Principle Of Operation - Emerson Fisher Y692 Instruction Manual

BLocK
VaLVE
SuPPLY
PRESSuRE
GaS BLanKETinG PRESSuRE
A6340
INLET PRESSURE
inLET PRESSuRE
OUTLET PRESSURE
conTRoL PRESSuRE
ATMOSPHERIC PRESSURE
aTMoSPhERic PRESSuRE
Figure 2. Type Y692 with Internal Registration
Operational Schematic

Principle of operation

The Type Y692 Gas Blanketing Regulator reduces a
high-pressure gas to maintain a positive low-pressure
of blanket gas over a stored liquid when the liquid is
being pumped out of the vessel (see Figures 2 and
3). Also when the vessel (or tank) is suddenly cooled,
causing vapors to contract, the regulator replaces
the volume of contracting vapors with a volume of
blanketing gas to prevent the internal vessel pressure
from decreasing. In both cases, a positive vessel
pressure prevents outside air from entering the vessel
and reduces the possibility of atmospheric pressure
collapsing the vessel.
Gas blanketing regulators respond to a slight decrease
in internal vessel pressure by throttling open to
increase the flow rate of gas into the vessel. When the
vessel's liquid level has been lowered to the desired
point and the vapor pressure re-established, the
regulator throttles closed.
VEnT
VaLVE
VEnT
VaLVE
BLocK
VaLVE
LiquiD
BLocK
VaLVE
SuPPLY
PRESSuRE
VEnT
PoinTED
DoWnWaRD
GaS BLanKETinG PRESSuRE
INLET PRESSURE
inLET PRESSuRE
OUTLET PRESSURE
conTRoL PRESSuRE
ATMOSPHERIC PRESSURE
aTMoSPhERic PRESSuRE
Figure 3. Type Y692 with External Registration
When the liquid level drops and vessel pressure
decreases below the setting of the control spring,
the spring force on the diaphragm opens the disk
assembly to supply the required flow of gas to the
vessel. When vessel pressure has been satisfied,
control pressure tends to increase slightly, acting on
the diaphragm. When the control (vessel) pressure
exceeds the control spring setting, the diaphragm
moves to close the disk assembly.
The Type Y692 Gas Blanketing Regulator provides
a constant set pressure for accurate gas blanketing.
When vessel pressure decreases below the control
spring setpoint, the force of the spring moves the disk
away from the orifice allowing gas to flow into the
vessel. As the vessel pressure increases, the increase
is sensed by the diaphragm through the pitot tube or
control line. This movement of the diaphragm causes
the disk to move toward the orifice, decreasing the
flow of blanketing gas. When the vessel pressure
reaches the system setpoint, the disk will seat against
the orifice shutting off the flow of gas.
Type Y692
VEnT
VaLVE
VEnT
VaLVE
BLocK
VaLVE
LiquiD
Operational Schematic
VEnT
PoinTED
DoWnWaRD
3