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2) Establish a flowrate in the sample line of from 0.2 to 5 liters/min. Allow the
sample to flow long enough to allow a stable low reading to be achieved.
When disconnecting the instrument, reverse the procedure: source fitting first, and then vent
fitting.
The objective of the connection -- disconnection procedure is to obviate the possibility of
pressurizing the manifold. IF A FLOWING SAMPLE WERE CONNECTED TO THE
MANIFOLD WITHOUT THE VENT FITTING IN PLACE, THE PRESSURE IN THE
MANIFOLD WOULD RISE AND BE EQUAL TO THE SAMPLE PRESSURE ALMOST
IMMEDIATELY. In such a situation, depending on the magnitude of the sample pressure,
leaks in the manifold might result.
3.4 Atmospheric Pressure Sampling
. If the sample is at atmospheric pressure (or
slightly negative), a sample pump will be required downstream from the analyzer. The inlet side
of the pump should also be equipped with a throttle valve -- so that sample flow can be reduced
to between 0.2 and 5 liters/min. If pump loading is a consideration, the inlet side of the pump
will have to include a bypass path that is open to the atmosphere through a second throttle valve.
The sample path and bypass path may then be balanced by manipulating the two valves, so that
the sample flow is within the prescribed limits.
UNDER NO CIRCUMSTANCES SHOULD THERE BE ANY RESTRICTIONS IN THE
LINE BETWEEN THE SAMPLE POINT AND THE ANALYZER -- as a partial vacuum
would then be drawn on the cell. Since the cell is a partial pressure sensitive device, any oxygen
readings taken under these conditions would be erroneous and vacuums in excess of one-third of
an atmosphere may damage the cell.
-7-
4. MAINTENANCE
4.1 Battery Power Supply Service
. The Model 311XL is designed to be
intrinsically safe, and therefore is for use ONLY when it is not connected to the AC power line.
TAI suggests