4 IN/ANAINST/032–EN Rev. B | Endura AZ20 series probe | Combustion oxygen monitor
5 Removing the diffuser flame arrestor
and cell
Referring to Fig. 5.1:
1. At the probe cell end, loosen 6 M4 x 50 bolts A using an
M4 spanner and 3 mm A/F hexagon wrench. Remove and
discard the 6 M4 x 50 bolts A and associated nuts.
If the bolts are seized, use a small hacksaw to cut the
through the bolts at the recess between the diffuser flame
arrestor C and probe end plate B.
2. Withdraw diffuser flame arrestor C while carefully
supporting cell D . Discard diffuser flame arrestor C.
If necessary, use a solvent, for example lighter fluid
(petroleum ether) or alcohol (surgical spirits) to lubricate the
joint between the diffuser flame arrestor and probe end.
3. Remove test gas injection pipe E from the cell housing.
Retain for re-assembly.
4. Carefully attempt to withdraw cell F from the cell housing
using minimal force. Retain for re-assembly.
— If the cell can be withdrawn freely, proceed to step 6.
— If the cell does not move (is stuck in the probe body),
use a spanner on the 2 flats to rock it sideways gently
(no more than 10 to 15 °) until loose. If this action frees
the cell proceed to step 6.
— If the cell cannot be withdrawn freely and / or is welded
to the thermocouple / electrode contact assembly,
proceed to step 5.
5. If the cell is welded to the helical contact at the end of the
thermocouple / electrode assembly, carefully withdraw the
cell and thermocouple / electrode contact assembly until
the cell tip G is visible.
If the assembly will not withdraw sufficiently to access
the joint between the cell and helical contact, disconnect the
red (Cell +), green (TC+) and white (TC–) wires (at the probe
head end) from the inner terminal block connections and
straighten the wires – refer to probe Maintenance guide
IM/AZ20M-EN.
Use a sharp blade to separate the wire nest from the cell tip
and separate the 2 items.
6. Remove and discard 'C-ring H.
If the C-ring is stuck, insert a small screwdriver blade in the
hollow of the C-ring I and gently prise it in several places
until free.
7. Proceed to Section 6, page 6 to fit the large surface area
filter.
WARNING – Bodily injury
High temperature
When in operation, the cell end of the probe reaches
temperatures up to 100 °C (212 °F). Allow the cell to
reach ambient temperature before starting maintenance
procedures.
IMPORTANT NOTE
Check all items for damage as they are removed. Do not
re-use the nuts or bolts, always replace damaged items
with new parts.
CAUTION – Potential damage to equipment
Do not use oil or release agents – these will damage
the components.
CAUTION – Potential damage to equipment
Take extreme care not to damage either item when
separating the cell tip from the wire nest on the
electrode assembly.
CAUTION – Potential damage to equipment
Do not touch the sealing face or ID of the probe
recess with the screwdriver blade. The surface finish
must be undamaged to maintain the C-ring’s sealing
properties.
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