AN-81
SS ZMT
ZFG2 Flue Gas Oxygen Probe
Introduction
The ZFG2 Flue Gas Oxygen Probe is one of the most
advanced in the world. A simplified design makes all the
component parts easily accessible and field serviceable. The
new universal probe construction gives the ultimate system
flexibility while retaining all the features, benefits and reliability
of the previous generation.
Fully interchangeable with previous model, and the ability to
upgrade from other manufacturer's products, the probe, in
common with earlier models of the in situ type, inserted
directly into the boiler smoke box, or flue duct, eliminating the
need for costly sampling installations.
Operating in the process temperature range of 20°C to 600°C
(68° to 1112°F) the system gives true wet analysis of net
excess oxygen in combustion gases. The probes can be fitted
with a flame trap, thereby extending their use to measurement
on gas fired boilers.
Installation and commissioning are particularly easy and the
level of in-service maintenance is extremely low.
Principle of Operation
The detector cell is constructed from stabilized zirconia
employing integral platinum electrodes and is specific to
oxygen. Air is supplied to the internal (reference) electrode to
provide a constant partial pressure of oxygen while the
measured gases are in contact with the outer electrode
producing a potential proportional to O
2
concentration.
The Probe
The zirconia probes, constructed from 316 stainless steel,
house a ceramic dust filter and flame trap, the detector cell,
cell heater and thermocouple. Wiring between the electronics
unit and the probe can be carried in a single 6m (20ft) flexible
conduit, which is PVC coated for IP65 (NEMA4) rated probes.
The conduit also contains the tubing for the reference air
supply. The standard probe insertion lengths available are 0.4,
1.0, 1.5 and 2.0m (16, 39, 58 and 78 inches) and fixing to the
duct or smoke box is by means of a drilled flange. Stand-off
fixings can be used to reduce the insertion length for smaller
ducts. A screwed bush is available for fixing the 0.4m probe to
the duct or smoke box. Longer length probes are available.
All components of the probe are easily removable and can be
replaced on site without the use of special tools or bonding
agents. Replacement of the zirconia oxygen sensor can be
made without the need for recalibration of the electronics unit.
A calibration gas inlet port is fitted to the probes to enable
accuracy checks to be made without removal of the probes
from their mountings.
The site-replaceable cell carries a 27 month warranty.
System Schematic Diagram, ZFG2 Probe
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