U.S. patent application number 11/162700 was filed with the patent office on 2006-04-13 for anodic protective seal in a blowout preventer.
This patent application is currently assigned to VARCO I/P, INC.. Invention is credited to David J. McWhorter, Richard M. Ward.
Application Number | 20060076526 11/162700 |
Document ID | / |
Family ID | 36144351 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060076526 |
Kind Code |
A1 |
McWhorter; David J. ; et
al. |
April 13, 2006 |
Anodic Protective Seal in a Blowout Preventer
Abstract
An anodic sacrificial seal element is installed at vulnerable
regions of a blowout preventer. A zinc cylinder, for example, is
included at the well-bore pressure side of a bonnet which seals
around a rod as it extends through a bonnet which joins an actuator
to the body of the BOP. Similarly, a zinc O-ring may be used in a
seal groove provided between the bonnet and the body of the BOP. In
this way, the high electropotential of the material from which the
additional seal element is made is oxidized first, before any
attack on the BOP material, thereby increasing the time period
between maintenance events on the BOP.
Inventors: |
McWhorter; David J.;
(Magnolia, TX) ; Ward; Richard M.; (Conroe,
TX) |
Correspondence
Address: |
TIM COOK
P.O. BOX 10107
LIBERTY
TX
77575
US
|
Assignee: |
VARCO I/P, INC.
10000 Richmond
Houston
TX
|
Family ID: |
36144351 |
Appl. No.: |
11/162700 |
Filed: |
September 20, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60618489 |
Oct 13, 2004 |
|
|
|
Current U.S.
Class: |
251/1.3 |
Current CPC
Class: |
E21B 41/02 20130101;
E21B 33/062 20130101; C23F 13/10 20130101 |
Class at
Publication: |
251/001.3 |
International
Class: |
E21B 33/06 20060101
E21B033/06 |
Claims
1. A blowout preventer actuator assembly joined to a blowout
preventer body, the assembly comprising: a bonnet; a cylinder body
coupled to the bonnet and enclosing a cylinder chamber having a
piston therein; a rod connected to the piston at one end and to a
ram head at the other end; and a first anodic seal element between
the bonnet and the rod.
2. The assembly of claim 1, wherein the first anodic seal element
is made of zinc.
3. The assembly of claim 1, further comprising a first pressure
seal element adjacent the first anodic seal element.
4. The assembly of claim 1, wherein the first anodic seal element
defines a cylinder.
5. The assembly of claim 1, further comprising a second anodic seal
element between the bonnet and the blowout preventer body.
6. The assembly of claim 5, wherein the second anodic seal element
is made of zinc.
7. The assembly of claim 5, wherein the second anodic seal element
is made of a material having an electropotential higher than the
material from which either the bonnet or the rod are made.
8. The assembly of claim 5, further comprising a second pressure
seal element adjacent the second anodic seal element.
9. The assembly of claim 8, wherein the second pressure seal
element and the second anodic element are each formed in the shape
of a ring.
10. A seal element between first and second metal components
comprising an anodic member having an electropotential higher than
either of the first and second metal components and positioned
adjacent a pressure seal element.
Description
DESCRIPTION
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/61 8,489 filed Oct. 13, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
metal systems subjected to harsh, corrosive environments, such as
for example blowout preventers for tubing, and, more particularly,
to a sacrificial anodic seal element for use in such an environment
on such a metal system.
BACKGROUND OF THE INVENTION
[0003] The use of a blowout preventer in drilling, completion,
workover, and production of oil and gas wells is well known. Such a
blowout preventer generally includes a housing with a bore
extending through the housing. Opposed chambers extend laterally on
either side of the bore in the housing and communicate with the
bore. Rams within the chambers are connected to rods that are
supported for moving the rams inwardly into the bore to close off
the bore. The rods also serve to retract outwardly from the bore to
open the bore.
[0004] A volume is provided within a bonnet to provide a space to
receive the ram when the rod is pulled back away from the bore.
This volume is typically filled with a stagnant liquid having
corrosive properties. Over time, the bonnet material which defines
the volume begins to corrode and eventually the entire actuator
assembly, including the ram, must be refurbished or replaced. This
maintenance evolution costs money and causes down time for the
well.
[0005] Relatively inaccessible blowout preventers, such as those
mounted on the ocean bottom, one typical solution involves coating
BOP surfaces which are subjected to the stagnant corrosive fluid
with a layer of Inconel.RTM. and machining the Inconel.RTM. to
design tolerances. However, this solution is expensive and is not
tolerable for most BOPs and applications. Inconel.RTM. is a
registered trademark of Inco Alloys International, Inc.
[0006] Thus, there remains a need for a structure which eliminates
or at least slows the corrosion of material of the bonnet of a BOP
and similar structures. The present invention is directed to
filling this need in the art.
SUMMARY OF THE INVENTION
[0007] The present invention addresses these and other needs in the
art by providing an anodic sacrificial seal element at vulnerable
regions of a blowout preventer. A zinc cylinder, for example, is
included at the well-bore pressure side of a bonnet which seals
around the rod as it extends through the bonnet. Similarly, a zinc
O-ring may be used in the seal groove provided between the bonnet
and the body of the BOP. In this way, the high electropotential of
the material from which the additional, sacrificial seal element is
made is oxidized first, before any attack on the BOP material,
thereby increasing the time necessary between maintenance events on
the BOP.
[0008] These and other features and advantages of this invention
will be readily apparent to those skilled in the art from a review
of the following detailed description along with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features,
advantages and object of the present invention are attained and can
be understood in detail, more particular description of the
invention, briefly summarized above, may be had by reference to
embodiments thereof which are illustrated in the appended
drawings.
[0010] FIG. 1 is an elevation section view of an actuator and
coiled tubing ram constructed in accordance with the teachings of
the present invention.
[0011] FIG. 2 is a detail view of an O-ring seal between the body
of the BOP and the bonnet.
[0012] FIG. 3 is a detail view of an anodic seal element around the
rod of the ram assembly.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] Referring now to all of the drawing figures, FIG. 1
illustrates the present invention in its intended environment.
While the present invention is illustrated at particular point in a
BOP, it will be immediately apparent to those of skill in the art
that the invention may be applied in other regions of this and
similar structures having pressure seals and stagnant, corrosion
fluid captured within a vulnerable metal body.
[0014] An actuator assembly 10 includes a cylinder body 12
enclosing a cylinder chamber 14 having a piston 16 therein. A close
port 18 directs hydraulic fluid pressure to one side of the piston
16 to close the ram, and an open port 20 directs hydraulic fluid
pressure to the other side of the piston to open the ram. The
piston 16 connects to a rod 22 which terminates at a ram head 24
which connects to a ram 26, for example, although any other
appropriate type of ram head may be used.
[0015] The ram 26 moves within a body 28 of a blowout preventer
which is aligned along a center axis 30. It is to be understood
that a similar ram and associated actuator assembly (not shown in
FIG. 1) are positioned opposite the ram 26 to enclose a tubular,
such as a coiled tubing 32, passing through a bore 33 of the
blowout preventer. Upon actuation, the ram 26 closes in around the
coiled tubing 32.
[0016] The rod 22 penetrates to well-bore pressure through a bonnet
36. A seal member 38 seals between the rod 22 and the bonnet 36.
Seals in this application are commonly known in the art. The
present invention, however, provides an anodic sacrificial element
40 between the seal member 38 and the bore 33 of the BOP. The
element 40 is preferably formed of zinc which has an
electropotential of +0.758, far higher than that of iron, which has
an electropotential of +0.441, although another appropriate
material may be used so long as its electropotential is higher than
that of the material from which the BOP is made.
[0017] The bonnet 36 defines a chamber 42 to receive the ram 26
when the ram is retracted. This chamber 42 serves as a reservoir of
stagnant fluid, typically well-bore fluid, over extended period
when the BOP is inactive. This stagnant fluid is an electrolyte
creating a corrosive atmosphere for the materials of the BOP. The
anodic element 40 thus corrodes in order to save the BOP
materials.
[0018] An O-ring seal 44 is also commonly used between the bonnet
36 and the body 28 of the BOP. In the present invention, however,
an anodic seal element 46 is provided between the seal 44 and the
well-bore 33 to provide an anodic protective function like that of
the element 40.
[0019] It should also be apparent to those skilled in the art that,
while the foregoing has emphasized the present invention in the
environment of a blowout preventer, the present invention should
not be perceived as limited to only this application. The present
invention may be adapted to use in any seal between two moving
metal elements which must exist in a corrosive environment.
[0020] The principles, preferred embodiments, and mode of operation
of the present invention have been described in the foregoing
specification. This invention is not to be construed as limited to
the particular forms disclosed, since these are regarded as
illustrative rather than restrictive. Moreover, variations and
changes may be made by those skilled in the art without departing
from the spirit of the invention.
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