Discovery TGA™ Getting Started Guide
Page 15
EGA Furnace for TGA 55 and TGA 550
The Evolved Gas Analysis (EGA) furnace is an optional accessory for the Discovery TGA 55 and TGA
550 that allows you to connect a spectrometer to the instrument so that the gases evolved by sample
decomposition can be analyzed. The EGA furnace and the Wire-wound furnace can be exchanged as
directed in the Online Help.
Figure 3
EGA furnace cut-away diagram.
The EGA furnace consists of a quartz glass sample tube surrounded by an electric resistance heater, both of
which are contained within a water-cooled furnace housing. The housing is mounted to a furnace base that
raises and lowers the furnace for sample loading and unloading.
The sample tube has a purge gas inlet that passes through the right side of the furnace housing. A fitting on
the left side of the housing allows connection of a transfer line to carry exhaust gas to a spectrometer such
as a mass spectrometer. Because the heater is external to the sample tube, evolved gases from sample
decomposition within the sample tube do not come in contact with the resistance elements or the furnace
ceramic refractory.
Cooling air enters through the furnace base and passes upward between the outside of the sample tube and
the inside of the furnace, completely separating the cooling air from the sample and the sample zone. The
furnace is a resistance heater wound on alumina ceramic, which allows sample zone temperatures as high
as 1000°C with heating rates up to 50°C/min. A Platinel II® thermocouple is positioned in the furnace, just
above the sample pan, where it monitors the sample environment temperature.
The furnace base moves the furnace assembly up around the sample pan to the closed position, or down
away from the sample pan to the open position.
Quartz tube
Water-cooled furnace housing
Electric resistance heater
Furnace base
