GE XMO2, User Manual

Page: 33 / 196

September 2007
3-2 Startup & Operation
Establishing a Sample
Gas Flow (cont.)
To establish a flow of sample gas through the system, complete the
following steps (see Figure 2-1 on page 2-2 as an example):
1. Set the sample system ball valves to direct only the sample inlet
stream to the inlet port of the XMO2 transmitter.
2. Use the sample inlet needle valve to regulate the flow of sample
gas until the flowmeter reads the same flow rate listed for your
unit in Table 3-1 on page 3-1.
3. Read the resulting system pressure on the pressure gauge. Make
sure that there are no unnecessary flow restrictions downstream of
the sample system.
IMPORTANT:
For atmospheric pressure-compensated units, the
XMO2 outlet port must be vented directly to
atmosphere with no restrictions, by installing all
sample system components and tubing upstream of
the XMO2 transmitter.
4. Take a reading of the XMO2 4-20 mA analog output.
In some applications, pressure changes due to flow rate changes can
cause noticeable errors in the oxygen measurement. In such cases,
consider the following corrective measures:
•
Reducing the flow rate to the minimum recommended value
minimizes flow rate sensitivity. A bypass flow type sample system
(speed loop) allows minimum flow through the XMO2 yet
maintains a fast transport of the sample gas to the XMO2.
•
For the fastest transport, minimize the sample line length from the
process.
•
If you cannot shorten the sample line length, reduce the sample
line pressure to less than 5 psig.
Proceed to the next section to complete the initial XMO2 startup.