Centrifuges are commonly used in biological research laboratories to separate cellular material from a suspending liquid medium. They can range from the small bench-models to the sophisticated ultracentrifuges. Low speed centrifuges can have a speed range of 2000 to 6000 rpm, while ultracentrifuges can run at 40,000 to 80,000 rpm. Needless to say, with components revolving at such high speeds, centrifuges constitute a potentially severe mechanical hazard. In addition, there are hazards which are related to the inherent toxicity of the material being centrifuged, such as with biohazardous or radioactive materials.
All centrifuge users must be trained in and be familiar with the safe operation of the equipment. Before using a particular centrifuge, the manufacturer's instructions for that model should be read and followed. Procedures for the safe operation of centrifuges include, but are not limited to, the following:
- Ensure that the loaded rotor or buckets and trunnions are properly balanced each time it is used.
- Load multiple containers symmetrically in the rotor. In addition to the potential physical hazard, failure to balance the rotor correctly will greatly increase the wear on the drive system, and can cause extensive damage to the rotor and centrifuge.
- All floor-standing centrifuges must be fitted with interlocks so that it is impossible to open the cover when the centrifuge is in operation. The newer models are built with interlocks; many older models were not built with such protective devices, however, the Ministry of Labour requires these units (centrifuges) to be retrofitted with interlocks, prior to operation.
For bench-centrifuges not fitted with interlocks:
- Always close the centrifuge lid during operation.
- At the end of a run, do not open until the rotating head has come to rest.
- Never stop the rotor by hand or with an object.
- There must be a sign displaying the fact that units must not be opened until the rotating head has come to a complete stop.
- Do not leave the centrifuge until it has attained its full operating speed, in order to ensure that it is running without vibration. Stop the centrifuge immediately and check the load balances if vibration does occur.
- Do not exceed the safe maximum speed of the centrifuge as specified by the manufacturer. A particular rotor may also be derated, meaning that it cannot run at it's maximum speed. Derating is usually necessary for rotors which have completed a certain number of runs and accumulated a certain number of hours, for rotors that have corroded, or for solutions with densities greater than 1.2g/cm3.
- Clean rotors and buckets after use and dry thoroughly. Spillages can seriously weaken the rotor due to corrosion. Rotor components of low-speed centrifuges can be made of brass, steel, plastics, or aluminum alloys. An aluminum rotor can be easily corroded by acid or alkaline solutions but even solutions containing low concentrations of salts at neutral pH can break down the protective oxide film covering the surface of the rotor.
When centrifuging toxic materials, such as the case with biohazardous or radioactive samples, extreme caution must be taken to avoid contamination of the centrifuge as well as the laboratory:
- Use capped tubes to contain the samples and to prevent the escape of potentially hazardous aerosols.
- Use containers made of unbreakable material whenever possible.
- Conduct regular inspection and testing for signs of contamination (i.e. swipe tests).
- Be aware of decontamination procedures that apply to your sample's hazard(s).
- Centrifuge biohazardous materials within sealed rotors or buckets. Load and unload these materials within the biosafety cabinet or chemical fume hood.
- Biocontainment features are commercially available for centrifuges. Further information can be obtained through the Biosafety Office by calling 416-978-3981, or from centrifuge manufacturers.
- Conduct regular maintenance, inspections and servicing of the centrifuge, as outlined in the manufacturer's instructions.
- Examine the centrifuge and it's components regularly for signs of corrosion, cracks, flaws, or undue wear, before each use.