TA Instruments TGA 2950, Operator'S Manual

Page: 84 / 264

Running Experiments
TA I
NSTRUMENTS
TGA 2950 3–18
It is important to maintain the proper ratio of
flow rates between the balance chamber and the
furnace housing. Having the separate balance
chamber purge prevents decomposition gases
from entering the balance chamber. The recom-
mended setting for the purge rate is 100 mL per
minute or less. When you use the standard TGA
2950 furnace, the flow distribution should be 40
percent to the balance chamber and 60 percent to
the furnace. When you use the TGA 2950 EGA
furnace, the flow distribution should be 10
percent to the balance chamber and 90 percent to
the furnace.
To maintain this flow distribution, you will need
to connect a flowmeter to each of the purge
fittings on the back of the TGA instrument. Set
the purge gas flow rates by adjusting these
meters. The PURGE port goes to the TGA
furnace, and the BALANCE PURGE goes to the
balance chamber.
Before you start the purge gas, make sure that
the desired gas is connected to the purge ports,
that all lines are clear, and that your supply of
purge gas is sufficient for the experiment.
Always maintain constant purge flow rates and
distribution throughout your experiment;
changing the purge during an experiment can
affect the data.