Data Sheet

Bulletin 74.2:Y696
3
E0751
Figure 3. Principal of Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
LOADING PRESSURE
VAPOR RECOVERY
VACUUM SOURCE
LIQUID
VAPOR PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
LOADING PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
TANK PRESSURE
VACUUM PRESSURE
PRE-EXPANSION PRESSURE
INTERMEDIATE BLEED PRESSURE
PILOT SUPPLY PRESSURE
INTERMEDIATE PRESSURE
LOADING PRESSURE
PUMP PRESSURE
BYPASS PRESSURE
BACK PRESSURE
BOOST PRESSURE
EXHAUST
PILOT LOADING PRESSURE
VENT HEADER PRESSURE
INLET BLEED PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
LOADING PRESSURE
Figure 2. Operational Schematic
Principle of Operation
The Type Y696 vapor recovery regulator is used to maintain
a constant blanket (inlet) pressure or vessel pressure with
the outlet owing to a system whose pressure is lower than
that at the inlet.
When vessel pressure increases above the setpoint of the
regulator due to pumping in or thermal heating, the force
of the control spring is overcome by pressure acting on the
diaphragm. This moves the disk away from the orice allowing
gas to ow from the vessel to the vapor recovery system.
As vessel pressure is reduced, the force of the control
spring causes the disk to move toward the orice
decreasing the ow of gas out of the vessel. As vessel
pressure drops below the setpoint of the regulator, the disk
will seat against the orice shutting off the ow of gas.
Sizing Vapor Recovery Systems
To determine the capacity required, you must consider the
amount of blanketing gas that must be displaced from the
tank when either lling the vessel with liquid (pump-in) or the
expansion of tank vapors during atmospheric thermal heating.
Using the established procedures from American Petroleum
Institute Standard 2000 (API 2000), determine the required
ow rate for outbreathing.