Troubleshooting DF-150E 55
12.2Troubleshooting Considerations
12.2.1 Gas Pressure Effects
Gas tubing should be kept as short as possible to minimize pressure drop and
overall system response time. Larger diameter tubing will help avoid pressure
drop but will lengthen the response time. In general
1
/8 inch tubing should be
limited to 15 foot runs. Longer runs should use
1
/4 inch tubing.
If the analyzer is not vented to atmosphere, downstream conditions may impact
sensor pressure. If the vent pressure is outside the range of +/- 2 psi, a
recalibration under operating conditions may be desirable to remain within the
stated analyzer accuracy.
12.2.2 Positive Pressure Operation
Gas pressure should be set to establish a nominal flow of 1.0 to 2.0 scfh. A
regulator may be used to adjust the flow rate if there is no downstream
restriction on the flow.
If the analyzer is not vented directly to atmosphere, downstream conditions
may restrict flow. Keep downstream plumbing lengths and restrictions to a
minimum. Do not exceed +/- 5 psi pressure on the sensor.
NOTE
All positive pressure flow control must be accomplished upstream
of the sensor.
12.2.3 Negative Pressure Operation
If the gas stream is between 2.0 psig vacuum (12.7 psia) and 2.0 psig, a pump
is recommended. If the analyzer is equipped with a pump, it will also have a
flow control valve in the flowmeter.
If there is a valve or regulator up stream of the analyzer, it should be kept fully
open and flow rate adjustments should be made with the downstream flow
control valve in the flowmeter.
NOTE
All negative pressure flow control must be accomplished
downstream of the sensor.
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