For smooth centrifuge operation and extended equipment life, it is essential that
you balance the loads as equally as possible. For best results, the use of a balance is
recommended to obtain loads of equal weight. The angular distribution of material to be
centrifuged is critical where loads are not of equal weight. If you cannot equalize the
amount of fluid in the opposite tubes, fill the shield around the lighter tube with water until
the loads are balanced.
Never attempt to balance by adding weights, mercury, or shot to the bottom of a
tube or shield.
SPEEDS AND RELATIVE CENTRIFUGAL FORCES
a. Maximum Velocities. Figure 1-2 lists the maximum angular velocities and
relative centrifugal forces obtainable with each of fourteen interchangeable rotor and shield
configurations. Tip radius for each configuration is also listed. The maximum velocities
and centrifugal forces in figure 1-2 were derived by operating the Model 0103 Centrifuge at
120 vac, 60 Hz and Model 0106 Centrifuge at 220 vac, 50 Hz. These maximum velocities,
however, can vary significantly with changes in line voltage and frequency, and with load,
age and condition of the centrifuge.
b. Speed Selection. Many tests require centrifugation at an intermediate rpm
between the minimum ("0") and maximum speed control settings. To obtain the desired
speed, turn the speed control knob clockwise from "0" until the tachometer needle
stabilizes at the required rpm.
Always return the knob to the "0" position after completion of a cycle.
c. Calculating RPM. Certain tests call for centrifugation at a specified relative
centrifugal force (rcf). Rcf is defined as the force acting on the sample being centrifuged
relative to the force acting on the sample in the earth's gravitational field. The operator
can calculate the correct tachometer speed (rpm in thousands) corresponding to the
required rcf specified for a test, using the following formula:
Rpm in thousands (tachometer speed) equals the square root of rcf divided by
Where: Rcf equals the relative centrifugal force specified for the particular
R equals tip radius of shield (in inches) obtained from Figure 1-2 for the rotor
centrifugation being used.