Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
This invention relates to gate valve actuators, and
more particularly to hydraulically operated actuators for
subset well gate valves.
For some time the oil and gas industry has required
hydraulic actuators for operating gate valves on subset
well Christmas trees, pipe manifolds, and other w~derwater
well apparatus, and such actuators of various designs are
in widespread use for this purpose. Preferably, an
lo actuator for this type of service would be capable of
manual operation in the event of hydraulic power failure,
would have provision for external adjustment to compensate
for valve gate drift, could be manually operated and
adjusted with readily available tools and minimal effort,
lo and would be compact in size and functionally reliable.
Summary of the Invention
According to an aspect of the invention, a fluid
powered actuator for a sliding gate valve comprises a
valve body with a flow passage there through, a bonnet
I connected to said body a valve gate in said body said
valve await havillg a flow passage there through, and a valve
stem connected to said gate and extending through said
bonnet, said actuator comprises:
a housing with first and second opposed closed ends r
fluid cylinder within said housing and having an end
portion;
a fluid-powered piston within said cylinder for
actuating said valve in an axial direction; an Atari
stem connected to slid piston and extending through Roth
of said opposed ends, said actuator stem comprising a
first stem element extending from said piston thrill said
first opposed housing end and terminating ill a means for
releasable connecting said actuator stem to said valve
stem, a second stem element extending prom sail piston
through said cylinder end portion and said second opposed
housing end and terminating in a means for rotating suckle
second stem element with respect to said first stem
element, s-top means on said second stem element
cooperating with said second opposed housing end to limit
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axial movement of said second stem element, and threaded
means adjustable interconnecting said first and second
stem elements in a end-to-end manner, sail threaded means
comprising an externally threaded annular spacer
releasable secured to one end of said first stem element
and an internally threaded bore in said second element,
said spacer and said bore cooperating to cause relative
axial movement between said first and second stem elements
when said second stem element is rotated with respect to
lo said first stem element; means on said valve stem for
cooperating with said releasable connecting means on said
actuator stem for releasable connecting and disconnecting
said actuator stem to said valve stem Chile the valve is
under operating pressure; and means or connecting and
disconnecting said housing to and from said valve bonnet
while the valve is under operating pressure and for
adjusting the position ox the valve Nate flow passage
relative to the valve body flow passage, said connection
and disconnecting means comprising an annular flange body
and a sleeve-like collar, said collar connected to the
housing by first thread means and connected to said flange
body by second thread means, said first and second thread
means constituting a differential thread system so that
rotation of said collar with respect to said housing and
said flange body will change I the axial spacing between
the housing and the Lange body and (2) the position ox
the valve gate with respect to the valve body and the
bonnet.
The present invention as embodied in a hydraulic
operated vale valve actuator has one or more of the
above features. Such an actuator can include an
externally adjustable valve vale drift adjustment system,
a manual override system that does not exercise the
hydraulic piston or its return spin at any time during
I the manual override operation, thereby requiring the
application of only minimal actuation torque ho the diver,
and what does not introduce a potential leak path to
control pressure fluid during said override cycle, an
externally adjustable unstop for the actuator stem that
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can be used instead of the backseat between the valve stem
and bonnet, and a separate and readily replaceable thread
assembly for the actuator stem that offers reduced
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manufacturing costs and less potential for thread galling
during the actuator's service life.
The actuator has a high spring load-to-actuation
piston area ratio with multiple control ports for more rapid
response to command control pressure. Should the control
pressure fail the spring automatically and quickly returns
the piston to its "valve closed" position, thereby providing
effective fail-safe closed protection to the fluid conduit
in which the valve is installed.
In its preferred form the actuator also includes a
hydraulic control pressure porting system that is integral
to the cylinder to minimize external plumbing requirements
and the overall length and diameter of the actuator. A
manifolding hydraulic distribution system for the control
pressure porting assures positive distribution of fluid to
the cylinder during actuation, and minimizes the number of
fabricated parts in the system.
In its preferred form the actuator further includes
an ambient pressure compensation porting system on eke
backside of the piston and piston cylinder to almost equalize
the pressure in the static non-operating mode control pressure
porting system caused by hydrostatic hydraulic head from sea
level to the installed subset valve. This compensation
system assures that the actuator is only operated to the
open position by a positive control pressure command from
the surface control system, and not by hydrostatic head
pressure in the control pressure porting system.
The preferred form of actuator additionally includes
an accommodation for an externally mounted electrical position
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indication package for monitoring the position of the actuator
stem and, ultimately, the valve gate to which the stem is
connected. Provision for manually monitoring the stem and
gate positions, from outside the actuator also is present
in the preferred embodiment in a form that is readily accessible
to a diver.
Brief Description of the Drawings
Figure 1 is a diagrammatic side elevation of a
subset well completion system, showing valve actuators
incorporating the present invention in functional position
on gate valves of a subset Christmas tree.
Figure 2 is a central longitudinal section, on an
enlarged scale, of a valve actuator that includes the features
of the present invention.
Description of the Preferred Embodime_
As diagrammatically represented in Figure l, valve
actuators 8 embodying the present invention are especially
suitable for use on subset well completion apparatus 10 to
open and close gate valves 12 located in the Christmas tree
14 that is tnounted on the subset Waldo assembly 16. The
illustrated Waldo assembly 16 typically includes a Waldo
housing 18, a tree connector 20 securing the crew 14 to the
housing 18, and a permanent guide base 22 surrounding and
secured to the housing 18 and associated Waldo components
24 by support struts 26. The actuators 8 are operated by
hydraulic pressure conducted from a suitable source (not
shown) through hydraulic lines (not shown), and the pressure
is applied to the actuator pistons through internal passages
in the actuator as described below.
Referring to Figure 2, the preferred embodiment of
the present invention is illustrated in one of the valve
actuators 8 that is shown attached to the bonnet 30 of one
of the gate valves 12 by a plurality of screws 31. The
actuator 8 broadly comprises a housing 32 secured to a
main body 34 by threads 36, a flange body 38 connected to
the main body 34 by a flange body collar 40, a stem
assembly 41 comprising an outer or manual override stem 42
and an inner or actuation cylinder stem 44, a sleeve-type
lo hydraulic cylinder 46 secured by threads 48 to the main
body 34, a cylinder cap 50 secured by. threads 52 and a
set screw 53 to the cylinder 46, a piston 54 mounted on
the inner stem 44 within the cylinder 46, and a
piston-return coil spring 56 surrounding the cylinder 46
and extending between the main body 34 and a spring
compression hub 58 that surrounds the outer stem 42.
The outer end of the housing 32; i.e., the right hand
end as viewed in Fig. 2, has a central opening into which
is threaded a packing gland 60, and threaded onto the
outer end of the packing gland is an end cap 62 with a
central opening aye. The outer stem 42 extends through
the packing gland 60 and into the end cap 62, preferably
terminating within the central opening aye when the stem
is in its "valve closed" position shown in Fig 2. Between
a radial flange aye of the packing gland 60 and the
adjacent end face of the actuator housing 32 is a spacer
ring 63 that is removed to facilitate further threading of
the gland into the housing to provide a stop for the
actuator stem, as will be more fully explained later. An
annular static seal 64
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provides fluid-tight integrity between the gland 60 and the
housing 32, and annular dynamic seals 66 provide a fluid
barrier between the gland and the actuator's outer stem 42.
The outer stem 42 has a radially enlarged area or
flange aye located within a central bore aye of the hub 58,
and a pair of bearing assemblies 68, 70, located on opposite
sides of the flange aye, provide relative rotation support
between the stem 42 and the hub 58. A retainer ring 72
holds the bearing assembly 70 in position against the stem
flange aye.
The outer stem 42 is connected to the inner stem
44 by moans of a stem adjustment screw 74 that is secured to
the end of the inner stem by a cap screw 76. The inner end
ox the stem adjustment screw 74 has a central transverse
tongue aye that cooperates with a matins groove aye in the
adjacent end of the inner stem 44 to prevent relative rotation
between the screw 74 and the stem 44 when properly assembled
as shown. The adjustment screw 74 and the adjacent portion
of the inner stem 44 reside in a central threaded bore 42b
in the outer stem 42, and external threads on the screw 74
cooperate with the threads in the bore 42b to axially change
the location ox the screw in the bore, and thus the axial
position of the inner stem 44 with respect to the outer stem
42, when the outer stem is rotated will respect Jo the inner
stem.
The outer stem 42 extends through a central bore
in the cylinder cap 50 and is sealed in a fluid-ti~ht manner
thereto by annular dynamic seals to. Between the inner end
of the outer stem 42 and the piston 54 is an annular bushing
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80 to prevent galling of the adjacent piston face by the
stem 42 when the stem is rotated with respect to the icier
stem 44 into the position shown in Fig. 2. When in that
position the outer stem 42 holds the piston 54 against an
annular shoulder 44b on the inner stem 44, and when the
actuator is operated by hydraulic pressure the piston 54,
inner stem 44 and outer stem 42 translate in unison. Annular
seals 82 assure a ~luid-tight barrier between the piston and
the inner stem.
When the actuator 8 is functionally connected to a
gate valve the actuator's inner stem 44 is connected to the
valve's bonnet stem 84 by suitable means such as the T-slot
arrangement shown in Fig. 2, so that when the actuator is
operated the stems 44, 84 translate in unison. The other
end portion of the valve bonnet stem 84 includes an annular
beveled shoulder aye that cooperates with an annular beveled
backseat surface aye on the valve bonnet 30 to establish a
metal-to-metal seal between the stem So and the bonnet when
the valve is closed as shown in Fig. 2. An annular packing
86, held in place in the bonnet 30 by a packing retainer nut
88, provides a dynamic seal between the bonnet and the
bonnet stem 84, and annular dynamic seals 90 provide a
~luid-tight barrier between the stem 84 and the packing nut
88. The packing nut 88 is sealed to the bonnet 30 by an
annular seal element 92, and an annular seal 94 provides
fluid-tight integrity between the bonnet and the actuator
main body 34.
Hydraulic Operation
The valve actuator 8 is designed for h~draulîc
operation but is provided with manual override capability
when required. When operated hydraulically, control pressure
is introduced through one or more ports 96 Sony one shown)
and conducted by an annular manifold 98 to and through a
plurality of circumferential spaced longitudinal passageways
100 in the wall of the cylinder 46 into an annular chamber
102 between the piston 54 and the cylinder cap 50. Annular
seals 104 between the piston and the cylinder and 106 between
the cylinder cap and the cylinder cooperate with the seals
78, I to confine actuation control pressure to the chamber
102, whereby in response to this pressure the piston, the
actuator stem assembly 41 and the valve bonnet stem 84
translate in unison Jo the left as viewed in Fig. 2, unseating
the bonnet stem shoulder aye from the bonnet backseat aye
and translating the valve gate (not show) into its open
position.
Pressure compensation for the actuator 8 Jo ease
its operation at deep sea depths is provided by an external
compensator (not shown) that is functionally connected to
one or more ports 108 only one shown in the actuator main
body 34. Compensated oil pressure entering port 108 is
conducted by a passageway 110 into an annular chamber 112 in
the cylinder 46 and in front of the piston 54, and also by a
passageway 114 into the spring housing 32. This pressure
compensation precludes external hydrosc~tic pressure from
crushing the housing 32 and rendering the actuator inoperable.
The actuator sprint 56 functions to automatically
close the valve whenever control pressure is lost or removed
from the backside of the piston 54. The spring I provides
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a force sufficient -to rapidly overcome the hydrostatic
head of the control pressure column situated above the
water surface; i . 2 ., platform control room height above
the water. Since the above-describea pressure
compensation system eliminates the effect of the ambient
water pressure on the actuator, which pressure can be vex
great depending upon the depth at which the actuator is
located, the size of the spring 56 required to close the
valve is substantially less than if such pressure
compensation were absent.
When the actuator is hydraulically operated by
control pressure command the outer stem 42 moves from its
illustrated "valve closed" position towards the valve
bonnet 30, carrying with it the spring compression hub 58
and the bearing assemblies 68, 70. This movement of the
hub 58 compresses the actuator spring 56 which remains
compressed as long as the valve remains open This
movement of the outer stem 42 also results in relocation
of -the stem's outer end face 42c, so that the position of
I the stem, and thus the position of the valve gate, can be
manually ascertained from the outside of the actuator
through the end cap opening aye.
Manual Override Operation
the present invention provides manual override
I operation of the valve operator 3, even under valve
operating pressure or hydraulic system control pressure,
by removing the end cap 62, installing a wheel crank 116
fig. I on the outer stem I and then rotating the stem.
As the stem 42 rotates the stem adjustment screw 74 is
forced to the let (Fig. 2); i.e., towards the valve
hornet 30, thereby translating the inner stem 44, the
bonnet stem 34, and the valve gate __ _ _ I_ _
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(not shown) to the left to open the valve. During this
valve opening rotation the operation resultant forces from
the stems 44 and 84 and the valve Nate are reacted through
the bearing assembly 70 by the stem 42, and the bearing
assembly 70 is reacted by the packing gland 60.
It should be noted that the manual override feature
of the present invention enables the stems 44 and 84, and of
course, also the valve gate, to translate without exercising
the piston 54, the spring 56 or the spring compression hub
58. Because of this, significantly less torque is required
to manually open the valve, and thus an important advantage
is achieved as compared with operation requiring spring
compression.
When using the manual override to close the valve
from its open position, the stem 42 is rotated by the wheel
crank 116 in the opposite direction. This rotation causes
the stem adjustment screw 74 to move to the right; i.e.,
towards the packing land 60, thereby pulling the stems 44
and 84 and thy valve gate in the same direction, and resulting
in closing the valve. During this valve-closing rotation
the operation resultant forces from the valve Nate and the
stems 84 and 44 are reacted through bearing assembly 68 by
the stem 42. Also during this valve-closing the bearing
assembly 68 is reacted by the spring compre~ion hub 58, and
the hub it reacted by the sprint 56.
It should be noted that the retainer ring 72,
which retains the bearing assembly 70 on the outer stem 42,
is required for normal hydraulic operation of eke actuator
when the stem 42, hub 58 and spring 56 cycle forward and aft
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many times during normal actuation of a subset valve by
control pressure command.
External Adjustments
The present invention further provides for externally
adjusting the position of the valve gate to which the actuator
8 is connected.
External adjustment of valve gate drift is accomplished
by rotating the flange collar 40 either clockwise or counter clock-
wise. The collar 40 has two sets of internal threads aye,
40b, one right-hand and the other left-hand, that engage
external threads on the flange body 38 and the main body 34.
Relative rotation of the bodies 38, 34 is prevented by an
anti-rotation key 118 that resides in opposed kiwi slots
in the adjacent body surfaces. Accordingly, rotation of eke
collar 40 either draws the main body 34 and the housing 32
towards the flange body 38 or forces them away from the body
38, thereby changing the position of the bonnet stem By and
the actuator's inner stem 44 with respect to the actuator
cylinder 46, and thus changing the drift; i.e., the valve
gate position with respect to the valve body/bonnet/ actuator
assembly.
External stop adjustment for the stems 42l 44, 84
and the valve gate is accomplished by rotation of the packing
gland 60. Thus, if it is desired to stop closing ulovement
of these stems and the Nate before the stem shoulder aye
backseat on the bonnet surface aye, the frangible spacer
ring 63 is knocked out and the gland 60 is threaded further
into the housing 32 until its axial position stops the
movement at the desire point.
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The ability to achieve these two adjustments from
outside the actuator offers significant cost savings in
assembly adjustment, both in the shop and in the field, as
well as adjustment when in a subset location.
Valve Gate Position Indication
As discussed above, the present invention facilitates
determination of the position of the valve gate by viewing
or feeling/measuring the relative position of the outer stem
42 to the end cap 62. A fully extended stem indicates the
valve gate is closed, and of course a fully retracted stem
indicates the valve gate is in its open position.
The invention also envisions determination of the
valve gate position by electrical means, such as by an
external electrical sensor (not shown) mounted on the end
cap 62. Using a permanently magnetized stem 42, the proper
sensor can determine the presence (valve closed position) of
the stem or the non-presence (valve open position) thereof,
and send an appropriate signal to the control room on the
surface platform (not shown).
It should further be noted that although the
above-described valve actuator is intended for use on gate
valves on subset well completion Christmas trees and/or
manifolds, the actuator also has utility on shore where
remote operation of gate valves is required. Thus the
adjustment features described above offer an economic advantage
where valve adjustments are required in the field, either on
land or subset.
Although the best mode contemplated for carrying
out the present invention has been herein shown and described,
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it will be apparent that modification and variation may be
made without departing from what is regarded to be the
subject matter of the invention.
