Metrohm 873 Biodiesel Rancimat Manual User Manual
Page 171
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6 Troubleshooting
873 Biodiesel Rancimat
￭￭￭￭￭￭￭￭
163
Problem
Cause
Remedy
During the measurement,
sample evaporates in the reac-
tion vessel and condenses in
the measuring vessel. This
results in contamination of the
conductivity measuring cell,
which in turn promotes adher-
ence of gas bubbles.
￭
Keep the measuring time as short as
possible, by about 4 to 6 h. The induc-
tion time can be reduced by about half
by increasing the temperature by
10 °C.
￭
Reduce the temperature so that less
sample evaporates or no sample at all.
However, this can substantially extend
the measuring time. The induction
time approximately doubles by reduc-
ing the temperature by 10 °C.
The curve shows a step
which means that the
induction time is no
longer determined cor-
rectly.
Side reactions occur at the
start or during the measure-
ment, which cause the con-
ductivity in the measuring cell
to rise.
￭
In the method, use the option Evalu-
ation delay or Evaluation suppres-
sion (see Chapter 4.5.2.2, page 64).
￭
Do not use Endpoint(s) as a stop cri-
terion in the method, but instead a
defined Conductivity (e.g.
200 µS/cm) (see Chapter 4.5.2.1,
page 60). The curves can then also be
evaluated manually after finishing the
determination.
The curve shows a step
at the start of the meas-
urement, which has not
occurred in previous
measurements.
The reaction vessel cover
(5-
still contain residues which are
transported into the measur-
ing vessel through the warm
air flow when a new measure-
ment is started.
￭
Thoroughly clean the reaction vessel
cover and the Iso-Versinic
®
tubing
￭
Replace the reaction vessel cover and
the Iso-Versinic
®
tubing from time to
time.
The induction time is
not evaluated automat-
ically, although a signif-
icant break point can
be noticed in the curve.
The option
Evaluate induc-
tion time is deactivated in the
method.
Activate the evaluation of the induction
time in the method (see Chapter 4.5.2.2,
page 64).
The option
Evaluation delay
or
Evaluation suppression is
defined in the method, which
prevents the evaluation of the
curve in the corresponding
time period.
Deactivate the corresponding option in
the method (see Chapter 4.5.2.2, page
64).
Automatic detection of the
induction time is not yet possi-
ble.
Keep the determination running until the
induction time is automatically found.