Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a valve o~ thé type
used for controlling the flow of fluid.
In the chemical process industry, especially in
the petrochemical and hydrocarbon refinery areas, the emission
of volatile organic hydrocarbon fluids, such as gases, to
the atmosphere has been a problem. One of the leakage
sources is from various valves used in the processing
apparatus. Most of these valves are constructed with
packings along the stems, but the stems must turn when the
valve is operated. To prevent leakage along the valve stems,
the packing must be tightened against the valve stems. This
induces high friction contact along the stems and makes the
valves difficult to operate.
According to the present invention there is
provided a valve for controlling the flow of a fluid,
the valve includin~ a body defining a valve chamber an~
having inlet and outlet connections, and a bonnet connected
to the body and further defining-the valve chamber. A
turnable valve stem passes through and projects from the body
and bonnet, and a valve closure element i5 provided in the
valve chamber connected to the stem so that upon turning
the stem the valve element moves between valve open and
closed positions, the closed position being defined when
the closure element is in the position to block the inlet
and outlet connections and the open position being defined
when the closwre element is in a position removed from the
inlet and outlet connections. An annular collar means
surrounds the stem and is connected to the bonnet, the
annular collar means having a cavity therein and defining
an annular seal chamber. A mechanical seal assembly surrounds
the stem and is disposed in the annular seal chamber, the
mechanical seal assembly being so constructed and arranged
for insertion as a unit into the annular seal cavity and
for removal and replacement as a unit therefrom. The mechanical
seal assembly includes an annular disc surrounding and connected
from rotation with the stem, the disc having a pair of lapped
faces, each face defining a seal face. The mechanical seal
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assembly also includes a pair o e annular seal rings and a
bellows connected to each of the seal rings o~ the paix,
each seal ring having a lapped seal face, and each ring
seal face contacting one of the seal faces of the disc.
The bellows is so constructed and arranged to resiliently
urge its connected seal ring toward the annular disc and
is further so constructed and arranged to restrict leakage
of fluid from the valve and along the stem to leakage
across the contacting seal faces. The contact seal faces
are relatively rotatable with respect o each other only
when the stem is rotated.
One way of carrying out the invention is described
in detail below with reference to drawings which illustrate
only one specific embodiment, in which:-
Fig. l is a section through a valve assembly
constructed according to this invention; and
Fig. 2 is a section through a second embodiment
of a valve assembly constructed according to this invention.
A low emission valve assembly 10, constructed
according to this invention, is illustrated in Fig. l of the
drawing~ The valve assembly 10 comprises a valve body 12
formed with a flow passage 14 and a generally cylindrical
valve chamber 16. The passage l~ has opposed inlet and
outlet openings 18 and 20, respectively, and inserts 22 and
2~ therein, each defining a valve seat 26 and 28, respectively,
the valve seats being within the chamber 16. 'I'he inlet and
outlet openings 18 and 20 can also ~unction as outlet and
inlet openings, respectively. A gate 30 is located in the
chamber 16 and it is formed with
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opposed ~aces 32 and 34 which are adapted to seat
on the val~e seats 26 and 28, respectively. The
gate 30 is formed with a shank 36 carrying an
internally threaded insert 38 located upwardly ~rom
the gate faces 32 and 34. The shank 36 and insert
38 receive a valve stem 40 having external threads
42 mating with the threads of the insert 38. As
can be readily seen, rotation of -the stem 40 causes
the gate 30 to move axially, either up or down, de-
pending on the direction o~ rotation o~ the stem,
the stem remaining in the position illustrated.
At its terminal end, -the stem 40 is provided with
a handle 44 to turn the stem 40. The handle 44 is
retained on the stem 40 by a nut 46 recei~ed on a
threaded portion of the stem.
A bonnet 50 is bolted or otherwise secured to
the body; it has a cavity 52 communicating with the
chamber 16 o~ the body 12 and a central opening
through which the stem 40 passes. The cavi-ty 52
is provided wlth a back seat 54 upon which -the
terminal end 56 o~ the shank 36 o~ the gate 30 seats
when the gate 30 is in its uppermost position. The
bonnet 50 is ~ormed to provide a cavity 58 to support
parts o~ a thrust bearing assembly 60, and a cavity
62 to receive a seal retaining collar 64. The collar
64 is connected, as by being welded (as illustrated
in Fig. 1), bolted or otherwise secured to the bonnet
and retains parts o~ a mechanical seal arrangement 66
to be described. To remove the collar 64 ~rom the
bonnet in the Fig. 1 embodiment, it is necessary to
unweld the collar and bonnet.
The thrust bearing assembly 60 comprises a
pair of thrust bushings 68, 70 shaped to receive a
generally annular stem retainer 72 which is connected
to the stem 40. The collar 64 has a lower annular
lip 74 which abuts the upper surface o~ the thrust
bushing 68, the retainer being threadably received
in the bonnet 50 or bolted thereto.
The collar 64 is provided with a cavity 76
defined in part by the lip 74, the cavity 76 re-
ceiving the mechanical seal arrangement 66. The
seal arrangement 66 comprises an upper ssal ring 78
and a lower seal ring 80 each having a lapped seal
face 82, 84~ respectively engaging respective
lapped seal ~aces 86, 88 of a seal rotor 90 connected
to the stem 40. Relative rotation between the en-
gaging seal ~aces occurs only when -the stem is ro-
tated. The seal rings and seal rotor can be con-
structed of materials ~rom which conventional, prior
ar,t mechanical seal rings are constructed.
A bellows 92 is welded or otherwise secl1red
at one end to the upp~r seal ring 78 and to a re~
tainer 94 at the other end. A bellows 96 is welded
or otherwise secured at one end -to the lower seal
ring 80 and is welded to a retainer 97 received in
the cavity 76 at its other end. The retainer 94
is received ln a cavity 98 in the collar 64 and-the
seal assembly 66 is secured in position by a collar
100 threadably received on a portion of the stem 40.
The bellows 92 and 96 may be formed of a plurality
of annular plates alternately welded together at the
inner and outer circumferences or alternately may
be formed of conventional seamless annular corrugated
tubing of materials as known in the art.
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The bellows 92 and 96 are installed to re-
siliently urge the seal rings to which they are
welded toward the rotor 90, so that the respective
seal ~aces are in sealing relationship with one
another. A leakoff connection 102 is provided in the
collar 64 which communicates with the cavity ?6
such that any leakage across the seal ~aces 84, 88
can be removed; the connection 102 can be used to
monitor leakage and emissions, i~ desired.
The mechanical seal assembIy 667 as can be
seen, is modular in construction and can be removed
and replaced, as a unit, even when the valve is
operational. For example, i~ the valve is open, the
gate can be seated on seat 54 permitting repair
and/or replacement of the thrust bushings and/or
the seal assembly.
In the event of iailure o~ the lowex position
o~ the seal, i.e., the ring 80 and its face 84,
the port 102 can be closed and the upper posi.-tion O:e
the seal including the rlng 78 and the ~ace~ 82
and 86 becorne operational as a secondary seal, still
substantially preventing emission O:e ~luids to the
~tmosphere.
Fig. 2 illustrates ano-ther embodiment o~ the
valve differing mainly in the construction of the
collar, identi~ied here as 110, the like parts of the
valve assembly being identiiied as in Fig. 1. The
collar 110 is constructed to be bolted, as by bolts
112, to the bonnet 50 and comprises a generally
inverted cup-like portion 114 to which is connected,
as by welding, a ring 116. The lower bellows 96
is connected to the ring 16 while the upper bellows
92 is connected as by welding to the portion 114.
A port 116 is formed in the portion 114, the function
o~ which is the same as the port 102 of ~ig. 1.
A hex head nut member 118 is provided to contact
the top of the rotor 90 and to locate a sleeve 120
for the passage of the stem 40. As readily seen,
the operation of this embodiment is substantially
the same as that of the ~ig. 1 embodiment.
The types and kinds of materials to be used
for constructing the described valve-seal assembly
are within the skill of one skilled in the art.
Preferably, the materials chosen should be corrosion
resistant and where parts are welded, they should be
of weldable materials. The choice of materials
can also depend upon temperature considera-tion~
within the knowledge o~ one skilled in the art.
