Analytical Industries GPR-1600 MS Series PPB Oxygen Analyzer - Manual (Page 7)

Advanced Instruments Inc.
7
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 4” 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 20-50 psig although the rating of the fitting itself is considerably higher.
Outlet Pressure: In positive pressure applications the vent pressure must be less than the inlet, preferably atmospheric.
Application Pressure - Positive: To reduce the possibility of leakage for low ppm measurements, position a metering needle
valve upstream of the sensor to control the flow rate and position a flow indicator downstream of the sensor. If necessary, a
pressure regulator (with a metallic diaphragm is recommended for optimum accuracy, the use of diaphragms of more
permeable materials may result in erroneous readings) upstream of the flow control valve should be used to regulate the inlet
pressure between 20-50 psig.
Application Pressure - Atmospheric or Slightly Negative: For accurate ppm range oxygen measurements, an optional
external sampling pump should be positioned downstream of the sensor to draw the sample (vacuum should no exceed 4”
water column) 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. 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.
Recommendations to avoid erroneous oxygen readings and damaging the sensor:
¾ 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 (thus voiding
the sensor warranty).
¾ Assure there are no restrictions in the sample or vent lines
¾ Avoid drawing a vacuum that exceeds 4” of water column pressure – unless done gradually
¾ Avoid excessive flow rates above 3 SCFH which generate backpressure on the sensor.
¾ Avoid sudden releases of backpressure that can severely damage the sensor.
¾ Avoid the collection of liquids or particulates on the sensor, they block the diffusion of oxygen into the sensor - wipe away.
¾ If the analyzer is equipped with an optional integral sampling pump (positioned downstream of the sensor) and a flow
control metering valve (positioned upstream of the sensor), completely open the flow control metering valve to avoid
drawing a vacuum on the sensor and placing an undue burden on the pump.
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 optional
components. Moisture and/or particulates do not necessarily damage the sensor, however, collection 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 when in fact the problem is easily remedied by blowing on the front of the sensor. Consult the factory for
recommendations concerning the proper selection and installation of 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 following the cleaning process. Moisture and/or particulates generally can be removed from the
sample system by flowing the purge gas through the analyzer at a flow rate of 4.5-5 SCFH for an hour.
Mounting: The analyzer is approved for indoor use, outdoor use requires optional enclosures, consult factory. Mount as
recommended by the manufacturer.
Gas Connections: Inlet and outlet vent gas lines for ppm analysis require 1/8” or ¼” stainless steel compression fittings; hard
plastic tubing with a low permeability factor can be used percentage range measurements.
Power: Supply power to the analyzer only as rated by the specification or markings on the analyzer enclosure. The wiring that
connects the analyzer to the power source should be installed in accordance with recognized electrical standards. Ensure that is
properly grounded and meets the requirements for area classification. Never yank wiring to remove it from a terminal
connection. AC powered analog analyzers consume 5 watts, digital analyzers 50 watts without optional heaters. Optional 110V
and 220V heaters AC powered heaters consume an additional 100-150 watts; DC powered digital analyzers consume 30 watts,
40 watts with the optional DC powered heater.