Analytical Industries GPR-1500 A Series Trace PPM Oxygen Analyzer - Manual (Page 8)

Advanced Instruments, Inc
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Caution: Do not place your finger over the vent (it pressurizes the sensor) to test the flow
indicator when gas is flowing to the sensor. Removing your finger (the restriction) generates a
vacuum on the sensor and may damage the sensor (voiding the sensor warranty).
Application Pressure - Positive
: A flow indicator with integral metering valve positioned
upstream of the sensor is recommended for controlling the sample flow rate between 1-5 SCFH. If a
separate flow control valve and a flow indicator is used, position flow control valve upstream of the sensor
and position a flow indicator downstream of the sensor. If necessary, a pressure regulator upstream of the
flow control valve should be used to regulate the inlet pressure between 5-30 psig.
Caution: If the analyzer is equipped with a H2S scrubber as part of an optional sample
conditioning system, inlet pressure must not exceed 30 psig.
Application Pressure - Atmospheric or Slightly Negative:
For % oxygen
measurements, an optional external sample pump may be used upstream of the sensor to push the sample
across the sensor and out to atmosphere. For PPM oxygen measurements, an optional external sampling
pump should be positioned downstream of the sensor to draw the sample from the process, by the sensor
and out to atmosphere. A flow meter is generally not necessary to obtain the recommended flow rate with
most sampling pumps. However, if the sample pump can pull/push more than 5 SCFH, a flow control must
be used to control the sample flow. The flow control valve must be positioned in such a way that it does not
generate any vacuum on the sensor.
Caution: If the analyzer is equipped with a flow indicator with integral metering valve or a
metering flow control valve upstream of the sensor and the pump is installed downstream of
sensor- open the metering valve completely before turning the pump ON to avoid drawing a
vacuum on the sensor and placing an undue burden on the pump.
If pump loading is a consideration, a second throttle valve on the pump’s inlet side may be necessary to
provide a bypass path so the sample flow rate is within the above parameters.
Moisture & Particulates: Installation of a suitable coalescing or particulate filter is required to
remove condensation, moisture and/or particulates from the sample gas to prevent erroneous analysis
readings and damage to the sensor or other optional components. Moisture and/or particulates do not
necessarily damage the sensor. However, collection of moisture/particulate on the sensing surface can
block or inhibit the diffusion of sample gas into the sensor resulting in a reduction of sensor signal output –
and the appearance of a sensor failure. Consult the factory for recommendations concerning the proper
selection and installation of optional components.
Moisture and/or particulates generally can be removed from the sensor by opening the sensor housing and
either blowing on the sensing surface or gently wiping or brushing the sensing surface with damp cloth.
Caution: Minimize the exposure of PPM sensors to air during this cleaning process. Air calibration followed
by purging with zero or a gas with a low PPM oxygen concentration is recommended after the cleaning
process is completed.
Mounting: The analyzer is approved for indoor as well as outdoor use. However, avoid mounting in an
area where direct sun might heat up the analyzer beyond the recommended operating temperature range. If
possible, install a small hood over the analyzer for rain water drain and to prevent over-heating of analyzer.
Gas Connections:
The Inlet and outlet vent gas lines require 1/8” or ¼” stainless steel compression
type tube fittings. The sample inlet tubing must be metallic, preferably SS. The sample vent line may be of
SS or hard plastic tubing with low gas permeability.