Y690VB Series
3
Note
If this equipment is shipped mounted on
another unit, install that unit according to
the appropriate instruction manual.
1. Only personnel qualified through training and experi-
ence should install, operate, and maintain this equip-
ment. For Y690VB Series equipment that is shipped
separately, make sure that there is no damage to or
foreign material in it. Also ensure that all tubing and
piping have been blown free.
2. This equipment may be installed in any position as
long as the flow through the body is in the direction
indicated by the arrow attached to the body. If continu-
ous operation is required during inspection or mainte-
nance, install a three-way bypass valve around the
equipment.
This equipment may vent some gas to the
atmosphere. In hazardous or flammable
gas service, vented gas may accumulate
and cause personal injury, death, or prop-
erty damage due to fire or explosion. Vent
equipment in hazardous gas service to a
remote, safe location away from air intakes
or any hazardous area. The vent line or
stack opening must be protected against
condensation or clogging.
Principle of Operation
The Y690VB Series vacuum breakers (figure 2) are used
in applications where an increase in vacuum must be
limited. An increase in vacuum (decrease in absolute
pressure) is transmitted to the lower side of the dia-
phragm, opening the disk assembly. This permits positive
pressure, atmosphere, or an upstream vacuum that has
Table 2. Vacuum Pressure Information
higher absolute pressure than the downstream vacuum, to
enter the system and restore the controlled vacuum to its
original pressure setting. A Type Y690VB (figure 3) direct-
operated vacuum breaker is self-contained and requires no
control line. A Type Y690VBM (figure 4) vacuum breaker
requires a control line from the 1/2-inch NPT tapping in the
diaphragm case assembly to the point where the vacuum
needs to be controlled.
Startup and Adjustment
All Y690VB Series equipment can be placed in opera-
tion by slowly introducing inlet vacuum or pressure. This
equipment takes control when vacuum is established.
This equipment is suitable for the pressure range stamped
on the nameplate (key 46), and listed in table 2. To adjust
the pressure setting, remove the closing cap (key 22)
and turn the adjusting nut (key 20) clockwise to in-
crease the pressure setting or counterclockwise to
decrease the setting. Replace the cap after making this
adjustment. If desired, the closing cap may be wired to
the hole provided in the spring case (key 3) to discour-
age tampering.
Shutdown
First close the nearest upstream shutoff valve and then
close the nearest downstream shutoff valve to vent the
equipment properly. Next, open the vent valve between
the equipment and the downstream shutoff valve
nearest to it. All pressure between these shutoff valves
is released through the open vent valve.
Maintenance
Equipment parts are subject to normal wear and must
be inspected and replaced as necessary. The frequency
of inspection and replacement of parts depends on the
severity of service conditions and upon applicable
codes and government regulations.
WARNING
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