Teledyne Model 300EU manual The A-Ref Valve Assembly, The Nafion→ Dryer, M300EU, Rev A1

M300EU	THEORY OF OPERATION
(Addendum to M300EU Manual - P/N 04145)

10.2.2. THE A-REF VALVE ASSEMBLY

The auto-reference valve assembly is located next to the optical bench, at the rear of the analyzer between the Nafion→ dryer and the outer wall of the instrument (see Figure 3-1). The following table describes the state of each valve during the analyzer’s various operational modes (see Figure 10-1).

Table 10-1:	Auto-Reference Valve Operating States
Mode	Valve State	VALVE PORT CONNECTIONS
SAMPLE	Gas stream from Nafion→ Dryer &	3 Æ 2
(Normal State)	SAMPLE inlet
A-REF DWELL	Gas stream from CO scrubber	1 Æ 2
A-REF MEASUREMENT	Gas stream from CO scrubber	1 Æ 2
SAMPLE DWELL	Gas stream from Nafion→ Dryer &	3 Æ 2
	SAMPLE inlet

10.2.3. THE NAFION→ DRYER.

Normal room air contains a certain amount of water vapor. While H2O is a very low-level interferent for IR absorption (in the same range as CO) it can cause enough interference to affect the high-resolution measurements of the M300EU.

To account for this the M300EU has a special dryer added to the gas stream. The dryer consists of a bundle of parallel tubes of Nafion®, a co-polymer similar to Teflon® that absorbs water very well but not other chemicals. The multiple tube design of this dryer creates a large reactive surface without causing a restriction in the higher gas flow rate required by the M300EU that a long single tube style dryer would.

Figure 10-3: Semi-Permeable Membrane Drying Process

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