21
Maintenance
SW 836502
Maintenance
General
A pH or redox measuring system require
maintenance with regular intervals.
Cleaning and buffer adjustment (calibration)
is a normal and necessary maintenance that
should be carried out regularly.
Intervals
The interval between buffer adjustments and
cleaning is depending widely on the working
conditions. Therefore, the easiest way to
find the most appropriate cleaning interval is
by feeling one's way.
For instance, start out with cleaning and
buffer adjustment every week.
If the measurement is unchanged or just
slightly changed after the buffer adjustment,
the electrode were not dirty or just slightly
dirty, and the cleaning interval can be chan-
ged to 2 weeks and after that 1 month.
The intervals are equally reduced if the elec-
trodes are very dirty and the measurement is
significally changed after buffer adjusting.
There are no general guidelines to clea-
ning and adjustment, men in most cases a
monthly adjustment is sufficient.
Before beginning a buffer adjustment, the
electrode must be thoroughly washed, first
in running water, if necessary a degreasing
fluid like for example 10% hydrochloric acid
solution, and there after in de-ionised water
before the electrode is put into the buffer
solution and in between every step of the
buffer adjustment.
Redox electrodes
Redox electrodes require cleaning like pH
electrodes, but not buffer adjusting.
However, MJK do deliver redox buffers for
control of electrode and transmitter.
If the transmitter does not show the correct
value when put into the buffer solution, the
electrode must be exchanged.
Cleaning of elektrodes
Use clean potable water for cleaning the
electrode.
A 10% hydrochloric acid solution can be
used for cleaning if the electrodes are gre-
asy. Protein coatings is removed with Pepsin
cleaning fluid (item number 163020).
Electrode lifetime
The expected lifetime of the electrodes is
dependant of the measurement.
The lifetime is given with reservation as the
physical conditions as well as the tempera-
ture, pressure and pollution of the fluid has
great influence on the stated lifetime.
The lifetime is based on 25 °C, but if the
temperature is doubled, the lifetime
will be halved!
PH electrodes in purifying plants for ordinary
household wastewater lasts approximately
1 year, whereas the lifetime of pH electrodes
in industrial plants is dependent on measu-
ring application and the process.
Redox electrodes have a lifetime of approxi-
mately 2 years, depending on cleaning.