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CR Scientific



There are a few important guidelines for operating a centrifuge, even a small one. Following them can prevent damage to the centrifuge and possible serious injury to you and others.

1. The work surface must be level and firm. Do not use the centrifuge on an uneven or slanted work surface.

2. Balance the tubes in the rotor!  If you want to run a tube with 10 mL of liquid, put another tube with 10 mL of water in the opposing hole on the rotor (see photo, below). If the liquid has a higher or lower density than water, you must balance the tubes by mass, not volume.  The total mass of each tube should be as close as possible - this becomes increasingly important at very high rotor speeds.  Running a centrifuge with unbalanced load could permanently damage the centrifuge.  It could also cause injury to you or someone else.

Balancing the masses to the nearest 0.1 gram is advisable.  (Ultracentrifuges should have masses balanced very carefully, to as high a precision as is practical.)

Make sure the load is balanced
It's also good to label the tubes so you don't mistake something dangerous for water. Black marker is handy for writing on the sides of the tubes. Be careful if you label only the caps... it's easy to mix them up.

You may notice that one of the tubes contains concentrated H2SO4.  The other one contains water.  The density of conc. H2SO4 is much higher than water, so equal volumes couldn't be used.  The tubes had to be balanced on a scale.

3. Do not open the lid while the rotor is moving. Even though many centrifuges have a "safety shutoff" if the lid is opened, the only thing this does is stop powering the rotor. The rotor will still spin due to its own inertia for a while until friction slows and eventually stops it.

4. If you see it wobbling or shaking, pull the plug. A little vibration is normal, but excessive amounts can mean danger. FIRST, double check that you correctly balanced the tubes.  If the answer is yes and the wobbling still happens, contact the manufacturer or dealer and get the unit serviced. If you bought the centrifuge from us, here's the contact info if the unit needs service or replacement. Do NOT continue to run a centrifuge that wobbles visibly when the rotor is spinning.

5. Wear a face shield and / or safety goggles if you have to work anywhere near a centrifuge that's in use.  Accidents happen-- sometimes under the most freakish or unexpected circumstances. The rotor is spinning very rapidly and generates extreme forces.
Although a physicist would tell you that centrifugal force is an "illusory force", the point makes not one bit of difference to the sample as it spins in the rotor. It might as well be experiencing a real force that "pulls" the particles toward the bottom / outside of the tube. These "illusory" forces have been known to tear apart enormous flywheels in factories, for example, with disastrous consequences (read some of the compilations of machinists' stories from Lindsay Publications, for instance). So much for illusions.
Centrifuge rotors are made to withstand these extreme "centrifugal forces" (i.e., they're designed to give enough centripetal force to keep the rotor together as it spins), but it's better to be prepared in case something fails. It may be fascinating to watch the tubes spin around in the centrifuge, but don't make it a habit. Turn the unit on and keep your distance until well after the timer shuts off the motor- this is just a basic safety rule for all centrifuges.

6. Do not bump, jar, or move the centrifuge while the rotor is spinning. Instruct all other persons in the area to stay clear of the unit while it's operating.  Make sure you don't have the cord dangling from a table edge where someone could catch their foot in it and pull down the centrifuge.


15-mL plastic centrifuge tube
Use tubes that are rated at or above the maximum speed of your centrifuge. Polystyrene or glass tubes are suitable for tabletop centrifuges; super high-speed floor models (ultracentrifuges) should use polypropylene or other tubes designed to withstand the severe strain.
Discard any centrifuge tubes that have cracks in them.




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