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19 Relative centrifugal force (RCF)
The relative centrifugal force (RCF) is given as a multiple of the acceleration of gravity (g). It is a unit-free value and
serves to compare the separation and sedimentation performance.
These values are calculated using the formula below:
1,118r
2
1000
RPM
RCF ××=
⎟
⎠
⎞
⎜
⎝
⎛
⇒ 1000
1,118r
RCF
RPM ×
×
=
RCF = relative centrifugal force
RPM = rotational speed (revolutions per minute)
r = centrifugal radius in mm = distance from the centre of the turning axis to the bottom of the centrifuge.
For more on the centrifugal radius see the chapter ” Anhang/Appendix,
Rotoren und Zubehör/Rotors and accessories”.
The relative centrifugal force (RCF) stands in relation to the revolutions per minute and the centrifugal
radius.
20 Centrifugation of materials or mixtures of materials with a density higher than 1.2 kg/dm
3
When centrifuging with maxim revolutions per minute the density of the materials or the material mixtures may not
exceed 1.2 kg/dm
3
.
The speed must be reduced for materials or mixtures of materials with a higher density.
The permissible speed can be calculated using the following formula:
[RPM] speed maximum x
[kg/dm³]density Greater
1.2
= )(n speed Reduced
red
e.g.: maximum speed RPM 4000, density 1.6 kg/dm
3
RPM 3464 = RPM 4000 x
kg/dm³ 1.6
kg/dm³ 1.2
= n red
In the exceptional case that the maximum loading indicated on the hanger is exceeded, the speed must also be
reduced.
The permissible speed can be calculated using the following formula:
[RPM] speed maximum x
[g] load actual
[g] load maximum
= )(n speed Reduced red
e.g.: maximum speed RPM 4000, maximum load 300 g, actual load 350 g
RPM 3703 = RPM 4000 x
g 350
g 300
= n red
If in doubt you should obtain clarification from the manufacturer.
21 Rotor Identification
After every start of a centrifugation run the rotor utilised is identified.
After a change of rotor the drive switches off and the rotor code (R xx) as well as the maximum rotational speed
(n-max=xxxxx) of the rotor are displayed.
A further operation of the centrifuge is only possible after a single opening of the lid.
If, following a rotor change, the maximum speed of the rotor is less than the set speed, the speed is limited to
the maximum speed of the rotor.
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