A robust, linear and stable binary gas analyzer for measurement of gas mixes present during the operation and maintenance of hydrogen cooled electricity generators. The primary measurement is looking for air as an impurity in hydrogen (H2). The second measurement is monitoring hydrogen in carbon dioxide (CO2) during system purging, and finally carbon dioxide/air during maintenance. The analyzer is suitable for hazardous areas and uses non-depleting sensor technology for minimal cost of ownership.

Product Features

  • Suitable for use in ATEX, IECEx, TC TR Ex & CCSAUS certified Hazardous Areas
  • Monitors all three phases of hydrogen cooled electricity generators - normal running, purging and maintenance
  • Remotely change the measurement phase to match your maintenance schedule
  • Range indication via 4-20 mA output
  • Touch-screen display allows calibration or adjustment without the need for a hot works permit
  • Compact and rugged design with an EExd enclosure
  • IP66 rated enclosure
  • Low cost of ownership due to minimal maintenance

Phase One

During normal operation the analyzer is monitoring the Air in Hydrogen (80/90-100% H2) for safety and efficiency.

Phase Two

Hydrogen is very flammable and is explosive in concentrations from 4% to 75% in air, so when routine maintenance is carried out, the plant can’t simply turn off the hydrogen and open the turbine due to the explosive potential of the hydrogen/air mixture that would result.
Instead, the turbine is purged with carbon dioxide to remove the hydrogen. When the carbon dioxide is at 100% (and therefore 0% hydrogen), it is safe to allow air into the turbines.

Phase Three

Before the units can be opened the carbon dioxide, which is an asphyxiant, must be purged with air. Once the unit reads 100% air, it is safe to break the seals and commence maintenance.
After maintenance is complete, the purging cycles are reversed to end up with pure hydrogen in the system and the turbine can be started back up.

Technical Specifications

PhasePhase 1 -
H2 in Air
Phase 2 -
H2 in CO2
Phase 3 -
CO2 in Air
Measurement Range80-100% or 90-100%0-100%0-100%
Display resolution0.01%0.1%1%
Response time (T90)<20 seconds<20 seconds<50 seconds
Recommended calibrationMontlyPrior to useAnnually
Measurement TechnologyThermal Conductivity sensor
Gas RequirementsNon-condensing sample with particles <3μm
Display TypeBacklit LCD
Repeatability±0.2% of span
Linearity±1% span
Sample Flow Rate100 to 600 ml/min
Sample Flow Effect
(calibrated at 300 ml/min)
< 1% of span for flows:
100 to 600 ml/min
Sample Pressure0 to 3 barg with atmospheric vent
Sample Temperature0 to +45°C max
Sample Cell Temperature+50°C
Electrical Specifications
Analog Inputs2 off 4-20 mA inputs
One to control phase selection
One for an external sensor that can be displayed on the screen
Analog Outputs2 off 4-20 mA outputs:
mA 1 = Concentration
mA 2 = Phase indication
Alarms2 off single pole changeover (SPCO) relays (250 V, 5 A max)
Digital CommunicationsMODBUS RTU over RS485 Protocol
Power Supply24 V DC; 1.5 A max
Operating Conditions
Ambient Temperature-15 to +55°C
Mechanical Specifications
Warm Up and Stabilization Time< 30 minutes
Dimensions234 x 234 x 172mm (w x d x h)
Wetted Materials316 stainless steel, boroscillicate glass, platinum, (plus O-ring)
O-Ring MaterialsViton
Gas Connection1/4” NPT to 1/4” tube (standard)
1/4" NPT to 6mm tube (optional)
Ingress ProtectionIP66, NEMA 4
Hazardous Area Classification
Ex d IIB +H2 T3 Gb
Ex tb IIIC T137°C Db IP66
IECExEx d IIB +H2 T3 Gb
Ex tb IIIC T137°C Db IP66
Temperature Ranges for ATEX and IECEx as per O-ring TypeViton: Ta = -15°C to +55°C
CCSAUSClass I, Division 1, Groups B,C,D T3C
TC TR1Exd IIB+H2 T3 Gb

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