Teledyne 9060Z - Zirconium oxide flue gas oxygen analyzer - Manual (Page 25)

Model 9060Z Manual
25
high impedance alarm, ‘Probe 1 (2) High Impedance’, is not active. The actual impedance can be
displayed on the lower line. It should be less than 9 KΩ at 720°C (1320°F).
Once it has been established that the impedance is normal, the offset may be set using the millivolt
value marked on the oxygen probe. See chapter 6.3.1, Probe Offset. The probe offset can be tested on
site. A small flow of air must be admitted to both the ‘REF’ and ‘CAL’ ports when testing the probe
offset. If the probe is in the process, the air must fully purge the probe sensor without interference
from the process gas sample. Teledyne Analytical Instruments probes can easily achieve this with or
without a probe filter and a gas flow of only 1 to 5 SLPM (2 to 10 SCFH) for a 9060H probe and up to
20 SLPM (40 SCFH) for an unheated probe. When a stable oxygen reading has been achieved, read the
‘Probe EMF’. Enter this value into the set‐up menu #1 for the probe 1 (set‐up #2 for the second probe
if it is installed).
4.17 FILTER PURGING
Purging probe filters is controlled from the ‘GAS/PURGE’ buttons on the transmitter when in ‘RUN’
mode. If ‘Automatic’ has been selected in either ‘Sol. 1 Auto/Man’ or ‘Sol. 2 Auto/Man’ in
Commissioning Menus 21 or 30, pressing the GAS/PURGE button will start the automatic cycle.
Pressing the button again will cancel the auto purge cycle. If ‘Automatic’ was not enabled, the
solenoid will only stay open for as long as the button is pressed. Gradually adjust the purge air supply
regulator, increasing the pressure until sufficient flow is obtained to clear the filter. This is best
checked with a dirty filter after a period of operation, by withdrawing the probe from service and
watching any build up on the filter being blown off at the set pressure. Normally 30 kPa (5 psi) is
adequate but the air pressure may be set as high as 100 kPa (15 psi).
4.18 CALIBRATION GAS CHECK
If the installation has a filter purge facility, set this up first. Refer to the previous paragraph. Press the
‘GAS/PURGE 1 or ‘GAS/PURGE 2’ button while in ‘SET UP’ mode to obtain a reasonable flow through
the calibration check gas flow meter. If air is being used as a calibration check gas, use the air from the
regulator for filter purge. Then, when setting up a gas for calibration checking, set the pressure from
the calibration gas cylinder so that it is the same as the pressure set on the air regulator. Then the
setting on the rotameter / flow regulator will be the same as that for the airflow. The flow required is
1 to 5 SLPM (2 to 10 SCFH) for a 9060H probe and up to 20 SLPM (40 SCFH) for an unheated probe.
Air is not the best gas for calibration checking on a zirconia sensor. The output of a zirconia sensor
with air on both sides of the sensor is zero millivolts. It is better to choose a gas value which provides
a reasonable output from the sensor and which is near to the process oxygen level. A cylinder with 2%
oxygen in nitrogen is a commonly used calibration gas. The maximum pressure on the calibration
check gas cylinder regulators is 100 kPa (15 psi).
Note: If ‘Dual probe’ was selected in commissioning menu 4, ‘Cal Gas 2’ must be connected to probe 2.
4.19 DUST IN THE FLUE GAS
For heated probes the preferred method of mounting for dust‐laden applications is facing vertically
For unheated probes with no filter, entrained solids or dust in the flue gas does not present a
problem unless the dust, when settled, is not porous. Allow the dust in the process to build up on
the probe. It will form a porous layer slowing the response time. To avoid mechanical abrasion of
the electrode material in installations with unheated oxygen probes, pack ‘SAFFIL’ or equivalent
alumina based ceramic fiber in the sensing holes to protect the electrode. Do not use silica based
ceramic fibers such as ‘KAOWOOL’, which can attack the electrode at high temperatures. Once the
dust has built up the response time of the probe will be slower.