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How to Balance a Centrifuge

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Running an unbalanced centrifuge poses great risks in the laboratory or clinic. Not only can it cause significant damage to the device itself, but an unbalanced centrifuge may also harm the operator and other lab personnel. In this regard, it is important that you know how to balance a centrifuge prior to operating it.

As a general rule, balancing masses to the nearest 0.1 gram is advisable, and that tubes should be balanced by mass, not volume. The total mass of each tube should be as close as possible as this becomes very important during high rotor speeds. For instance, do not balance a sample consisting of liquid that has higher or lower density than water with an equal volume of water.

Among the tips to balance a centrifuge are:

  • Ensure that all sample tubes are evenly filled. Check that they are all equal in mass, not just in volume.
  • Add a tube of equal weight directly opposite a tube inserted in the rotor, in case when you are just running a test on one sample.
  • Rotate the rotor 90 degrees then add 2 additional tubes directly opposite one another.

Balancing 3 tubes, 5 tubes, or 7 tubes in a centrifuge with 12 positions

Not all placements of a centrifuge are occupied during a testing activity. There are instances when you only have to run 3, 5, or 7 tubes in a centrifuge with 12 positions. Balancing these can be tricky, so it is important to know how to balance the tubes prior to operating the centrifuge.

  • Three tubes may be spaced evenly around the rotor.
  • To balance 5 tubes, create one balance tube and place 2 sets of 3 tubes across from each other.
  • To balance 7 tubes, create 1 balance tube and place 2 sets of 4 tubes across from each other.