Specifications

7
THEORY OF OPERATION
19
The supply of gaseous product is the primary opera-
tion of the liquid cylinder. An additional regulator must
be added to the gas use valve to step down the pres-
sure to the application. The liquid cylinder is usually
at a high pressure after the filling and delivery opera-
tion. When it is connected to the gas application and
the gas use valve and pressure building valves are
opened, it will automatically deliver gas.
The Dura-Cyl MP/Dura-Cyl MCR MP model with a 230
psi relief valve operates between the pressure building
setting (125 psig) and the economizer setting (140
psig). When the operating pressure is above the econ-
omizer setting (140 psi) the regulator will open (Figure
P). The gas that is being supplied to the application will
be pulled out of the vapor space in the top of the tank.
It will travel through the regulator and then the vapor
-
izer coils. It will be warmed before it reaches the final
line regulator. The action of removing gas from the
tank reduces the tanks pressure.
When the operating pressure is reduced to the econ-
omizer setting (140 psi), the regulator will close (Figure
Q). Gas is still required by the application and will pull
liquid up the dip tube and into the vaporizer. This will
turn the liquid into gas and warm it before it is deliv-
ered to the final line regulator. The pressure decay
will be much slower since a small amount of liquid can
be vaporized into a large amount of gas.
Pump Transfer
The pump transfer method lowers the product losses
a
ssociated with filling. Liquid may be pumped into the
cylinder so that venting is not necessary. The vent
valve on the liquid cylinder has a spray header that
will splash the incoming cold liquid onto the some-
what warmer gas in the tank. The cold liquid will
actually collapse the vessel pressure while being
sprayed into the warmer gas. This method of filling
works well with vessels that are used regularly and
do not warm up between fills. Figure O shows the
pump transfer method.
Gas Withdrawal
When a Dura-Cyl liquid cylinder is used for gas with-
drawal, the normal operating pressure range is from
approximately 75-175 psig and the pressure relief
valve has a set pressure of 230 psig When a Dura-
Cyl HP liquid cylinder is used for gas withdrawal, the
normal operating pressure range is from approximately
100-350 psig and the pressure relief valve has a set
pressure of 350 psig. On both liquid cylinders the
economizer portion of the control regulator is automat-
ically set approximately 15 psig higher than the
pressure building portion of the control regulator.
WARNING: Before conducting a gas (or liquid)
withdrawal operation, make sure protective eye-
glasses and gloves are being used.
VAPORIZER
GAS IN
PRESSURE
BUILDING
COIL
GAS
OUT
OPEN
VAPORIZER
LIQUID IN
PRESSURE
BUILDING
COIL
GAS
OUT
CLOSED
Figure P
Figure Q
Economizer
Closed
Economizer
Open