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Description
Run Speeds
Run Speeds
The centrifugal force at a given radius in a rotor is a function of speed. Comparisons of forces
between different rotors are made by comparing the rotors' relative centrifugal fields (RCF). When
rotational speed is adjusted so that identical samples are subjected to the same RCF in two different
rotors, the samples are subjected to the same force. The RCF at each speed is automatically
calculated by the centrifuge software; if the RCF is entered, the centrifuge calculates the equivalent
revolutions per minute (rpm).
The maximum run speed listed in the rotor specifications is for operation when all conditions are
within the standard specifications.
The maximum run speed listed in the rotor specifications is for operation when all conditions are
within the standard specifications.
• If nonprecipitating solutions more dense than 1.2 g/mL are centrifuged, the maximum
allowable run speed must be reduced according to the following equation:
where ρ is the density of the tube contents. This speed reduction will protect the rotor from
excessive stresses due to the added tube load. Note, however, that the use of this formula may still
produce maximum speed figures that are higher than the limitations imposed by the use of certain
tubes or adapters. In such cases, use the lower of the two figures.
• Further speed limits must be imposed when self-forming-gradient salts are centrifuged, as the
equation does not predict concentration limits/speeds that are required to avoid precipitation
of salt crystals.
2-12
reduced maximum speed = (14,800 rpm)
1.2 g/mL
--------------------- -
ρ
PN A49436AG
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