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9487 Dielman Rock Island Ind Dr, St. Louis, MO 63132
www.becs.com
Operation and Maintenance Manual
Rev: L13
Section D: Maintenance
The BECSys controller requires no maintenance other
than a periodic calibration check and sensor cleaning.
D – 1: Potentiometric Sensors (pH and ORP)
D – 1.1: Electrode Cleaning
Slow response time and large offsets may indicate the
electrode has become coated. The nature of the
coating will dictate the type of cleaning technique
that should be used.
Soft coatings, like bacterial films, are best removed
using a squirt bottle or the water jet from a faucet.
If this is not successful, then gently wipe with a
soft wet cloth.
For a more severe coating, first try a strong
detergent (something similar to Dawn liquid
detergent) and warm water, using a soft brush (like
a toothbrush). Isopropyl alcohol on a Q-tip is
another good choice. Rinse the measuring end in
distilled water before reinstallation.
Greasy and oily coatings are best removed with a
detergent solution or a solvent that will not attack
the sensor body. Methanol and isopropyl alcohol
are good choices for solvents. Acetone, MEK,
THF, or trichloroethane will irreparably harm the
electrode.
Hard coatings, like calcium or lime scale, are best
removed with a solvent appropriate for the
particular coating. A 5% solution of hydrochloric
acid (HCl) would be a good choice for calcium
scale. If unsure of the proper solvent to remove a
hard mineral coating, then alternate between a 5%
hydrochloric acid and a 4% sodium hydroxide
(NaOH) for 10 minutes each. After treating the
electrode with these strong acids or bases, rinse the
electrode with water and soak it in a pH 4 buffer
for at least 1/2 hour.
The platinum tip of an ORP sensor can be cleaned
with an abrasive as a last resort. Gently scour the
platinum with a 600 grit wet emery cloth, or
preferably, a 1-3 micron alumina polishing powder.
D – 1.2: Long-Term Storage
Save the wetting cap that came with the sensor for
long-term storage. After removing the sensor
from the flow cell, clean it as in routine
maintenance, then store it in the wetting cap using
a pH 4 buffer saturated with potassium chloride
(KCl). The potassium chloride will prevent
electrolyte from leaching out of the sensors
reference cell. The wetting cap only needs to be
half full. If a number of sites are going to be
serviced, for example, at the end of a season, then
it might be a good idea to carry a pint of 4.0/KCl
storage solution.
D – 2: Free Chlorine Sensor
Check the sensor measurement at regular intervals (at
least once a month), and perform a recalibration if
necessary.
As a rule of thumb, refill the measuring cell with
electrolyte once per season (or every 12 months).
D – 2.1: Cleaning
If the sensor membrane is visibly soiled, then
remove the sensor from the flow cell and clean the
membrane with a gentle water jet, or soak the
membrane for a few minutes in a 1% to 10%
hydrochloric acid (HCl) solution. Avoid chemical
additives as they may damage the membrane.
Replace a heavily soiled or damaged membrane.
D – 2.2: Long-Term Storage
Save the yellow protective cap that came with the
sensor for long-term storage. After removing the
sensor from the flow cell, empty the measuring cell
of electrolyte (particularly if dehydration of the
membrane is possible). Rinse the measuring
chamber and electrode shaft with cold water and
let them dry. Then screw the measuring cell down
loosely and not to the stop, so that the membrane
remains unstressed. When the sensor is put back
into service, it will have to be refilled with
electrolyte and run through an initial polarization
before calibration.
D – 2.3: Filling electrolyte
Unscrew the measuring chamber from the shaft.
Hold the measuring chamber at an angle and fill in
approximately 7 to 8 ml electrolyte, up to
approximately 1 cm under the top edge.
Tap the filled chamber several times on a flat
surface to release any air bubbles.
Screw the electrode shaft into the measuring
chamber vertically from above, displacing all air
from inside. Tighten slowly to the stop.
Warning: You may lightly blot the water
On a pH sensor tip on a paper towel, but never
vigorously rub or wipe the pH bulb because this
may scratch the delicate outer layer on the pH
glass impairing its response.