How to balance a centrifuge and why it is so important to have a balanced centrifuge

Why balancing a centrifuge matters 

Reliable centrifuges play an essential role in laboratories. But, running one with an unevenly loaded rotor can greatly compromise performance, negatively impact the reliability of your testing results and cause irreversible damage to your equipment. Moreover, it’s crucial for safe operations and for protecting your lab personnel from potential injury.

On the other hand, a balanced centrifuge runs quieter, lasts longer, and performs optimally.

Thus, before each and every operation, the simplest and most effective action to avoid issues is balancing your laboratory centrifuge.

How to balance a centrifuge 

Aside from ensuring utmost performance, balancing your centrifuge is a safety precaution that you cannot neglect. Here are a few star tips to consider:

• Get familiar with the equipment. A prerequisite to using any lab equipment is having proper knowledge about it. Reading and following the manufacturer’s instructions/user manual will inform you on how to install, handle, operate, and maintain the equipment. For instance correcting rotor misalignments periodically and securing that all tube holders are in place are very important.
  
  

• Consider sample weight and placement when loading. Before switching it on, evenly distribute the weight of your lab samples around the rotor. It is advisable to balance masses to the nearest 0.1 gram. This means that for each sample placed, a sample with the exact same weight must be placed on the opposite side as if they are joined by a line directly through the center of the rotor. If you find yourself spinning down only one sample, make a ‘balance’ sample with the same size and weight to keep the rotor symmetrically loaded. 
  
  

• Use the centrifuge rotor specifically designed for samples to be centrifuged.  Loading the tubes to ensure that the center of gravity is on the center of the rotor can be achieved for different instrument types and tube numbers.  
  
  

• • Fixed angle rotor devices . In loading a centrifuge with fixed angle rotor, think of the sample tubes in pairs, placing them across  from each other. The two tubes opposite each other should be filled with the same volumes of sample. 
    

    • Note that if you have an odd number of tubes, you should add a balance tube to be placed opposite the ‘single’ sample test tube. The balance tube doesn’t have to contain the same value of liquid - it must have the same mass as the sample tube on  the other side of the rotor. Another option would be to space the sample tubes evenly around the rotor. 

• • Swinging bucket rotor devices. Make sure that all rotor positions are equipped with buckets, regardless if you leave them empty or not. Moreover, you need to inspect if the buckets can swing out smoothly.

  • • During the loading of tubes into the buckets, see to it that the opposing buckets are loaded symmetrically to avoid imbalance across the center of rotation. Additionally, each bucket has to be balanced across its pivotal axis. If these conditions can’t be met with the sample tube number that you have, use ‘balance tubes’ to help.

Centrifuge Safety Precautions  

In operating the centrifuge, it is crucial to do the following:

• Always ensure a sturdy, level worksurface. An uneven surface can cause your rotors to be imbalanced, even before you have loaded your tube samples. 
  
  

• Do not open the lid while the rotor is functioning. Though many centrifuges have a ‘safety shutoff’, this can stop power to the rotor which will still spin to its own inertia until such time that it is slowed to a stop by friction. 
  
  

• Pull the plug if the centrifuge is wobbling or shaking. Excessive shaking or wobbling can mean danger. Double-check if the tubes are in place. If the shaking is still not resolved, do not use the centrifuge until it has been serviced by the manufacturer.   
  

Centrifuge care and maintenance

These few simple steps can keep your centrifuge functioning properly, and consequently keeping them balanced.