Rosemount Oxymitter 4000, Instruction Bulletin

Page: 100 / 127

IB-106-340
6-15
6-9. CERAMIC DIFFUSION ELEMENT
REPLACEMENT.
NOTE
This refers to the ceramic diffusion element
only.
a. General. The diffusion element protects the cell
from particles in process gases. It does not nor-
mally need to be replaced because the vee deflec-
tor protects it from particulate erosion. In severe
environments, the filter may be broken or subject
to excessive erosion. Examine the ceramic diffu-
sion element whenever removing the probe for
any purpose. Replace if damaged.
Damage to the ceramic diffusion element may
become apparent during calibration. Compare
probe response with previous response. A broken
diffusion element will cause a slower response to
calibration gas.
Hex wrenches needed to remove setscrews and
socket head screws in the following procedure
are available as part of a Probe Disassembly Kit,
Table 8-1.
b. Replacement Procedure.
1. Follow the instructions in paragraph 6-4a to
remove the Hazardous Area Oxymitter 4000
from the stack or duct.
2. Loosen setscrews, Figure 6-10, using hex
wrench from Probe Disassembly Kit, Table
8-1, and remove vee deflector. Inspect set-
screws. If damaged, replace with stainless
setscrews coated with anti-seize compound.
3. On systems equipped with abrasive shield,
remove dual dust seal gaskets.
4. Use spanner wrenches from Probe Disas-
sembly Kit, Table 8-1, to turn hub free from
retainer.
5. Put hub in vise. Break out old ceramic
diffusion element with chisel along cement
line. Use a 3/8 in. (9.5 mm) pin punch and
clean fillet from the cement port.
6. Break out remaining ceramic diffusion
element by tapping lightly around hub with
hammer. Clean grooves with pointed tool if
necessary.
7. Replace ceramic diffusion element using the
ceramic diffusion element replacement kit in
Table 8-1. This consists of a diffusion ele-
ment, cement, setscrews, anti-seize com-
pound, and instructions.
8. Test fit replacement ceramic diffusion
element to be sure seat is clean.
Do not get cement on ceramic diffusion
element except where it touches the hub.
Any cement on ceramic diffusion element
blocks airflow through element. Wiping
wet cement off of ceramic only forces
cement into pores. Also, do not get any
cement onto the flame arrester element.
9. Thoroughly mix cement and insert tip of
squeeze bottle into cement port. Tilt bottle
and squeeze while simultaneously turning
ceramic diffusion element into seat. Do not
get any cement on upper part of ceramic dif-
fusion element. Ensure complete penetration
of cement around 3 grooves in hub. Cement
should extrude from opposite hole. Wipe
excess material back into holes and wipe top
fillet of cement to form a uniform fillet. (A
cotton swab is useful for this.) Clean any
excess cement from hub with water.
10. Allow filter to dry at room temperature
overnight or 1 to 2 hours at 200°F (93°C).
11. Wipe a heavy layer of anti-seize compound
onto the threads and mating surfaces of the
flame arrester, diffusion hub, and probe
tube.
12. Assemble flame arrester and diffusion hub
with two pin spanner wrenches. Torque to
10 ft-lbs (14 N·m). Secure with hub retain-
ing setscrew.
13. On systems equipped with abrasive shield,
install dust seal gaskets with joints 180
(
apart.
14. Reinstall vee deflector, orienting apex
toward gas flow. Apply anti-seize compound
to setscrews and tighten with hex wrench.
15. Reinstall probe on stack flange.