IEC TC31 (Explosive Atmospheres) – Gas Detection as Method of Protection
Jon Miller Detector Electronics Corporation
Approvals Engineering Manager
Convener of IEC TC31 MT60079-29 (Gas Performance) IECEx USNC voting member (ISA Representative)
Chairman of UL STP 60079 SP12.13 (Gas Performance) Chairman of ISA SP92 (Toxic Gas Performance)
Agenda Combustible Gas Detection – Method of Protection 1) Codes & Standards 2) Technologies 3) Applications
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But, First the Basics 1) Process Control Gas concentration monitoring only
2) Risk Area Protection (IEC 60079-29)
• Alarm Notification • Equipment Shut-down • Ventilation Actuation
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‘Risk Area Protection’ using Gas Detection DOES mitigate risk of ignition in the classified area DOES NOT change the area classification
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Zone 2 Non-hazardous Zone 1
Point Detector
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Codes of Practice
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Gas Detection as Method of Protection
{gas detection + action = mitigation}
Product Standards
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Agenda Combustible Gas Detection - Method of Protection
1) Codes & Standards 2) Technologies 3) Applications
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Technologies
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Technologies (Catalytic, Point)
0% LFL
20% LFL
50% LFL
100% LFL
Gas
Clo
ud
75% LFL
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1) Concentration measurement at detector
5) Flow consideration with detector position
Air Flow Direction
3) %LFL output
2) Detector must be in the gas cloud for detection
Zone 1 Point
Detector
4) K-factor for target gas
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Technologies (Infrared, Point)
0% LFL
20% LFL
50% LFL
100% LFL
Gas
Clo
ud
1) Concentration measurement at detector
5) Flow consideration with detector position
Air Flow Direction
3) %LFL output
2) Detector must be in the gas cloud for detection
Zone 1 Point
Detector
4) Linearized for target gas
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Technologies (Infrared, Open Path)
1) Concentration measurement between two points
3) LFL-meter output (NOT actual concentration)
2) Detector need NOT be in the gas cloud for detection
4) Linearized for target gas
5) Perimeter detection (air flow coverage)
*** Intended to supplement (not replace) Point Detection ***
Gas
Clo
ud
0 LFL-meter
2.5 LFL-meter
5 LFL-meter
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12 Product images courtesy of New Cosmos Electric Co., Dräger, General Monitors, Honeywell, Det-Tronics
Technologies Summary
Technology Catalytic, Point Infrared, Open Path Infrared, Point
Advantages • Low initial cost • Hydrogen detection • Versatile, broad range
• Large area coverage • Fail safe • Infrequent calibration • Low maintenance
• Environmental superiority • Fail safe • Low cost of ownership • High reliability
Disadvantages
• Frequent calibration cycle • Susceptible to poisoning • Not fail safe, monthly
degradation
• Alignment challenges • LEL-m read out • Expensive
• No hydrogen detection
Agenda Combustible Gas Detection - Method of Protection
1) Codes & Standards 2) Technologies 3) Applications
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Application (Control Panel)
Safe Area
IEC 60079-29-1 Gas Controller
A spill evaporates or process piping leaks
Visible alarm
Audible alarm
As counter measure, increased ventilation activated
Zone 2 Room Ex
As counter measure, de-energize control panel when 40% LFL is detected within Zone 2 room
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1
3
Control Panel (non-hazardous)
(@40%LFL Alarm)
* Zone 1 Point
Detector
* Zone 1 Point
Detector
* Zone 1 Point
Detector (@20%LFL Alarm)
2 Upon detection of 20% LFL inside control panel de-energize control panel
* IEC 60079-29-1 Gas Detector
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Application (Interior Room)
Safe Area
IEC 60079-29-1 Gas Controller
A spill evaporates or process piping leaks
Visible alarm
Audible alarm Zone 2 Room Ex
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Non hazardous Room • Analyzer Room • Control Room • Office
(@40%LFL Alarm)
* Zone 1 Point
Detector
* Zone 1 Point
Detector
* Zone 1 Point
Detector
(@20%LFL Alarm)
Equipment
As counter measure, increased ventilation activated when 20% LFL detected in Zone 2 area.
Upon detection of 20% LFL inside non hazardous room, de-energize equipment
As counter measure, de-energize equipment when 40% LFL is detected within Zone 2 room
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2
3
* IEC 60079-29-1 Gas Detector
Clean Air
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Application (Low Ventilation Rate)
Safe Area
IEC 60079-29-1 Gas Controller
A spill evaporates
Visible alarm
Audible alarm
As counter measure, ventilation activated
Zone 1 Room Ex
As counter measure, power switched OFF
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1
2
Zone 2 Equipment EPL Gc • Variable speed drive • Control equipment • Power supply • Transformer
(@40%LFL Alarm)
* Zone 1 Point
Detector
* Zone 1 Point
Detector
* Zone 1 Point
Detector
(@20%LFL Alarm)
* IEC 60079-29-1 Gas Detector
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Application (Gas Detection + Action = Mitigation) R
isk
Ass
essm
ent
Risk – ignition from non-Ex rated equipment dangerous
safe
Existing Condition
Increase Ventilation
De-energize
Gas Detection
residual risk
risk reduction
necessary risk reduction
actual risk reduction
tolerable risk
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Gas
Det
ectio
n S
yste
m
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Application Summary
%LEL
20
40
Power ‘OFF’ Ventilation ‘ON’
Gas
det
ecto
r sig
nal
1st Alarm
2nd Alarm
Gas concentration decreases - countermeasure is effective
Gas concentration still rises - countermeasure not effective
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Questions Combustible Gas Detection - Method of Protection
1) Codes & Standards 2) Technologies 3) Applications
THANK YOU! 19
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