Micromeritics TRISTAR II PLUS Operator's Manual page 295

D M H
AINTAIN
The analysis system was designed to accurately measure the surface area of all types of
materials. It is important that the gases (especially krypton) used for these measurements be of
highest purity, especially when analyzing low surface area samples. Three ways to ensure high-
purity gases are to always maintain:
Thoroughly purged gas pressure regulators.
n
Non-permeable gas lines.
n
Leak-free connections.
n
Impure gas is strongly indicated, for example, if a series of measurements on a low surface area
material yields decreasing specific surface areas with decreasing quantities of sample. The
analyzer uses very small amounts of helium; therefore any residual air in the regulator can distort
results of subsequent analyses for quite some time.
Micromeritics offers the following suggestions to assist in maintaining high-purity gases
(particularly helium):
Use metal gas lines only.
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Remove trapped air from the regulator and gas lines.
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U M G
SE ETAL AS
Always use metal gas lines which have been carefully cleaned of any oils and greases used in the
manufacturing process. Do not use plastic or rubber gas lines. When these types of permeable,
nonmetallic gas lines are used with helium, contaminants accumulate at a much faster rate. This
causes errors in analysis results and can also contaminate a clean sample.
R T
EMOVE RAPPED
When connecting the regulator to the gas cylinder, air is unavoidably trapped on the high and low
pressure sides of the regulator, as well as in the gas lines. Remove as much of this air as is
possible before opening the gas cylinder valve. If this air is allowed to remain in the regulator, it
will mix with the helium and cause inaccurate results in subsequent analyses. Or if the valve is
open for any length of time, the air trapped on the high pressure side may diffuse back into the gas
cylinder and contaminate its entire contents.
There are two methods for removing trapped air from the regulator lines: the Purge Method and
the Evacuation Method.
TriStar II Plus Operator Manual
303-42800-01 (Rev M ) — Sep 2023
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IGH URITY ASES
L
INES
A
IR
D Maintain High-Purity Gases
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