train-
-
or
ppli-ct/
eld
tation
ices
time
next
r
such
dera-
other
mber,
kely
for
lu-
g
i-
ben-
other
dd up
ange
the
relative to the seat axis and to the sym-
metrical axis of the valve. This allows for
a camming action of the disc as it
rotates. In addition, the valve seat is
manufactured in a conical form where
the apex of the cone has been oriented to
an asymmetrical axis of the valve, which
introduces a third offset. This character-
istic eliminates any rubbing action of the
seal ring with the seat during the 90
degrees of rotation.
Figure 1. Unseated (above) and seated TOV
(below)
; Offset 1 is achieved by placing
the shaft behind the plane of the
surface. The purpose of this offset is to provide a continuous
seat path.
; Offset 2 is achieved by placing
the shaft offset to one side of
the pipe and valve centerline.
The purpose of this offset is to
drive the seal away from the
seat during the 90° of opening.
; Offset 3 is achieved by inclining
the seat and seal cone centerline
in respect to the pipe and valve
centerline. This third offset eliminates rubbing. The chances of
associated wear and leakage
between the seat and disc-mount-ed seal ring during travel are
non-existent.
Figure 2
U.S. ALLOYS, INC
red
n
g the
at
gh-r a
nde-chase
its
an
s to
tful
has-ight
tical
ts
Since 1976, Round Bar Supplier for Valve & Fitting Manufacturers
of
Petrochemical / Power Generation / Nuclear / Aerospace
Round Bar Stock
GRADES:
(Domestic and Import)
A105
A350 LF2
SA105
A675 GR 70
A696 GR C
SIZES:
304/304L
316/316L
317/317L
321/321H
347/347H
F- 11
ost of
e mar-ooga,
y.com.
7/8” to 24”
Cut to length 7/8” – 24” OD
ASTM/ASME/(Latest editions)
NACE MR01-75/NACE MR0103
DIN 3. 1.B/EN 10204
Phone (713) 644-1983 Fax (713) 644-9889 www.usalloys.cc
which is a significant difference from
position-seated, high-performance butterfly valves where only the position and
the interference between the sealing elements generate tightness.
In a high-performance butterfly
valve, a stopper is cast into the body to
prevent the disc going through, which
would have catastrophic consequences.
Because the seat is the natural stopper
in a TOV, it is physically and mechanically impossible for the disc to go
through under any service conditions.
This design reduces maintenance and
substantially extends the life expectancy
of the valve with corresponding advantages in operability and possible speed
of operation.
