3600 Analyzer for O
2
Measurement—Operator’s Manual 29
3600O2.OM.E9903
(The sensor mask may be installed as well.)
Pry off the membrane holding ring either with
your fingers or, if the ring has a wide outer
groove, with the tool model 28116 included
with your recharge kit.
Take care to avoid contact with the electrolyte
in the sensor. It can irritate skin, so rinse hands
with plenty of tap water during this procedure.
Note too that the electrolyte can permanently
stain clothing, so exercise care in handling.
Throw out the membrane (and mask, if applicable), keep the holding ring, and
shake out any electrolyte.
Using the membrane support tool, match
up the prongs of the tool to two of the
holes in the membrane support. Turn
counterclockwise to remove this
support. Note: Each membrane support
is individually machined at the factory to
match its sensor. It is ESSENTIAL when
servicing several sensors at a time to
keep the appropriate membrane support
matched to its respective sensor.
Rinse the membrane support with water. If discolored, you may elect to clean it
with concentrated (approximately 70% by weight, but no stronger) nitric acid
(HNO
3
) for about 30 seconds, rinsing with water after the process is completed.
The discoloration does not affect performance, but cleaning permits better viewing
of the sensor.
WARNING: Nitric acid is dangerous! Should your skin be exposed to nitric
acid, wash immediately and thoroughly with water.
Empty and rinse the electrolyte reservoir with water.
1.5.4 Electrochemical Cleaning
The optional model 32301 Sensor Cleaning and Regeneration Center employs an
electrochemical cleaning technique. This method reverses any chemical reactions
that take place in the sensor during normal operation, and easily removes the
electrode deposits that reduce sensor efficiency. The cleaning center also allows a
check of the sensor’s electronics to verify that the system is working correctly. See
the model 32301 operator’s manual for instructions on its proper use. Note that
the plastic base supplied with the sensor must be removed to use the 32301
cleaning center.
Alternatively, you may use the chemical cleaning and polishing method described
in the following section. This method also works efficiently as a preliminary
approach to the cleaning center’s electrochemical cleaning procedure.
1.5.5 Chemical Cleaning
Depending on the appearance of the sensor electrodes you can try either of the
following two cleaning procedures, ammonia or nitric acid cleaning. If the
electrodes appear fairly clean and bright, try the ammonia cleaning procedure; if
very dirty or discolored, use the nitric acid cleaning procedure.
Note: If the following procedures are not closely adhered to, there is a risk of
shortening the useful life of your sensor.
Removing membrane holding ring
Using membrane support tool to remove
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