Flow Rate Control - Critical Flow Orifices - Teledyne T200 Operation Manual

Teledyne API – T200 NO/NO
Table 13-2: T200 Valve Cycle Phases
NO/ NO
X
Phase Valve
Status
Open to
NO
Auto Zero
Measure
valve
Open to
NO
X
NO
2
Measure
converter
Open to
Auto
Auto Zero
Zero
valve

13.2.2. FLOW RATE CONTROL - CRITICAL FLOW ORIFICES

06858E DCN7057
/NO Analyzer Operation Manual
2 X
Auto Zero
Time
Valve
Index
Status
0 - 2 s
Open to
reaction cell
2 - 4 s
4 – 6 s
Open to
reaction cell
6 – 8 s
Cycle repeats every ~8 seconds
0 – 4 s
Open to
vacuum
manifold
4 - 6 s
Cycle repeats every minute
Sample gas flow in the T200 analyzer is created via the use of several flow control
assemblies (see Figure 13-6 for an example) located in various places in the gas streams
of the instrument. These assemblies consist of:

a critical flow orifice

two o-rings, Located just before and after the critical flow orifice, the o-rings seal the
gap between the walls of assembly housing and the critical flow orifice

a sintered filter

a spring (applies mechanical force needed to form the seal between the o-rings, the
critical flow orifice and the assembly housing)
Figure 13-6: Flow Control Assembly & Critical Flow Orifice
Activity
Wait period (NO dwell time). Ensures reaction cell has
been flushed of previous gas.
Analyzer measures chemiluminescence in reaction cell.
Wait period (NO dwell time). Ensures reaction cell has
X
been flushed of previous gas.
Analyzer measures NO + O
reaction cell.
Wait period (AZERO dwell time). Ensures reaction cell
has been flushed of sample gas and chemi-
luminescence reaction is stopped.
Analyzer measures background noise without sample
gas
Principles of Operation
chemiluminescence in
3
Figure
Figure
13-3
Figure
13-3
Figure
13-4
293