球阀设计特点 BALL VALVE DESIGN FEATURES
BALL VALVE DESIGN FEATURES
BALL SEAT
ALIGNMENT
Mechanical stops
ensure control
over ball rotation.
EMERGENCY
SEALANT INJECTION
Each valve is supplied complete with
emergency sealant injection feature
located between the upper O-rings
and the graphite gasket.
An emergency sealant injection feature
on seats is available upon request only,
for 6” full port and larger.
Emergency grease injection features
are not available on low-and high-
temperature valves.
STEM SEALING
Two O-rings and one graphite gasket ensure
the stem seal.
The graphite gasket can be replaced while the
valve is under pressure and with the ball in any
position. First, release any pressure that may
exist between the upper
O-ring and the graphite
hole and then remove
the adaptor plate.
The O-rings can be
replaced with the valve
in fully open or fully
closed position by
removing the stem
cover (after having
released all the
pressure in the
body cavity).
BODY SEALING
The double sealing
action of O-rings and
graphite gaskets in all
the static joints of the body components
ensures zero leakage and the Fire Safe feature.
Lip-seal rings and/or graphite gaskets can be used
for special service.
Ball
(closed)
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Stem
Upstream
pressure
Body cavity Downstream
pressure pressure
DOUBLE BLOCK AND BLEED
All Valbart Srl trunnion-mounted ball valves
are designed and manufactured to seal off
both seats at the same time and allow
bleeding of the entrapped cavity pressure
(DBB) with the ball in the closed position.
Both seats hold their respective pressures
independent of the body cavity pressure.
The double block and bleed feature makes
it possible to do such things as flush the
valve under pressure and verify that the
seats are sealing properly.
EXTENDED
BONNET
Valve designs are
available with
extended bonnets —
for applications in
extreme temper-
ature service.
Extended bonnets
are recommended
for service at
temperatures
below -50°C (-
or above 220°C
(428°F).
58°F)
