BBBBflt] «BlJIUrIrlr - Clpdigital.org

138
iron and steel combustion in an atmosphere rich in
oxvgen when raised to their ignition temperatures We
are all familiar with the classic experiments made by
chemistry teachers wherein a piece of watch spring
with burning charcoal or sulphur attached is lowered
into a jar of oxvgen. The steel spring is ignited by
the burning charcoal or sulphur and burns freely in
the oxygen rich atmosphere. This is the principle employed'
in the present dav modern cutting torch which
has found such wide use in the scrapping of battleships,
old railroad cars, cutting scrap to charging box
size for open hearth steel furnaces, and for cutting
machine members to shape, etc.
Oxygen Purity.
Until quite recently oxygen users were contented
with oxvgen of 97-98.5 per cent purity, but today, at
least in'the United States, such is not the case. By
improving the apparatus and operation of liquid air
plants it has been found possible to manufacture, commercially,
oxygen of much higher purity. By stages
the purity of oxygen has been increased until now it is
possible to obtain, continuously by that method, oxygen
with a guaranteed purity of 99.5 per cent, plus
or minus a tolerance of 0.1 per cent.
The question naturally arises what benefits are to
be derived from small increments in purity as we
approach the ultimate limit of 100 per cent oxygen,
and to answer this question the Air Reduction Sales
Company has carried out two series of experiments
extending over a period of several years, and it is the
results of these experiments which are presented in
this paper.
Method of Test.
The experiments were made on steel plates and
rolled steel billets, ranging in thickness from V% inch
to 12 inches. To eliminate the human element or per-
TABLE I
Average consumption of various purities required to cut
metals of various thicknesses, using 100 cubic feet of 99.5
per cent oxygen as basis of comparison.
Thicknr.ss
of Metal
Inches
H
Vi
Va
1
2'A
2 3/16
4^
6
6
12
12
Average
99 5
Series
Xo.
1
1
1
1
2
1
1
2
1
2
Cons
Difference for
decrease in
99 5
Per Cent
Cu. Pt.
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
each Yi
oxygen
OXYGEN PURITY
99.0
Per Cent
Cu. Ft.
114.1
111.1
116.0
1154
108.0
112.1
113.3
108.8
114.8
108.4
108.9
111.9
98.5
Per Cent
Cu. Ft.
125.5
121.5
140.0
135.0
123.4
127.5
141.5
133.6
131.7
119.5
122.0
1292
per cent
purity... 11.9 17 3 16.7
Forging-Stamping- Heat Tieating
98 .0
Per Cent
Cm Ft
148.8
150.1
139.0
145.9
97.5
Per Cent
Cu.Ft.
173.9
169.3
161.0
168.1
21.5
sonal equation as far as possible, all the cutting done
in the first series was done with a hand torch mounted
on a machine (Radiagraph) geared to give variable
speeds from a few inches per minute up to 60 inches
or more per minute, and in the second test series the
cutting was done with a machine torch mounted in
the same manner (see Fig. 1).
April, 192b
The speed of the Radiagraph was checked with a
stop watch. The pressures, where practicable, were
measured with mercury manometers, and the higher
pressures were measured with standard test gauges,
frequently calibrated and tested on a dead weight
gauge tester. The gas (oxygen and acetylene) consumptions
were obtained by weighing the cylinders be-
3XYGErJ PUPITY CUTTING TEST
3 12'BILLET STEEL i j
PPESSUPE CHrlBT ~7\
i. -
/ / 1
/
oxygen pubity cutting test
6'billet steel
ppessube cH/ier
St
/
7
XZl
OXYGEN PUBITY ire C£" ®
OXYGEN PUBITY CUT TING CHAgT
OXYGEN PUPITY CUTTING TEST
\%
le'aiLLET STEEL / *