Teledyne 9060 - Zirconium oxide flue gas oxygen analyzer - Manual (Page 17)

9060-Zirconia Analyser
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1.3 PURGE & CALIBRATION CHECK ACCESSORIES
Due to the absolute measurement characteristics of zirconia sensors and the self-
calibration features of Teledyne transmitters, probe calibration checks with calibrated gas
are not normally required. In some installations however, automatic gas calibration checks
are required by Environmental Protection Authorities and by engineering management in
Power Stations, Oil Refineries and similar large end users.
Teledyne probes and transmitters provide a ready method of connecting on-line
calibration check gases. They provide on-line automatic checking of probe and transmitter
calibration, as well as a probe purge facility.
The absolute characteristics of zirconia sensors require only one calibration check
gas to properly check the probe’s performance. Where required however, the dual gas
calibration check facility can be utilised.
Dirty flue gas applications often require the back purge facility to keep a probe filter
free from blockage. (In these applications, it is more reliable to install probes pointing
vertically downwards with no filter). Purge and calibration check solenoid valves can be
operated manually or automatically from a 9060 Analyser.
The external components required for automatic / manual gas calibration checking are:
• A calibration check gas flow meter/regulator
• A mains voltage (240 or 110 VAC) solenoid valve for each calibration check gas
The external components required for automatic / manual purging are:
• A mains voltage (240 or 110 VAC) purge solenoid valve
• A purge pressure switch, 0 to 35 kPa (0 to 5 psi), to test for filter blockage.
The user should supply:
• Span gas cylinder(s), typically 2 % oxygen in nitrogen or a similar percentage of 02
close to the normal level in the gas stream being measured, to ensure fast recovery.
• A 100 kPa (15 psi) clean and dry instrument air supply when filter purging is required.
1.4 FILTER PURGE PRESSURE SWITCH
To automatically sense a blocked probe filter, a pressure sensor should be
connected to the ‘purge’ line to the probe ‘cal’ port. It should be adjusted so that it
energises just above the purge pressure with a new or clean filter installed. The switch
contacts should be connected to terminals 12 & 13 (PURGE FL SWITCH).
If the filter is still blocked or partly blocked after an auto purge cycle, the pressure
switch will energise and cause a ‘Probe Filter Blocked’ alarm. The contacts must be
normally closed.
The pressure switch should have an adjustable range of 0 to 100 kPa (0 to 15 psi).