What is the operation principle of dental autoclave?
How an dental autoclave
works (simplified): (1) Steam flows in through a pipe at the bottom and
around a closed jacket that surrounds the main chamber (2), before entering the
chamber itself (3). The steam sterilizes whatever has been placed inside (in
this case, three blue drums) (4) before exiting through an exhaust pipe at the
bottom (5). A tight door lock and gasket seal (6) keeps the steam securely
inside. A safety valve (7) similar to the ones on a pressure cooker will pop
out if the pressure gets too high.
Once the chamber is sealed, all the air is
removed from it either by a simple vacuum pump (in a design called pre-vacuum)
or by pumping in steam to force the air out of the way (an alternative design
called gravity displacement). Next, steam is pumped through the chamber at a
higher pressure than normal atmospheric pressure so it reaches a temperature of
about 121–140°C (250–284°F). Once the required temperature is reached, a
thermostat kicks in and starts a timer. The steam pumping continues for a
minimum of about 3 minutes and a maximum of about 15–20 minutes (higher
temperatures mean shorter times)—generally long enough to kill most
microorganisms. The exact sterilizing time depends on a variety of factors,
including the likely contamination level of the items being autoclaved (dirty
items known to be contaminated will take longer to sterilize because they
contain more microbes) and how the autoclave is loaded up (if steam can
circulate more freely, autoclaving will be quicker and more effective).
Autoclaving is a bit like cooking, but as
well as keeping an eye on the temperature and the time, the pressure matters
too! Safety is all-important. Since you're using high-pressure,
high-temperature steam, you have to be especially careful when you open an
autoclave that there is no sudden release of pressure that could cause a
dangerous steam explosion.
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