U.S. patent application number 11/466161 was filed with the patent office on 2008-02-28 for fluid saving blowout preventer operator system.
Invention is credited to John T. Mangan, David J. McWhorter, Melvyn F. Whitby.
Application Number | 20080048140 11/466161 |
Document ID | / |
Family ID | 39107304 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080048140 |
Kind Code |
A1 |
Whitby; Melvyn F. ; et
al. |
February 28, 2008 |
FLUID SAVING BLOWOUT PREVENTER OPERATOR SYSTEM
Abstract
A hydraulic blowout preventer operator comprises a piston rod
having one end coupled to a closure member. The operator further
comprises an operator housing having one end coupled to a bonnet
and a second end coupled to a head. The piston rod extends through
the bonnet into the operator housing where it is coupled to a
piston that is disposed within the operator housing. The piston
comprises a body and a flange. A flange seal is disposed on the
flange and is sealingly engaged with the operator housing. A body
seal is disposed on the body and is sealingly engaged with the
operator housing. The flange seal has a sealing diameter greater
than a sealing diameter of the body seal.
Inventors: |
Whitby; Melvyn F.; (Houston,
TX) ; Mangan; John T.; (Houston, TX) ;
McWhorter; David J.; (Magnolia, TX) |
Correspondence
Address: |
CONLEY ROSE, P.C.;David A. Rose
PO BOX 3267
HOUSTON
TX
77253-3267
US
|
Family ID: |
39107304 |
Appl. No.: |
11/466161 |
Filed: |
August 22, 2006 |
Current U.S.
Class: |
251/1.3 |
Current CPC
Class: |
E21B 33/062
20130101 |
Class at
Publication: |
251/1.3 |
International
Class: |
E21B 33/06 20060101
E21B033/06 |
Claims
1. A hydraulic blowout preventer operator comprising: a closure
member; a first piston rod comprising a first end coupled to the
closure member; a first operator housing comprising a first end
coupled to a bonnet and a second end coupled to a head, wherein the
first piston rod extends through the bonnet, wherein a second end
of the first piston rod is at least partially disposed within the
operator housing; a first piston at least partially disposed within
the first operator housing, wherein the first piston comprises a
body and a flange, wherein the second end of the first piston rod
is coupled to the body of the first piston; a first flange seal
disposed on the flange and sealingly engaged with the operator
housing; a first body seal disposed on the body and sealingly
engaged with the operator housing, wherein the first flange seal
comprises a sealing diameter greater than a sealing diameter of the
first body seal; wherein the engagement of the first flange seal
with the first operator housing creates a first extend chamber
between the first flange seal and the head; wherein the engagement
of the first body seal with the first operator housing creates a
first retract chamber between the first body seal and the bonnet;
and wherein the first extend chamber and first retract chamber
provide volumes for fluid to hydraulically actuate the first piston
and wherein the first extend chamber volume is larger than the
first retract chamber volume.
2. The hydraulic blowout preventer operator of claim 1 further
comprising a slack fluid chamber formed within the first operator
housing between the first flange seal and the first body seal.
3. The hydraulic blowout preventer operator of claim 2 wherein the
slack fluid chamber is open to a surrounding environment.
4. The hydraulic blowout preventer operator of claim 1 wherein the
closure member is moveable between an extended position and a
retracted position relative to the bonnet.
5. The hydraulic blowout preventer operator of claim 4 wherein the
closure member is moved to the extended position by a first volume
of fluid disposed in the first extend chamber and the closure
member is moved to the retracted position by a second volume of
fluid being disposed in the first retract chamber.
6. The hydraulic blowout preventer operator of claim 1 further
comprising: a sleeve slidingly disposed within a cavity disposed
within the first piston, wherein the sleeve is rotationally fixed
relative to the first piston; and a lock rod rotatably coupled to
the head and threadedly engaged with the sleeve, wherein rotation
of the lock rod translates the sleeve relative to the first
piston.
7. The hydraulic blowout preventer operator of claim 6 further
comprising a motor rotationally coupled to the lock rod.
8. The hydraulic blowout preventer operator of claim 1 further
comprising: a second piston rod coupled to the closure member,
wherein the second piston rod comprises a longitudinal axis that is
parallel to a longitudinal axis of the first piston rod; a second
operator housing comprising one end coupled to the bonnet, wherein
the second piston rod extends through the bonnet into the second
operator housing; and a second piston coupled to the second piston
rod and disposed within the second operator housing.
9. The hydraulic blowout preventer operator of claim 8 wherein the
second piston further comprising: a second flange seal disposed on
the second piston and sealingly engaged with the second operator
housing; a second body seal disposed on the second piston and
sealingly engaged with the second operator housing, wherein the
second flange seal comprises a sealing diameter greater than a
sealing diameter of the second body seal; wherein the engagement of
the second flange seal with the second operator housing creates a
second extend chamber between the second flange seal and the head;
wherein the engagement of the second body seal with the second
operator housing creates a second retract chamber between the
second body seal and the bonnet; and wherein the second extend
chamber and second retract chamber provide volumes for fluid to
hydraulically actuate the second piston and wherein the second
extend chamber volume is larger than the second retract chamber
volume.
10. A hydraulic blowout preventer comprising: a body comprising a
bore therethrough; a cavity disposed through the body and
intersecting the bore; a closure member moveably disposed within
the cavity; a first piston rod comprising a first end coupled to
the closure member; a bonnet coupled to the body adjacent to the
cavity; a first operator housing comprising a first end coupled to
the bonnet, wherein the first piston rod extends through the
bonnet, wherein a second end of the first piston rod is at least
partially disposed within the operator housing; a first piston
disposed within the first operator housing, wherein the first
piston comprises a body and a flange, wherein the second end of the
first piston rod is coupled to the body of the first piston; a
first flange seal disposed on the flange and sealingly engaged with
the operator housing along a first diameter; and a first body seal
disposed on the body and sealingly engaged with the operator
housing along a second diameter, wherein the first diameter is
larger than the second diameter; wherein the engagement of the
first flange seal with the first operator housing creates a first
extend chamber between the first flange seal and the head; wherein
the engagement of the first body seal with the first operator
housing creates a first retract chamber between the first body seal
and the bonnet; and wherein the first extend chamber and first
retract chamber provide volumes for fluid to hydraulically actuate
the first piston and wherein the first extend chamber volume is
larger than the first retract chamber volume.
11. The hydraulic blowout preventer of claim 10 further comprising
a slack fluid chamber formed within the first operator housing
between the first flange seal and the first body seal.
12. The hydraulic blowout preventer of claim 11 wherein the slack
fluid chamber is open to a surrounding environment.
13. The hydraulic blowout preventer of claim 10 wherein the closure
member is moveable between an extended position and a retracted
position relative to the bonnet.
14. The hydraulic blowout preventer of claim 13 wherein the closure
member is moved to the extended position by a first volume of fluid
disposed in the first extend chamber and the closure member is
moved to the retracted position by a second volume of fluid being
disposed in the first retract chamber.
15. The hydraulic blowout preventer of claim 10 further comprising:
a sleeve slidingly disposed within a cavity disposed within the
first piston, wherein the sleeve is rotationally fixed relative to
the piston; and a lock rod rotatably coupled to the bonnet and
threadedly engaged with the sleeve, wherein rotation of the lock
rod translates the sleeve relative to the piston.
16. The hydraulic blowout preventer of claim 15 further comprising
a motor rotationally coupled to the lock rod.
17. The hydraulic blowout preventer of claim 10 further comprising:
a second piston rod coupled to the closure member, wherein the
second piston rod comprises a longitudinal axis that is parallel to
a longitudinal axis of the first piston rod; a second operator
housing comprising one end coupled to the bonnet, wherein the
second piston rod extends through the bonnet into the second
operator housing; and a second piston coupled to the second piston
rod and disposed within the second operator housing.
18. The hydraulic blowout preventer of claim 17 wherein the second
piston further comprising: a second flange seal disposed on the
second piston and sealingly engaged with the second operator
housing; a second body seal disposed on the second piston and
sealingly engaged with the second operator housing, wherein the
second flange seal comprises a sealing diameter greater than a
sealing diameter of the second body seal; and wherein the
engagement of the second flange seal with the second operator
housing creates a second extend chamber between the second flange
seal and the head; wherein the engagement of the second body seal
with the second operator housing creates a second retract chamber
between the second body seal and the bonnet; and wherein the second
extend chamber and second retract chamber provide volumes for fluid
to hydraulically actuate the second piston and wherein the second
extend chamber volume is larger than the second retract chamber
volume.
19. A method for actuating a hydraulic blowout preventer operator
comprising: supplying a volume of hydraulic fluid to an extend
chamber disposed within an operator housing so as to move a closure
member into a bore of a blowout preventer, wherein the extend
chamber is formed between one end of the operator housing and a
first end of a piston; and supplying a volume of hydraulic fluid to
a retract chamber disposed within the operator housing so as to
move the closure member out of the bore of the blowout preventer,
wherein the retract chamber is formed between an opposite end of
the operator housing and a second end of the piston, wherein first
end of the piston has a larger diameter than the second end of the
piston.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable
BACKGROUND OF THE INVENTION
[0003] The invention relates to methods and apparatus for
controlling pressure within a wellbore. In particular, embodiments
of the invention comprise methods and apparatus for operating e
ram-type blowout preventers.
[0004] Blowout preventers are used in hydrocarbon drilling and
production operations as a safety device that closes, isolates, and
seals the wellbore. Blowout preventers are essentially large valves
that are connected to the wellhead and comprise closure members
capable of sealing and closing the well in order to prevent the
release of high-pressure gas or liquids from the well. One type of
blowout preventer used extensively in both low and high-pressure
applications is a ram-type blowout preventer. A ram-type blowout
preventer uses two opposed closure members, or rams, disposed
within a specially designed housing, or body. The blowout preventer
body has bore that is aligned with the wellbore. Opposed cavities
intersect the bore and support the rams as they move into and out
of the bore. A bonnet is corrected to the body on the outer end of
each cavity and supports an operator system that provides the force
required to move the rams into and out of the bore.
[0005] The rams are equipped with sealing members that engage to
prohibit flow through the bore when the rams are closed. The rams
may be pipe rams, which are configured to close and seal an annulus
around a pipe that is disposed within the bore, or may be blind
rams or shearing blind rams, which are configured to close and seal
the entire bore. A particular drilling application may require a
variety of pipe rams and blind rams. Therefore, in many
applications multiple blowout preventers are assembled into blowout
preventer stacks that comprise a plurality of ram-type blowout
preventers, each equipped with a specific type of ram.
[0006] Ram-type blowout preventers are often configured to be
operated using pressurized hydraulic fluid to control the position
of the closure members relative to the bore. Although most blowout
preventers are coupled to a fluid pump or some other active source
of pressurized hydraulic fluid, many applications require a certain
volume of pressurized hydraulic fluid to be stored and immediately
available to operate the blowout preventer in the case of
emergency. For example, many subsea operating specifications
require a blowout preventer stack to be able to cycle (i.e., move a
closure member between the extended and retracted position) several
times using only pressurized fluid stored on the stack assembly. In
high-pressure, large blowout preventer stack assemblies, several
hundred gallons of pressurized fluid may have to be stored on the
stack, creating both size and weight issues with the system.
[0007] Because many subsea drilling applications require the use of
large diameter, high pressure blowout preventers, the height,
weight, and hydraulic fluid requirements of these blowout
preventers is an important criteria in the design of the blowout
preventers and of the drilling rigs that operate them. Thus, the
embodiments of the present invention are directed to ram-type
blowout preventers that that seek to overcome these and other
limitations of the prior art.
SUMMARY OF THE PREFERRED EMBODIMENTS
[0008] Embodiments of the present invention include a hydraulic
blowout preventer operator that comprises a piston rod having one
end coupled to a closure member. The operator further comprises an
operator housing having one end coupled to a bonnet and a second
end coupled to a head. The piston rod extends through the bonnet
into the operator housing where it is coupled to a piston that is
disposed within the operator housings The piston comprises a body
and a flange. A flange seal is disposed on the flange and is
sealingly engaged with the operator housing. A body seal is
disposed on the body and is sealingly engaged with the operator
housing. The flange seal has a sealing diameter greater than a
sealing diameter of the body seal.
[0009] Thus, the embodiments of present invention comprise a
combination of features and advantages that enable substantial
enhancement of the operation and control of a ram-type blowout
preventer. These and various other characteristics and advantages
of the present invention will be readily apparent to those skilled
in the art upon reading the following detailed description of the
preferred embodiments of the invention and by referring to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more detailed understanding of the present invention,
reference is made to the accompanying Figures, wherein:
[0011] FIG. 1 is a ram-type blowout preventer constructed in
accordance with embodiments of the present invention;
[0012] FIG. 2 is a cross-sectional view of a hydraulic operator in
a retracted position and constructed in accordance with embodiments
of the present invention;
[0013] FIG. 3 is a cross-sectional view of the hydraulic operator
of FIG. 2 shown in an extended, unlocked position;
[0014] FIG. 4 is a cross-sectional view of the hydraulic operator
of FIG. 2 shown in an extended and locked position;
[0015] FIG. 5 is an isometric view of a double ram blowout
preventer constructed in accordance with embodiments of the present
invention;
[0016] FIG. 6 is a schematic comparison view of a single cylinder
operator and a parallel dual cylinder operator;
[0017] FIG. 7 is a cross-sectional view of a dual cylinder
hydraulic operator constructed in accordance with embodiments of
the present invention;
[0018] FIG. 8 is a cross-sectional view of the dual cylinder
hydraulic operator of claim 7;
[0019] FIG. 9 is a partial cross sectional view of a motor and
transmission for a dual cylinder hydraulic operator constructed in
accordance with embodiments of the present invention;
[0020] FIG. 10 is an end view of the operator of FIG. 9; and
[0021] FIG. 11 is a blowout preventer stack assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] In the description that follows, like parts are masked
throughout the specification and drawings with the same reference
numerals, respectively. The drawing figures are not necessarily to
scale. Certain features of the invention may be shown exaggerated
in scale or in somewhat schematic form and some details of
conventional elements may not be shown in the interest of clarity
and conciseness.
[0023] Referring now to FIG. 1, blowout preventer 10 comprises body
12, bonnets 14, operator systems 16, and closure members 17. Body
12 comprises bore 18, opposed cavities 20, and upper and lower
bolted connections 22 for assembling additional components above
and below blowout preventer 10, such as in a blowout preventer
stack assembly. Bonnets 14 are coupled to body 12 by connectors 24
that allow the bonnets to be removed from the body to provide
access to closure members 17. Operator systems 16 are mounted to
bonnets 14 and utilize a hydraulic piston 26 and cylinder 28
arrangements to move closure members 17 through cavities 20, into
and out of bore 18.
[0024] FIGS. 2-4 illustrate one embodiment of an operator system
that reduces the volume of fluid needed to cycle the operator by
utilizing significantly less hydraulic fluid to retract than to
extend. Operator system 30 is mounted to bonnet 32 and is coupled
to closure member 34. Operator system comprises piston rod 36,
piston 38, operator housing 40, head 42, sliding sleeve 44, and
lock rod 46. Piston 38 comprises body 48 and flange 50 Body seal 52
circumferentially surrounds body 48 and sealingly engages operator
housing 40. Flange seal 54 circumferentially surrounds flange 50
and sealingly engages operator housing 40. The sealing diameter of
flange seal 54 is larger than the sealing diameter of body seal
52.
[0025] The engagement of body seal 52 and flange seal 54 with
operator housing 40 divides the interior of the operator into three
hydraulically isolated chambers, extend chamber 56, slack fluid
chamber 60, and retract chamber 64. Extend chamber 56 is formed
between head 42 and flange seal 54. Extend port 58 provides
hydraulic communication with extend chamber 56. Slack fluid chamber
60 is formed in the annular region defined by operator housing 40
and piston 38 in between body seal 52 and flange seal 54. Slack
fluid port 62 provides hydraulic communication with slack fluid
chamber 60. Retract chamber 64 is formed in the annular region
defined by operator housing 40 and piston 38 in between body seal
52 and bonnet 32. Retract port 66 provides fluid communication with
retract chamber 64.
[0026] In general, extend chamber 56 and retract chamber 64 are in
fluid communication with a hydraulic fluid supply that is regulated
by a control system. Depending on the configuration of the
hydraulic fluid supply and control system, fluid expelled from the
extend chamber 56 and retract chamber 64 may be recycled into the
hydraulic fluid supply or may be vented to the surrounding
environment. Slack fluid chamber 60 may be pressure balanced with
the surrounding environment such that the fluid pressure within the
slack chamber does not resist movement of piston 38. In certain
embodiments, slack fluid chamber 60 is left open to the surrounding
environment or coupled to a pressure compensation system that
maintains the balanced pressure within the slack fluid chamber.
[0027] In FIG. 2, operator, system 30 is shown in a retracted
position where piston 38 is disposed against head 42. Supplying
pressurized hydraulic fluid to extend port 58 actuates operator
system 30 and moves piston 38 toward bonnet 32. As piston 38 moves
toward bonnet 32, fluid within slack fluid chamber 60 is pushed
through slack fluid port 62 and fluid within retract chamber 64 is
pushed through retract port 66. The fluid pushed from slack fluid
chamber 60 and retract chamber 64 may be retained in a hydraulic
reservoir or ejected to the surrounding environment. As hydraulic
fluid is supplied to extend chamber 56, piston 38 will continue to
move until the piston contacts bonnet 32, as is shown in FIG.
3.
[0028] Because piston 38 must move the same axial distance during
extension and retraction, the difference in fluid requirements is
achieved by using a smaller diameter hydraulic area for retraction
than extension. This imbalance of fluid requirements results in a
reduced total volume of fluid that is required to cycle the
operator system between an extended and a retracted position. The
reduction in required fluid volume may be of special interest in
subsea applications where performance requirements necessitate the
storage of large volumes of fluid with the blowout preventer
assembly. Reducing the volume of fluid needed to move the operator
system to the retracted position reduces the volume of fluid that
needs to be stored with the blowout preventer assembly.
[0029] Using a smaller diameter hydraulic area for retraction has
the added benefit of generating less force during retraction. In
certain situations, the force generated by the operator system in
moving to the retracted position is insufficient to move the
closure member but exceeds design loads for certain components of
the system. In these situations, if the operator system is actuated
some components within the system may fails. Therefore, reducing
the force generated during retraction helps to minimize damage when
the operator system attempts, but fails to retract a closure member
and helps prevent unintentional release of hydrocarbons by
preventing the opening of the closure member when under
pressure.
[0030] Although operator 30 is actuated by hydraulic pressure, many
applications also require a mechanical lock in order to maintain
the position of the closure member in the case of loss of hydraulic
pressure. In order to positively lock piston 38 in position,
sliding sleeve 44 is rotationally fixed relative to piston 38 and
threadably engaged with lock rod 46, which is rotatably coupled to
head 42. Sliding sleeve 44 moves axially relative to lock rod 46
when the lock rod is rotated.
[0031] Referring now to FIG. 4, once piston 38 moves toward bonnet
32 lock rod 46 is rotated. The threaded engagement of lock rod 46
and sliding sleeve 44 causes the sleeve to move axially relative to
the lock rod. Lock rod 46 is rotated until sleeve 44 contacts
shoulder 68 of piston 38 as is shown in FIG. 4. Sliding sleeve 44
will engage and piston 38 and prevent the movement of the piston
away from bonnet 32.
[0032] The threaded engagement of lock rod 46 and sliding sleeve 44
is `self-locking` to the extent that axial force on the sliding
sleeve will not rotate the sleeve relative to the lock rod, Thus,
when sliding sleeve 44 is in contact with shoulder 68, piston 38 is
prevented from moving away from bonnet 32. Once sliding sleeve 44
is engaged with shoulder 68, the pressure within extend chamber 60
can be reduced and piston 38 will remain in the extended position.
In this manner, sliding sleeve 44 and lock rod 46 operate as a
locking system that can be engaged to prevent closure member 34
from opening unintentionally. Although only shown in the fully
extended and locked position, sliding sleeve 44 can engage and lock
against piston 38 in any position.
[0033] In order to move operator system 30 back to the retracted
position of FIG. 2, hydraulic pressure is first applied to extend
chamber 56. This removes any axial compressive load from sliding
sleeve 44 and lock rod 46 and allows the lock rod to be rotated.
The rotation of lock rod 46 moves sliding sleeve 44 away from
shoulder 68. Hydraulic pressure can then be applied to retract
chamber 64 so as to move piston 38 back toward the retracted
position of FIG. 1.
[0034] Lock rod 46 can be rotated by a variety of electric motors,
hydraulic motors, or other rotating devices In certain embodiments,
the motor is a hydraulic motor that can provide 15,000 inch-pounds
of torque. In FIG. 3, lock rod 46 is coupled to motor 72 via
transmission system 70 that transfers motion from the motor to the
lock rod. FIG. 4 shows motor 72 being directly linked to lock rod
46 without a transmission system. In certain embodiments, both
system 70 of FIG. 3 and motor 72 of FIG. 4 are equipped with backup
systems that allow manual operation of lock rod 46, such as by a
remotely operated vehicle (ROV). The ROV could be used to supply
hydraulic fluid or electrical power to operate motor 72 or could be
used to directly rotate lock rod 46.
[0035] As discussed previously, operator system 30 can operate
effectively while utilizing a smaller hydraulic area for retraction
than for extension because less force is required to retract
closure member 34 than to extend the closure member into the
wellbore. The maximum diameter of the operator system for a
ram-type blowout preventer is often determined by the hydraulic
pressure area that is required to close the wellbore under full
working pressure. In high-pressure applications, the diameter, of
the operating system is often larger than the height of the bonnet
that is coupled to the blowout preventer body. As many ram-type
blowout preventers are constructed with multiple rams operating in
a single body with multiple cavities, the diameter of the operator
system often determines the overall height of the assembly as the
individual cavity openings must be spaced apart to allow clearance
for the operator assemblies.
[0036] FIG. 5 illustrates a double ram blowout preventer 80
comprising parallel dual cylinder operators 82 coupled to body 84
by bonnets 86. Operators 82 utilize two smaller diameter hydraulic
cylinders to provide an equivalent closing force to a single,
larger diameter hydraulic cylinder. Using smaller diameter
hydraulic cylinders allows adjacent bonnets 86 to be located close
together so that blowout preventer body 84 has a minimum height as
measured between upper connection 85 and lower connection 87.
[0037] The parallel dual cylinder operators 82 are schematically
illustrated in FIG. 6 where area 90 represents the pressure area of
single cylinder having a large diameter 92. A dual cylinder
operator is represented by areas 94 having smaller diameter 96.
Diameter 96 is selected such that the total area 94 of both dual
operators is at least equal to area 90 of the single large diameter
cylinder. To provide a substantially equivalent pressure area, it
is believed diameter 96 is approximately 0.71 times diameter 92.
For example, a seventeen inch diameter operator can be replaced by
an operator having parallel twelve inch pistons. Calculations
suggest that this reduction decreases the minimum spacing between
adjacent cavities from seventeen inches to twelve inches.
[0038] FIGS. 7 and 8 illustrate one such parallel cylinder operator
that also features reduced fluid volume for retraction. Parallel
dual cylinder operator system 100 comprises is mounted to bonnet
102 and comprises two parallel operating cylinders 104. Each
operating cylinder 104 comprises piston rod 106, piston 108,
operator housing 110, sliding sleeve 112, and lock rod 114. Each
piston rod 106 is coupled to support member 116 that couples to a
closure member (not shown) and ensures that pistons 108 remain
axially synchronized. Cylinder head 118 is coupled to both housings
110.
[0039] Each piston 108 comprises body seal 120 disposed on body 122
and flange seal flange 124 disposed on flange 126. Seals 120 and
124 sealingly engage operator housings 110 such that the housing is
divided into an extend chamber 128, slack fluid chamber 130, and
retract chamber 132. The sealing diameter of flange seal 124 is
larger than the sealing diameter of body seal 120 such that less
fluid is required to fill retract chamber 132 than is required to
fill extend chamber 128.
[0040] Parallel dual cylinder operator system 100 operates in
essentially the same sequence as operator system 30 described in
relation to FIGS. 2-4. In FIG. 8, operator system is shown in an
extended and locked position. Sliding sleeve 112 is disengaged by
first pressurizing extend chamber 128 through extend port 134 and
then rotating lock rod 114 so that the sleeve moves toward cylinder
head 118. Once sliding sleeve 112 is disengaged, pressurized fluid
is applied through retract port 136 to retract chamber 132. The
pressurized fluid filling retract chamber 132 will move piston 108
toward head 118 and pull support member 116 toward bonnet 102 until
operator system 100 is in the fully retracted position of FIG.
8.
[0041] Operator system 100 is returned to the extended position of
FIG. 7 by applying hydraulic fluid through extend port 134 to
extend chamber 128. As piston 108 moves toward bonnet 102, fluid
within slack fluid chamber 130 is pushed through slack fluid port
138 and fluid within retract chamber 132 is pushed through retract
port 136. The fluid pushed from slack fluid chamber 130 and retract
chamber 132 may be retained in a hydraulic reservoir or ejected to
the surrounding environment. Once piston 108 is fully in the
extended position, lock rods 114 are rotated so that sliding
sleeves 112 engage the pistons and prevent movement of the pistons
from the extended position.
[0042] Support member 116 ensures that pistons 108 and piston rods
106 remain synchronized during the operation of system 100. The
hydraulic system that supplies fluid to operator system 100 may
also be configured to supply hydraulic fluid to the operator system
in such a way that pistons 108 remain synchronized while
moving.
[0043] Referring now to FIGS. 9 and 10, operator system 100 may
further comprise drive system 140 that rotates locking rods 114 to
move sliding sleeve 112 into and out of locking engagement with
piston 108. Drive system 140 comprises motor 142, transmission 144,
and ROV override 146. Drive system 140 is mounted to head 118 with
motor 142 disposed generally between operator housings 110. Motor
142, which may be a hydraulic, electric, or other motor, is coupled
to transmission 144 and override 146. Transmission 144 comprises a
plurality of gears that rotationally couple motor 142 to locking
rods 114. Override 146 is positioned so as to allow access in the
case of failure of motor 142 or the supply of fluid or power to the
motor. Override 146 may provide for direct mechanical rotation of
transmission 144 or may provide for the external supply of
hydraulic fluid or power to motor 142.
[0044] The features of the above described operator system
embodiments may be used alone or in cooperation. For example, the
reduced volume retraction operator of FIGS. 2-4 may be used in
combination with the locking rod and sliding sleeve lock
arrangement as shown or may be used with other locking systems.
Similarly, the locking rod and sliding sleeve lock arrangement can
be used with other operator systems or in other types of linear
actuated systems. The parallel cylinder operator system may also be
used in other applications and with other types of piston and
cylinder assemblies as well as other locking systems.
[0045] Although these features can be used in other applications,
the described features provide a synergistic benefit when used in
combination. As an example, a double ram blowout preventer that
uses a parallel cylinder operator system having reduced volume
retraction (the operator system of FIGS. 7-8) is lighter, shorter,
and uses less hydraulic fluid than a conventional blowout preventer
using conventional operator systems. The use of the locking rod and
sliding sleeve lock arrangement also provides a simplified locking
system when compared to many conventional locking systems.
[0046] FIG. 11 illustrates a blowout preventer stack 200 coupled to
a wellhead 202. Blowout preventer stack 200 comprises a lower stack
assembly 204 and an upper stack assembly 206, or lower marine riser
package. Lower stack assembly 204 comprises a wellhead connector
208, ram blowout preventers 210, annular blowout preventer 212,
choke and kill valves 214, and hydraulic accumulators 216. Upper
stack assembly 206 comprises annular blowout preventer 218, choke
and kill connectors 220, riser adapter/flex joint 222, control pods
224, and collet connector 226. Collet connector 226 provides a
releasable connection between upper stack assembly 206 and lower
stack assembly 204. Hydraulic accumulators 216 are mounted to frame
228 that surrounds lower stack assembly 204.
[0047] Therefore, the preferred embodiments of the present
invention relate to apparatus for improved ram-type blowout
preventers. The present invention is susceptible to embodiments of
different forms. There are shown in the drawings, and herein will
be described in detail, specific embodiments of the present
invention with the understanding that the present disclosure is to
be considered an exemplification of the principles of the
invention, and is not intended to limit the invention to that
illustrated and described herein. In particular various embodiments
of the present invention provide systems that allow a reduction in
the size, weight, complexity, and fluid requirements of ram-type
blowout preventers. Reference is made to the application of the
concepts of the present invention to ram-type blowout preventers,
but the use of the concepts of the present invention is not limited
to these applications, and can be used for any other applications
including other subsea hydraulic equipment. It is to be fully
recognized that the different teachings of the embodiments
discussed below may be employed separately or in any suitable
combination to produce desired results.
[0048] The embodiments set forth herein are merely illustrative and
do not limit the scope of the invention or the details therein. It
will be appreciated that many other modifications and improvements
to the disclosure herein may be made without departing from the
scope of the invention or the inventive concepts herein disclosed.
Because many varying and different embodiments may be made within
the scope of the inventive concept herein taught, including
equivalent structures or materials hereafter thought of, and
because many modifications may be made in the embodiments herein
detailed in accordance with the descriptive requirements of the
law, it is to be understood that the details herein are to be
interpreted as illustrative and not in a limiting sense.
* * * * *