Atmospheric Pressure Sampling - Teledyne 311 Instruction Manual

1) Before making any connections to the instrument, establish a flowrate in the
sample line of from 0.1 to 10 liters/min. Allow the sample to vent to accomplish
long enough to purge the line free of air.
2) Install the vent fitting first, and then the sample source fitting. Be prepared to
make the connections in rapid order, so that atmospheric diffusion time through
the vent fitting is held to a minimum.
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.
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 0.1 and 10 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 still another throttle
valve. The sample path and bypass path may then be balanced by manipulating the two valves,
so that sample flow is within the prescribed limits without loading the pump.
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.
IF A FLOWING SAMPLE WAS CONNECTED TO THE
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