(A)utoclave
AUTOCLAVE
A.
What is an autoclave ?
o
The autoclave was invented by Charles Chamberland in 1879
o
Autoclaves are large vessels that are pressurized and brought to high
temperatures. They are usually cylindrical since the rounded shape is better
able to safely withstand high pressures.
o
Autoclaves are designed to hold
items that are placed inside and then the lid is sealed. In fact, the words
“auto” and “clave” mean automatic locking.
o
Due to the pressures involved, safety valves are important to ensure that
pressure of the steam inside is safely maintained.
o
Autoclaves are commonly used for sterilizing equipment and tools, but
they have a range of uses.
B. PRINCIPLE OF AUTOCLAVE-
• The
autoclave works on the principle of moist heat sterilization where steam under
pressure is used to sterilize the material present inside the chamber.
• The high
pressure increases the boiling point of water and thus helps achieve a higher
temperature for sterilization.
• Water
usually boils at 100°C under normal atmospheric pressure (760 mm of Hg);
however, the boiling point of water increases if the pressure is to be
increased.
• Similarly,
the high pressure also facilitates the rapid penetration of heat into deeper
parts of the material, and moisture present in the steam causes the coagulation
of proteins causing an irreversible loss of function and activity of microbes.
• This
principle is employed in an autoclave where the water boils at 121°C at the
pressure of 15 psi or 775 mm of Hg.
• When this
steam comes in contact on the surface, it kills the microbes by giving off
latent heat.
• The
condensed liquid ensures the moist killing of the microbes.
• Once the sterilization phase is completed (which depends on the level of contamination of material inside), the pressure is released from the inside of the chamber through the whistle.The pressure inside the chamber is then restored back tot eh ambient pressure while the components inside remain hot for some time.
C. Types of autoclaves
I. Pressure cooker type/ Laboratory bench
autoclaves (N-type)
·
·
The
more modern type has a metal chamber with a secure metal lid that can be
fastened and sealed with a rubber gasket.
·
It
has an air and steam discharge tap, pressure gauge, and safety valve. There is
an electric immersion heater in the bottom of the chamber.
II.
Gravity
displacement type autoclave
· This is the common
type of autoclave used in laboratories.
· In this type of
autoclave, the steam is created inside the chamber via the heating unit, which
then moves around the chamber for sterilization.
· This type of
autoclave is comparatively cheaper than other types.
III. Positive pressure displacement type (B-type)
·
In
this type of autoclave, the steam is generated in a separate steam generator
which is then passed into the autoclave.
·
This
autoclave is faster as the steam can be generated within seconds.
·
This
type of autoclave is an improvement over the gravity displacement type.
IV. Negative pressure displacement type (S-type)
·
·
Here,
the vacuum generator pulls out all the air from inside the autoclave while the
steam generator creates steam.
·
The
steam is then passed into the autoclave.
·
This
is the most recommended type of autoclave as it is very accurate and achieves a
high sterility assurance level.
·
This
is also the most expensive type of autoclave.
D.
USES AND APPLICATIONS OF
AUTOCLAVES
Autoclaves
date back to 1884 when they were invented by Charles Chamberland. Today they
remain the technology of choice for sterilizing medical equipment. That is the
function that most commonly comes to mind, but autoclaves have uses far beyond
that.
Regardless
of the application, the autoclave working principle remains the same, but the
size of the autoclave needed, and target temperature and pressure depend upon
how the autoclaves will be used.
1. Medical Equipment Sterilization
It
is obviously important that any reused medical tools are properly cleaned to
destroy bacteria and other contaminants. This includes surgical equipment,
vessels, and any other items that will encounter bodily fluids or contamination
from the air.
A
hospital autoclave is not suitable for treating materials that can’t withstand
high heat, but hospital autoclaves are used to sanitize a range of other
equipment. A medical autoclave is used for surgical equipment but medical
autoclaves are also used to sterilize the tools and equipment used by
veterinarians, morticians, tattoo artists, dentists, and medical testing
facilities.
2. Laboratory Equipment
Researchers
need sterilized equipment for several processes. Specialty research-grade
autoclaves are available for use in laboratory settings. Research-grade
autoclaves are not approved for sterilizing items that will be used directly on
humans, but lab autoclaves are designed to be more economical to operate than
medical-grade autoclaves.
3. Polymer Curing
Polymer
composites are used in a range of industries. Autoclaves are used for polymer
curing when it is important to ensure consistent hardening of the polymer
material like when producing parts and components for the aerospace and
shipbuilding industries.
4. Vulcanization
Autoclaves
are used in the vulcanization of rubber since the autoclaves provide the
regulated heat and pressure necessary to produce consistent, high-quality
products.
5. Synthetic Crystals
Crystals are used extensively by
the electronics industry. Autoclaves provide the temperatures and pressures
needed to produce high-quality synthetic quartz crystals.
E.
References
· wikipedia
· youtube
· www.generon.com
· Here is an animated
video to know about principle and working of autoclave-
https://www.youtube.com/watch?v=SpAbCqXIXns&feature=youtu.be
By –
SASWATA
TRIPATHY
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