Muffle furnace Parts Construction

1. 1
Muffle Furnace
A muffle furnace is a furnace with an externally heated chamber, the walls of which radiantly
heat the contents of the chamber, so that the material being heated has no contact with the flame.
Muffle furnaces are most often utilized in laboratories as a compact means of creating extremely
high-temperature atmospheres. They are employed to test the characteristics of materials at
extremely high and accurate temperatures. A muffle furnace is also known as a retort furnace.
CONSTRUCTION OF MUFFLE FURNACE
Furnace consists of:
 a vented heating chamber
 a temperature controller
 a door safety switch for operator safety
 Horizontal Rectangular light weight with Triple walled construction.
 Working Chamber Made of Ceramic with Alumina Muffle
 Chamber Made of Mild Steel finished with High Temperature Resistant Aluminum Paint.
 Exterior Made of Heavy SWG. Mild Steel Powder coated.
 High Dense Insulation Between Two Walls ( Asbestos free)
 With Exhaust Pipe fitted with Rear side of the Furnace
 High Quality Heating System (Kanthal A-1), Embedded in ceramic Muffle
 Long service life
 Fully Open able Door System.
 Temperature up to Maximum: 16000
C
 Temperature Controller: By Microprocessor Based PID Digital Controller.

2. 2
WORKING OF MUFFLE FURNACE
A muffle furnace isapiece of oven-type equipment that can reach high temperatures. It usually works
by putting a high-temperature heating coil in an insulated material. The insulating material
effectively acts as a muffle, preventing heat from escaping.
Furnace is usually heated to desired temperatures by:
 Conduction
 Convection
 Blackbody radiation from electrical-resistance heating elements
A precious metal thermocouple senses the temperature in the chamber and transmits this
information to the temperature control in millivolts. The control section consists of a
temperature controller, a current controller, a transformer, a contactor (relay), a circuit
breaker. The temperature controller senses the furnace temperature (by means of the
thermocouple) and adjusts electricity to the heating elements by means of the current
controller. The current controller controls electricity to the heating elements by adjusting the
magnitude of the electrical current (rather than turning the electricity completely on or off).
This is the preferred method of controlling electricity to molybdenum disilicide heating
elements. When all the necessary work is done and the current is controlled then sample gets
heated to the desired temperature and then removed.
There is usually no combustion involved in the temperature control of the system, which allows
for much greater control of temperature uniformity and assures isolation of the material being
heated from the by-products of fuel combustion.
Applications
It is used for high-temperature applications such as:
 Fusing glass
 Creating enamel coatings
 Ceramics
 Soldering
 Brazing
They are also used in many research facilities, for example by chemists in order to determine
what proportion of a sample is non-combustible and non-volatile. Advances in materials for
heating elements facilitate more sophisticated metallurgical applications.