Analytical Industries GPR-3500 MO Portable Oxygen Analyzer - Manual (Page 5)

Advanced Instruments Inc.
5
Installation
Gas Sample Stream: Ensure the gas stream composition of the application is consistent with the specifications and review the
application conditions before initiating the installation. Consult the factory to ensure the sample is suitable for analysis. Note: In
natural gas applications such as extraction and transmission, a low voltage current is applied to the pipeline itself to inhibit corrosion.
As a result, electronic devices can be affected unless adequately grounded.
Contaminant Gases: A gas scrubber and flow indicator with integral metering valve are required upstream of the of the analyzer to
remove interfering gases such as oxides of sulfur and nitrogen or hydrogen sulfide that can produce false readings, reduce the
expected life of the sensor and void the sensor warranty if not identified at time of order placement. Installation of a suitable scrubber
is required to remove the contaminant from the sample gas to prevent erroneous analysis readings and damage to the sensor or
optional components. Consult the factory for recommendations concerning the proper selection and installation of components.
Expected Sensor Life: With reference to the publish specification located as the last page of this manual, the expected life of all
oxygen sensors is predicated on oxygen concentration (< 1000 ppm or air), temperature (77°F/25°C) and pressure (1 atmosphere) in
“normal” applications. Deviations are outside the specifications and will affect the life of the sensor. As a rule of thumb sensor life is
inversely proportional to changes in the parameters.
Accuracy & Calibration: Refer to section 5 Operation.
Materials: Assemble the necessary zero, purge and span gases and optional components such as valves, coalescing or particulate
filters, and, pumps as dictated by the application; stainless steel tubing is essential for maintaining the integrity of the gas stream for
ppm and percentage range (above or below ambient air) analysis; hardware for mounting.
Operating Temperature: The sample must be sufficiently cooled before it enters the analyzer and any optional components. A coiled
10 foot length of ¼” stainless steel tubing is sufficient for cooling sample gases as high as 1,800ºF to ambient. The maximum
operating temperature is 45º C on an intermittent basis unless the user is willing to accept a reduction in expected sensor life – refer to
analyzer specification - where expected sensor life is specified at an oxygen concentration less than 1000 ppm oxygen for ppm
analyzers and air (20.9% oxygen) for percent analyzers, but in all instances at 25°C and 1 atmosphere of pressure. Expected sensor
varies inversely with changes in these parameters.
Pressure & Flow
All electrochemical oxygen sensors respond to partial pressure changes in oxygen. The sensors are equally capable of analyzing the
oxygen content of a flowing sample gas stream or monitoring the oxygen concentration in ambient air (such as a confined space such
in a control room or an open area such as a landfill or bio-pond). The following is applicable to analyzers equipped with fuel cell type
oxygen sensors. With respect to analyzers equipped with Pico-Ion UHP and MS oxygen sensors, refer to the analyzer’s specifications.
Analyzers designed for in-situ ambient or area monitoring have no real inlet and vent pressure because the sensor is exposed directly
to the sample gas and intended to operate at atmospheric pressure, however, slightly positive pressure has minimal effect on accuracy.
Inlet Pressure: Analyzers designed for flowing samples under positive pressure or pump vacuum (for samples at atmospheric or
slightly negative atmospheres) that does not exceed 14” water column are equipped with bulkhead tube fitting connections on the side
of the unit (unless otherwise indicated, either fitting can serve as inlet or vent) and are intended to operate at positive pressure
regulated to between 5-30 psig although their particular rating is considerably higher. Caution: If the analyzer is equipped with an
optional H2S scrubber, inlet pressure must not exceed 30 psig.
Outlet Pressure: In positive pressure applications the vent pressure must be less than the inlet, preferably atmospheric.
Sample systems and flowing gas samples are generally required for applications involving oxygen measurements at a pressure other
than ambient air. In these situations, the use of stainless steel tubing and fittings is critical to maintaining the integrity of the gas
stream to be sampled and the inlet pressure must always be higher than the pressure at the outlet vent which is normally at
atmospheric pressure. Flow Through Configuration: The sensor is exposed to sample gas that must flow or be drawn through metal
tubing inside the analyzer. The internal sample system includes 1/8” compression inlet and vent fittings, a stainless steel sensor
housing with an o-ring seal to prevent the leakage of air and stainless steel tubing.