Teledyne T200, Operation Manual, Page: 293 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Principles of Operation
291
13.2. PNEUMATIC OPERATION
I
MPORTANT
I
MPACT ON
R
EADINGS OR
D
ATA
Could either affect accuracy of instrument readings or cause loss of data.
Note
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 cannot be compromised.
Therefore, it is important that the sample airflow system is both leak tight and not
pressurized over ambient pressure.
Regular leak checks should be performed on the analyzer as presented in the
maintenance schedule, Table 13-1. Procedures for correctly performing leak checks can
be found in Section 13.3.12.
13.2.1. SAMPLE GAS FLOW
Note 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).
The gas flow for the T200 is created by a pump that is pneumatically downstream from
the rest of the instrument‟s components. This is either:

An external pump pneumatically connected to the analyzer’s exhaust port located
on the rear panel. This is the most common configuration for the T200 or,

An optional internal pump pneumatically connected between the vacuum manifold
and the exhaust outlet (special order).
In either case, the pump creates a vacuum of approximately 5 in-Hg-A at one standard
liter/minute, which is provided to various pneumatic components by a vacuum manifold
located just in front of the rear panel (see Figure 3-5).
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.
06858E DCN7057