Operation
37
Filling the centrifuge tubes
Check carefully whether your tubes
are approved for the respective RCF
value. Follow tube manufacturers
recommendation.
For common borosilicate glass tubes the maximum
permissible rcf is limited to 4000 xg!
The tube manufacturers normally limit the respective
maximum allowed RCF value to the fixed angle rotor.
Please note that for the same RCF value
the stress for the tubes in a swinging-
bucket rotor is higher!
Because of the higher difference of the
radii (r
max
- r
min
) the pressure of liquid column to the
tube bottom is appreciably higher and strongly
depended on filling.
Plastic tubes and bottles – especially for the highest
load (speed, temperature) – have a limited life time
only and must to be replaced as recommended by
the manufacturer.
Maximum permissible load difference
The smaller the imbalance of the centri-
fuge
, the better the separation effect,
because as imbalance is minimized, so is
the resultant vibration that could affect
separation quality.
Therefore it is important, that the tubes are balanced
properly.
The maximum permissible load difference depends
on several factors (e.g. rotor, loading). For a swing-
ing bucket rotor 7500 6445 this amounts to at least
20 g in opposite carriers.
The values refer to a weight difference on the bottom
of the tube. If there is a weight difference resulting
from inhomogeneously filled tubes, the centrifuge
can operate with larger weight differences as well,
without causing an imbalance interruption.
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