Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 158)

<10. Other Functions>
10-20
IM 11M12A01-02E
10.6 Methods of Operating Valves in the ZA8F
Flow Setting Unit
The ZA8F Flow Setting Unit is used as a calibration device for a system conforming to System
2. Calibration in such a system is to be manually operated. So, you have to operate the valve of
the Flow Setting each time calibration is made (starting and stopping the calibration gas flow and
adjusting the flow rate). This applies even if you are using the ZR40H Automatic Calibration Unit.
For operation of the converter, see Section 7.12, earlier in this manual.
10.6.1 Preparation Before Calibration
To operate the ZA8F Flow Setting Unit, prepare for calibration as follows:
(1) Check for a complete closing of the zero gas flow setting valve in the unit and open the
regulator valve for the zero gas cylinder until the secondary pressure equals sample gas
pressure plus approx. 50 kPa (or sample gas pressure plus approx. 150 kPa when a check
valve is used, maximum pressure rating is 300 kPa).
(2) Check that the oxygen concentration of the zero gas and span gas (instrument air 21
vol%O
2
) in the cylinder is set in the converter.
10.6.2 Operating the Span Gas Flow Setting Valve
The following description is given assuming that instrument air, the same as the reference gas, is
used as the span gas.
(1) When the display shown in Figure 10.15 appears during calibration, open the span gas
flow setting valve of the flow setting unit and adjust the flow rate to 600 ± 60 ml/min. Turn
the valve slowly counterclockwise after loosening the lock nut if the valve has a lock nut. To
check the flow rate, use the calibration flowmeter. If the sample gas pressure is extremely
high, adjust the sample gas pressure to obtain pressures (listed in Table 10.6) ± 10%.
Table 10.6
Sample gas pressure (kPa) 50 100 150 200 250
Flow rate (ml/min) 500 430 380 350 320
(2) Adjust the flow rate and select “Valve opened” from the Manual calibration display.
Check the Trend graph display to see that the measured value is stabilized. Then press the
[Enter] key. The Manual calibration display shown in Figure 10.16 appears.
(3) Close the span gas flow setting valve to stop the span gas (air) flow. If the valve has a lock
nut, be sure to tighten the lock nut to prevent any leakage of span gas into the sensor during
measurement.
8th Edition : Jan.13,2012-00