Lenny Kouwenhoven presented on using a hydrogen sensor to ensure safety when using hydrogen as a carrier gas in gas chromatography systems. The presentation covered the benefits of using hydrogen as a carrier gas, safety measures for its use, the operating principles of hydrogen sensors, and an overview of sensor hardware. The hydrogen sensor monitors for leaks using a catalytic combustion reaction and electrical resistance measurement in a Wheatstone bridge circuit. It provides real-time readings, alarms, and can detect hydrogen levels up to the lower explosive limit.

1. A Hydrogen Sensor can ensure
safety when using Hydrogen Carrier
Gas in a Chromatographic System
A Gulf Coast Conference Presentation
Presenter: Lenny Kouwenhoven
Director of Research & Development
Da Vinci Laboratory Solutions
Abstract #27
October 17th, 2012
www.davinci-ls.com

2. Overview
 Four reasons for using H2 as a carrier gas
 Safety measures
 Hydrogen sensor
 Principle of operation and measurement
 Hardware overview
 Summary
 Contact information

3. Reasonsfor using H2 as a Carrier Gas
1. Fast Analysis:
 Fast diffusion rate; 4
times faster than N2
 Half as viscous as
helium; higher linear gas
velocity and shorter
retention times
2. High Efficiency:
 Flattest Van Deemter
curve

4. Reasonsfor using H2 as a Carrier Gas
3. Prolonged Column Life:
□ Some applications have a lower elution
temperature, therefore the column life is
longer
4. Cost effective:
□ 3x’s less expensive than its helium equivalent
□ Bottle or generator

5. Reluctant to use H2 as a Carrier Gas?
 Hydrogen is an Explosive Gas: Undetected
gas leaks can lead to an explosion in the GC oven
 LEL 4% hydrogen in Air

6. Safety measures
 Monitor hydrogen usage
 Safety measures in GC hardware
□ Safety Shutdown: when gas pressure set points
are not met, the valve and heater are shut off
to prevent explosion
□ Flow Limiting Frit: if valve fails in open
position, inlet frit limits the flow
□ Oven ON/OFF Sequence: Fan purges the oven
before turning on heater to remove any
collected H2
□ Explosion Test: GC designed to contain parts in
case of explosion
 Hydrogensensor in the oven or
valve box

7. Principleof Operation
Hydrogen Sensor
 Catalytic combustion by
catalytized resistor or “pellister”
 Surface of the pellet acts as a
catalyst when hot
 Exothermal oxidation of
flammable gases
 2 H2 + O2 → 2 H2O(g) + heat
 Temperature rise results in a
change in the electrical
resistance

8. Principle of Measurement
Hydrogen Sensor
 Compensator pellet is identical but without
catalyst
 Compensator pellet removes the effect of
environmental factors
 Measurement circuit: a Wheatstone Bridge
8 18 October 2012

9. Hardware overview for a Hydrogen Sensor
for GC applications

10. Summary
 Catalytic Pellistor gas specific sensor, linear range
of 0-2% H2 (0-50% LEL)
 Unaffected by humidity, stable output for long
periods, more resistant to shocks and vibrations.
 Expected lifetime: over five years
 Long term stability drift sensitivity: less than 2mV
 User defined alarm: optical, acoustic and/or SMS
up to 50% LEL

11. SummaryContinued
 Instrument readings: provide real time sensor
readings with alarm levels, channel states
 Valve : High pressure 3 way solenoid valve
 Oven operating temperature: up to 450◦C
 Multiple Sensors: Max 4 sensors individually
controlled
 Sensor options: temperature, barometer, level,
oxygen or hydrogen as a leakdetector.

12. Contact Lenny Kouwenhoven, Director of R&D, with
questions or to request additional information on the
DVLS³ Simply, Smart Sensor for gas chromatography
systems.
Email:lenny.kouwenhoven@davinci-ls.com
T: +31 (0) 10 258 1870
F: +31 (0) 10 258 1879
www.davinci-ls.com