Ametek TRACE ANALYTICAL ta5000R, User Manual

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12 | Model ta5000R Gas Purity Monitor
Reduction Gas Detection
Species eluting from the RGD column set pass immediately into the
heated bed of mercuric oxide (HgO) and the photometric detector. Within
the HgO bed, the general reaction occurs:
X + HgO (solid) => XO + Hg (vapor)
where X is any appropriate reducing gas. The resulting mercury vapor
is quantified by means of an ultraviolet photometer located immediately
downstream of the mercuric oxide bed. The relative ease of measuring
mercury vapor at low concentrations lends the technique its inherent
sensitivity.
For carbon monoxide and hydrogen, the equilibrium reactions are as fol-
lows:
CO + HgO (solid) => CO
2
+ Hg (vapor)
H
2
+ HgO (solid) => H
2
O + Hg (vapor)
Under continuous operation, the effective life of the mercuric oxide bed is
approximately one year. Contamination of carrier gases with reactive com-
pounds such as sulfides, chlorides, and aromatics will irreversibly impair
reactivity and will necessitate bed replacement. Care should be taken to
bypass the instrument if these compounds are present in the sample gas
stream.
High concentrations of hydrogen and carbon monoxide will use up the
active sites in the reaction bed faster than lower level concentrations.
Operating System
A six-button keypad enters commands to the microprocessor, which moni-
tors detector operation, controls heated zones, and operates all internal
valve functions. External signal outputs for a data collection system or
host computer are located at the rear panel.
The microprocessor control system allows complete unattended operation
of the ta5000R. This onboard system performs necessary operational and
analytical functions such as:
• Analyzer Status Control
• Contaminant Identification
• Concentration Calculations
• Calibration
• Sampling
Frequency
• Data Output
• Alarm Output