Laboratory Oven

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.