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A Practical Guide to Industrial Gas Detection from Honeywell Analytics
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Agenda
• Why Monitor Gas?• Hazard Recognition• Sensor Technology Overview• Application Summary• Maintaining a Working System• Trends in Gas Detection• Summary
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Why Monitor for Gases?
• Protect Personnel• Protect Infrastructure• Protect the Environment• Gather Evidence• Maintain Legal Compliance• Control Processes/Gather
Data• Improve Productivity• Confirm a Safe Area can be
Re-occupied
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What does Gas Monitoring check for?
• Build up of Flammable Gas levels• Release of Toxic Gases & Volatile Compounds• Chemical Warfare Agents• Oxygen Deficiency or Enrichment
A gas detector system indicates the presence of these hazardous events and enables executive actions to be implemented in accordance with
appropriate safety protocols
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Gas Monitoring System
• A complete gas monitoring system goes beyond simple air monitoring.• Complete systems may include the following:
– Gas detection equipment to detect the presence of target materials– Intelligent controls to facilitate
• Automatic shut off of target material
• Initiation of evacuation alarms and strobes
• Interface with other building systems and/or fire alarm systems
– Networked computer system with graphical user interfaces to display gas monitoring point locations and gas levels present
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Gas Hazards Categorized
ToxicRisk of poisoning,e.g. Carbon Monoxide, Phosgene, Chlorine, GB-Sarin
AsphyxiantRisk of suffocation,e.g. Oxygen deficiency, Nitrogen, Carbon Dioxide
Flammable Risk of fire and or explosion,e.g. Methane, Butane, Propane
There are three main types of gas hazard
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Flammable Risk: % LEL
FUEL
HEATAIR
Too Rich
Too Lean
Flammable RangeFIRE
100% v/v gas0% v/v air
UEL - (upper explosive limit)
LEL - (lower explosive limit)
0% v/v gas100% v/v air
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Toxic Risk: parts per million (ppm)
Effects of exposure to Carbon Monoxide
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Asphyxiant (oxygen deficiency) Risk
20.9 % v/v normal
16 % v/v depletion
6 % v/v fatal
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Gas Detection Application Overview
• Personal Monitoring– Alerting the operator to the presence of harmful gases in the
vicinity of their personal working zone– Typically a single or multi gas configuration is used
• Fixed Gas Detection– A local sensor connected to a control and/or annunication
system that detects the gas levels and sends signals to other control devices to take executive actions such as alarms & strobes, turn on ventilation, valve switch off etc.
– Typically used to protect the plant and the workers within the process area
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Portable Gas Detection Applications• Confined Space Entry
– Tanker / Ship / Tunnel– Container Unit / Pipeline
• Chemical Spill / Environmental Discharge– Detection /Assessment
– Rescue– Remediation
• Rescue– Fire /Explosion / Natural Disaster / Vehicle– Hazmat
• First Responder– Unknown Materials – Suspected or Threatened Terror Incident
• Law Enforcement– Drug Labs
– Customs Inspection– VIP Protection– Arson Investigation
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Fixed Gas Monitoring Systems
Sieger Searchline Excel open
path gas detector is
used to detect
potential methane gas release from an offshore
platform
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Sensors are part of an Integrated System
Transmitters
Analyzers
Control Racks
Alarms
Strobes
HMI
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Typical Monitoring Point Locations
Ambient Air(Operator Breathing Zone)
Exhausted Enclosure(Tool Gas Box)
Gas Supply Exhaust(Gas Cabinet and ValveManifold Boxes)
Vacuum Pump Enclosures(Highly Toxic Gases)
Gas Storage Locations(Gas Storage Bunkers)
Stack/Emissions Monitoring(depending on permit conditions)
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Selecting the Right Sensor• Many technologies are available• No single technology can measure all your needs• Devise selection criteria that meet your specific r equirements
– Specificity– Sensitivity / Lower Detection Limit– Speed of Response– Range of Gases– Cost of Ownership /Cost of Installation– Ease of Maintenance – Reliability– Application– Compliance Criteria
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Broad Selection of Gas Sensor Technologies
• Catalytic Bead• Thermal Conductivity Sensor• Electro Chemical Cell• Infra Red & FT IR• Photo Ionization Detector• Surface Acoustic Wave• Colorimetric Tape & Tubes• Gas Chromatography & Mass
Spectrometry• Ion Mobility Spectroscopy• Flame Ionization Detector
Practical
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Catalytic Gas Detection: Flammable
• Pellistor (Pellet resistor)– Catalytic beads – low cost Flam detection
– Requires Oxygen to operate
• 450 - 500OC operating temp– Gas combustion on sensitive bead
• Sensitive bead– Platinum wire coil
– Rhodium catalyst
• Non sensitive bead– Gas coated or restricted inlet
– Stability from pressure & temp changes
• Poison resistant– Long life porous structure
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Electrochemical (EC) Cells
• Speed of response– 10-90 seconds (T90)
• Sensitivity– Part Per Billion / Million (ppb /ppm)
• Life– 1 to 2 years
• Range– Large number of detectable gas
• Low powered– Ideal for portable devices
• Costs– Low initial cost
– Routine maintenance costs
Gas permeable membrane
Measuring electrode
Reference electrode
ElectrolyteV
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Photo Ionization Detector PID for VOCs
anode + vecathode - ve
+ +
Broad spectrum
Not truly specific in a mixed VOC environment
Relatively expensive purchase cost
Needs frequent calibration
A
Air molecule
VOC molecule
Ionized VOC
Electron
+
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Infrared Sensors: Flammable & CO2
Sample detector
Reference detector
Gas Flow
Permeable Sinter
IR active molecule absorbs a portion of the transmitted light energy; the detectors see this as
a decrease in light intensity that can be characterized by the type and number of
molecules present
N2, O2 molecules
IR active molecule
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Infrared Gas Detection
• All flammable hydrocarbon gas molecules absorb light in the infrared region of the Spectrum
• Many toxic gases have IR absorption• Absorption can be directly related to
actual ppm or % LEL readings• Point Infrared and Fourier Transform
(FT) IR devices measure wide variety of gases
• Will not detect di-atoms• Costs
– High cost of installation– Low ongoing maintenance
IR Spectrum of Methane Gas at 3.4 microns
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Colorimetric Gas Detection: Tube Based
�Lightweight and easy to operate via hand held pumps
�Quick visual screening and first screen quantitative
�Physical evidence of chemical presence
�Pre-calibrated for immediate deployment
�Costs: Low cost per basic test
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Colorimetric Gas Detection: Tape Based
• Speed of response– 5-15 seconds
• Ideal for very toxic gases– AsH3, SiH4, Cl2, NF3, HF, NH3,
COCl2, N2H4 etc.
– High Sensitivity– Part Per Trillion (ppt) to ppm
levels
• Low cross sensitivities• No calibration required• Physical evidence of gas • Higher Cost per Point but lower
cost of maintenance
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SAW - Surface Acoustic Wave
• Detect nerve & blister agents from 1 picogram of vapor
• Ideal for nerve and blister agents– GA, GB, GD, GF
– Mustard Gas, Phosgene, HCN
• Solid state sensor• Arrays specific to certain
groups for sensitivity• Environmentally sensitive to
extremes of temperature and humidity
• Cost: high, specialist sensor
Piezoelectric crystals that detect the mass of chemical vapors absorbed onto coatings and absorption changes detected
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Ion Mobility Spectroscopy
• Portable detection of chemical warfare agents
• Radioactive ionization of gaseous sample and detection of ionized molecules across a known electrode system
• Specific to a narrow group of chemicals• Cost: relatively expensive per portable unit
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Semiconductor Gas Detection
• Metal oxide film deposited onto a silicon slice– Similar to computer Silicon ‘Chips’
• Surface heated to 200-400ºC depending on design– Thin film, thick film, MOS, MMOS
• Absorption of the sample gas on the oxide surface plus catalytic oxidation– Causes change of electrical resistance– Resistance change can be related to
sample gas concentration
Heater
Metal Oxide
Voltage Source
Meter
Silicon
Gas Sample
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Comparison of Gas Detection Technologies
Can not detect all flammable gases; not able to differentiate between mixtures of gases.
Detects a broad array of volatile compounds. Simple to use.PID
DisadvantagesAdvantagesSensor Type
Higher initial cost of installation.Highly sensitive and selective for toxic gases. Leaves physical evidence of the gas exposure.Colorimetric
Expensive dedicated sensor. Not able to work in all environmental conditions.
Detects nerve agents and other CWA.IMS /SAW
Susceptible to contaminants and changes in environmental conditions. Non linear response effects complexity.
Mechanically robust, works well in constant high humidity conditions.Semiconductor
Not all gases have IR absorption. Sequential monitoring is slower on multi point analyzers. More user expertise required.
Uses a physical rather than chemical technique. Less sensitive to calibration errors. No unseen failure modes. Can be used in inert atmospheres.
Infrared
Failure modes are unrevealed unless advanced monitoring techniques used.
Measures toxic gases in relatively low concentrations. Wide range of gases can be detected.
Electrochemical
Can be poisoned by lead, chlorine and silicones that remains an unrevealed failure mode. Requires oxygen or air to work.
Simple, measures flammability of gases. Low cost proven technology.Catalytic
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Maintaining a Gas Detection System
• Service support is important– Quick response to needs/knowledgeable service engineers– Provide site-specific training
• Bump tests • Calibrations / check the gas quality• Battery recharging• Replacement sensors at certain timescales• Analog output calibration• Check programming logic / relays• Data download
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Key Issues for Portable Gas Detectors
• Portability – wearable versus ‘luggable’• Specificity to discrete gases• Immune from false alarms and non-target vapors• Broadest array of sensors per platform• Speed of response – real time display• Ease of use – working under stress and using PPE• Communications – data stream to other locations• Traceability – calibrated and proven for accuracy• Stealth versions when approaching criminal scenes
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Imminent Trends in Gas Detection• New lower TLV requirements change gas detection landscape
– Some sensors can’t see new low levels– Proposed AsH3 TLV
• New SEMI & UL codes affect gas detector design /install– Site locations and Authority Having Jurisdiction may require different
monitoring schemes and coverages• Increase use of WIRELESS technology
– Wireless networks and GPS locators –– linked perimeters and operators
• Easier interconnectivity of field devices (PoE)– Ethernet capability easily networks all components together
• Continued reduction of perfluorocompounds– ISO 14001 and “Green manufacturing” may require limiting releases of
certain compounds• Further need to monitor and ensure safe area for longer term
exposure– Protect corporation against long-term liability issues– Prove odors are not over-exposing employees
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Imminent Trends in Gas Detection
• More sensors per platform• Lighter weight; more portable; longer battery lifetime• Greater automation on species detection• Easier to configure – web based GUI, docking stations, lower cost
of maintenance• More solid state technologies: greater specificity /speed of
detection– Nano sensors
– Bio sensors– Laser based spectroscopy techniques
• Calibration free; immunity to environmental extremes
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Wireless Communications Growth
Communications between detectors,
operators and supervisors
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Wired Trends - PoE/PLC Control System
PLC
Annunciators with Annunciators with Annunciators with Annunciators with
local or network controllocal or network controllocal or network controllocal or network control
AudibleAudibleAudibleAudible
HMI StationHMI StationHMI StationHMI StationCimplicity, etc
Standard 100BaseT Standard 100BaseT Standard 100BaseT Standard 100BaseT Network InfrastructureNetwork InfrastructureNetwork InfrastructureNetwork Infrastructure
Or PoE Or PoE Or PoE Or PoE
PoE SwitchPoE SwitchPoE SwitchPoE Switch(16(16(16(16----24 port)24 port)24 port)24 port)
MIDAS Gas DetectorsMIDAS Gas DetectorsMIDAS Gas DetectorsMIDAS Gas DetectorsModbus/TCP Servers (slaves)Modbus/TCP Servers (slaves)Modbus/TCP Servers (slaves)Modbus/TCP Servers (slaves) Modbus/TCP Clients (master)Modbus/TCP Clients (master)Modbus/TCP Clients (master)Modbus/TCP Clients (master)
PoE SwitchPoE SwitchPoE SwitchPoE Switch(16(16(16(16----24 port)24 port)24 port)24 port)
To other NetworksTo other NetworksTo other NetworksTo other Networks
VisibleVisibleVisibleVisibleAudibleAudibleAudibleAudible VisibleVisibleVisibleVisible
(master)(master)(master)(master)
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Trends in Legislation
• International Safety Equipment Association (ISEA) / ANSI new standards for gas detection for incident response and confined space entry
• Canadian law for communications in confined space entry• More CO requirement• Lowering of certain TLVs• OSHA Interpretations for gas monitoring records
– Treat all gas monitoring records the same as employee exposure records for data retention
• TGMS – networked computer system to collect and retain data
– http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25398
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Practical Gas Detection - Summary
• Diverse technology options are available• No single technology will suffice• Understand the application in its entirety to avoid spurious results• Cost and complexity will vary by target chemical• Training and expertise is readily available!
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Gas Book
• What is a Gas Book?– The Gas Book is Honeywell Analytics’ 84-
page detailed guidebook on the principles of gas detection needed for personnel, plant and environmental protection.
• How do I get one?– Call 1-800-538-0363 and make a request… – Send an email request to: sales@zelana.com