Specifications

7
THEORY OF OPERATION
20
When the pressure falls below the pressure building
regulator setting (125 psi), the regulator will open
(Figure R). This will allow liquid to run into the pressure
builder vaporizer located at the bottom of the tank. The
liquid will turn into gas and be delivered back into the
top vapor space of the tank. The results of this opera-
tion is a rise in pressure in the tank.
Liquid Withdrawal
If the liquid cylinder is to be placed in permanent liq-
uid withdrawal service, it is recommended that the
cylinder be refitted with a 22 psig relief valve to mini-
mize loss due to flash-off.
Note:
In a Dura-Cyl HP/Cryo-Cyl HP the pressure must
be kept above 70 psig for CO
2
to prevent solidifying
the CO
2
.
CAUTION:
Before making a liquid transfer, be sure
that protective eye glasses and gloves are being worn.
To withdraw liquid from a liquid cylinder, connect a
transfer line from the liquid valve fitting to the user's
receiving vessel (Figure S). Open the liquid valve to ob-
tain the preferred rate of flow. Close the liquid valve
when the user's vessel has been filled. To prevent con-
tamination, when the cylinder has been emptied, all
valves should be closed. To minimize flash-off and
spillage, use a phase separator on the end of the trans-
fer line. Normal liquid withdrawal operations are per-
formed at lower pressure (approximately 22 psig) to
reduce flash-off losses and splashing. For this reason,
t
he pressure building valve is customarily closed during
liquid withdrawals. Transfer of liquid at higher pres-
sures can lead to excessive splashing of the cryogenic
liquid which could result in burns to the operator and/or
nearby personnel. All personnel should be fully in-
structed in the cautions associated with handling
cryogenic fluids and the proper clothing and protective
gear to be used.
If a higher operating pressure is desired (other than
that available through normal heat leak), the pressure
building valve may be opened for a short time until the
preferred pressure has been obtained. If automatic
pressure building for liquid service is necessary, a low
pressure building regulator may be installed to replace
the pressure building regulator supplied with the unit.
Liquid carbon dioxide, used for freezing or cooling can
be completely withdrawn from a Dura-Cyl HP/Cryo-Cyl
HP liquid cylinder, leaving just 2% residual gaseous
product. Connect a transfer line from the liquid fitting of
the liquid cylinder to the receiving vessel. Open the liq
-
uid valve to obtain the desired rate of flow.
The Dura-Cyl HP/Cryo-Cyl HP will deliver a continuous
flow of liquid CO
2
at rates of 1,000 pounds/hour or
greater, having a refrigeration content of 119
BTU/pound at 350 psig Leave the pressure building
valve open for high withdrawal rates.
VAPORIZER
GAS IN
LIQUID IN
PRESSURE
BUILDING
COIL
O
PEN
VAPORIZER
LIQUID IN
PRESSURE
BUILDING
COIL
LIQUID
OUT
Figure R
Figure S
Pressure
Builder
Liquid
Withdrawal