Type S402Y
3
Figure 2.
Type S402Y Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
FlaPPER
DRillED ClOSing CaP WiTH TRaVEl STOP
TO OPEn REliEF ValVE
Main SPRing
REliEF ValVE SPRing
DiaPHRagM
CaM STEM
DiSk HOlDER aSSEMBlY
ValVE DiSk
ORiFiCE TuBE aSSEMBlY
inlET SCREEn
lOWER CaSing
inlET PRESSuRE
OuTlET PRESSuRE
aTMOSPHERiC PRESSuRE
M1162
volume flow rate is demanded downstream, the pressure
under the diaphragm decreases. The control spring
force pushes the diaphragm/diaphragm head/cam stem
assembly downward and the valve disk moves away
from the orifice.
At the lockup (complete shutoff) position the ratio of
the diaphragm travel to disk travel is 4 to 1 giving the
regulator an effective 4 to 1 lever ratio for positive lockup.
The cam stem is characterized for higher downstream
demand to produce a mechanical boost effect.
Type S402Y regulator includes an internal relief valve
for overpressure protection. If the downstream pressure
exceeds the regulator setting and the regulator is not
able to achieve complete shutoff (lockup) due to foreign
matter lodged between the orifice and the valve disk
or a failure in the valve disk, the regulator diaphragm
assembly moves upwards trying to push the valve
disk against the orifice. The valve disk and disk holder
being pressed against the orifice will prevent the cam
stem from being able to travel any further upward in
conjunction with the diaphragm assembly. The continued
leakage of the inlet pressure into the regulator cavity
will then force the diaphragm and diaphragm head up
off of the seating area of the relief valve overcoming
the relief valve spring which was pressing them
together. The resulting gap will allow pressure to exit the
regulator cavity and exhaust through the openings in the
diaphragm head and out the spring case vent
to atmosphere.
installation
!
WaRning
Personal injury, equipment damage, or
leakage due to escaping accumulated
gas or bursting of pressure-containing
parts may result if this regulator is
overpressured or is installed where
service conditions could exceed the
limits given in Specification Section.
To avoid such injury or damage, provide
pressure-relieving or pressure-limiting
devices (as required by Title 49, Part 192,
of the u.S. Code of Federal Regulations,
by the national Fuel gas Code Title 54 of
the national Fire Codes of the national
Fire Protection association, or by other
