Laboratory
ovens finds good use in a variety of thermal processing applications. Ovens
are basically lower temperature thermal processing units operating below
1400 degrees F. Normally they function without refractory insulation. A
simple oven resembles a chamber heated by a resistance coil. A light
indicates the heating. There is also a control for the temperature. For
measuring temperature a simple thermometer is used. It has its bulb in the
chamber while a scale sticks out of the top of the unit. Some lab ovens
feature a built-in fan for moving the air from the coils and put it into the
chamber. However latest ovens are coming today with double doors,
temperature recorders, and temperatures that have been digitally selected
These ovens offer better temperature regulation as compared to simple ovens.
That is why sometimes they are used as dry incubators for culture
preparation.
Application of Laboratory Oven
Laboratory Ovens are used for a number of useful applications, this
includes the following
- Drying of samples
- Evaporating, dehydrating, or sterilizing
- Though on a limted basis lab ovens are also used as a dry incubator
- Drying of glassware
- Core hardening
- Component and stability testing
Selection Guide for Laboratory
Ovens
Following points are important while choosing a Laboratory Oven.
»
Temperature - It is always wise to choose an oven that has a
maximum temperature rating more than your maximum temperature requirements.
This will enable maintaining the set temperature more accurately.
»
Circulation - For heating the contents, Ovens normally use
either mechanical draft (forced draft) or gravity convection. Forced draft
ovens are preferred for use by ASTM and AASHTO standards. To produce even
heating Mechanical or forced draft ovens have fans for inducing air flow
through the oven. On the other hand Gravity convection ovens consist of "cold"
and/or "hot" spots because the air inside the oven shows a
tendency to become stagnant. Circulation is dependant upon the air
temperature difference within the oven.
»
Size - For a proper oven size sample container size, number
of samples as well as personal preference if any are very important factors.
Ovens that give an extra interior capacity might be nice to possess but
oversized ovens generally need more energy to heat, special electrical power
and taking up precious space in the laboratory. So multiple smaller ovens in
place of a single large oven is a judicious choice. Nevertheless, large
ovens can be necessity in high-production laboratories or in case the
requirement is of large sample sizes like aggregate or asphalt testing.
»
Mounting - Should you require a table top or floor mount
model can do the job?
»
Motor Protection - Is the oven explosion-proof for handling
volatile samples?
»
Controls - Ovens with digital controls are now permiting
operators to set the temperature requirements easily and properly display
the real oven temperature.
»
Quantity - Choice of models also depends on quantity of
materials to be processed.
Types of Laboratory
Ovens
Mechanical
Convection Ovens
Mechanical Convection Ovens, are very effective for laboratory applicaions.
The oven typically contains a fan or blower which is used for continuously
circulating heated air. This aids in maintaining an uniform temperature
throughout the chamber. Mostly dry heat sterilizers are essentially
Mechanical Convection Ovens.
Gravity Convection Ovens
Gravity Convection ovens can be an excellent choice as low-cost substitute
to mechanical convection ovens in cases where uniformity of temperature is
not that essential to the process. Gravity Convection ovens are perfect for
applications where to heat or dry a powder or substance disturbance can be
made with a fan-generated airflow.
Cleanroom
Ovens
Cleanroom Ovens are specifically designed for cleanroom
operations.Cleanroom ovens are also primarily mechanical convection ovens.
They can be used for applications like electronic parts curing, cleaning of
semi-conductor chips and wafer baking. Cleanroom Ovens can be available with
or without HEPA filters.
Vacuum Ovens
Vacuum ovens are the perfect choice for applications needing inert
atmosphere. In Vacuum ovens the heat-treating process takes place inside
airtight vessels. This enables the drawing of vacuum inside the vessel. As
heating takes place in vacuum, without air convection, this is achieved by
placing the sample on the shelf of the unit. So heat gets conducted from the
side walls to the sample through the metal shelf. The Vacuum ovens need a
separate vacuum pump. Heat treating this way under vacuum has some very
useful applications which are as follows.
- Prevent surface reactions like uch as oxidation or decarburization
- Removing of surface contaminants in the form of oxide films and
residual traces of lubricants
- General drying and incubation applications
- Polymerization of resins
- Other applications like embedding, desiccating, outgassing, plating,
and quality control
