Pneumatic Operation; Sample Gas Flow - Teledyne T200 User Manual

PNEUMATIC OPERATION

Important
Regular leak checks should be performed on the analyzer as presented in the maintenance
schedule, Table 5-1. Procedures for correctly performing leak checks can be found in
Section 5.6.11.
S
AMPLE
Note
The sample gas flow is created by an external vacuum pump that is located pneumatically
downstream from the rest of the instrument's components.
The pump creates a vacuum of approximately 5 in-Hg-A which is distributed to
•
various pneumatic components by a vacuum manifold, located just in front of the rear
panel (see Figure 2-3).
Gas flow is created by keeping the analyzer's sample gas inlet near ambient pressure,
usually by means of a small vent installed in the sample line at the inlet, in effect pulling
the gas through the instrument's pneumatic systems.
By placing the pump downstream from the analyzer's reaction cell, several problems are
avoided.
• First, the pumping process heats and compresses the sample air complicating the
measurement process.
• Additionally, certain physical parts of the pump itself are made of materials that might
chemically react with the sample gas.
Finally, in certain applications where the concentration of the target gas might be high
•
enough to be hazardous, maintaining a negative gas pressure relative to ambient
means that should a minor leak occur, no sample gas would be pumped into the
atmosphere surrounding the analyzer.
184 Teledyne API T200 NO/NO
IMPACT ON READINGS OR DATA
The sample gas is the most critical flow path in the analyzer. At
any point before and in the reaction cell, the integrity of the
sample gas must not be compromised. Therefore, it is important
that the sample airflow system is both leak tight and not
pressurized over ambient pressure.
G F
AS LOW
In this section of the manual vacuum readings are given in inches
of mercury absolute (In-Hg-A). This pressure value is referenced
against zero (a perfect vacuum).
/NO Analyzer with NumaView™ Software
2 x
083730200A DCN7962