High Flow; Sample Flow Is Zero Or Low But Analyzer Reports Correct Flow - Teledyne T200 User Manual

HIGH FLOW

Flow readings that are significantly higher than the allowed operating range (typically ±10-
11% of the nominal flow) should not occur in the analyzer unless a pressurized sample,
zero or span gas is supplied to the inlet ports.
• Ensure to vent excess pressure and flow just before the analyzer inlet ports.
• When supplying sample, zero or span gas at ambient pressure, a high flow could
indicate a broken critical flow orifice (very unlikely case), allowing more than nominal
flow, or were replaced with an orifice of wrong specifications.
• If the flows are within 15% above normal, we recommend measuring and recalibrating
the flow electronically (Section 5.6.11.3), followed by a regular review of these flows
over time to see if the new setting is retained properly.
Also, check the flow assembly o-rings and replace as needed.
•
SAMPLE FLOW IS ZERO OR LOW BUT ANALYZER REPORTS CORRECT
The analyzer can report a correct flow rate even if there is no or a low actual sample flow
through the reaction cell.
• The sample flow is only calculated from the sample pressure and critical flow
condition is verified from the difference between sample pressure and vacuum
pressure.
• If the critical flow orifice assembly is partially or completely clogged, both the sample
and vacuum pressures are still within their nominal ranges (the pump keeps pumping,
the sample port is open to the atmosphere), but there is no flow possible through the
reaction cell.
Although measuring the actual flow is the best method, in most cases, this fault can also
be diagnosed by evaluating the two pressure values.
• Since there is no longer any flow, the sample pressure should be equal to ambient
pressure, which is about 1 in-Hg-A higher than the sample pressure under normal
operation.
• The reaction cell pressure, on the other hand, is significantly lower than under normal
operation, because the pump no longer has to remove 500 cc/min of sample gas and
evacuates the reaction cell much better.
Those two indicators, taken together with a zero or low actual flow, indicate a clogged
•
sample orifice.
The analyzer features a new orifice holder, which makes switching sample and ozone flow
orifices very easy; refer to Section 5.6.9 on how to change the sample orifices.
Again, monitoring the pressures and flows regularly will reveal such problems, because
the pressures would slowly or suddenly change from their nominal, mean values. Teledyne
API recommends reviewing all test data once per week and to do an exhaustive data
analysis for test and concentration values once per month, paying particular attention to
sudden or gradual changes in all parameters that are supposed to remain constant, such as
the flow rates.
144 Teledyne API T200 NO/NO
FLOW
/NO Analyzer with NumaView™ Software
2 x
083730200A DCN7962