1. Gas Detection in Water Treatment
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2. Gas Detection Applications
Occupancy Sensing
Safety
Explosive Gas Hazards
Toxic Environment
Oxygen Depletion
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3. Gas Detection in Water Treatment
Must withstand the Corrosive environment
Provide accurate sensing information
Reliably activate safety equipment
Be safe to use in hazardous atmospheres
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4. NEMA Ratings National Electrical Manufacturer’s Association
NEMA 1: Finger Proof
NEMA 3R: Weatherproof Outdoor
NEMA 4: Hose down rated (4X: Corrosion Resistant)
NEMA 7: Explosion Proof – Rated for Gasses
NEMA 9: Explosion Proof – Rated for Dust
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5. Explosive Gases
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6. Methane Hazard Primary component of Natural Gas
Produced by the decomposition of Organic Matter
Highly Combustible
Lighter than Air
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7. Methane Hazard (Cont.) Methane Hazards fall under CSA Class 1, Group B
Hazardous areas require CSA rated devices
Sensors should be located near the ceiling
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8. Methane Detectors Methane is measured by its Percentage of LEL
QEL offers two methane sensors that are CSA Class 1 Div. 1
QIR-8000
QTS-8000
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9. QIR-8000: Combustible Gases
Explosion Proof Enclosure (NEMA 4X, 7 and 9)
Uses infrared light to detect the presence of combustible gas
Outputs a 0-10V or 4-20mA signal
Optional add on for RS485, Opto-22, Modbus, and relays.
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10. QTS-8000: Toxic/Combustible Gases
Explosion Proof Enclosure (NEMA 4X, 7 and 9)
Uses Catalytic Bead Technology to sense gas
Outputs a 0-10V or 4-20mA signal
Optional add on for RS485, Opto-22, Modbus and relays
Can sense non-combustible gases, as well as Methane
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11. Toxic Gases
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12. Toxic Gases in Water Treatment
Hydrogen Sulfide (H2S)
Ammonia (NH3)
Ozone (O3)
Chlorine (Cl2)
All of these are sensible on the QTS-8000
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13. Hydrogen Sulfide
Sometimes called “Sour Gas” when present in Natural Gas
Smells like Rotten eggs
Highly Potent Toxin
Combustible at higher concentrations
Heavier than air
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14. Ammonia Pungent smell Used in water decontamination
Extended contact can be hazardous
Heavier than air
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15. Chlorine Used for sanitizing water and equipment
Gas is toxic in high enough concentrations
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16. Oxygen Depletion
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17. Oxygen Sensors Other gases can displace oxygen in the room
Once the concentration drops below 17% Oxygen, blackouts can occur
QTS-8000 can sense Oxygen depletion, and increase ventilation
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18. Selecting the
Right System
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19. System Overview Sensors/Transmitters Communication Standard Control
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20. Sensors and Transmitters
Devices are “in harm’s way”
IR based sensors last longer, especially in high concentration areas.
Can be used as stand alone devices, or in a system
Need calibration to ensure accuracy (Startup is included)
Performance is dependent on placement
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21. Communications Sensors often communicate with a controller or BAS
Design must account for signal interference
Two primary modes: Analog and Digital
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22. Communications: Analog
The Good
The Bad
The Ugly
Very High Resolution
Simple: It Works
4-20mA is very reliable
Active Zero
Signal is one-way
Configuration is more involved
Susceptible to noise
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23. Communications: Digital
Sensors are “Daisy-Chained” into wire runs
Modbus RS-485 protocol
Two-way Communication: controller can talk back to sensor
Easier to troubleshoot
Resolution is very workable, but not as high as analog signals
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24. Controls
Both Modbus and 4-20mA analog signals are widely adopted standards
Sensors can be tied together by BAS or QEL’s controllers
A control scheme is very practical in all medium and large systems
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25. Controls: Cont. Centralizes electrical connections
Simplifies troubleshooting
Enables advanced functionality
Logging
Remote alerts
Analog control output – like VFDs
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26. Summary
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27. Conclusions Hazardous areas require certified equipment
Gas detection is vital for hazardous environments
Sensors need to be selected and placed properly
Communications allow for devices to work together
Controls ease wiring and sequence of operation concerns
March 19, 2015