U.S. patent application number 15/753174 was filed with the patent office on 2018-09-06 for rod locking apparatus.
This patent application is currently assigned to Electrical Subsea & Drilling AS. The applicant listed for this patent is ELECTRICAL SUBSEA & DRILLING AS. Invention is credited to John L. ALSUP, Marion E. EAGLES, Thor Arne H VERSTAD, J. Gilbert NANCE, Erik NORBOM, Bolie C. WILLIAMS, III.
Application Number | 20180252060 15/753174 |
Document ID | / |
Family ID | 54258861 |
Filed Date | 2018-09-06 |
United States Patent
Application |
20180252060 |
Kind Code |
A1 |
H VERSTAD; Thor Arne ; et
al. |
September 6, 2018 |
ROD LOCKING APPARATUS
Abstract
A rod locking apparatus includes a housing which includes a
first tubular passage and a second tubular passage which are
arranged to intersect with each other, the first tubular passage
including a serrated locking surface, and a wedge piston slidably
arranged in the first tubular passage. The wedge piston includes a
front side which includes a wedge surface which engages an end
surface of a rod to be locked, and a serrated rear side which
engages with the serrated locking surface.
Inventors: |
H VERSTAD; Thor Arne;
(Vennesla, NO) ; NORBOM; Erik; (Hoevik, NO)
; WILLIAMS, III; Bolie C.; (Houston, TX) ; NANCE;
J. Gilbert; (Katy, TX) ; ALSUP; John L.;
(Houston, TX) ; EAGLES; Marion E.; (Houston,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRICAL SUBSEA & DRILLING AS |
Straume |
|
NO |
|
|
Assignee: |
Electrical Subsea & Drilling
AS
Straume
NO
|
Family ID: |
54258861 |
Appl. No.: |
15/753174 |
Filed: |
August 15, 2016 |
PCT Filed: |
August 15, 2016 |
PCT NO: |
PCT/NO2016/050167 |
371 Date: |
February 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 33/062 20130101;
F15B 15/261 20130101; E21B 33/06 20130101 |
International
Class: |
E21B 23/02 20060101
E21B023/02; E21B 33/06 20060101 E21B033/06; E21B 19/00 20060101
E21B019/00; E21B 33/129 20060101 E21B033/129 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 19, 2015 |
GB |
1514762.2 |
Claims
1-27. (canceled)
28. A rod locking apparatus comprising: a housing comprising a
first tubular passage and a second tubular passage which are
arranged to intersect with each other, the first tubular passage
comprising a serrated locking surface; and a wedge piston slidably
arranged in the first tubular passage, the wedge piston comprising
a front side which comprises a wedge surface which is configured to
engage an end surface of a rod to be locked, and a serrated rear
side which is configured to engage with the serrated locking
surface.
29. The rod locking apparatus as recited in claim 28, wherein, the
serrated locking surface is arranged to be integral with the
housing, or the serrated locking surface is arranged on a separate
support part which is fixed relative to the housing.
30. The rod locking apparatus as recited in claim 28, wherein the
serrated rear side of the wedge piston is inclined at an angle of
between 10 and 20.degree. relative to the wedge surface.
31. The rod locking apparatus as recited in claim 28, wherein the
first tubular passage extends at an angle of between 100 and
110.degree. relative to the second tubular passage.
32. The rod locking apparatus as recited in claim 28, wherein the
wedge piston is movable between a closed position in which the
wedge piston substantially blocks the second tubular passage, and
an open position in which the second tubular passage is open.
33. The rod locking apparatus as recited in claim 32, wherein the
wedge piston further comprises a through passage which is arranged
to extend from the front side to the serrated rear side of the
wedge piston generally parallel to the second tubular passage so
that, when the wedge piston is in the open position, the through
passage is generally coaxial with the second tubular passage, and
when the wedge piston is in the closed position, the through
passage is not aligned with the second tubular passage.
34. The rod locking apparatus as recited in claim 32, wherein the
wedge piston further comprises two end surfaces which extend
generally perpendicular to the serrated rear side of the wedge
piston.
35. The rod locking apparatus as recited in claim 34, wherein, the
two end surfaces comprise a first end surface, the first tubular
passage further comprises a first end and a second end, and the
first end surface comprises a first piston face on which a
pressurized fluid introduced into the first end of the first
tubular passage acts to push the wedge piston along the first
tubular passage towards the second end of the first tubular
passage.
36. The rod locking apparatus as recited in claim 35, wherein, the
two end surfaces further comprise a second end surface, and the
second end surface comprises a second piston face on which a
pressurized fluid introduced into the second end of the first
tubular passage acts to push the wedge piston along the first
tubular passage towards the first end of the first tubular
passage.
37. The rod locking apparatus as recited in claim 36, wherein, a
movement of the wedge piston from the open position to the closed
position comprises a movement of the wedge piston from the second
end of the first tubular passage towards the first end of the first
tubular passage, and a movement of the wedge piston from the first
end of the first tubular passage towards the second end of the
first tubular passage.
38. The rod locking apparatus as recited in claim 36, wherein, the
first piston face comprises a first piston face surface area, the
second piston face comprises a second piston face surface area, and
the first piston face surface area is greater than the second
piston face surface area.
39. The rod locking apparatus as recited in claim 35, wherein the
housing further comprise a first end cap which is configured to
close the first tubular passage at the first end.
40. The rod locking apparatus as recited in claim 39, wherein the
first end cap comprises an aperture and a pressurized fluid supply
device configured to supply a pressurized fluid into the first end
of the first tubular passage via the aperture in the first end
cap.
41. The rod locking apparatus as recited in claim 40, wherein the
housing further comprises a second end cap which is configured to
close the first tubular passage at the second end.
42. The rod locking apparatus as recited in claim 41, wherein the
second end cap comprises an aperture and a pressurized fluid supply
device configured to supply a pressurized fluid into the second end
of the first tubular passage via the aperture in the second end
cap.
43. The rod locking apparatus as recited in claim 42, wherein, the
wedge piston further comprises a bore, and the housing further
comprises a supply tube which extends from the aperture in the
second end cap into the bore in the wedge piston, the rod locking
apparatus further comprising: a seal arranged between the supply
tube and the wedge piston, the seal being configured to provide a
substantially fluid tight seal between an interior surface of the
wedge piston surrounding the bore and an exterior surface of the
supply tube.
44. An assembly comprising: the rod locking apparatus as recited in
claim 28; and a rod arranged in the second tubular passage, the rod
comprising a rod first end which is arranged in the second tubular
passage and a rod second end which is arranged to extend out of the
second tubular passage.
45. The assembly as recited in claim 44, wherein, the rod first end
comprises a rod first end surface area, the serrated locking
surface comprises a serrated locking surface area, and the serrated
locking surface area is greater than the rod first end surface
area.
46. A rod locking apparatus comprising: a housing comprising a
first tubular passage and a second tubular passage which are
arranged to intersect with each other, the first tubular passage
comprising a first end and a second end; and a wedge piston
slidably arranged in the first tubular passage, the wedge piston
comprising a front side which comprises a wedge surface which is
configured to engage an end surface of a rod to be locked, a rear
side, and a first end surface and a second end surface which each
extend generally perpendicular to the rear side of the wedge
piston, the wedge piston being movable between a closed position in
which the wedge piston substantially blocks the second tubular
passage, and an open position in which the second tubular passage
is open, wherein, the first end surface comprises a first piston
face on which a pressurized fluid introduced into the first end of
the first tubular passage acts to push the wedge piston along the
first tubular passage to the second end of the first tubular
passage, the second end surface comprises a second piston face on
which a pressurized fluid introduced into the second end of the
first tubular passage acts to push the wedge piston along the first
tubular passage to the second end of the first tubular passage, a
movement of the wedge piston from the open position to the closed
position comprises a movement of the wedge piston from the second
end of the first tubular passage to the first end of the first
tubular passage, and vice versa, and a surface area of the first
piston face is greater than a surface area of the second piston
face.
Description
CROSS REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a U.S. National Phase application under
35 U.S.C. .sctn. 371 of International Application No.
PCT/NO2016/050167, filed on Aug. 15, 2016 and which claims benefit
to Great Britain Patent Application No. 1514762.2, filed on Aug.
19, 2015. The International Application was published in English on
Feb. 23, 2017 as WO 2017/030444 A1 under PCT Article 21(2).
FIELD
[0002] The present invention relates to a rod locking apparatus,
and in particular to a rod locking apparatus suitable for use in
locking the actuators in ram-type blow out preventers.
BACKGROUND
[0003] The present invention relates to a rod locking device for
locking reciprocating piston type fluid actuators in a preferred
position. Actuators of this type are particularly suited for
positioning the rams of ram-type blow out preventers. It is
advantageous and desirable to mechanically lock the rods of these
actuators to provide that the blow out preventer rams will be
maintained in a preferred position should hydraulic pressure be
lost.
[0004] Relevant prior art systems include U.S. Pat. No. 4,969,390
which describes a ram locking apparatus for blowout preventer rams
which allows the rams to be locked in the closed position. A
tapered end of a rod and a wedge surface of a piston have serrated
surfaces to increase friction between the wedging surfaces and to
provide a self-locking engagement in a small, compact
apparatus.
[0005] Other related prior art includes U.S. Pat. No. 2,632,425,
U.S. Pat. No. 3,050,943, U.S. Pat. No. 3,242,826, U.S. Pat. No.
3,918,478, U.S. Pat. No. 3,941,141, U.S. Pat. No. 4,188,860, U.S.
Pat. No. 4,290,577, U.S. Pat. No. 4,305,565, U.S. Pat. No.
4,519,571, U.S. Pat. No. 4,601,232, U.S. Pat. No. 4,840,346, U.S.
Pat. No. 4,969,627, U.S. Pat. No. 5,025,708, and U.S. Pat. No.
5,056,418.
SUMMARY
[0006] In an embodiment, the present invention provides a rod
locking apparatus which includes a housing comprising a first
tubular passage and a second tubular passage which are arranged to
intersect with each other, the first tubular passage comprising a
serrated locking surface, and a wedge piston slidably arranged in
the first tubular passage. The wedge piston comprises a front side
which comprises a wedge surface which is configured to engage an
end surface of a rod to be locked, and a serrated rear side which
is configured to engage with the serrated locking surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention is described in greater detail below
on the basis of embodiments and of the drawings in which:
[0008] FIG. 1 is a perspective view of a cross-section through an
assembly of a rod locking apparatus according to the present
invention and a tail rod of a blowout preventer actuator;
[0009] FIG. 2 is a longitudinal cross-section through the assembly
illustrated in FIG. 1 in the open position;
[0010] FIG. 3 is a longitudinal cross-section through the assembly
illustrated in FIG. 2 in the closed position;
[0011] FIG. 4 is a perspective view of the wedge piston and
serrated rear side of the rod locking apparatus illustrated in FIG.
1; and
[0012] FIG. 5 is a perspective view of the serrated locking surface
of the rod locking apparatus illustrated in FIG. 1.
DETAILED DESCRIPTION
[0013] In an embodiment, the present invention provides a rod
locking apparatus comprising: [0014] a housing having a first and
second intersecting tubular passages, the first tubular passage
being provided with a serrated locking surface; and [0015] a wedge
piston slidably arranged in the first tubular passage; [0016] the
wedge piston having a front side with a wedge surface adapted in
use to engage an end surface of a rod to be locked; [0017] wherein,
the wedge piston has a serrated rear side which engages with the
serrated locking surface.
[0018] Providing the rear side of the wedge piston with serrations
which engage with the serrated locking surface means that the area
of contact between the two serrated surfaces can be larger than in
the arrangement described in U.S. Pat. No. 4,969,390. This provides
a higher frictional locking force, and therefore provides more
secure locking and/or allows a larger wedge angle to be used. A
larger wedge angle allows for a shorter stroke length, and thus a
shorter and more compact locking device.
[0019] The serrated locking surface may be integral with the
remainder of the housing, or may be provided on a separate support
part which is fixed relative to the housing.
[0020] The wedge piston is movable between a closed position in
which it substantially blocks the second tubular passage, and an
open position in which the second tubular passage is open.
[0021] The wedge piston may be provided with a through passage
which extends from the front side to the rear side of the wedge
piston generally parallel to the second tubular passage so that,
when the wedge piston is in the open position, the through passage
is generally coaxial with the second tubular passage, and when the
wedge piston is in the closed position, the through passage is not
aligned with the second tubular passage.
[0022] The rear side of the wedge piston may be inclined at an
angle of between 10 and 20.degree. to the wedge surface. In an
embodiment, the rear side of the wedge piston can, for example, be
inclined at an angle of around 12.degree. to the wedge surface.
[0023] The first tubular passage may extend at an angle of between
100 and 110.degree. to the second tubular passage. In an
embodiment, the first tubular passage can, for example, extend at
an angle of 102.degree. to the second tubular passage.
[0024] The wedge piston may further be provided with two end
surfaces which extend generally perpendicular to the rear side of
the wedge piston.
[0025] A first one of the two end surfaces may provide a first
piston face on which pressurized fluid introduced into a first end
of the first tubular passage acts to push the wedge piston along
the first tubular passage towards a second end thereof.
[0026] A second one of the two end surfaces may provide a second
piston face on which pressurized fluid introduced into the second
end of the first tubular passage acts to push the wedge piston
along the first tubular passage towards the first end thereof.
[0027] Movement of the wedge piston from the open position to the
closed position may comprise movement of the wedge piston from the
second end of the first tubular passage towards the first end of
the first tubular passage, and vice versa.
[0028] The surface area of the first piston face may be greater
than the surface area of the second piston face.
[0029] The rod locking apparatus is further provided with a seal
which extends between the housing and the wedge piston to
substantially prevent a flow of fluid along the first tubular
passage past the seal, while allowing the wedge piston to slide
along the first tubular passage. The seal is advantageously mounted
on the wedge piston. In an embodiment, the seal can, for example,
comprise an O-ring mounted in a groove in the wedge piston.
[0030] The housing may further be provided with a first end cap
which closes the first tubular passage at a first end thereof. The
first end cap may be provided with an aperture and a pressurized
fluid supply device which supplies a pressurized fluid into the
first end of the first tubular passage via the aperture in the
first end cap.
[0031] The housing may further be provided with a second end cap
which closes the first tubular passage at a second end thereof. The
second end cap may be provided with an aperture and a pressurized
fluid supply device which supplies a pressurized fluid into the
second end of the first tubular passage via the aperture in the end
cap.
[0032] The housing may be provided with a supply tube which extends
from the aperture in the second end cap into a bore in the wedge
piston, there being a seal between the supply tube and the wedge
piston which provides a substantially fluid tight seal between an
interior surface of the wedge piston surrounding the bore and an
exterior surface of the supply tube. In this case, an end portion
of the bore is the second piston face.
[0033] In an embodiment, the present invention provides an assembly
of a rod locking apparatus having a rod located in the second
tubular passage, the rod having a first end which is located in the
second tubular passage and a second end which extends out of the
second tubular passage.
[0034] The surface area of the serrated locking surface is
advantageously greater than the surface area of the first end of
the rod.
[0035] In an embodiment, the present invention provides a rod
locking apparatus comprising: [0036] a housing having a first and
second intersecting tubular passages; [0037] a wedge piston
slidably arranged in the first tubular passage; [0038] the wedge
piston having a front side with a wedge surface adapted in use to
engage an end surface of a rod to be locked, and two end surfaces
which extend generally perpendicular to the rear side of the wedge
piston; [0039] the wedge piston being movable between a closed
position in which it substantially blocks the second tubular
passage, and an open position in which the second tubular passage
is open; [0040] a first one of the two end surfaces providing a
first piston face on which a pressurized fluid introduced into a
first end of the first tubular passage acts to push the wedge
piston along the first tubular passage to a second end thereof; and
[0041] a second one of the two end surfaces providing a second
piston face on which pressurized fluid introduced into the second
end of the first tubular passage acts to push the wedge piston
along the first tubular passage to the first end thereof; [0042]
movement of the wedge piston from the open position to the closed
position comprising movement of the wedge piston from the second
end of the first tubular passage to the first end of the first
tubular passage, and vice versa, [0043] wherein, the surface area
of the first piston face is greater than the surface area of the
second piston face.
[0044] This advantageously allows for a reliable unlocking due to
the higher force from the larger piston. A rod locking apparatus
having a large interacting locking area may in particular have a
large frictional locking force, and may thus need higher force to
unlock.
[0045] The rod locking apparatus according to this embodiment may
have any of the features or any combination of features of the rod
locking apparatus according to the previously described
embodiments.
[0046] In an embodiment, the present invention provides a new and
improved subsea ram type blowout preventer which is a hydraulically
actuated mechanical ram locking device. The device may be actuated
as part of the single, overall rams closing function, or as a
separate ram locking only function. The ram locking device is
mounted as an integral sub-assembly to the pressure containing and
controlling ram BOP bonnet assembly, whereby the bonnet assembly is
mounted to the ram type BOP main pressure controlling and
containing body member.
[0047] Blowout preventers were developed to cope with extreme
erratic pressures and uncontrolled flow emanating from a well
reservoir during drilling. Known as a "kick", this flow of pressure
can lead to a potentially catastrophic event called a "blowout". In
addition to controlling the downhole well pressure and the flow of
oil and gas, blowout preventers are intended to prevent tubular
goods used in well drilling, such as, drill pipe, casing, collars,
tools and drilling fluid, from being blown out of the wellbore when
a kick or blowout threatens. Blowout preventers are critical to the
safety of the crew, the drilling rig, the environment, and to the
monitoring and maintenance of well integrity; blowout preventers
are thus intended to provide an additional and fail-safe barrier to
the systems that include them.
[0048] Ram-type blowout preventers are part of an overall pressure
control system used in oil and gas operations commonly used as
pressure containment and unexpected wellbore pressure spikes and
well pressure control events. A conventional ram-type BOP is
similar in operation to a gate valve, but uses a pair of opposing
steel plungers or rams. The rams extend toward the center of the
wellbore to restrict flow or retract open in order to permit flow.
The inner and top faces of the rams are fitted with composite steel
and elastomeric packers that press against each other, against the
wellbore, and around well tubular members running through the
wellbore. Outlets at the sides of the BOP housing (body) are used
for connection to choke and kill lines or valves.
[0049] Rams, or ram blocks, are generally of five common types:
pipe, variable bore pipe, blind, shear, and blind shear. The ram
type blow out preventer is further usually integrated with
additional well containment and control devices that inclusively
make up a subsea blowout preventer stack.
[0050] FIG. 1 illustrates an embodiment of a rod locking device 100
according to the present invention. The rod locking device 100
comprises a main housing 1 having a first tubular passage 22 and a
second tubular passage 23. In this embodiment, the main housing 1
is provided with a mounting attachment 5 to attach the rod locking
device 100 to the BOP bonnet 20, as illustrated in FIG. 2. The
first tubular passage 22 is provided with a serrated locking
surface 4a, which in this embodiment is provided on a support part
4 (illustrated in detail in FIG. 5), which is fixed relative to the
main housing 1 and which is described in further detail below. It
should be appreciated, however, that the support part 4 may be
integral with the main housing 1.
[0051] A wedge piston 12 is slidably provided in the main housing
1. The wedge piston 12 has a front side with a wedge surface 11
which engages a back end surface 13a of a tail rod 13 of a blowout
preventer actuator. The wedge piston 12 also has a serrated rear
side which engages with the serrated locking surface 4a.
[0052] The tail rod 13 is coupled to a hydraulic, ram operating
piston 14 provided in the BOP bonnet 20 (see FIG. 2), and extends
into the second tubular passage 23. The wedge piston 12 is movable
between a closed position in which it substantially blocks the
second tubular passage 23 and an open position in which the second
tubular passage 23 is open.
[0053] In this embodiment, the wedge piston 12 has a transverse
bore forming a through passage 17 which extends from the front side
to the rear side of the wedge piston 12 generally parallel to the
second tubular passage 23 and, when the wedge piston 12 is in the
open position, is aligned with the second tubular passage 23 so
that the tail rod 13 may extend along the second tubular passage
23, as shown in FIG. 2. When the wedge piston 12 is in the closed
position, the through passage 17 is not aligned with the second
tubular passage 23, as illustrated in FIG. 1.
[0054] The wedge piston 12 incorporates a spline shaped serrated
rear side 16 which utilize a series of ridges, or teeth, that mesh
with grooves in the serrated locking surface 4a (see FIG. 5). The
design of the serrations on the serrated rear side 16 of the wedge
piston 12 and the serrated locking surface 4a may be according to
one of the alternatives described in U.S. Pat. No. 4,969,390 or any
other suitable design. This may include splines, grooves, ridges,
or teeth, or a combination thereof, suitable for producing a mating
motion and a friction-based locking effect between the serrated
rear side 16 of the wedge piston 12 and the serrated locking
surface 4a.
[0055] The serrated rear side 16 of the wedge piston 12 is inclined
at an angle of between 10 and 20.degree. to the wedge surface 11.
In this embodiment, the serrated rear side 16 of the wedge piston
12 is inclined at an angle of around 12.degree. to the wedge
surface 11. The first tubular passage 22 extends at an angle of
between 100 and 110.degree. to the second tubular passage 23. In
this embodiment, the first tubular passage 22 extends at an angle
of 102.degree. to the second tubular passage 23. Designing the
first tubular passage 22 to extend at an angle to the second
tubular passage 23 which corresponds to the angle of inclination
between the serrated rear side 16 of the wedge piston 12 and the
wedge surface 11 permits the back end surface 13a of the tail rod
13 to extend perpendicularly to the rod longitudinal axis. Other
combinations of inclination angle and angle between the first
tubular passage 22 and the second tubular passage 23 are, however,
possible.
[0056] The wedge piston 12 is further provided with two end
surfaces 9, 24 which extend generally perpendicular to the serrated
rear side 16 of the wedge piston 12. A first end surface 9 of the
two end surfaces 9, 24 provides a first piston face on which
pressurized fluid introduced into a first end 27a of the first
tubular passage 22 acts to push the wedge piston 12 along the first
tubular passage 22 towards a second end 27b thereof. A second end
surface 24 of the two end surfaces 9, 24 provides a second piston
face on which pressurized fluid introduced into the second end 27b
of the first tubular passage 22 acts to push the wedge piston along
the first tubular passage 22 towards the first end 27a thereof.
[0057] In this embodiment, movement of the wedge piston 12 from the
open position to the closed position comprises a translational
movement of the wedge piston 12 in a direction extending from the
second end 27b of the first tubular passage 22 towards the first
end 27a of the first tubular passage 22, and vice versa.
[0058] A first end cap 8a and a second end cap 8b close the first
tubular passage 22 at the first end 27a and second end 27b,
respectively. Apertures in the form of channels 21a and 21b are
provided through the first end cap 8a and the second end cap 8b
along with a device for supplying pressurized fluid therethrough
and into the first tubular passage 22. The rod locking device 100
is provided with a seal 26 which extends between the main housing 1
and the wedge piston 12 to substantially prevent the flow of fluid
along the first tubular passage 22 past the seal 26, while allowing
the wedge piston 12 to slide along the first tubular passage 22. In
this embodiment, the seal 26 is provided in the form of an O-ring
mounted in a groove on the wedge piston 12, to seal against the
inner surface of the first tubular passage 22 and delimit a cavity
15. Providing pressurized fluid through channel 21a and into cavity
15 produces a pressure force on the first end surface 9 of the
wedge piston 12 and acts to push the wedge piston 12 along the
first tubular passage 22 in a direction away from the first end
27a. This moves the wedge piston 12 into the open, or unlocked,
position of the rod locking device 100 and BOP ram.
[0059] In this embodiment, from the second end cap 8b, a supply
tube 2 extends into the first tubular passage 22 and into a wedge
piston bore 10 provided in the wedge piston 12. The supply tube 2
has an internal bore permitting hydraulic fluid communication from
a hydraulic fluid supply (not shown in the drawings) through
aperture/channel 21b in the second end cap 8b and into wedge piston
bore 10. The supply tube 2 is sealed against wedge piston bore 10,
for example, by O-rings 25 (see FIGS. 2 and 3). The second piston
face 24 is therefore formed by the end face of the wedge piston
bore 10. Provision of hydraulic fluid pressure into wedge piston
bore 10 through supply tube 2 generates a pressure force on the
second piston face 24 in the wedge piston bore 10 and urges the
wedge piston 12 away from second end 27b along the first tubular
passage 22 and to a locked position of the rod locking device 100
and BOP ram.
[0060] As a result of using a wedge piston bore 10 and supply tube
2, it will be appreciated that, in this embodiment of the present
invention, the surface area of the first piston face 9 is greater
than the surface area of the second piston face 24. This means
that, for a given fluid pressure, the force moving the wedge piston
12 to the open position is greater than the force moving the wedge
piston 12 to the closed position. This may have the advantage of
allowing a reliable unlocking of the rod locking device 100 and
consequent opening of the BOP.
[0061] This need not be the case, however, and in an alternative
embodiment of the present invention, the second piston face 24 may
be provided on the end of the wedge piston 12 facing the second end
27b of the first tubular passage 22, the second piston face 24 of
the wedge piston 12 being sealed against the inner surface of the
first tubular passage 22, in a similar way to the arrangement
provided by first piston face 9. Referring now to FIG. 2, a rod
locking device 100 is shown in an open, or unlocked, position. The
BOP ram is open in this state. The rod locking device 100 is fixed
to a BOP bonnet 20 by mounting attachment 5. A ram operating piston
14 is provided in the BOP bonnet 20 to operate the ram. In this
position, the through passage 17 of the wedge piston 12 is aligned
with the second tubular passage 23 and the tail rod 13 extends
through the through passage 17.
[0062] FIG. 3 shows the closed position of the rod locking device
100. In this state, closing of the BOP ram has been performed by
ram operating piston 14 and the tail rod 13 has been moved out of
the through passage 17. Subsequently, fluid pressure is provided
through channel 21b and into wedge piston bore 10 to move the wedge
piston 12 towards the first end 27a. As the wedge piston approaches
its end position towards the first end 27a, the wedge surface 11
engages the back end surface 13a of the tail rod 13. The serrated
rear side 16 of the wedge piston 12 is inclined by approximately
12.degree. to the wedge surface 11, thus moving the wedge piston 12
towards the first end 27a produces a wedging force between the
wedge piston 12 and the back end surface 13a and support part 4.
This produces a mating motion between the serrated rear side 16 of
the wedge piston 12 and the serrated locking surface 4a (see FIG.
5), which provides a friction-based self-locking effect. Even in
the case of loss of fluid pressure in wedge piston bore 10 and a
back force acting by the tail rod 13 on the wedge surface 11, the
friction between the serrated rear side 16 of the wedge piston 12
and the serrated locking surface 4a will thus keep the wedge piston
12 in the locked position.
[0063] To open the rod locking device 100, fluid pressure is
provided through channel 21a to act on first piston surface 9 as
described above. Advantageously, as first piston surface 9 is
provided with a larger area than second piston face 24' (see FIG.
1), the rod locking device 100 can be securely unlocked even in the
case of a strong friction locking effect.
[0064] FIG. 4 shows details of the wedge piston 12 with the
serrated rear side 16 and the through passage 17. FIG. 4 further
shows the support part 4. The support part 4 may have a throughbore
27 which is aligned with the second tubular passage 23 (see FIG. 1)
to allow the tail rod 13 to extend through the throughbore 27 in
the open position of the ram locking device 100, as shown in FIG.
2. FIG. 4 shows further details of a part of the support part 4,
showing the serrated locking surface 4a which, in use, engages with
the serrated rear side 16 of the wedge piston 12.
[0065] Advantageously, the serrated rear side 16 is provided along
substantially the full length of the wedge piston 12. The area of
the serrated locking surface 4a may be adapted for a particular use
or operating requirements, thus providing freedom to, for example,
use a large locking surface in applications with high safety
requirements.
[0066] The rod locking device according to the present invention
thus provides a simple, robust, and more reliable, hydraulically
actuated, mechanical assembly that provides a way to lock the rams
of a ram-type blowout preventer in the closed and sealed position,
even if hydraulic pressure is lost or removed, and only allows the
rams to open when hydraulic pressure is intentionally applied to
the BOP and locking mechanism's operating system for the expressed
purpose of opening the blowout preventer's ram assemblies.
[0067] The rod locking device according to the present invention is
suitable to lock any type of ram (pipe, variable bore pipe, shear,
blind, shearing blind) in an infinite range of closed positions,
providing a ridged mechanical locking mechanism for rams that will
not allow them to open, or retreat from their closed position, even
if no closing pressure is applied, or maintained. The rod locking
device is equally suited for use with wellbore control devices
utilizing gates, including such gates having shearing
capability.
[0068] When used in this specification and claims, the terms
"comprises" and "comprising" and variations thereof mean that the
specified features, steps or integers are included. The terms are
not to be interpreted to exclude the presence of other features,
steps or components.
[0069] The features disclosed in the foregoing description, or the
following claims, or the accompanying drawings, expressed in their
specific forms or in terms of a means for performing the disclosed
function, or a method or process for attaining the disclosed
result, as appropriate, may, separately, or in any combination of
such features, be utilized for realizing the present invention in
diverse forms thereof.
[0070] The present invention is not limited to embodiments
described herein; reference should be had to the appended
claims.
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