Specifications

Trace Oxygen Analyzer Module
Rosemount Analytical NGA 2000
748420-A
August 1999
23
M
AINTENANCE AND
T
ROUBLESHOOTING
4
4.6 P
RINTED
C
IRCUIT
B
OARDS
All three printed circuit boards can be replaced, if necessary. Refer to Figure 1-2 for location
of the Power, Network and Computer Boards.
To remove any PCB, disconnect the associated cables first. Tag each connector and its
location before disconnecting any wiring. This helps in reassembly. The Power board and
Computer board are located on a common bracket.
4.7 T
ROUBLESHOOTING
The following provides a short list of common troubleshooting tips. Additional information is
contained in the Platform Manual.
The TO2 analyzer fails to purge down to ppm levels.
Prior to conducting any changes to the system, try running a quick start sequence (see
section 3.4) to see if the oxygen reading goes lower. If the reading does decrease, the
sensor has not been allowed sufficient time to consume the dissolved oxygen in the
electrolyte. If the reading continues to read high a leak may exist in the sample lines. The
number one problem associated with trace oxygen analyzer installation is the occurrence of
leaks in your sample plumbing. If the oxygen reading will not come down to ppm levels or is
reading higher than expected, the sample plumbing prior to the instrument may have a leak.
A quick check can be conducted by observing the oxygen reading at two different flow
levels; 0.5 and 2.0 scfh. If the oxygen reading drops significantly when the flow is increased
from 0.5 to 2.0 scfh, this is a good indication that a leak exists.
To check for leaks prior to the sensor, disconnect the Analyzer Module and cap the inlet
line. Pressurize the inlet line to 5 - 10 psig and check all connections with a soapy solution
(SNOOP
®
) to identify leaks.
WARNING: SENSOR DAMAGE
Do not pressure check the sample line with the sensor connected. Over-
pressurization of the sensor can result in damage.
The TO2 analyzer exhibits flow sensitivity.
Check to make sure that your vent line is not blocked. If you see a rise in reading with an
increase in flow, you may be over-pressurizing the sensor due to a blocked vent. Since the
sensor is a partial pressure measuring device, an increase in sample pressure will cause an
increase in reading. If the reading drops with increased flow, conduct the leak check
outlined in the troubleshooting tip above.