Note: Descriptions are shown in the official language in which they were submitted.
CA 02783442 2012-07-20
ROTATING FLOW CONTROL DEVICES HAVING STABILIZED BEARINGS
INVENTOR(S): Michael Boyd
DOCKET NO.: 65924.34
Field of the Invention
[0001] The present invention relates to rotating flow control devices, and
more particularly to
rotating flow control devices having stabilized bearings.
Background
[0002] In the oil and gas industry it is conventional to mount a rotating
blowout preventer or
rotating flow control diverter at the top of a blowout preventer (BOP) stack
beneath the
drilling floor of a drilling rig while drilling for oil or gas. The rotating
flow control diverter
serves multiple purposes including sealing pipe that is being moved in and out
of the wellbore
while allowing rotation of same. The rotating flow control diverter may also
be used to
contain or divert fluids and gases such as drilling mud, hydrocarbon wellbore
products, and
surface injected gas into a recovery line.
[0003] Typically, a rotating flow control diverter consists of rubber
strippers or sealing
elements and an associated hollow quill that both rotate with the drill string
within a robust
housing. Rotation of the strippers and the hollow quill within the housing is
facilitated by a
bearing assembly usually having an inner race that rotates with the drill
string and an outer
race that remains stationary with the housing. The bearing assembly is
isolated from fluids
and gases emanating from the wellbore by a series of seals. A rotating blow
out preventer
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consists of the same elements as a rotating flow control diverter provided
that in a rotating
blow out preventer, the stripping element is subjected to external hydraulic
force to seal onto
the drill pipe. In a rotating flow control diverter, the stripping element
normally seals on the
drill pipe by means of a stretch fit system that is augmented by fluid
pressure from the
wellbore.
[00041 Downtime in drilling operations must be minimized to maximize
efficiency and
productivity. Further, it is imperative that production equipment must be
robust and reliable
to safeguard workers operating on and about the drill floor. It is therefore
desirable that
rotating flow control devices be designed with components that function in a
trouble free
manner, and that are at least substantially as durable as other associated
drilling components.
[00051 Bearing failure is one of the more prevalent manners in which a
rotating flow control
device may encounter mechanical problems. A common cause of premature bearing
failure in
rotating flow control devices is movement or shifting of the bearings during
operations
resulting is misalignment. Misalignment of the bearings can result in excess
bearing loads
and friction that can greatly shorten the life of a bearing.
[00061 Prior art solutions designed to prevent uncontrolled movement of the
bearings during
operation of a rotating flow control device are limited. Typically, in
practice great time and
effort is expended to shim any possible space out of the stacked assembly to
ensure the
bearings stay in place. However, even after the bearings in a rotating flow
control device are
carefully shimmed with conventional metal shims, they still have a tendency to
move or
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compress through time as the rotating flow control device is operated,
particularly when the
rotating flow control device experiences varying loads and temperatures.
[0007] Accordingly there is a need for an apparatus and a method that promotes
the stability
of the bearings of a rotating flow control device. It would be preferable if
the apparatus is
simple, robust and efficient to use and if it mitigates the problems
associated with the prior art
solutions.
Summary of the Invention
[0008] In one aspect of the present invention, the invention comprises a
rotating flow control
device apparatus having stabilized bearing elements, the apparatus comprising;
(a) a stationary housing having a central bore;
(b) a tubular shaft rotatably mounted in the central bore of the stationary
housing,
the tubular shaft having an inner surface and an outer surface, the outer
surface
of the tubular shaft defining a shoulder having an upper face and a lower
face,
the shoulder defining a plurality of passages extending from the upper face to
the lower face;
(c) a coil spring disposed in each passage;
(d) a bearing assembly axially and radially supporting the tubular shaft, the
bearing
assembly comprising;
(i) an outer housing releasably mounted to the stationary housing, the outer
housing and the outer surface of the tubular shaft defining an annular
space between them;
(ii) bearing elements disposed in the annular space, the bearing elements
being mounted on the outer surface of the tubular shaft in a position
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adjacent to the upper and the lower faces of the shoulder whereby the
coil springs in the passage are compressed by the bearing elements and
exert a resistive push force on the bearing elements.
[0009] In one embodiment, the passages and the tubular shaft are aligned
longitudinally. In
other embodiment, the apparatus further comprises shims mounted on the outer
surface of the
tubular shaft adjacent to the bearing elements such that the bearing elements
are sandwiched
between the shoulder and a shim. In another embodiment, the apparatus further
comprises a
top cap that releasably attaches to the outer housing of the bearing assembly,
the top cap
retaining the bearing elements within the annular space and compressing the
bearing elements
against the springs.
[0010] In one embodiment the rotating flow control device is a rotating flow
control diverter.
In another embodiment, the rotating flow control device is a rotating blow out
preventer.
[0011] Ina further aspect of the present invention, the invention comprises a
rotating flow
control device apparatus having a stabilized bearing elements, the apparatus
comprising;
(a) a stationary housing having a central bore;
(b) a tubular shaft rotatably mounted in the central bore of the stationary
housing,
the tubular shaft having an inner surface and an outer surface, the outer
surface
of the tubular shaft defining a shoulder having an upper face and a lower
face,
the shoulder defining a plurality of pockets recessed into the upper face and
the
lower face;
(c) a coil spring disposed in each pocket;
(d) a bearing assembly axially and radially supporting the tubular shaft, the
bearing
assembly comprising;
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(i) an outer housing releasably mounted to the stationary housing, the
outer housing and the outer surface of the tubular shaft defining an
annular space between them;
(ii) bearing elements disposed in the annular space, the bearing elements
being mounted on the outer surface of the tubular shaft in a position
adjacent to the upper and the lower faces of the shoulder whereby the
coil springs in the pockets are compressed by the bearing elements and
exert a resistive push force on the bearing elements.
[0012] In one embodiment, the pockets and the tubular shaft are aligned
longitudinally. In
other embodiment, the apparatus further comprises shims mounted on the outer
surface of the
tubular shaft adjacent to the bearing elements such that the bearing elements
are sandwiched
between the shoulder and a shim. In another embodiment, the apparatus further
comprises a
top cap that releasably attaches to the outer housing of the bearing assembly,
the top cap
retaining the bearing elements within the annular space and compressing the
bearing elements
against the springs. In one embodiment, the pockets are only defined in one of
the faces of the
shoulder and a single bearing element is mounted on the outer surface of the
tubular shaft
adjacent to such face.
[0013] In a further aspect of the invention, the invention comprises a method
of stabilizing
bearing elements in a bearing assembly of a rotating flow control device, the
bearing assembly
comprising an outer housing, the bearing elements and a rotatable tubular
shaft having an
outer surface, the tubular shaft being disposed within the outer housing and
being supported
axially and radially by the bearing elements, the method comprising;
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(a) defining a shoulder having an upper face and a lower face on the outer
surface
of the tubular shaft;
(b) defining a plurality of passages through the shoulder extending from the
upper
face to the lower face;
(c) inserting a coil spring into each passage; and
(d) mounting the bearing elements on the outer surface of the tubular shaft in
a
position adjacent to the upper and lower faces of the shoulder such that the
coil
springs in the passages are compressed and exert a resistive push force on the
bearing elements.
[0014] In one embodiment of the method, the passages and the tubular shaft are
aligned
longitudinally. In another embodiment, the method further comprises the step
of securing a
top cap to the outer housing to retain the bearing elements and to compress
the bearing
elements against the coil springs. In one embodiment of the method, the
rotating flow control
device is a rotating flow control diverter. In one embodiment of the method,
the rotating flow
control device is a rotating blow out preventer.
[0015] In one embodiment of the method, instead of defining passages in the
shoulder,
pockets are defined in the upper face and the lower face of the shoulder and
coil springs are
inserted into each such pocket. In a further embodiment of the method, pockets
are only
defined in one of the faces of the shoulder.
Brief Description of the Drawings
[0016] In the drawings, like elements are assigned like reference numerals.
The drawings are
not necessarily to scale, with the emphasis instead placed upon the principles
of the present
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invention, Additionally, each of the embodiments depicted are but one of a
number of
possible arrangements utilizing the fundamental concepts of the present
invention. The
drawings are briefly described as follows:
[0017] Figure 1 is an elevated diagrammatic depiction of one embodiment of a
rotary flow
control diverter,
[0018] Figure 2 is an elevated diagrammatic depiction of the tubular shaft of
one embodiment
of the present invention.
[0019] Figure 3 is an exploded diagrammatic view of one embodiment of the
present
invention showing how it inserts into the outer housing of a bearing assembly
of a rotary flow
control device.
[0020] Figure 4 is a diagrammatic depiction of the springs in the passages of
one embodiment
of the present invention.
[0021] Figure 5 is a diagrammatic depiction of the springs in the pockets of
one embodiment
of the present invention.
Detailed Description of Preferred Embodiments
[0022] The invention relates to an apparatus for stabilizing the bearings in
the bearing
assembly of a rotating flow control diverter. When describing the present
invention, all terms
not defined herein have their common art-recognized meanings. To the extent
that the
following description is of a specific embodiment or a particular use of the
invention, it is
intended to be illustrative only, and not limiting of the claimed invention.
The following
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description is intended to cover all alternatives, modifications and
equivalents that are
included in the spirit and scope of the invention, as defined in the appended
claims.
[0023] A rotating flow control diverter generally comprises a stationary
housing adapted for
incorporation into a wellhead and a rotating quill portion adapted to
establish a seal to a
tubular such as tubing or drill pipe that is passed through the quill. The
quill is rotatably and
axially supported by an internal rotating assembly comprising bearings and a
seal assembly for
isolating the bearings from well fluids.
[0024] Figure 1 depicts one embodiment of a rotating flow control diverter
(10) that forms the
subject of co-pending PCT Application CA 2011/000668, owned by the Applicant.
As can be
seen in Figure 1, the rotating flow control diverter (10) comprises a
stationary housing (14)
adapted at a lower end by a flange connection (16), to operatively connect
with a wellhead or
blow out preventer (not shown), In operation for diverting and recovering
fluids and gases
from the wellbore, the stationary housing (14) can be fit with one or more
outlets along a side
portion of the housing (14) for the selective discharge of well fluids and
gases.
[0025] The stationary housing (14) has a bore (28) for receiving fluid and gas
from the
wellbore. The rotating flow control diverter (10) has a sealed bearing
assembly (15) having an
axially rotatable inner tubular shaft (12) disposed therein. The inner tubular
shaft (12) has an
elastomeric stripper element (18) supported at a downhole end of the inner
tubular shaft (12).
[0026] The bearing assembly (15) has a robust outer housing (22). The outer
housing (22)
and the inner tubular shaft (12) form an annular space disposed in which is a
sealed fluid
chamber (24). The sealed fluid chamber (24) is enclosed by the outer housing
(22), the inner
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tubular shaft (12) and an upper cap (26) and a lower seal (20) The upper cap
(26) is attached
to outer housing (22) using set screws (19) or such other suitable attachment
means as would
be selected by one skilled in the art, The sealed fluid chamber (24) contains
bearing elements
(not shown) and lubricating fluid (not shown) for lubricating the bearing
elements. It can be
understood from Figure 1 that the bearing elements disposed in the sealed
fluid chamber (24)
radially and axially support the inner tubular shaft (12).
[0027] One skilled in the art will appreciate that a rotating blow out
preventer is comprised of
the same elements as a rotating flow control diverter. The difference between
the two pieces
of equipment is that in a rotating blow out preventer, the stripping element
is subjected to
external hydraulic force to seal onto the drill pipe while the stripping
element in a rotating
flow control diverter typically seals on the drill pipe by means of a stretch
fit system. The
Figures and the following description of the invention will be described in
the context of a
rotating flow control diverter, but it should be understood that the invention
described herein
may be utilized in the same manner in a rotating blow out preventer. The term
"rotating flow
control device" as used herein shall include both a rotating flow control
diverter and a rotating
blow out preventer.
[0028] Figure 2 depicts a modified inner tubular shaft (40) of the apparatus
of the present
invention for use in rotating flow control devices to support, stabilize and
centralize the
multiple encased bearings. As will be described in more detail, when
installed, the inner
tubular shaft (40) preloads the bearing elements (30) with an external push
force created by
the compression multiple coil springs (46). The inner tubular shaft (40) has
an inner surface
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(46) and an outer surface (48), the outer surface (48) comprising at least one
shoulder (44)
having an upper face (43) and a lower face (45). The shoulder has a plurality
of passages (42)
extending through the shoulder from the upper face (43) to the lower face
(45). Each passage
(42) is adapted to accommodate a metal coil spring (46) as shown in Figure 4.
The metal coil
spring (46) is sized such that it protrudes from each end of the passage (42).
In one
embodiment, the passages (44) are orientated such that they have a
longitudinal axis which is
parallel with the longitudinal axis of the tubular shaft (40). The tubular
shaft (40) and the
shoulder (44) thereon may be constructed from any suitable metallic material
including
without limit 41/30 alloy steel. The passages (42) may be machined though the
shoulder (44).
[0029] While the embodiment described herein references the use of metallic
compression
springs (46) to exert the push force on the bearing elements (30), such
description is not
intended to be limiting of the invention claimed herein. One skilled in the
art will recognize
that other suitable types of spring may be used with the apparatus of the
present invention.
[0030] Assembly and insertion into the bearing assembly (15) of a rotary flow
control device
(10) will now be described having reference to Figure 3. Metallic compression
springs (46)
are loaded into the passages (42) defined by the shoulder (44). Bearing
elements (30) are
positioned immediately above and below the shoulder (44) such that the bearing
elements (30)
are in contact with both ends of the springs (46) and such that they compress
the spring within
the passage (42). Shims (31) are placed above and below the bearing elements
(30) as shown
in Figure 3 to further restrain movement of the bearing elements (30). The
springs (46) resist
compression and exert a preload force on the bearing elements (30). The inner
tubular shaft
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(40) is lowered into the outer housing (22) of the bearing assembly (15). The
cap (26) screws
into the top of the housing (22) to restrain the inner tubular member (40) and
the bearing
elements (30) mounted thereon within the outer housing (22).
100311 Specifically, as the inner tubular shaft (40) complete with springs
(46), bearings (30)
and shims (31) are locked into the outer housing (22) of the bearing assembly
(15) of the
rotating flow control diverter (10) by tightening and securing the screws (19)
of the upper cap
(26), the compression of the springs (46) will apply a balanced preload force
equally to the
bearings (30). This preload force keeps the bearing elements (31) aligned and
floating in a
neutral position. This reduces the occurrence of friction and excess bearing
load arising from
misalignment of the bearings or an inability to properly shim the bearings.
Springs of varying
sizes and compressive resistivity may be selected to vary the spring loaded
force exerted on
the bearing elements. The passages (42) are placed at regular intervals around
the shoulder
(44) to promote balanced loading of the adjacent bearing elements (30). The
number of
passages required is partially dependent on the size and strength of the
springs utilized.
[0032] The bearing elements may comprise any suitable encased race bearings
employed by
those skilled in the art in rotating flow control devices.
[0033] In one embodiment as shown in Figure 5, instead of utilizing passages
extending
through the shoulder, the shoulder defines a series of pockets (50) extending
part way through
the shoulder, each pocket containing a spring (46) that protrudes out of the
opening of the
pocket (50). The pockets (50) may be defined on a single face of the shoulder
(44), in which
case a push force may be exerted on a single bearing element positioned
adjacent to the face
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of the shoulder (44) having the pockets (50). Alternatively pockets (50) may
be defined on
both faces of the shoulder (44) in which case a push force may be exerted on
bearing elements
(30) positioned on either side of the shoulder (44) adjacent to the faces of
the shoulder (44).
The pockets (50) may be machined into the shoulder. In a preferred embodiment,
the pockets
(50) have a longitudinal axis that is aligned with the longitudinal axis of
the tubular shaft (40).
[00341 As will be apparent to those skilled in the art, various modifications,
adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope
of the invention claimed herein.
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