Calibration Responses; Everything Is Fine; Forced Flow Problem; Plugging Or Dead Space Problem - GE CGA 351 User Manual

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Calibration Responses

Everything Is Fine

Forced Flow Problem

Plugging or Dead Space
Problem
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Service and Maintenance
Chapter 4, Setup and Calibration, describes the procedures for
calibrating the CGA 351 in great detail. However, the response of the
unit to the calibration procedures can provide valuable clues to
potential problems with the installation. The three most common
situations are described in this section.
Calibration of the analyzer at the tagged calibration gas flow rate has
been successfully completed. Upon switching off the calibration gas,
the analyzer quickly returns to monitoring and displaying the sample
gas concentrations accurately. This indicates that proper operating
conditions have been achieved and the analyzer can be expected to
perform reliably.
If a flow rate higher than the tagged calibration gas flow rate is
required to calibrate the analyzer, the sample gas feed pressure is too
high. Under such conditions, the sample is not entering the oxygen
sensor by diffusion only, but it is being forced into the sensor instead.
In addition to the calibration problem, sensor life may be shortened
and analyzer plugging may occur. If forced flow is confirmed as the
problem, refer to Chapter 2, Installation, for instructions on proper
installation of the analyzer.
The analyzer was successfully calibrated at the tagged calibration gas
flow rate, and the analyzer responded quickly to the calibration gas.
However, there is a significant delay in reading the correct sample gas
concentrations, after turning off the calibration gas.
When this problem occurs, it is very likely that the sample gas inlet is
located in a dead space. After the analyzer is correctly reading the
sample gas concentration, switch on the calibration gas just long
enough to get the correct reading. As soon as the analyzer reads the
correct value, quickly shut off the calibration gas. One of two
responses should occur:
1. If the recovery time is still too long, the sample gas path through
the oxygen sensor may be plugged with particulates. Use of a
blowback system (contact the factory for assistance) should clear
the analyzer and restore proper operation.
2. If the analyzer reading recovers promptly, dead space is the likely
problem. Internal structures can cause dead spaces that are not
evident from an external examination. It may sometimes be
necessary to relocate the analyzer to a more suitable installation
site.
Note: If the calibration "Failed", repeat the calibration procedure
on pages 4-33 to 4-35. If another failure or any situations not
covered in this chapter are encountered, contact the factory
for assistance.
December 2004
5-11