Analytical Industries GPR-3100 Series Oxygen Purity Analyzer - Manual (Page 11)

Advanced Instruments Inc.
5 Operation
GPR-3100 Rev 2/05 4
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.
An eductor jet pump is an alternative to a pump that is used in classified areas since it has no moving
parts or to eliminate the maintenance associated with mechanical pumps. The eductor must be
positioned downstream of the sample outlet. The eductor has three (3) orifices and requires a source of
compressed gas which enters through the top and exits at the bottom while drawing a mild vacuum (and
sample gas) through the side orifice. A flow indicator with an integral metering valve positioned
downstream of the sensor is recommended for controlling the sample flow rate between 1-5 SCFH.
To avoid erroneous oxygen readings and damaging the sensor:
¾ Assure there are no restrictions in the sample line that could create and draw a vacuum exceeding
14” of water column on the sensor.
¾ Avoid excessive flow rates above 5 SCFH which generate backpressure on the sensor.
¾ Avoid sudden changes in pressure that can severely damage the sensor – assure a flow control valve
is positioned upstream of the analyzer’s inlet.
¾ Assure no particulates, liquids or condensation collect on the sensor that could block the diffusion of
oxygen into 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 (voiding the sensor warranty).