Note: Descriptions are shown in the official language in which they were submitted.
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- l - GOK 102-215
SPHERICAL ~ALVE SYSIEM
This invention generally relates to a
spherical valve suitable for use with a hydraulic
turbine and-more particularly to the rotor for the
valve.
In one prior art spherical valve construc-
tion the rotor for the valve is cast as a one piece
rotor complete with trunnions or is fabricated of
plate steel with bolted on, cast or forged trunnions
and the valve body is split into two pieces which are
10 bolted together once the rotor is inserted therein.
Variations in this prior art construction revolve
around the location of the split in the valve body. In
the most common variation, the valve body is split
along the vertical plane passing through the trunnion
15 bearings. In another variation, the valve body is
split along a vertical plane passing through the
upstream to downstream path of the valve at 90 degrees
to the trunnion bearings. Although the one piece cast
rotor has superior strength characteristics, the pressure
20 that the valve is able to withstand may be limited
by the strength of the split valve body.
In other prior art spherical valve construc-
tions attempts have been made to improve the strength
of the valve body by employing a one piece valve body
25 in one variation and by splitting the valve body
offset from and parallel to the vertical plane passing
through the trunnion bearings in another variation.
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However, to utilize such a construction the rotor is
formed by bolting two separate trunnions onto the
valve plug member. The trunnions are provided with
flanges through which cap screws extend to screw into
the plug member. Although in this construction the
strength of the valve body is improved, the ability of
the spherical valve to withstand pressure is more limited
by the rotor. In this COnstrUCtiQn~ when the valve
is closed, the force acting against the plug member is
transferred to the trunnion bearings through the
trunnions. One problem with this construction is
that the force transfer from the plug to the trunnion
is purely effected through the cap screws which hold
the trunnion to the plug. This results in shearing
and tensile forces acting on the screws and a large
bending moment being applied to the flange. The
ability of the screws and flange to withstand the
combined stress from the shearing force, tensile
force, and bending moment determines the ability of
the spherical valve to withstand high pressure loads.
One disadvantage with this construction, which is
encountered during the course of valve construction,
i8 that the drilling and tapping of the flange and
plug member for the flange bolts or screws prior to
a8sembly requires prestressing of the flange and
plug member at final assembly. Another disadvantage,
which is encountered during the erection of the rotor
in the valve body, is that the rotor assembly must be
accurately located on temporary supports and the plug
member and trunnions must then be rotated while in
centered relation within the valve body in order to
install the cap screws.
In another prior art spherical valve construc-
tion designed to overcome the disadvantage of flange
bolting on the valve body, two half bodies are welded
together around a partially machined rotor with integral
trunnions. Finish machining of trunnions, trunnion
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GOK 102-215
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bores, sealing faces etc. is accomplished after welding
and stress relieving the assembly. This operation is
associated with special, unusual machining set-ups and
increases the overall cost of the valve. It also does
not allow any future disassembly of the valve should
operating difficulties or field failure make it necessary.
It is therefore the general object of this
invention to provide a spherical valve construction
that is not subject to the above-mentioned problems and
disadvantages.
This invention relates to a spherical valve
and a method of manufacturing the spherical valve.
The spherical valve includes a valve body having a
central chamber therein and a spherically shaped rotor
located in the chamber. The valve body has
diametrically opposed trunnion bearings. The rotor
comprises a closure plug member capable of blocking
flow through the valve, and two separate trunnions
fixedly secured to the closure plug member and
rotatably supported in the trunnion bearings. The
closure plug member has diametrically opposed trunnion
housings which are located adjacent the trunnion
bearings to which the trunnions are fixedly secured.
The trunnions are insertable from the interior of the
closure plug member through a respective trunnion
houRing and the adjacent trunnion bearings, making
possible the assembly of the closure plug member into
the valve body, and assembly of the trunnions with the
rotor within the central chamber of the valve body. In
operation the forces acting on the closure plug member,
when the valve is closed, are transferred from the
plug member by the trunnion housings to the trunnions
and thence to the trunnion bearings. The form of
trunnion housings through which the trunnions pass,
the manner of securing of the trunnions to the trunnion
housings, and the adjacency of the trunnion housings
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GOK 102-215
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to the trunnion bearings all contribute to improve
the capability of the present valve construction to
withstand the shearing forces, tensile forces and
bending moments which comprise the maximum load
forces acting on the rotor construction when the valve
is closed.
In accordance with an aspect of this
invention there is provided in a spherical valve
including a valve body having a central chamber therein,
a flow channel therethrough, and diametrically opposed
trunnion bearings, a rotor capable of:being inserted
within said chamber, comprising a closure plug
member having an interior flow passageway therethrough,
a generally spherical closure surface, and diametrically
opposed trunnion housings located adjacent the trunnion
bearings, each for receiving a respective trunnion
in secured relation to its trunnion housing, each
trunnion being supported for rotation by a corresponding
trunnion bearing whereby the trunnions are rotatable
within the trunnion bearing, between a closed valve
position where the closure surface blocks the flow
channel and an open valve position where the interior
flow passageway communicates with the flow chanel,
the respective trunnion being insertable from within
the interior flow passageway of the plug member through
the trunnion housing into the corresponding trunnion
bearing.
In accordance with another aspect of the
invention there is provided a method of manufacturing
a spherical valve wherein the valve includes a valve
body having a central chamber therein and diametrically
opposed trunnion bearings, a rotor comprises a closure
plug member having diametrically opposed trunnion
housings and trunnions. The method comprises the
steps of positioning the closure plug member within
the central chamber so that each of the trunnion
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GOK 102-215
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housings is located adjacent a respective trunnion
bearing, and inserting each trunnion from within the
interior of the closure plug member through,~a res-
: pective trunnion hous;ing into a respective trunnion
~bearing so that each trunnion is fixedly secured in~its respective~trunnion housing.
For~a better understanding of the nature
~and objects~of;ehe~invention~disclosed herein reference
; may be had by way of~example to the accompanying
diagrammatic drawings~for a preferred~embodiment in
which:
' Figure 1 is a side eIevation view of a
spherical valve.
Figure 2 is a top sectional view of the
~; 15 spherical valv- of Figure l~wherein-the cl~sure plug
member of the valve is shown in its open position.
Figure 3 is~a~top sectional vi-w of the
spherical valve of Figure l wherein the cLosure plug
member of the valve~is shown~1n its closed~position.
Figure 4 is a;partial sectional view of a
~, trunnion housing and;trunnion,taken along~section line
4-4 of Figure 2.~
- Ref-rrlng now to Figure 1 there is shown a
~pherical valve l0 suitable for use with a hydraulic
turbine. The spherical valve of the preferred embodiment
has a diameter in,the order of about 3.25 meters~and
iB operational for heads in the order of 300 meters.
A rotor ~not shown) is located inside valve body 12
of 8pherical~valve 10 and is rotated by crank arms 14
connected to the trunnions~(not shown) of the rotor.
Each crank arm 14 is connected to the drive,shaft 16 of
an operating cylinder 18. When the valve 10 is open,
water flows in through intake port 20'through valve 10
and exits through exhaust port 22.
Referring now to Figures 2 through 4 crank
arms 14 are shown connected to hollow trunnions 24
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by bolts 26 inserted into drilled or tapped holes 28.
The one piece cast valve body 12 has diametrically
opposed trunnion bearings 29 which house stem portions
25 of trunnions 24. The valve body 12 has a central
chamber 30 therein and a flow channel wherein flow
arrows 32 are illustrated (Figure 2).
The rotor 34 is sufficiently-small to be
inserted into chamber 30, the valve having axially
movable annular seals 36 adjacent to the valve inlet
and valve outlet, which seals 36 are selectively
movable clear of rotor 34, or into sealing contact
with rotor 34.
The valve rotor 34 comprises a closure
plug member 40 having a generally spherical closure
surface 38 which blocks flow channel 32 of valve 10
(Figure 3) when the valve 10 is in the closed position.
The closure plug member 40 has a central passageway
42 (Figure 3) therethrough extending substantially
normally to the polar axis of closure surface 38
which permits the passage of water through the valve 10
when valve 10 is in its open position (Figure 2).
The rotor 34 also includes trunnions 24 secured to
closure plug member 40, whereby the plug member 40
can be rotated between its open and closed positions
by crank arm 14 rotating trunnions 24 within bearings 29.
Generally the present invention relates to the
manner in which the trunnions 24 are fixedly secured to
the plug member 40. Plug member 40 has a pair of
diametrically opposed trunnion housings 44 positioned
adjacent the trunnion bearings 29. The trunnions 24
are fixedly secured to the trunnion housings 44 by
insertion from within the interior, central passageway
42 of plug member 40 through the trunnion housings 44.
As shown in the drawings, each trunnion housing 44 com-
prises an annular ring portion extending outwardlyof the plug member 40 towards a corresponding one of
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GOK 102-215
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the trunnion bearings 29. The annular ring surrounds
a portion of its respective trunnion 24. Each trunnion
housing 44 includes a lip portion 46 at its end
adjacent the corresponding trunnion bearing 29. The
lip portion 46 extends radially inward to form a
recessed seat portion 48. Trunnions 24 have stem
portions 25 and flange portions 50 abutting the recessed
seat portion 48 of the annular ring or trunnion
housing 44. The flange portion 50 is press fitted
into the recessed seat portion 48, and further secured
by the provision of at least one threaded hole drilled
between the abutting surfaces of flange portion 50
and seat portion 48 into each of which a locking~cap
screw is secured. Lastly, sealing members 52 are
sealed by annular seal welds 54 to prevent water
seepage therepast.
It should be understood that in alternate
embodiments the lip portion of trunnion housing 44
may be dispensed with. Also, the trunnion housing may
comprise a tapered annular ring portion into which a
trunnion having a tapered flange is press fitted.
In operation, when the valve is closed as
shown in-Figure 3, the head of water creates a large
force that acts against the closure plug member 40.
This force is transferred through the trunnion
housings 44 and trunnions 24 to the trunnion bearings
29. The present invention provides a large area of force
transfer between the trunnions and the trunnion
housings. The rotor construction has the ability to
withstand large operating forces because the force
acting on the plug is distributed over a pair of large
surface areas and transferred directly to the trunnions.
The adjacency of the trunnion housings 24 to the
trunnion bearings 29 minimizes the resultant trunnion
bending moment, whereby the stresses acting on the
valve components are minimized. As shown, the distance
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lllS678
GOK 102-215
- 8 -
between each trunnion housing 24 and its corresponding
adjacent trunnion bearing 29 is minimized to a distance
that provides adequate clearance therebetween.
The spherical~ valve construction shown-in
5~ Figures 2 through 4 provides a method of manufacture
~wherein~assembly of~the rotor 34 of the valve 10
; may be completed within chamber 30 of the~valve body
12.; Such~a method~is~significant~becau~se it permits
the use of a one piece valve body which~possesses
inherently greater;mechanical strength than a two-
piece split valve~body~o~f bolted construction. The
method includes~the~step~of~positloning the~closure plug
member in the~central~chamber of the valve body so
that each of the trunnion housings is located adjacent
a respective trunnion~bearing.; The method further
- includes the step of inserting~each trunnion from
within the interior~of the~closure~plug~member through
its respective~trunnion housing and into the respective
trunnion bearing,~each trunnion being~press~fitted
into its trunnion housing.~ The method has the advantage
that bolts are not relied~upon~to;attach~the trunnion
flange to the closure~plug member. Thus no prestressing
of the trunnion flange~and plug member is necessary to
enable the drilling of~holes~for~;~such securing bolts.
Also, during the completion of~the~rotor while within
the valve body, supports for the plug member need not
be shifted and the plug member and trunnions rotated
aB they would have to be if bolts were required to
~ecure the trunnion flange to the plug member.
It should~be understood that the foregoing
has been a description of the preferred embodiment and
that alternate embodiments may be readily apparent
to a man skilled in the art in view of this disclosure.
Accordingly, the invention is to be limited to that which
i8 claimed in the accompanying claims.
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