ARGON PURITY LEVEL
 WHAT IS ARGON:
Argon is chemically-inert, monatomic gas, heavy and available in quantity at
reasonable cost. Its chemical symbol is Ar. Atomic weight is 40. Molecular
weight is 40.
 APPLICATION OF ARGON IN BHEL :
In the welding process, Argon is used for SHIELDING and BACKING
purpose. The atmosphere in which we live is composed of about 4/5 th of
Nitrogen and 1/5th Oxygen. The welding process when exposed to air, most
metals exhibit a strong tendency to combine with Oxygen, and to lesser
extend with Nitrogen, especially when in the molten condition. The rate of
oxide formation will vary with different metals, but even a thin film of oxide on
the surface of metals to be welded can lead to difficulties. For the most part,
the oxides are relatively weak, brittle materials that in no way resemble the
metal from which they are formed. A layer of oxide can easily prevent the
joining of two pieces by welding.
Argon is a shield gas used in Gas Tungsten Arc Welding (GTAW), Root
Shielding and Plasma cutting. Argon protects welds against oxidation as well
as reduces fume emissions during welding.
 PRODUCTION OF ARGON :
A co-product of oxygen and nitrogen production, argon is manufactured
commercially by means of air separation technology. In a cryogenic process,
atmospheric air is compressed and cooled. Following liquefaction, the air is
fractionally distilled based on the different boiling points of each component.
(The boiling point of argon is between those of nitrogen and oxygen.).
During distillation, liquid nitrogen is the first product extracted from the highpressure column. Next, a stream containing oxygen and argon (plus other
gases) is withdrawn. The crude stream, containing approximately 10 percent
argon, is refined in a separate distillation column to produce argon with 98
percent purity.
Manufacturers can further refine the stream by mixing the argon with
hydrogen, catalytically burning the trace oxygen to water, drying and, finally,
distilling the stream to remove remaining hydrogen and nitrogen. Using this
process, producers can achieve an argon product with 99.9995 percent
purity.
The compressed argon is supplied in cylinders and liquid argon is supplied in
tanks. The cylinder used for argon will have the body colour of BLUE without
band, size of 25 cms dia. & 1.5 m length, capacity of 6.2 M 3 and pressure
when fully charged at 150C (approx) 137 Kg/Cm2 (1949 psi).
 PURITY LEVEL OF ARGON
 INDIAN STANDARD for ARGON, Compressed & Liquid Specification no. IS
5760 : 1998 shall be referred.
There are 3 grades of argon, namely:



Grade 1 : Ultra high purity argon for use in electronics and allied industries
and indirect reading vacuum spectrograph,
Grade 2 : High purity argon for use in lamp and allied industries and
Grade 3 : Commercial grade argon for use in welding industry and for other
metallurgical operations.
Accordingly the argon shall comply with the requirements given
below:
Sl.
no.
i.
ii.
iii.
iv.
v.
vi.
vii.
CHARACTERISTIC
Oxygen, ppm, Max.
Nitrogen, ppm, Max.
Hydrogen, ppm, Max.
Water vapours, ppm. Max.
Carbon dioxide, ppm, Max.
Carbon monoxide, ppm, Max.
Hydrocarbons, ppm, Max.
REQUIREMENT
Grade
Grade
Grade
1
2
3
0.5
2.0
1.0
0.5
0.5
0.5
0.2
5.0
10.0
2.0
4.0
0.5
0.5
0.5
10.0
300
5.0
7.0
3.0
2.0
-
 PURCHASE SPECIFICATION FOR ARGON :
BHEL - WELDING TECHNOLOGY CENTRE, Trichy recommends the
specifications for purchasing the Argon for welding process is,
“Argon as per Grade 3 of IS-5760 : 1998 with Oxygen & Water Vapours
restricted to max. 6 PPM each and with Argon purity level of min.
99.99%. The supply should accompany Test Certificate for the batch
indicating individual element ‘PPM’ level and overall purity level.”
Hence, it is recommended to purchase the Argon with above specification by
BHEL as well as by our Sub-contractors engaged at sites.