The transfer unit pumps carbon dioxide in its
liquid phase only. This is true of all CO2 transfer
units. The amount of liquid carbon dioxide
contained in a fully charged cylinder varies with
t h e p r e s s u r e a n d t e m p e r a t u r e ; t h e r e f o r e , a
standard 50-pound cylinder contains approx-
imately 38 pounds of carbon dioxide in its liquid
phase and approximately 12 pounds in its gaseous
phase at an atmospheric temperature of 70°F.
Therefore, the cooler the supply cylinder and the
cylinder being recharged, the more efficient the
operation of the transfer unit. Consequently, all
cylinders should be kept in the coolest location
possible. Conversely, the time required to charge
an empty cylinder increases with increased
temperature of the cylinder. When recharging a
smaller cylinder, we found that if you invert the
cylinder during the recharging period, it remains
cooler and fills faster than it would if placed in
an upright position. Larger cylinders should be
placed horizontally on the scale when they are
After all the liquid carbon dioxide is trans-
ferred from the supply cylinder, which is approx-
imately 80 percent of the net contents, the transfer
of CO2 to the cylinder being recharged stops.
After this, another fully charged supply cylinder
must be used to finish recharging the cylinder to
its full-rated capacity. The majority of gas
remaining in the other supply cylinder can be
used when you recharge another empty cylinder.
The gas transfers itself under its own pressure until
the pressure in both cylinders is equal. This
method is called cascading. Through this method,
the most economical use of the contents of the
supply cylinder is made.
To prevent expansion of carbon dioxide in the
supply hose, and consequently blocking the hose
with CO2 s n o w , you should use a valve with
an outlet opening of at least one-eighth inch in
diameter-preferably three-sixteenths of an inch.
Standard supply cylinders in 50-pound sizes are
obtainable with or without a syphon tube. When
you order cylinders, specify the ones with a
syphon tube. Those without syphons must be
inverted during the transfer process.
M a i n t e n a n c e m u s t b e p e r f o r m e d o n a ll
carbon dioxide equipment on a periodic basis.
These maintenance procedures are discussed in the
Once Every Month
Check the level of the oil in the crankcase. See
that it is within one-fourth inch of the top of the
filling cup or to the upper groove in the measur-
ing stick if the unit is so equipped. If you must
add any oil, use only a good grade of SAE
viscosity #30 automotive crankcase lubricating
Once Every 6 Months
L u b r i c a t e t h e i d l e r s h a f t . T h i s s h a f t is
equipped with a fitting of the variety that is
commonly used in the automotive field. Two or
s h o t s
o f l i g h t c u p g r e a s e w i l l be
Lubricate the gear teeth with a thin coating
of light cup grease.
With a small piece of wood, or preferably a
small brush, apply a light coating of Vaseline to
the piston rod. To do this, dip the brush in
Vaseline, hold the brush against the piston rod,
and manually rotate the gears until the piston rod
i s c o m p l e t e l y a n d t h o r o u g h l y c o a t e d w i th
If necessary, tighten the packing at the piston
stem. A special wrench is provided for this
purpose. Do not tighten excessively. Because of
the design of the packing, it must only fit snugly
to hold tightly.
Keep the motor commutator clean and main-
tain a clean surface. Under normal operating
conditions, the commutator will require only
occasional cleaning with a dry piece of nonlinting
cloth. Do not lubricate the commutator.
Every 12 Months
The oil should be drained from the crankcase
and replaced with clean, fresh oil of the quality
and viscosity specified.
Once Every 2 Years
The bearing housings of the electric motor
should be removed and lubricated. To do this,
disassemble the bearing housing. Then clean the
inside of the housings, the plates or caps, and the
bearings with carbon tetrachloride. Wipe off all
grease and reassemble all parts except the outer
caps or plates. Apply the new grease, either from
a tube or by hand, over and between each ball.
When you do this, do not apply more than
one-half of an ounce of grease at each bearing.