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SEMI C3.23-1000 © SEMI 1984, 2004 5 Figure 1 Figure 2

SEMI C3.23-1000 © SEMI 1984, 2004 4

4.6.2 Flow Requirements

4.6.2.1 High purity, hydrocarbon-free (less than 0.1

ppm) hydrogen, 35–40 mL/min or 40% hydrogen in

either helium or nitrogen at 75–80 mL/min.

4.6.2.2 Dry, hydrocarbon-free (less than 0.1 ppm) air,

350 mL–400 mL/min.

4.6.2.3 Set sample flow rate in accordance with the

instrument manufacturer’s instructions.

4.6.3 Calibration Standards

4.6.3.1 Zero oxygen with a known quantity of

hydrocarbons of approximately 0.1 ppm.

4.6.3.2 Upper level balance oxygen span gas of not

more than five times the concentration specified in

Section 2 of this Standard.

4.6.4 Operating Procedure

4.6.4.1 Do not change initial flow settings for

hydrogen, air and sample once established.

4.6.4.2 Introduce the zero oxygen with a known

quantity of hydrocarbons and, using the 0–1 ppm range,

set the output to read the correct level, using the zero

adjust knob.

4.6.4.3 Introduce the span gas standard in oxygen and,

using the span adjust knob, set the output to the level in

the span gas.

4.6.4.4 Introduce the oxygen sample into the analyzer

and read the quantity of hydrocarbons on the analyzer.

The result may not exceed the specification in Section 2

of this standard.

4.7 Water — This procedure is for the determination

of trace moisture (water) in oxygen using a continuous

flowing, cooled-surface condensation, dewpoint/frost-

point hygrometer. (See Note 9.)

4.7.1 Detection Limit — 0.6 ppm (vol/vol) at -79°C (-

100°F)

4.7.2 Flow Requirements

4.7.2.1 Set sample flow rate and pressure in

accordance with the instrument manufacturer’s

instructions.

4.7.3 Calibration Standard — A calibration ther-

mometer designed to indicate temperatures in the -79°C

(100°F) range is required.

4.7.4 Operating Procedure

4.7.4.1 An appropriately cleaned stainless steel or

copper sampling line must be used. If it has been

exposed to ambient moisture, it must be purged with

dry gas prior to use.

4.7.4.2 Flow the sample gas through the hygrometer

until the sampling system and instrument have reached

equilibrium with the gas.

4.7.4.3 After equilibrium has been reached, cool the

mirror of the hygrometer, as specified by its

manufacturer, to determine the dewpoint/frostpoint of

the sample gas.

4.7.4.4 Verify the dewpoint/frostpoint reading for at

least 30 minutes after it becomes stable.

4.7.4.5 Correct the dewpoint/frostpoint reading to 1

atm pressure. Convert it to ppm (vol/vol) using an

appropriate table. The result may not exceed the

specification in Section 2 of this standard.

4.8 Notes

Note 1: Introduce the calibration standard as many

times as necessary to achieve the desired precision.

Note 2: All gases used in the analysis of the sample

should not contain more than 10% of the specified

value of the component of interest, unless otherwise

stated.

Note 3: A flow restrictor should be installed on the vent

from port 8 to match the pressure drop of the detector.

Note 4: A flow controller is required on each carrier

inlet.

Note 5: An example of an operating procedure is

outlined below for the sample system shown in Figure

1. This procedure is appropriate only when the infrared

gas cell is designed to withstand the 200 psig sample

pressure.

Note 6: Operating procedures for other non-dispersive

infrared analyzers vary depending on manufacturer.

Refer to individual instrument vendor instructions in

each case.

Note 7: As the flow rate and heat capacity of the matrix

gas affect the instrument output, the zero and span gas

matrices must coincide with that of the sample gas.

Note 8: The effective response of a flame ionization

detector-equipped total hydrocarbon analyzer can vary

among different hydrocarbons and must be

approximated. However, the response of the most

common hydrocarbon impurities can be accurately

totaled and compared to methane.

Note 9: The sampling system and hygrometer must be

designed to operate at the sample pressure, or the

sample pressure must be reduced by a regulator with a

diaphragm of stainless steel or other suitable material.

Figure 1

Figure 2

Figure 3

Sample System for NDIR Analyzer

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