Use of Laboratory Centrifuges

• Laboratory centrifuge: An apparatus used in the laboratory for separating substances of different density or particle size, when suspended in a fluid, by spinning them about an axis in a suitable container.
• Rotor: Primary component of a centrifuge which holds the material to be subjected to centrifugal force (in some form of tube/container) and which is rotated by the drive system.

Hazards

• Mechanical failure of rotating parts (often violent).
• Contact with rotating parts.
• Sample leaks causing aerosols, stress corrosion, contamination.
• Sample imbalance causing machine movement / walking (or stress failure of component parts).
• Fire or explosion.
• Health (contact with contaminated components / vapours).

Operation

• Only suitably trained persons may operate a centrifuge.
• Where necessary, the machine log book must be filled in (a log book must be kept for ultra centrifuge rotors as the hours run determine the life of the rotor).
• Before use the rotor, its lid and seals must be examined for cleanliness and damage (a build-up of chemicals from spillages may cause a tube to jam in the rotor or cause corrosion that could lead to a rotor failure). Damaged rotors must not be used and should be reported to the Supervisor, dirty rotors must be cleaned by the approved method. (see rotor care).
• Never fill centrifuge tubes above the maximum recommended by the manufacturer. (see manufacturers catalogue).
• Never exceed the maximum stated speed for any rotor.
• Derate the rotor speed whenever:-
  • the rotor speed/temp combination exceeds the solubility of the gradient material and causes it to precipitate.
  • the compartment load exceeds the maximum specified.
  • Failure to reduce rotor speed under these conditions can cause rotor failure.
• Balance the rotor to within the limits specified (take care that materials of similar densities are in opposite positions of the rotor).
• Do not operate the centrifuge without the appropriate rotor cover securely fitted and its seals in place.
• Check compatibility of tube material to solvent medium.(some solvents may cause the tubes to swell or crack in the rotor)
• Use only correctly fitting tubes.
• Clean up spillages immediately. (use appropriate PPE if necessary).
• Do not use chemicals that are explosive, highly flammable or have vigorous chemical interaction without observing the appropriate safety precautions to minimise risk of vapour build-up.
• Never attempt to open the lid of a centrifuge or slow the rotor by hand or open the lid while rotor is in motion as serious injuries may be incurred.
• Only authorised and suitably trained persons may service or repair a centrifuge, report all faults promptly, do not attempt repairs yourself. Do not use the centrifuge until the fault has been inspected or repaired.

Rotor Care

• Stress corrosion is thought to be initiated by certain combinations of stress and chemical reaction. If the rotor is not kept clean and chemicals remain on the rotor, corrosion will result. Also, any moisture left for an extended time can initiate corrosion. It is important that the rotor is left clean and dry. (Wash with mild detergent and warm water, careful use of a nylon bottle brush when necessary). Dry the rotor thoroughly and store upside down with the cover and tubes removed.
• Do not autoclave at temperatures above 100°C.
• Do not expose aluminium rotor components to strong acids or bases, alkaline lab detergents or salts (chlorides) of heavy metals (e.g. caesium, lead, silver or mercury.) Use of these can initiate corrosion.

Pre-run safety checks

• Make sure each tube compartment is clean and corrosion free.
• Make sure the rotor itself is clean, corrosion and crack free and that there are no scratches or burrs around its rim.
• Check centrifuge chamber, drive spindle and tapered mounting surface of the rotor are clean and free of scratches or burrs.
• Wipe drive surfaces prior to installing the rotor.
• If the temperature of the chamber is below room temperature, pre-cool the rotor to the lower temperature before securing the rotor (this will minimise the chance of it seizing to the tapered spindle).
• Make sure that any rotor lid securing device and any rotor to spindle securing device is fully secured before starting the machine.

Training

All new users of centrifuges must be trained by an appointed instructor (who may be an appropriately qualified or experienced member of staff) before attempting to use a centrifuge.

Level of Risk Remaining

Centrifuges are potentially lethal pieces of equipment and care and vigilance need to be exercised at all times. Following the procedures outlined here will reduce risk to a low level.

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Adapted with permission from School of Chemistry, University of Bristol