There are
three general classes of centrifuges in use at the University of
Kentucky. Low speed centrifuges which do not exceed 5000 rpm are
commonly found on the bench top. High speed centrifuges which do
not exceed 25000 rpm are generally floor models. Ultracentrifuges
which may exceed 100000 rpm are often found in core equipment areas
and are the most expensive and most dangerous centrifuges on campus.
Knowledgeable use, careful procedures, and preventative maintenance
are important for all centrifuges but especially for ultracentrifuges.
Over time centrifuge
rotors show signs of metal fatigue as a result of the powerful mechanical
forces to which they are subjected. Manufacturer guidelines should
be followed regarding when to derate (permanently lower the speed)
and when to retire centrifuge rotors. Centrifuges are designed to
contain the rotor in the event of a failure but there have been
documented incidences of rotor failures that were not contained
and caused injury to property and personnel. Preventive maintenance
for centrifuges should include an inspection of the rotors by trained
personnel. Keeping a use log for ultracentrifuges can assist in
calculating hours of use which can then be used to determine when
a rotor should be derated or retired.
Operators of
centrifuges on campus should be trained by supervisors or colleagues
in the proper use of centrifuges. User error is the biggest cause
of centrifuge malfunction.
Common causes
of centrifuge malfunctions include:
- Failure to
place the lid on the rotor.
- Failure to
properly secure the rotor lid.
- Failure to
properly secure the rotor to the drive.
- Overloading
the rotor’s maximum mass.
- Running swinging
bucket rotor with missing buckets.
- Buckets hooked
incorrectly and unable to swing freely.
- Improper
balancing of centrifuge tubes.
- Utilization
of centrifuge tubes that are not rated for the correct speed.
If a centrifuge
malfunctions:
- Turn off
the centrifuge and do not attempt to open the lid.
- Contact your
supervisor or administrative assistant to determine who to call
for centrifuge repairs.
- If there
is evidence of leakage or tube damage when centrifuging infectious
materials, close the lid immediately, allow aerosols to settle,
and plan the disinfection procedure.
All centrifugation
shall be done using centrifuge safety buckets or sealed centrifuge
tubes in sealed rotors. If any spills or leakage are apparent in
the centrifuge the rotor should be cleaned with a mild detergent,
rinsed thoroughly with distilled water, and allowed to air dry completely.
Do not use abrasive or corrosive materials to clean the rotor as
this can cause damage to the rotor.
The following
procedures for centrifugation are recommended:
- Examine tubes
and bottles for cracks or stress marks before using them.
- Fill and
decant all centrifuge tubes and bottles within the biological
safety cabinet.
- Wipe outside
of tubes with disinfectant before placing in safety cups or rotors.
- Never overfill
centrifuge tubes as leakage may occur when tubes are filled to
capacity. The maximum capacity for centrifuge tubes is 3/4 full.
- Always cap
tubes before spinning. Use screw cap tubes.
- Place all
tubes in safety buckets or sealed rotors when centrifuging infectious
materials. Inspect the "O" ring seal of the safety bucket
and the inside of safety buckets or rotors. Open safety buckets
or rotors in a biological safety cabinet.
- Never exceed
safe rotor speed.
- Ensure that
the load is balanced. A difference of 0.5 grams at 500000 x g
is equivalent to a 250 kilogram difference.
- Stop the
centrifuge immediately if an unusual condition (noise or vibration)
begins.
Centrifuge Safety
Online:
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