Teledyne 311D - Portable trace oxygen analyzer with digital meter - Manual (Page 8)

If, on the other hand, the instrument is not to be used immediately after calibration, and a low
ppm oxygen gas is being employed as a purge, allow the manifold to be purged overnight, and
then disconnect both male fittings. ALWAYS DISCONNECT THE SOURCE FITTING FIRST,
AND IMMEDIATELY THEREAFTER, THE VENT FITTING.
3.3 Positive Pressure Sampling: When connecting the instrument to a positive
pressure sample source, ALWAYS proceed as follows:
1. Before making ANY connections to the instrument, establish a sample line
flow rate of 0.1 to 10 liters/min. Allow the sample to vent to atmosphere
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 connect-disconnect procedure is to obviate the possibility of pressurizing
the manifold. IF A FLOWING SAMPLE WAS 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
0.1 - 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.
-6-
UNDER NO CIRCUMSTANCES SHOULD THERE BY ANY RESTRICTIONS IN THE
LINE BETWEEN THE SAMPLE POINT AND THE ANALYZER -- partial-pressure-
sensitive device, any oxygen readings taken under these conditions would be erroneous, and
vacuums in excess of 1/3 atmosphere may damage the cell.
4. MAINTENANCE
4.1 Battery Power Supply Service. The Model 311D is for use ONLY when it is
not connected to the AC power line. TAI suggests that an overnight recharge be accomplished