hardik patel's blog : Working Principle and Construction of Hot Air Oven
Let us see the meaning of a hot air oven
and the key points to remember about a hot air oven.
From the name, it is pretty clear that
this device uses hot or dry air, and it functions as an insulator chamber, in
which the hot air moves continuously within the chamber. The killing action of
a hot air oven depends upon the principle of heat conduction in which the dry
heat first sterilizes the surface of an object and then the center.
Using a hot air oven, you can sterilize
different articles or glasswares like test tubes, Petri plates, flasks, etc.
Depending upon the volume of the content needed to be sterilized, the holding
temperature ranges between 150 to 180 degrees Celsius. The holding time ranges between
20 to 150 minutes.
The mechanism of dry heat sterilization
is the oxidation of the micro-organisms. The organisms are killed by
oxidation. Hot air oven manufacturers make use of
different materials and insulators to design the hot air oven. Hot air oven is
specially designed for rubber industries, oil industries, manufacturing
instruments, glassware industries, manufacturing metal equipment, manufacturing
medical items, and more.
Construction
Now let us see the construction of a hot
air oven by understanding its parts and functions.
Parts and their
functions of hot air oven
1. Main Switch
2. Temperature Regulator knob
3. Timer
4. Heat Regulator Knob
5.Asbestos door jacket
6.Thermostat
7.Perforated aluminum tray
8. Double-walled insulated Chamber
1. Main switch -
Switch on or switch off the device. The main switch contains a Green Light
indicator that Indicates the device is switched on.
2. Temperature
regulator knob - Regulates the temperature when you
rotate the knob to the right or left.
3. Timer - Sets
the time according to the desired temperature.
4. Heat regulator
knob - Monitor the flow of heat.
5. Asbestos door jacket -
Outer Double-walled door jacket which is made of glassware jacket. Thus, it
confines heat within the chamber and also safeguards the instruments against
heat damage.
6. Thermostat - This
thermostat is placed at the top of the chamber, continuously monitoring the
temperature inside.
7. Perforated aluminum
tray - Articles like glassware, metals, etc., are kept on the
perforated aluminum tray. The perforation allows uniform distribution of the
heat to the articles that are kept inside.
8. Double-walled
insulated Chamber - Insulates heat within the chamber.
Hence, these are all the parts and their
functions of a hot air oven. And we can see that Hot air oven
manufacturers designed it exquisitely.
Working principle of
hot air oven
Now let's see how it works and how it
destroys the micro-organisms. So you would have understood that a hot air oven
depends upon dry heat sterilization, but you need to know how it functions or
sterilizes the different objects or articles.
So, the hot air oven sterilizes the
object via a heat conduction mechanism in which the heat within the chamber
first sterilizes the object and then the center of the object.
Let us see how hot airflow inside the
chamber:
The electric coil at the bottom of the
hot air oven will allow the upward flow of the hot air. The hot air increases
towards the top of the chamber, but once it comes in contact with the surface
of the chamber, it goes down and moves down the chamber.
Therefore, the hot air flow inside the
hot air oven is circular or uniform, which permits uniform heating throughout
the chamber.
Description of hot air
oven
The chamber or the inner portion of the
hot air oven is made of aluminum or stainless steel. It is a double-walled
structure. The inner portion of the double wall is filled with glass wool for
insulation purposes.
The opening or the door of the hot air
oven is made of asbestos. The lining in it prevents the escaping of dry air or
hot air from the oven. This opening is also thick-walled, and the inner portion
of this opening is filled with glass wool. Glass wool is a type of insulator
made from glass filaments. Various Glasswares are placed on the shelves or
trays for sterilization purposes.
The procedure to
sterilize include:
● First, you need to clean and wash the
glassware.
● Then wrap the glassware with aluminum
foil.
● Now, place the glassware into the hot
air oven and close the door.
● Start the oven by rotating the knob
and setting the temperature.
● For an hour, the temperature is set to
160 degrees Celsius and 250 degrees Celsius for half an hour.
● Note the temperature value from the
thermometer. Once it reaches the desired temperature, switch off the oven by
rotating the knob anticlockwise.
● Now, remove the glassware from the
oven carefully.
Practical uses of hot
air oven
● Hot air ovens can sterilize metal
equipment like scissors, spatula, forceps, etc.
● It is commonly used in practical labs
or research labs to sterilize different articles to maintain aseptic
conditions.
● As the hot air oven uses dry heat, it
can also be used in baking, drying, and curing processes.
● Powders and Non-volatile compounds
like sulphonamides, zinc, starch powder, etc., can also be sterilized in the
hot air oven.
● Heat-stable glasswares made of a
brute-like pipette, burettes, test tubes, flasks, etc., can also be sterilized
using a hot air oven.
● A hot air oven is used for dry heat
sterilization of glassware, powders, oils in pharmaceutical microbiology labs.
Advantages
● The operation and maintenance of the
hot air oven are easy.
● It occupies minimal workspace because
of its small size.
● It does not corrode the metal
equipment like scissors, forceps, etc., as it uses dry heat.
Disadvantages
● The hot air oven is insufficient to
kill the heat-resistant spores like endospores and organisms like prions.
● It can only sterilize the objects that
are heat or thermostable.
Conclusion
A hot air oven is a sterilizing
appliance that sterilizes many substances. It is used mainly for laboratory
purposes and not for food processing purposes. Hence, Hot air oven manufacturers ensure
that it stabilizes the operation.
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