatureSubstances with a boiling point of > 350o C have a negligible value (almost no vaporization)
© MSA 2007
© MSA 2007
Flash PointFlash Point
Liquid classification related to flash point
< 21o Celsius≥ 21o Celsius en ≤ 55o Celsius> 55o Celsius en < 100o Celsius≥ 100o Celsius
© MSA 2007
Flash Point
© MSA 2007
Measuring Methods CombustiblesMeasuring Methods Combustibles0-100% LEL range
Catalytic Oxidizing (also leak)Semi Conductor (also leak)IR FID (leak)PID
0-100 Vol% / %GasThermal ConductivitySemi ConductorIR
© MSA 2007
Platinum thread
The PelementHuman Hair
© MSA 2007
Ceramic bead
The MSA Pelement
Catalytic material (Palladium)
© MSA 2007
CatalystCatalyst
A (chemical) substance which starts a process and/or accelerates it and ends up unchanged
Example: Burned ashes in combination with sugar
© MSA 2007
The MSA PelementNeedle
© MSA 2007
Glass coating on passive pelement(compensator)
The MSA Pelement
No gas entryPossible!
© MSA 2007
Wheatstone Bridge
© MSA 2007
Wheatstone BridgeWheatstone Bridge
Used by catalytic, and the thermal conductivity measuring methodsAlteration of the electrical resistance, due to changing of the temperature The unbalance is electronically amplified and displayed as a value corresponding with the gas concentration
© MSA 2007
The Catalytic SensorThe Catalytic Sensor
♦ Operating temperature 450° C or higher
♦ Detection sensor (D) is catalytic active
♦ Compensation sensor (K) is catalytic inactive
D-Sensor C-Sensor
18 LEL
© MSA 2007
Variety Types of Instruments available with Catalytic LEL Sensor
Variety Types of Instruments available with Catalytic LEL Sensor
© MSA 2007
MonitoringMonitoring
Observe:DensityAir flowTemperature
CHCH44
CC44HH1010
HH22SS
CHCH44COCO
© MSA 2007
1009080706050403020100
0 10 20 30 40 50 60 70 80 90 100
METERREADING
% LEL
2 to 1RATIO
METHANE
100 % LEL METHANE = 5 % BY VOLUME
PENTANE
100 % LEL PENTANE = 1.5 % BY VOLUME
© MSA 2007
1009080706050403020100
0 10 20 30 40 50 60 70 80 90 100
PENTANE
METERREADING
% LEL
2 to 1RATIO
100 % LEL METHANE = 5 % BY VOLUME
100 % LEL PENTANE = 1.5 % BY VOLUME
METHANE CALI BRATED TO THE SAFE SIDE
C2H2H2
GASOLINE
NH3
CH4 CO
© MSA 2007
Catalytic Detector
Requires 9% for accurate readings
Minimum 4% required for explosion
© MSA 2007
© MSA 2007
Sensor Poisoning
Responds only to combustible gases
Poisons (H2S, silicons, Freons, Fluorinated Hydrocarbons) can decrease the sensitivity
© MSA 2007
Thermal Conductivity PrincipleThermal Conductivity Principle
Sample of the gas creates an unbalance in temperature, due to exchange or admission of heatThe unbalance is electronically amplified and displayed as a value corresponding with the gas concentration
© MSA 2007
Thermal conductivity SensorThermal conductivity Sensor
♦ Operating temperature 450° C or higher
♦ Sensors are catalytic inactive
♦ Resistor change due to heat exchange 26
© MSA 2007
INFRARED SENSORSINFRARED SENSORSThe IR sensors uses the gases property to absorb infrared radiation at different wave lengths.
© MSA 2007
HC-LEL, CO2, CO
Refrigerants / Toxic gases
3-5.5 μ 8-15 μ
© MSA 2007
IR SensorIR Sensor
© MSA 2007
Open Path IR SensorOpen Path IR Sensor
© MSA 2007
Open Path IR SensorOpen Path IR Sensor
© MSA 2007
LEL Meter (1)LEL Meter (1)
© MSA 2007
LEL Meter (2)LEL Meter (2)
© MSA 2007
Catalytic x IRCatalytic IR
Implantation cost
Low High
Maintenance cost
High Low
Life 2 to 3,5 years 5 to 10 yearsMonthly Biannual - AnnualZero + Span Zero (usually)
Detects almost any combustible gas
Don’t detect diatomic gases (H2)
Sensible to poisoning substances
Don’t affected by other compounds interference
Lack of sensibility with the continuous gas exposure
Sensibility don’t changes with the continuous gas exposure
Simple Maintenance Maintenance on the manufacturer
Needs Oxygen Works on inert atmospheres
Limitations
Calibration
© MSA 2007
Measuring Methods ToxMeasuring Methods Tox
Electro ChemicalDetector Tubes (Reagents)Semi Conductor
PID Photo Ionization DetectorFID Flame Ionization DetectorIR Infra Red
© MSA 2007
DefinitionsDefinitions
PPM Part Per Million (0,000.1 vol%)
PPB Part Per Billion (0,000.000.1 vol%)
TLV Treshold Limit Value
TWA Time Weighted Average (8 hrs)
LTEL Long Term Exposure Level (8 hrs)
STEL Short Term Exposure Level (15 min)
T90 Response Time
© MSA 2007
T90 Response Time
100 -
80 -
60 -
40 -
20 -
0 -
%%
90
2,5 T
63,2
1T
95
3T
98,2
4T
99,34
5T
99,76
6T
99,9
7T
100
8T2T
86,5
Time = n x T (seconds)= % of end value
© MSA 2007
T90 Response Time
100 -
80 -
60 -
40 -
20 -
0 -
%%
90
2,5 T
63,2
1T
95
3T
98,2
4T
99,34
5T
99,76
6T
99,9
7T
100
8T2T
86,5
Time = n x T (seconds)= % of end value
© MSA 2007
Effects of low OxygenEffects of low Oxygen
Above 19,5% Necessary for normal life
14 - 19,5 %Threatening danger, don’t enter the room, use independent breathing protection (SCBA)
12 - 14 %Deep breathing, higher pulse rate, worsecoordination
10 - 12 %Faster and superficial breathing, dizzy, bad judgement, blue lips
8 - 10 % Nausea, vomit, unconscious, pale6 minutes = 50% fatal, 8 minutes = 100% fatal
4%Coma in 40 seconds, spasm, breathing stops, death
0% Unconscious, death in 10 seconds
EFFECTS OF LOW OXYGEN
© MSA 2007
Electrochemical O2 SensorElectrochemical O2 SensorMembraneCounter Electrode
OXYGEN
Membrane
Signal7-15 mV
Sensing ElectrodeElectrolyte10% KOH
Reaction at Sensing Electrode O2+2H2O+4e => 4OH
Reaction at Counter Electrode 2Pb+4OH => 2PbO+2H2O+4e
Nett reaction 2Pb+O2 => 2PbO
LED is being consumed!
Pb
Au
© MSA 2007
Measuring CO2 by O2displacement?Measuring CO2 by O2displacement?
CO2 is heavier than OxygenTWA value = 5000 ppm (0.5% Vol)0.5% CO2 displacement = 0.1% O2
O2 Alarm = 19.5%19.5% O2 = 8% CO2
Answer is NO!!
© MSA 2007
CO2 in relation to O2
25 -
20 -
15 -
10 -
5 -
0 -0,5
20,83
2,0
20,53
8,0
19,3320,93
0,03
Vol%
O2
Vol% CarbonVol% Carbon DioxideDioxide
© MSA 2007
Effects of CO2Effects of CO2
4-6 Vol% 40.000-60.000 ppmchanges of bleeding in veinsin the brain, head aches, dizziness
6-8 Vol% 60.000-80.000 ppmparalyzing as if curare has been used
8-10 Vol% 80.000-100.000 ppm
extinguishing of a burning candle, spasm, fast unconsciousness, death
20 Vol% 200.000 ppmDeadly within a few seconds
0.5% Vol 5000 ppm TWA Value
Effects of CO2
© MSA 2007
Effects of COEffects of CO
PPM Vol% Effect25 0.0025 TWA value, safe during 8hrs
200 0.02 Headache, discomfort
800 0.08 Dizziness, nausea, unconsciousness within 2 hrs
1600 0.16 Lethal within 1 hour
Effect of Carbon Monoxide on People
© MSA 2007
PhysiologicalPhysiological
PPM Vol% Effect0.1 0.00001 Dirty smell (rotten eggs)10 0.001 TLV value, safe during 8 hrs
100 0.01Paralyzing smelling nerves in 3-15 min. Irritation on eyes and throat. Life danger after exposure of 8-48 hrs
200 0.02Smelling nerves immediately paralyzed, Irritation on eyes and throat. Life danger after exposure of 4-8 hrs
500 0.05
Disturbance of balance, paralyzing of respiration in 30-45 min. Immediate need for artificial respiration, lethal after exposure of 30-60 minutes
700 0.07Fast unconscious (max. 15 min), respiration stops, lethal after exposure of 2-15 minutes
1000 0.1Immediately unconscious, brain damage, lethal after 3 minutes
Effect of Hydrogen Sulfide on People
© MSA 2007
Important Properties of H2SImportant Properties of H2S
Relative gas density: 1.2Heavier then air, may accumulate at ground level in dips or holes
Highly water solubleWater can contain large amounts of H2S which may evaporate quickly at temperature or pressure changesIs absorbed if tubing used for sampling or calibration is wet. It has to made sure that they are absolutely dry.
© MSA 2007
Electrochemical H2S SensorElectrochemical H2S Sensor
Reaction at Sensing Electrode H2S+4H2O =>Pt=> CO2+H2SO4+8H+8e
Reaction at Counter Electrode 2O2+8H+8e =>Au=> 4H2O
Nett reaction H2S +2O2 => O2+ H2SO4
CounterElectrode
Membrane
Membrane
OP
Ref. Electrode
Sensing Electrode
Electrolyte
6N H2SO4Ref. Voltage
Signal
HYDROGEN SULFIDE
OP
Au
Pt
Au
© MSA 2007
RH
ISOBUTEN
0,0 ppm⏐⏐⏐⏐⏐⏐
RH
e-
RH+
h x v
13.4
The gas sample is transferred into the measuring chamber of the PID.
One part of the sample is ionized by UV-light.
The electrical charged particles formed move to the oppositely charged electrode and get discharged
The electrical current is proportional to the concentration of the component(s)
+
-
PIDPID PPhoto hoto IIonization onization How does it work?How does it work?
DDetectoretector
© MSA 2007
PIDPID
Most substances can be ionizedSome easier than others, depends on their ionization potential
Measured on an eV [electron volt] scale
From 7 to about 16
© MSA 2007
Ionize - Convert into “+” charged ionsIon - An electrically charged particle or group of atomsPotential - Ability to be ionizedIP is measured in Electron Volts [eV]
PID [ Ionisation Potential ]PID [ Ionisation Potential Ionisation Potential ]
© MSA 2007
Enough energy to Enough energy to ionize any compound ionize any compound less than 9.6 eVless than 9.6 eV
Enough energy to Enough energy to ionize any ionize any compound less than compound less than 10.6 10.6 eVeV
•Toluene 8.83 eV
•Benzene 9.25 eV
•Styrene 8.47 eV
•Propy alcohol 10.20 eV
•Phosphine 9.87 eV
•Vinyl chloride 10.00 eV
Enough energy to Enough energy to ionize any compound ionize any compound less than 11.7 less than 11.7 eVeV
•Methylene chloride 11.32 eV
•Chloroform 11.37 eV
Lamps Come in Different EnergiesLamps Come in Different Energies
PID [ eV Scale ]PID [ eV Scale eV Scale ]
© MSA 2007
PID [Why not 11.7eV as standard?]PID [Why not 11.7eV as standard?Why not 11.7eV as standard?]
The window is made up of lithium fluoride
Very hydroscopic = absorbs water vaporDecrease the transmission of the photons!Over time you lose the ionization energy!!
© MSA 2007
What is a VOCVOC?
VVolatile - Compounds in the vapor state at a low temperature
OOrganic - Compounds containing carbon atoms
CCompound - Composed of two or more elements
© MSA 2007
Examples of VOCs
BenzeneHexaneAcetoneTolueneXyleneVinyl Chloride
ButadieneCumeneEthyleneStyreneMethyl Ethyl Ketone
Hundreds of others !!Hundreds of others !!
© MSA 2007
ApplicationsApplications
Leak detection from process equipmentValvesFlanges and other connectionsPump or compressor sealsPressure relief devicesProcess drainsOpen-ended lines Degassing & vessel vents
© MSA 2007
Variety of Instruments available with Sensors for Toxic gases
Variety of Instruments available with Sensors for Toxic gases
© MSA 2007
Selection Criteria for InstrumentsSelection Criteria for InstrumentsApplication
Portable or PermanentWhich GasesSingle or Multi GasPumped or Diffusion
ApprovalsEx ApprovalPerformance approvalVerification of most critical Properties by independent test house
Supplier CompetenceSupplier Availability
© MSA 2007
Selection Criteria for InstrumentsSelection Criteria for Instruments
Trust
© MSA 2007
What is a Confined Space(OSHA 29CFR 1910.146)What is a Confined Space(OSHA 29CFR 1910.146)
Confined spaces exist in many settings. In any area:Not intended or designed primarily as a place of workIs large enough for a worker to enter and perform workHas limited or restricted means for entry or exitIs not designed for continuous human occupancy
© MSA 2007
What is a Confined Space(OSHA 29CFR 1910.146)What is a Confined Space(OSHA 29CFR 1910.146)
Where the potential for engulfement,inadequate ventilation, a contaminated atmosphere or Oxygen deficient atmosphere may exist
© MSA 2007
What must be done before entering a confined spaceWhat must be done before entering a confined space
Obtain an entry permit from the employerTest for a safe Oxygen levelTest for Toxic gases, vapours or fumesTest for flammable gases or vapoursVentilate and cleanEnsure a stand-by person is present (with PPE)Wear appropriate PPE as necessary
© MSA 2007
HOW TO OPERATE IN A CONFINED SPACEHOW TO OPERATE IN A CONFINED HOW TO OPERATE IN A CONFINED SPACESPACE
© MSA 2007
Continuous TestingContinuous TestingContinuous Testing meansleaving the instruments on during the entire time that workers occupy the confinedspace. Through continuous monitoring, workers are alerted immediately to any atmospheric changes in the confined space
© MSA 2007
VAPOR DENSITYVAPOR DENSITYWhere to detect the gas hazard:Take samples at the top, middle and bottom of a confined space
© MSA 2007
SAFETY TIPSSAFETY TIPS
Never entry a confined space without an entry permitTest for hazards-know how to use the equipment and interpret the resultsLeave immediately if you experience dizziness,headedness or difficultiesStay alert at all times-do not take your safety as granted
© MSA 2007
CalibrationCalibration
OSHA guidelinesNIOSH standard for confined spacesNFPA 306 for control of gas hazards on sea vesselAll of these standards recommend calibration checks prior to each use.Use a known concentration of test gas.Do not use self-contrived techniques whichcan lead to misleading conclusions about instrument’s ability to detect gases
© MSA 2007
Calibration StandardCalibration Standard
The National Institute of Occupational Safety & Health’s ( NIOSH ) Confined Workplaces Training Resources Manual says the only way to be sure an instrument is performing properly is to check the calibration on a daily basis
© MSA 2007
Built-in boot
Lithium Ion battertechnology
Best in class triple alarm system
Missing sensor alarm
SOLARIS
© MSA 2007
Detection of combustible gases, O2, H2S, CO, NH3, Cl2, NO2, HCN, O3, COCl2, PH3, SO2, CO2, ClO2
Very largeeasy to read graphicdisplay for quickdata viewing
Robust,easy to gripdesign
Simple one handoperation
Clear andintuitive to use
IR – Sensor Technologyfor CO2, HC, CH4
ORIONplusplus Compact. Durable. Ingenious.Compact. Durable. Ingenious.[ The handiest 5 gas detector under the starsThe handiest 5 gas detector under the stars ]
© MSA 2007
Detection of combustible gases, Oxygen, Hydrogen Sulfideand Carbon monoxide
Very largeeasy to read graphicdisplay for quickdata viewing
Robust,easy to gripdesign
Simple one handoperation
Extremely loud horn
PID – Sensor Technologyfor VOC like Benzene,JP8
SIRIUSSIRIUS®® [Compact and Versatile Compact and Versatile ––for all your needsfor all your needs]
© MSA 2007
Audible alarm 95dB at 30cm
Easy to read displayshows gas concentration
Broad range of sensors:Detection of either O2, H2S, CO, Cl2, HCN, ClO2, SO2, NO2, NH3 and PH3with replaceable sensors
Replaceable battery
Bump test check-mark displayed for 24 hours
Battery life indicator
Simple one buttonoperation
Highly visible LEDs
ALTAIR PRO [Main Features]ALTAIR PRO [Main Features]
Robust, easy to grip design
© MSA 2007
High-end Single-Gas Detectormeasures and displays gas concentrationcan be turned on and off
Available for:O2CO, CO Fire, CO SteelH2SNH3Cl2ClO2HCNNO2PH3SO2
ALTAIR PRO [Product Description]ALTAIR PRO [Product Description]
© MSA 2007
Economical bump test stationDesigned for use with ALTAIR and ALTAIR PROManual and automatic versions available
ALTAIR PRO [ALTAIR QuickCheck]ALTAIR PRO [ALTAIR QuickCheck]
Instrument cradle
Powered by AC power supply
Easy to read LEDs
Connection to gas cylinder
© MSA 2007
GALAXY [ Overview ]GALAXY [ OverviewOverview ]
Standalone StationBump check stationCalibration stationCharging station
Multiple Bump check & calibration System for SOLARIS, SIRIUS & ORIONSOLARIS, SIRIUS & ORION
© MSA 2007
GALAXY [ Overview ]GALAXY [ Overview Overview ]
Protectivesystem door
Connection for multiple system
Easy-to-understand visual and audible indicators
OPTIONAL: Wired orwirelessnetworkinterfacemodule,batterypack, orprotectiveend cap
© MSA 2007
GALAXY [ Operating Instructions ]GALAXY [ OperatingOperating Instructions Instructions ]
Open the doorInsert the instrumentClose the door
© MSA 2007
Thank You!Thank You!