Field of the invention
[0001] The invention relates to the field of couplings for connecting elongated elements,
such as pipes, tubes, shafts and axles. More specifically, the invention concerns
a coupling assembly as specified in the preamble of claim 1, and a method of assembly
as specified in the preamble of claim 11.
Background of the invention
[0002] Pipe sections or tubular sections used for drilling deep wells in e.g. oil or gas
reservoirs or geothermal formations, utilize long sections of drill pipe, well casing
or tubing that usually have a tapered, exteriorly-threaded male end called a pin member.
In use, the pin members are threaded into corresponding couplings, collars or integral
female pipe sections; their threaded ends are called a box member. These box members
have an interiorly-threaded tapered thread corresponding to their respective pin members.
[0003] A dominant type of pin-box connection has been the American Petroleum Institute (API)
threaded and coupled connection that achieves its assembly with threads and torque
shoulders. These tapered connections provide increasing bearing stresses to the seal
between the pin member and box member with increasing engagement produced by rotational
torque. It is well known in the petroleum industry that the performance of API and
premium double shoulder connections are highly dependent on the make-up assembly (engagement)
condition of the joint, and therefore it is important to determine if the joint is
made-up properly. Assembly conditions include friction-related factors such as thread
dope/lubrication, surface finishes, tong position and type/model, eccentricity, and
impurities (dirt or rust). Hydraulic tongs, often referred to as an "iron roughneck",
or manually operated tongs are normally used to make up connections between drill
pipe, while so-called "casing tongs" are used to make up casing and production pipe
(or liner).
[0004] As the well depths and lengths (as well as the number of long horizontal wells and
directional wells) have increased, the drilling and production environment has become
more demanding. For example, a well of 6000 meters may require as much as 7000 connections
and disconnections of pipe, with varying torque. The threaded pin-box connections
need to meet rigorous demands regarding pressure loss across the connection, tension
/ compression resistance, higher torque, and resistance to internal and external pressure.
The threaded connections developed to meet these demands are referred to as "premium"
connections and "double-shoulder connection" (DSC).
[0005] In a premium coupling, the externally-threaded member (i.e. the "pin") includes tapered
threads, seal portions (i.e. metal to metal seal portions) and shoulders (e.g. torque
shoulders) or these two combined. The internally-threaded member (i.e. the "box")
also includes tapered threads, and seal portions and shoulders similarly to the pin.
The tapered threads are important for quickly and firmly fixing the pipe joint, the
seal portions play a role of ensuring fluid and gas tight by bringing the box and
the pins into metal contact at such portions, and the shoulders form a shoulder faces
which play a role of abutments during make-up of the coupling. Connecting ("making")
and disconnecting ("breaking") a premium coupling requires higher torque than for
an API coupling. A premium coupling normally has thinner wall thicknesses than the
API coupling, among other reasons to reduce hydrodynamic drag around the outside portion
of the coupling. These thinner wall thicknesses place an increased demand on the tongs
in order to avoid coupling deformation. Due to the higher make-up torque, a premium
connection must withstand higher radial clamp force from the iron roughneck during
make and break.
[0006] So-called "extended-reach drilling" (ERD) places high demands on the couplings, in
order to overcome friction loss between the drill string and the formation or casing,
and the required torque (to rotate the drill string) increases with the length of
the well. Circulating drill fluids in such long wells is also more complicated and
demanding, as each connection represents a restriction in the annulus between the
drill pipe and casing.
[0007] Various means and methods exist for verifying proper abutment during mating as well
as correct torque during make-up.
[0008] The prior art includes
GB 2 064 041 A, which discloses a pipe connector for interconnecting pipe sections to form a pipe
string for use in the drilling and/or completion of offshore oil or gas wells. The
pipe connector comprises a tubular box member for connection to the end of a pipe
and a tubular pin member for connection to the end of a pipe and which is telescopically
receivable within the box member. The members have corresponding generally frusto-conical
peripheral surfaces which overlie one another when the members are fully telescoped
together. The surfaces comprise interengageable helical projection and groove means
which extend therealong between end portions which are arranged to be a shrink fit
one on the other. The members of the connector are engageable and releasable by the
use of fluid under pressure which is injected between the frusto-conical surfaces
when the members are partially interengaged. A radial clearance is provided between
the crest and root surfaces of the projection and groove means along which the pressurized
fluid can flow.
[0009] The prior art also includes
US 4 648 627, which discloses a connector assembly including a pin connector for receipt by a
box connector. The pin connector features a neck portion having external threads,
and the box connector features a collar portion having internal threads, generally
complementary for meshing with the external threads. The connectors may be threadedly
joined together by longitudinally inserting the pin connector into the box connector,
whereupon the two connectors are mutually sealed at two locations on opposite sides
of the internal and external threads to define, with the threads, an annular region.
Application of fluid pressure to the annular region may radially expand the region
to permit further insertion of the pin connector into the box connector to mutually
align the internal and external threads. Release of the fluid pressure permits mutual
meshing between the threads to threadedly connect the pin and box connectors. The
connector assembly may be released by like application of fluid pressure to radially
expand the annular region, or by mutual rotation between the pin and box connectors,
to disengage the meshing between the internal and external threads.
[0010] While the above prior art includes threaded connections, various thread-less connectors
also exist.
[0011] For example,
US 2012/049513 A1 shows a thread-less connection for coupling segments of a pipe (e.g. drill pipe used
in the drilling of wellbores) longitudinally end to end. The coupling includes a pin
end having a groove for receiving a locking ring. A box end has a groove for receiving
the locking ring therein when the pin end is inserted into the box end. The locking
ring has an uncompressed diameter selected to exert lateral force on the groove in
the box end when assembled to the pin end.
[0012] WO 2005/061852 A1 shows a method of connecting tubular elements, particularly pipe for strings to be
used in oil and gas wells. The pin and box have complementary stepped profiles. The
pin and box are compressed and/or expanded, respectively, by means of a swaging die
head. A key issue in this publication is that - prior to assembly - one or both of
the pin/box external surfaces are at least partially coated by plasma spraying with
hard angular material.
[0013] US 2004/065446 A1 shows an expander tool for connecting two tubulars by expanding a first tubular into
a second surrounding tubular within a wellbore. The lower casing string has been expanded
using the expander tool into frictional contact with the inner wall of the upper casing
string. A sealing member is optionally disposed on the outer surface of the lower
string of casing. The sealing member serves to provide a fluid seal between the outer
surface of the lower string of casing and the inner surface of the upper string of
casing after the lower casing string has been expanded.
[0014] US 2011/147009 A1 shows a drill pipe connector assembly capable of connecting drill pipe segments without
rotation. The assembly includes the pin end of a first drill pipe stabbed within the
connector end of a second drill pipe. A connector nut is thread-connected or snap-locked
to the connector end of the second drill pipe. The connector nut includes a retaining
shoulder cooperating with a beveled shoulder on the pin end of the first drill pipe
to retain the first drill pipe. The assembly includes seals to provide pressure integrity
and prevent leaking. Cooperating rotational torque transfer profiles in the first
and second drill pipes enable operational rotation of the drill string.
[0015] US 3 923 324 A describes a drill collar for a rotary drill string, including a threadless drill
collar body having pins being frictionally mounted by means of a shrink-fit on opposite
ends of the body, to corresponding boxes of opposite subs. The frictional connection
between the matching conical surfaces between conical pins of the drill collar body,
and the corresponding subs, respectively, is accomplished as by the application of
pressure fluid between the adjacent contacting surfaces, while simultaneously applying
an axial force, as by fluid or hydraulic pressure, to push or force the box shaped
portion of each sub onto its companion conical pin of the drill collar body, until
such box shaped member abuts a shoulder adjacent the connection of the conical pins
with the main drill collar body. A port is provided in the box shaped portions of
each sub for introduction of gaseous or hydraulic fluid pressure into the space between
the box and pin, for laterally expanding the sub box during shrink-fitting thereof
onto the corresponding pin.
[0016] GB 2 113 335 A describes a pipe connector comprising a tubular box member which is telescopically
engageable with a tubular pin member, the members having corresponding frusto-conical
inner and outer peripheral surfaces. To axially lock the member together, when they
are fully telescoped together, the surfaces are provided with interengageable projections
and grooves which have varying axial extents and spacings so that, as the members
are telescoped together, in all intermediate positions of the members, there is sufficient
contact between crests of the grooves and surfaces between the projections to prevent
inadvertent engagement of a projection with a groove. The members may be fully engaged
by the application of pressurized hydraulic fluid to the overlapped portions of the
surfaces following initial contact, and may be disengaged in the same way, the pressurized
fluid both expanding the box and/or contracting the pin to permit engagement and lubricating
the crest surfaces of the projections and surfaces between the grooves to facilitate
sliding of these surfaces over one another. For this purpose, the box member may be
provided with a radial duct for connection to a source of pressurized hydraulic fluid.
The duct opens inwardly of the box into the region of the frusto-conical surface of
the box which is provided with the projections or grooves. To ensure that the hydraulic
fluid is able to flow along the full extent of the overlapped portions of the surfaces
of the members, axially extending grooves are provided in both the box member and
the pin member, duct opening into groove in the box member. The pressurized fluid
is only required to assist engagement of the members after initial contact has been
made.
[0018] The prior art couplings are predominantly concerned with handling either torque or
compression/tension. There is a need for an improved coupling, that is more reliable
and efficient, and which offers more operational advantages over the prior art.
Summary of the invention
[0019] The invention is set forth and characterized in the main claim, while the dependent
claims describe other characteristics of the invention.
[0020] It is thus provided a coupling assembly for elongate elements, comprising:
- a pin member having an outward-facing pin surface, and a box member having an inward-facing
box surface, said pin surface and box surface configured for mating engagement, and
- at least one bore having as a first opening a port configured for connection to an
injection fluid reservoir and a second opening penetrating the pin surface or the
box surface;
characterized in that:
- the pin surface comprises a plurality of pin protruding portions separated by pin
recessed portions, and
- the box surface comprises a plurality of box protruding portions separated by box
recessed portions; and
wherein a pin protruding portion is shaped and dimensioned to fit into a designated
box recessed portion, and
wherein a box protruding portion is shaped and dimensioned to fit into a designated
pin recessed portion.
[0021] This key-and-lock feature (hereinafter referred to as "Key-Loc") ensures that all
ring- and-recess pairs must be aligned before the initial mating is complete.
[0022] In one embodiment, the pin and box members comprise complementary and respective
frusto-conical pin and box mating surfaces.
[0023] In one embodiment, one or more portions of the surfaces are plain surfaces without
helical threads or other pronounced protrusions configured for mating engagement.
In one embodiment, one or more portions of the surfaces comprise a textured finish
in order to augment static friction between the surfaces when the surfaces are connected.
[0024] The pin protruding portions, pin recessed portions, box protruding portions and box
recessed portions are preferably circular portions, extending around the respective
surface. The mating surfaces may comprise single frusto-conical sections, but may
also comprise several frusto-conical sections with different taper angles in order
to obtain an optimally distributed contact pressure between the mating surfaces.
[0025] The "Key-Loc" concept contributes to the axial/tensile strength and/or torque performance,
as well as positioning of the connected coupling, of the connected coupling. In addition,
the "Key-Loc" concept contributes to avoiding progressive failure mechanisms, such
as micro-slip, from occurring under repetitive loading cycles, especially in a so-called
"dog leg" situation during directional drilling.
[0026] In one embodiment, the axial widths of the pin portions decrease in the direction
towards a pin member free end, and the axial widths of the box portions increase in
the direction towards a box member free end. The larger widths are associated with
the larger diameter of the frusto-conical shape of the pin and box surfaces, and the
smaller widths are associated with the smaller diameter of the frusto-conical shape
of the pin and box surfaces.
[0027] In one embodiment, the coupling assembly comprises a friction-enhancing device, configured
for being arranged on the pin surface. The pin surface may comprise a plurality of
stepped surfaces of diminishing surface radius towards the pin free end, and the box
surface may comprises a plurality of stepped surfaces of increasing surface radius
towards the box free end.
[0028] In one embodiment, a region of the box surface comprises a wall thickness which is
less than the thicknesses of the adjacent box walls. Also, a region of the pin surface
may comprise a wall thickness which is less than the thicknesses of the adjacent pin
walls.
[0029] In one embodiment, a region of the box surface comprises a material of a lower modulus
of elasticity than the material of a corresponding region of the pin surface, or vice
versa.
[0030] In one embodiment, at least a portion of the pin and box mating surfaces comprise
grooves. The grooves may extend in a double-helical formation.
[0031] It is also provided a method of mating the invented coupling assembly, characterized
by:
- a) performing an initial mating step until a cavity is formed between the first and
second mating surfaces;
- b) injecting a fluid under pressure into the cavity, and maintaining the fluid pressure
while exerting an axial force to push the first and second mating members a predetermined
distance towards each other;
- c) releasing the fluid pressure.
[0032] In one embodiment, the fluid pressure and axial force in step b) are balanced and
controlled to ensure a predetermined elastic deformation and prevent plastic deformation
in the mating members. Step a) may be performed until the pin and box gaskets or seals
engage and facilitates the injection of a fluid between the pin and the box. The pin
and box may comprise more than one seal, in order to maintain the sealing function
when crossing a protrusion or recess.
[0033] Also, one or more injection channels may be located on the pin shoulder, to facilitate
easy access and port protection during operation.
[0034] The invented coupling assembly may be connected and disconnected without rotational
motion (as is necessary with a threaded connection), only axial motion and application
of hydraulic pressure are required. The pin and box surfaces may be smooth or comprise
complementary stepped profiles (protruding and recessed portions). Adhesion between
the surfaces may be augmented by friction coating (e.g. electrode-less nickel coating
with diamonds or similar), a serrated surface, particles in the injected fluid, "double-helix
engravement" (fluid pressure distribution and friction particles distribution), separate
friction sleeves, or/and by increasing surface roughness (by e.g. sandblasting or
similar).
[0035] Besides the bias created by hydraulics and steel elastic properties, the friction
factor between the pin and box will be decisive. The hydraulic fluid may be water
or glue with or without a corrosion inhibitor, with or without particles , together
with a surface structure or/and a separate friction shim, or/and an applied friction
increasing coating, seeking the highest possible friction factor. The invented coupling
exhibits improved performance over the prior art, in that it can handle combined torque,
tension and compression.
[0036] The invented coupling assembly may be useful for connecting any elongated elements
that may rotate and transfer torque; such as pipes, propeller shafts, axles, as well
as various tubulars such as drill pipe (drill string) and casing for casing-drilling.
The invented coupling assembly transfers torque equally well in both rotational directions
(as opposed a prior art threaded coupling). This "bidirectional" torque capability
is particularly useful is a drill pipe is jammed and it is necessary to counter-rotate
to release the drill bit or other dowhhole tools. The coupling assembly may also be
useful for non-rotating elongated elements, such as rods, different process pipe lines,
borehole casings and liners.
[0037] In the prior art, connections between pipe joint having electrical (power, signals)
cables (so-called "wired pipe", "powered pipe", or "intellipipe") are accomplished
by elaborate rotatable connections or by inductive couplings. With the invention,
the cables may be connected by a metal-to-metal connection, for example by embedded
and electrically insulated metal portions in the pin free end and the box inward shoulder.
Such "plug-and-socket" connection is possible with the invention, as the pipe joints
need not rotate during the connection process, but merely move axially towards each
other. The electrical connectors may also be used to verify that the connection has
been completed.
[0038] The invention may also replace the prior art top drive saver sub connection, which
is time consuming to replace.
[0039] Well tractor: When installing well tractor modules, it is often not possible to rotate
the pipe which makes up the barrier against pressure and other mechanical forces during
operation, due to internal contacts and connections. With the invention, the prior
art complex connection comprising a combination of sleeves, nuts and seals may be
eliminated.
[0040] Also, in various bottom-hole assemblies and completions, the invention may replace
all threaded connections. The axial movement of the invented coupling assembly will
make design of connections and internal components much easier, as rotation is not
required to make the connection. Furthermore, the invention may replace complex and
time-consuming welding operations associated with the connection and laying of trunk
lines and pipes, both on the seabed and on land.
[0041] The invention is suitable with any materials commonly used in pipes, propulsion shafts,
axles, drill pipe (drill string), drilling risers, rods, borehole casings, liners,
etc., such as stainless steel. However, the invented coupling also lends itself to
the use of various steel grades (e.g. 689,5 MPa (100 ksi) box and 896,35 MPa (130
ksi) pin), light-weight materials, such as fibre-reinforced composites, titanium,
aluminum and similar alloys. That is, both the coupling and the associated elongated
elements may be made of such materials (or in combination). This will allow for a
significant weight reduction of e.g. drill strings, compared to the steel drill strings
of the prior art.
Brief description of the drawings
[0042] These and other characteristics of the invention will become clear from the following
description of a preferential form of embodiment, given as a non-restrictive example,
with reference to the attached schematic drawings, wherein:
Figure 1 is a perspective view of a first embodiment of the coupling assembly according
to the invention, in a disconnected state;
Figure 2 is a sectional view of the coupling assembly shown in figure 1, in a plane
along the longitudinal central axis x-x, in a disconnected state;
Figure 3 corresponds to figure 2, but shows the coupling assembly in a partly connected
state;
Figure 4 corresponds to figure 3, but shown the coupling assembly in a connected state;
Figure 5 is a perspective and transparent view of the coupling assembly shown in figure
1, in a connected state, i.e. corresponding to the state shown in figure 4;
Figure 6 is a schematic sectional view of an embodiment of the coupling assembly according
to the invention, in a plane along a longitudinal central axis, in a disconnected
state;
Figure 7 corresponds to figure 6, and illustrates a method of connecting the pin member
and box member;
Figure 8 is a perspective view of a second embodiment of the coupling assembly according
to the invention, in a disconnected state;
Figure 9 is a sectional view of the coupling assembly shown in figure 8, in a plane
along the longitudinal central axis x-x, in a disconnected state;
Figure 10 corresponds to figure 9, but shows the coupling assembly in a partly connected
state;
Figure 11 is an enlarged view of the section marked "B" in figure 10;
Figure 12 corresponds to figure 11, but shows a state in which the coupling assembly
has been further connected;
Figure 13 corresponds to figure 11 but shows a state in which the coupling assembly
has been fully connected;
Figure 14 corresponds to figure 9, but shows a state in which the coupling assembly
has been fully connected, i.e. corresponding to the state shown in figure 13;
Figure 15 shows an embodiment of a pin surface;
Figure 16 an enlarged view of the section marked "A" in figure 4;
Figure 17 is a transparent side view of an alternative embodiment of a box and pin,
in which portions of the pin and the box have a reduced wall thickness;
Figure 18a is an enlarged view of the section marked "C" in figure 17;
Figure 18b is an enlarged view of the section marked "D" in figure 17;
Figure 19a is a perspective view of an embodiment of the invented pin, in association
with a friction sleeve;
Figure 19b corresponds to figure 19a, and illustrates the friction sleeve fitted onto
the end of the pin;
Figure 20 is a perspective view of an alternative embodiment of the invented pin,
having a stepped pin profile;
Figure 21 is a sectional perspective view of an embodiment of a pin-and-box coupling
having dual seals, in a partially interconnected state
Figure 22 is an enlarged view of the section marked "G" in figure 21;
Figure 23 is a side view of the section marked "H" in figure 22;
Figure 24 is a transparent perspective view of an embodiment of the invented pin,
illustrating wires or cables extending inside the pin body and an electrical contact
surface;
Figure 25 is a perspective view corresponding to that of figure 24, illustrating an
electrical contact surface;
Figure 26 is a variant of the embodiment illustrated in figures 24 and 25, in which
more than one wire may be connected to a contact surface.
Detailed description of embodiments
[0043] The following description will use terms such as "horizontal", "vertical", "lateral",
"back and forth", "up and down", "upper", "lower", "inner", "outer", "forward", "rear",
etc. These terms generally refer to the views and orientations as shown in the drawings
and that are associated with a normal use of the invention. The terms are used for
the reader's convenience only and shall not be limiting.
[0044] Referring initially to figure 1 and figure 2, the invented coupling assembly comprises
a first mating member 5 and a second mating member 6. In the illustrated embodiment,
the first mating member is a pin member 5 which forms an end portion of a first pipe
1 having an internal bore 3. The second mating member is a box member 6 which forms
an end portion of a second pipe 2 having an internal bore 4. It should be understood
that only a part of the first and second pipes 1,2 are shown, and the skilled person
will understand that these pipes may be several meters long. The pipes 1,2 may for
example be drill pipes, liners, casing joints or other tubular elements configured
for rotational movement and for conveying a fluid. In fact, although not illustrated,
the pipes may be replaced by other elongated elements such as shafts and axles. The
invention shall therefore not be limited to a coupling assembly for tubular elements,
but be applicable to a coupling assembly for any elongated elements. For the purpose
of this description, however, the elongated elements 1,2 will be referred to a tubulars
1,2.
[0045] The pin member 5 comprises a first mating surface 12, hereinafter also referred to
as a pin surface 12, here in the shape of a frusto-conical surface facing outwards
with respect to the central axis x-x. The pin surface ends at a pin shoulder 14.
[0046] The box member 6 comprises a second mating surface 13, hereinafter also referred
to as a box surface 13, here in the shape of a frusto-conical surface facing inwards
with respect to the central axis x-x. The box surface ends at an internal box shoulder
16.
[0047] Such pin-and-box shapes are per se well known in the art, and need therefore not
be described in further detail here. Seals (not shown) may be arranged at the pin
shoulder 14 and the pin free end 15, or (more common) at the pin free end 15 and the
box inner shoulder 16. The seals may be integrated (as profiles in the pin and/or
box) or may be removable, and may comprise materials such as elastomers and/or metals.
It should be understood, however, that the pin-and-box coupling may also be used without
seals.
[0048] In the embodiment illustrated in figures 1-5, the pin surface 12 and box surface
13 are plain surfaces, without helical threads or other pronounced protrusions configured
for mating engagement.
[0049] The pin and box surfaces are thus generally smooth, but may comprise a textured finish
(roughness) of a certain topography in order to augment static friction (and hence
adherence) between the pin and box when connected. Such topography may be obtained
by friction coating (by for example nickel coating with diamonds) or by increasing
surface roughness through sandblasting or similar. Although not illustrated, the pin
and/or box surfaces, or portions of these surfaces, may be furnished with serrations
in order to increase the torque capacity of the connected coupling.
[0050] Another adherence-enhancing topography is illustrated in figure 15. Here, the frusto-conical
pin surface 12 is provided with grooves 23, extending in a double-helical formation
22. It should be understood that the grooves preferably are quite shallow in relation
to the dimensions of the pin and box. As a non-limiting example, the groove 23 depth
may be on the order of one tenth of a millimeter for a pin having an outer diameter
(OD) of 120mm. Although not illustrated, it should be understood that a double-helix
may also be formed in the box surface, either in lieu of the double-helical formation
22 or as supplement to it. The helical grooves serve two functions, by providing a)
fluid distribution channels during mating and b) distribute friction-enhancing fluid
with particles.
[0051] Referring again to figure 1 and figure 2, arranged in the external wall of the box
member 6 is an opening (a port) 9a which is the outward opening of a bore 9 extending
through the box member wall and into the box member interior, penetrating the box
surface 13 in an inward opening 9b (another illustration of the bore 9 is provided
in i.a. figure 6 and figure 16). The bore 9 therefore provides a fluid access channel
into the box. It should be understood that although only one bore 9 is shown in the
figures, a practical embodiment of the invention may comprise several bores.
[0052] Figure 3 illustrates an initial step in a mating process of the pin-and-box coupling
shown in figure 1 and figure 2, in which the pin member 5 has been inserted a distance
into the box member 6. Figure 4 and figure 5 illustrate the state in which the mating
process has been completed and the connection between the pin member and box member
has been made.
[0053] Figure 6 illustrates an embodiment of the invention that in principle is similar
to the embodiment described above with reference to figures 1-5. In addition, however,
figure 6 shows how seals 7, 8 are arranged in the region of the pin shoulder and pin
free end, respectively. It should be understood that the seals may be arranged on
the box instead, and that a combination of the two arrangement is conceivable. The
seals serve to form a frusto-conical annular cavity during the initial mating, to
contain injected fluid. Figure 6 also shows how a pressurized fluid reservoir 10 is
connected to the bore 9 via a conduit 10a. The reservoir 10 preferably contains a
liquid, such as (but not necessarily limited to) water, which may be injected under
pressure into the box member 6, controlled via the control valve 11. Figure 6 also
illustrates an alternative configuration in which the reservoir 10 is connected to
a bore 9' which extends through the pin member 5 body, and where the bore 9' penetrates
the pin surface 12 with the opening 9b. The effect of this configuration is equivalent
to the configuration in which the bore 9 extends through the box member 5 wall inasmuch
as both bore configuration deposit the injected fluid at more or less the same location
during a mating operation. However, connecting the reservoir 10 to the bore 9' extending
through the pin member 5 body may have certain operational advantages.
[0054] Referring additionally to figure 16, which shows an enlargement of the section marked
"A" in figure 4, the wall thicknesses of the pin and box, respectively, correspond
inversely in the illustrated embodiment. That is, the wall thickness of the pin free
end 15 corresponds (i.a. is more or less equal) to the wall thickness of the box outer
end 17, and the wall thickness of the pin rear end (in the region immediately before
the pin shoulder 14) corresponds to the wall thickness of the box rear end (in the
region immediately before the box shoulder 16).
[0055] A mating process will now be described in more detail, with reference also to figure
7, in addition to figure 6. In figure 7, the pin member 5 and box member 6 have been
moved together in an axial movement (i.e. no rotation necessary), a pressurized hydraulic
liquid (e.g. water) is injected from the reservoir 10 through the bore 9 (or bore
9') when the seal 7 and the seal 8 have created a cavity V between the pin surface
12 and the box surface 13. This cavity V, which essentially is an annular, frusto-conical,
cavity, is very small compared to the dimensions of the pin and box surfaces and therefore
only appears as a solid black line in figure 7. The fluid pressure inside the cavity
V causes elastic deformation in the pin member and box member, such that the box member
wall expands radially (see arrows "E" in figure 7) and the pin member is compressed
radially (see arrows "C" in figure 7). This deformation allows the pin member to be
inserted an additional distance d into the box member. At the stage where the box
free end 17 meets the shoulder 14 on the pin member, the fluid pressure is released,
causing the pin and box members to resume their original shape and thus forming a
tight and high-tension connection.
[0056] Figures 8-14 illustrate a second embodiment of the invented coupling assembly. This
embodiment has several similarities to the embodiments described above with respect
to figures 1-7 (and may thus be combined with that embodiment), but exhibits an additional
feature that the pin surface 12 and box surface 13 each comprise radially protruded
portions and radially recessed portions. More specifically, referring initially to
figure 9, the pin surface 12 comprises successive (in the axial direction) circular
and radially protruding portions 18
1-3 (hereinafter referred to as "pin rings") and circular and radially recessed portions
19
1-4 (hereinafter referred to as "pin recesses"). Reference number 8' denotes a seal groove,
in which a seal (not shown) may be arranged as described above with reference to figure
6. It should be understood that metal seals (embedded or inserted) may also be used,
a purpose being to form a frusto-conical annular cavity into which fluids may be injected.
[0057] The box surface 13 comprises successive (in the axial direction) circular and radially
protruding portions 20
1-3 (hereinafter referred to as "box rings") and circular and radially recessed portions
21
1-4 (hereinafter referred to as "box recesses"). It should be understood that the number
of rings and recesses shown in the figure is an example only; as the invention is
equally applicable to any number (i.e. also one) of rings and recesses.
[0058] As is readily apparent from the figures, the axial widths of the pin rings 18
1-3 and pin recesses 19
1-4 decrease in the direction towards the pin free end 15; that is, the widths are greater
in the region of the pin shoulder 14 than in the region of the pin free end 15. Conversely,
the axial widths of the box rings 20
1-3 and box recesses 21
1-4 increase in the direction towards the box free end 17; that is, the widths are smaller
in the region of the box inner shoulder 16 than in the region of the box free end
17 (opening). This is illustrated in figure 14, in which w
1 represents the largest width, w
2 represents a width smaller than w
2, and w
n represents the smallest width. Thus, the larger widths are associated with the larger
diameter of the frusto-conical shape of the pin and box surfaces, and the smaller
widths are associated with the smaller diameter of the frusto-conical shape of the
pin and box surfaces.
[0059] The rings and recesses serve as individual abutment surfaces. Any pin ring 18
n is shaped and dimensioned to fit with a designated box recess 21
n, and any box ring 20
n is shaped and dimensioned to fit with a designated pin recess 19
n. This is illustrated in figure 13. Such key-and-lock concept (hereinafter referred
to as "Key-Loc") ensures that all ring- and-recess pairs must be aligned before the
initial mating is complete. The regions on the pin and box furnished with the above-mentioned
rings and recesses will thus be referred to as "Key-Loc" regions K (see e.g. figure
14). The "Key-Loc" concept contributes to the axial/tensile strength and/or torque
performance of the connected coupling. In addition, the "Key-Loc" concept contributes
to avoiding progressive failure mechanisms, such as micro-slip, from occurring under
repetitive loading cycles, especially in a so-called "dog leg" situation during directional
drilling.
[0060] In the embodiment illustrated in figures 17, 18a and 18b, portions of the pin 5 and
box 6 are (in the region of the respective surfaces 12, 13) formed with wall thicknesses
that are thinner than the wall thicknesses of adjacent portions. In these figures,
the region R
b of the box 6 has a wall thickness t
a which is less than the thicknesses t
b, t
c of the adjacent box walls. Similarly, the region R
p of the pin 5 has a wall thickness t
d which is less than the thicknesses t
e, t
f of the adjacent pin walls. It should be noted that t
a and t
d do not have to be constant. It should be noted that the regions R
b, R
p of reduced wall thickness generally correspond with the respective pin and box contact
surfaces (e.g. reference numbers 12, 13; cf. above described embodiments). In figures
17, 18a and 18b, the regions R
b, R
p correspond to the above-mentioned pin and box "Key-Loc" regions. It will be understood
that the walls of reduced thickness (t
a, t
d) will deform elastically relatively more than the adjacent walls when fluid is applied
between the pin and box to make or break a connections as described above with reference
to figures 6 and 7. This "ballooning" effect is particularly advantageous as the enhanced
elastic deformation in these regions allows the "Key-Loc" rings and recesses to be
more pronounced (i.e. taller and deeper) that what is possible if the wall thicknesses
are uniform. Although not illustrated, it should be noted that a similar elastic deformation
("ballooning" effect) may be achieved if the material in the region R
b, comprises a material of a lower modulus of elasticity than that of a corresponding
region R
p of the pin. It will be understood that such material properties may be combined with
the reduced wall thicknesses. Although not illustrated, it should be understood that
the "ballooning" effect may be achieved (although to a lesser extent) if only the
pin or the box is furnished with such regions of reduced wall thickness.
[0061] Figures 19a and 19b illustrate another friction-enhancing device, in the form of
a friction sleeve 24 which may be arranged on the free end of the pin surface 12,
outside of the "Key-Loc" region K. The friction sleeve may comprise a coating of a
friction-enhancing materials (e.g. diamond coating) which per se is known in the art.
The coating may be applied on both sides of the sleeve 24. Although figures 19a and
19b illustrate the friction sleeve in conjunction with a pin and box having "Key-Loc"
regions, it should be understood that the friction sleeve may be installed on other
embodiments as well, for example the embodiment described above with reference to
figures 1-5.
[0062] Figure 20 illustrates an alternative embodiment of the invented pin, having a stepped
pin surface, such that the pin surface radius is diminishing, in steps, towards the
pin free end 15. In figure 20, three pin surfaces 12a, 12, 12c are shown, but it should
be understood that more or fewer stepped surfaces are possible. The pin free end 15
and the transition between each step comprise a chamfered portion 25. Although not
illustrated, it should be understood that the box surface will have a corresponding
stepped surface. It should also be understood that the pin surfaces 12a-c may be cylindrical,
or frusto-conical. In the latter case, the pin taper angles increase towards the pin
free end, and the box taper angles decrease correspondingly. One or more of the pin
surfaces may also comprise a "Key-Loc" region.
[0063] Figures 21, 22, 23 illustrate an embodiment of a pin-and-box coupling having dual
seals. The figures illustrate two seal grooves 8a, 8b in the box surface (but it should
be understood that a corresponding seal configuration may be incorporated in near
the pin free end. It should also be understood that the figures illustrate the seal
grooves only, but the skilled person will understand that appropriate seals may be
installed in the grooves 8a,b. Seals may also be integrated in the pin and box, as
described above. It should also be understood that more than two seals may be included.
A purpose of the dual seals, which is particularly visible in figure 23, is to preserve
the sealing function the pin (or box) slides across a protrusion ("ring") or recess.
[0064] Figures 24 and 25 illustrate an embodiment in which electrical wires 26 extending
along the tubular (or shaft) 1 and terminating at a ring contact 27a on the pin 5
(a corresponding ring contact is arrangen inside the box; not shown). The wires (or
cables) may be connected by a metal-to-metal or plug-and-socket connection when the
pin and box are mated. Although not illustrated, it should be understood that the
contact rings may be arranged at one or more selected pin/box rings or recesses, whereby
the electrical contacts may serve as a tool for verifying proper connection between
the pin and box. Figure 26 illustrates a similar configuration, illustrating how several
wires (indicated as 28a,b) may be connected to a contact surface. It should be understood
that a plurality of wires and contacts may be incorporated in the pin and box. It
should also be understood that the wires may be embedded in the tubular wall or be
arranged inside the tubular (or shaft).
[0065] The mating sequence of the embodiments of the coupling assembly described above,
including the injection of pressurized hydraulic fluid in order to temporarily elastically
deform the desired region of the pin member and box member, is performed as described
above with reference to figures 6 and 7.
[0066] In all of the embodiments described above, break-out is accomplished by applying
a suitable liquid pressure through one (or more) of the conduits (9; 9') similarly
to the procedure explained above, whereupon the pin may be released (and withdrawn)
from the box.
[0067] In all of the embodiments described above, the invented coupling assembly is without
conventional threads and therefore requires no rotation during connection or disconnection.
The time required to connect and disconnect the coupling is therefore reduced significantly.
By injecting the hydraulic fluid between the frusto-conical pin surface and box surface,
elastic expansion of the box member and elastic compression of the pin member is accomplished,
which enables a completion of the connection.
[0068] Concurrent with the injection of fluids, the pin and box are pushed further together.
There should be a correlation between the axial forces, pushing the pin into the box,
and the injection pressure, in order to create optimal conditions for the seals, pin
member 5 and box member 6 and prevent plastic deformation of the coupling assembly.
Thus, during the assembly procedure, the axial force (provided by handling tools)
and the fluid injection pressure need to be balanced. Due to the frusto-conical shape
of the coupling, an increase in the fluid injection pressure will cause an increased
axial reaction (separation) force. To overcome the separation tendencies, a correlating
axial assembly force must be applied. This assembly force will always have a predefined
value which must be sufficient to overcome the separation force and to ensure that
the seals engagement clearance is within design limits. The assembly data will be
a part of the coupling operation verification.
[0069] When the pin and box surfaces meet and further advancement is not possible, due to
contact between the pin member shoulder 14 and box free end 17, the hydraulic pressure
between the pin and box surfaces is released, whereby the coupling is locked by means
of circular preload and friction. Using the enveloping contact surface will remove
restrictions associated with traditional API/DSC threaded connections. The invented
coupling assembly will also allow the pipe joint cross-section to be reduced, as there
is no need for traditional iron-roughneck, manual rig tongs or bucking units. Onsite
handling challenges are therefore mitigated.
[0070] The hydraulic friction coupling as described above will also allow drilling of significantly
longer and deviated wellbores, as friction loss by circulating drilling fluid is reduced,
and the torque capacity of the pipe joint is increased. The invented coupling assembly
will also lower the sequence time (make / break) significantly and hence the cost
of drilling.
1. A coupling assembly for elongate elements (1, 2), comprising:
- a pin member (5) having an outward-facing pin surface (12), and a box member (6)
having an inward-facing box surface (13); said pin surface and box surface configured
for mating engagement, and
- at least one bore (9; 9') having as a first opening a port (9a) configured for connection
to an injection fluid reservoir (10) and a second opening (9b) penetrating the pin
surface (12) or the box surface (13);
wherein:
- the pin surface (12) comprises a plurality of pin protruding portions (181-n) separated by pin recessed portions (191-n), and
- the box surface (13) comprises a plurality of box protruding portions (201-n) separated by box recessed portions (211-n); and
wherein a pin protruding portion (18
n) is shaped and dimensioned to fit into a designated box recessed portion (21
n), and
wherein a box protruding portion (20
n) is shaped and dimensioned to fit into a designated pin recessed portion (19
n);
characterized in that:
- the pin protruding portions (181-n), pin recessed portions (191-n), box protruding portions (201-n) and box recessed portions (211-n) are circular portions, extending around the respective surface; and
- the axial widths (wn) of the pin portions (181-n, 191-n) decrease in the direction towards a pin member free end (15), and the axial widths
of the box portions (201-n, 211-n) increase in the direction towards a box member free end (17).
2. The coupling assembly of claim 1, wherein the pin member (5) and the box member (6)
comprise complementary and respective frusto-conical pin and box mating surfaces (12,
13).
3. The coupling assembly of claim 2, wherein the larger widths are associated with the
larger diameter of the frusto-conical shape of the pin and box surfaces, and the smaller
widths are associated with the smaller diameter of the frusto-conical shape of the
pin and box surfaces.
4. The coupling assembly of any one of claims 1-3, further comprising a friction-enhancing
device (24), configured for being arranged on the pin surface (12).
5. The coupling assembly of any one of claims 1-4, wherein the pin surface comprises
a plurality of stepped surfaces (12a-c) of diminishing surface radius towards the
pin free end (15).
6. The coupling assembly of any one of claims 1-5, wherein the box surface comprises
a plurality of stepped surfaces of increasing surface radius towards the box free
end (17).
7. The coupling assembly of any one of claims 1-6, wherein a region (Rb) of the box surface (13) comprises a wall thickness (ta) which is less than the thicknesses (tb, tc) of the adjacent box walls.
8. The coupling assembly of any one of claims 1-7, wherein a region (Rp) of the pin surface (12) comprises a wall thickness (td) which is less than the thicknesses (te, tf) of the adjacent pin walls.
9. The coupling assembly of any one of claims 1-8, wherein a region (Rb) of the box surface (13) comprises a material of a lower modulus of elasticity than
the material of a corresponding region (Rp) of the pin surface (12), or vice versa.
10. The coupling assembly of any one of claims 1-9, wherein the elongate elements (1,2)
comprise tubular elements such as drill pipes or wellbore casings, or axles or shafts.
11. A method of mating the coupling assembly as defined by any one of claims 1-10,
characterized by:
a) performing an initial mating step until a cavity (V) is formed between the first
and second mating surfaces (12, 13);
b) injecting a fluid under pressure into the cavity, and maintaining the fluid pressure
while exerting an axial force to push the first and second mating members (5, 6) a
predetermined distance towards each other;
c) releasing the fluid pressure.
12. The method of claim 11, wherein the fluid pressure and axial force in step b) are
balanced to ensure a predetermined elastic deformation and prevent plastic deformation
in the mating members (5, 6).
13. The method of claim 11 or claim 12, wherein step a) is performed until the pin and
box gaskets or seals engage and facilitates the injection of a fluid between the pin
and the box.
1. Kupplungsvorrichtung für längliche Elemente (1, 2), umfassend:
- ein Stiftelement (5), das eine nach außen gewandte Stiftoberfläche (12) aufweist,
und ein Kastenelement (6), das eine nach innen gewandte Kastenoberfläche (13) aufweist;
wobei die Stiftoberfläche und die Kastenoberfläche zum paarenden Eingriff ausgelegt
sind, und
- mindestens eine Bohrung (9; 9'), die als eine erste Öffnung einen Eingang (9a),
der zur Verbindung mit einem Injektionsfluidbehälter (10) ausgelegt ist, und eine
zweite Öffnung (9b) aufweist, die die Stiftoberfläche (12) oder die Kastenoberfläche
(13) durchsetzt;
wobei:
- die Stiftoberfläche (12) eine Mehrzahl von Stift-vorspringenden Abschnitten (181-n) umfasst, die von Stift-ausgesparten Abschnitten (191-n) getrennt sind, und
- die Kastenoberfläche (13) eine Mehrzahl von Kasten-vorspringenden Abschnitten (201-n) umfasst, die von Kasten-ausgesparten Abschnitten (211-n) getrennt sind; und
wobei ein Stift-vorspringender Abschnitt (18
n) dazu geformt und abgemessen ist, in einen zugewiesenen Kasten-ausgesparten Abschnitt
(21
n) hineinzupassen, und
wobei ein Kasten-vorspringender Abschnitt (20
n) dazu geformt und abgemessen ist, in einen zugewiesenen Stift-ausgesparten Abschnitt
(19
n) hinein zu passen;
dadurch gekennzeichnet, dass:
- die Stift-vorspringenden Abschnitte (181-n), die Stift-ausgesparten Abschnitte (191-n), die Kasten-vorspringenden Abschnitte (201-n) und die Kasten-ausgesparten Abschnitte (211-n) kreisförmige Abschnitte sind, die sich um die jeweilige Oberfläche herum erstrecken;
und
- die axialen Breiten (wn) der Stiftabschnitte (181-n, 191-n) in Richtung eines freien Endes (15) des Stiftelements abnehmen, und die axialen
Breiten der Kastenabschnitte (201-n, 211-n) in Richtung eines freien Endes (17) des Kastenelements steigen.
2. Kupplungsvorrichtung nach Anspruch 1, wobei das Stiftelement (5) und das Kastenelement
(6) komplementäre und jeweilige kegelstumpfförmige Stift- und Kastenpaarungsoberflächen
(12, 13) umfassen.
3. Kupplungsvorrichtung nach Anspruch 2, wobei die größeren Breiten mit dem größeren
Durchmesser der kegelstumpfförmigen Form der Stift- und Kastenoberflächen assoziiert
sind, und die kleineren Breiten mit dem kleineren Durchmesser der kegelstumpfförmigen
Form der Stift- und Kastenoberflächen assoziiert sind.
4. Kupplungsvorrichtung nach einem der Ansprüche 1-3, ferner umfassend eine die Reibung
verbessernde Vorrichtung (24), die zum Anordnen auf der Stiftoberfläche (12) ausgelegt
ist.
5. Kupplungsvorrichtung nach einem der Ansprüche 1-4, wobei die Stiftoberfläche eine
Mehrzahl von gestuften Oberflächen (12a-c) mit einem sich vermindernden Oberflächenradius
in Richtung des freien Endes (15) des Stifts umfasst.
6. Kupplungsvorrichtung nach einem der Ansprüche 1-5, wobei die Kastenoberfläche eine
Mehrzahl von gestuften Oberflächen mit einem steigenden Oberflächenradius in Richtung
des freien Endes (17) des Kastens umfasst.
7. Kupplungsvorrichtung nach einem der Ansprüche 1-6, wobei ein Bereich (Rb) der Kastenoberfläche (13) eine Wanddicke (ta) umfasst, die kleiner als die Dicken (tb, tc) der angrenzenden Kastenwände ist.
8. Kupplungsvorrichtung nach einem der Ansprüche 1-7, wobei ein Bereich (Rp) der Stiftoberfläche (12) eine Wanddicke (td) umfasst, die kleiner als die Dicken (te, tf) der angrenzenden Stiftwände ist.
9. Kupplungsvorrichtung nach einem der Ansprüche 1-8, wobei ein Bereich (Rb) der Kastenoberfläche (13) ein Material mit einem niedrigeren Elastizitätsmodul als
das Material eines entsprechenden Bereichs (Rp) der Stiftoberfläche (12), oder umgekehrt, umfasst.
10. Kupplungsvorrichtung nach einem der Ansprüche 1-9, wobei die länglichen Elemente (1,2)
rohrförmige Elemente umfassen, wie beispielsweise Bohrgestänge oder Bohrlochgehäuse,
oder Wellen oder Achsen.
11. Verfahren zur Paarung der Kupplungsvorrichtung wie definiert in einem der Ansprüche
1-10,
gekennzeichnet durch:
a) Durchführen eines einleitenden Paarungsschrittes, bis eine Kavität (V) zwischen
der ersten und zweiten Paarungsoberfläche (12, 13) gebildet ist;
b) Injizieren eines unter Druck stehenden Fluids in die Kavität, und Aufrechterhalten
des Fluiddrucks, während eine axiale Kraft ausgeübt wird, um das erste und zweite
Paarungselement (5, 6) um eine vorgegebene Strecke gegeneinander zu drücken;
c) Freigabe des Fluiddrucks.
12. Verfahren nach Anspruch 11, wobei der Fluiddruck und die axiale Kraft im Schritt b)
ausgewogen werden, um eine vorgegebene elastische Verformung zu gewährleisten und
eine plastische Verformung in den Paarungselementen (5, 6) zu verhindern.
13. Verfahren nach Anspruch 11 oder Anspruch 12, wobei der Schritt a) durchgeführt wird,
bis die Stift- und Kastendichtungen oder -Versiegelungen in Eingriff gelangen, wodurch
das Injizieren eines Fluids zwischen dem Stift und dem Kasten erleichtert wird.
1. Ensemble de couplage pour des éléments allongés (1, 2), comprenant :
- un élément de broche (5) ayant une surface de broche tournée vers l'extérieur (12),
et un élément de boîte (6) ayant une surface de boîte tournée vers l'intérieur (13)
; ladite surface de broche et la surface de boîte étant configurées pour une mise
en prise d'accouplement, et
- au moins un alésage (9; 9') ayant en tant que première ouverture un orifice (9a)
configuré pour être relié à un réservoir de fluide d'injection (10) et une deuxième
ouverture (9b) pénétrant dans la surface de broche (12) ou la surface de boîte (13)
;
dans lequel :
- la surface de broche (12) comprend une pluralité de parties de broche en saillie
(181-n) séparées par des parties de broche évidées (191-n), et
- la surface de boîte (13) comprend une pluralité de parties de boîte en saillie (201-n) séparées par des parties de boîte évidées (214-n) ; et
une partie de broche en saillie (18
n) étant formée et dimensionnée pour s'ajuster dans une partie de boîte évidée et désignée
(21
n), et
une partie de boîte en saillie (20
n) étant formée et dimensionnée pour s'ajuster dans une partie de broche évidée et
désignée (19
n) ;
caractérisé en ce que :
- les parties de broche en saillie (181-n), les parties de broche évidées (191-n), les parties de boîte en saillie (201-n) et les parties de boîte évidées (211-n) sont des parties circulaires s'étendant autour de la surface respective ; et
- les largeurs axiales (wn) des parties de broche (181-n, 191-n) diminuent dans la direction vers une extrémité libre d'élément de broche (15), et
les largeurs axiales des parties de boîte (201-n, 211-n) augmentent dans la direction vers une extrémité libre d'élément de boîte (17).
2. Ensemble de couplage selon la revendication 1, dans lequel l'élément de broche (5)
et l'élément de boîte (6) comprennent des surfaces d'accouplement de broche et de
boîte tronconiques (12, 13) complémentaires et respectives.
3. Ensemble de couplage selon la revendication 2, dans lequel les plus grandes largeurs
sont associées au plus grand diamètre de la forme tronconique des surfaces de broche
et de boîte, et les plus petites largeurs sont associées au plus petit diamètre de
la forme tronconique des surfaces de broche et de boîte.
4. Ensemble de couplage selon l'une quelconque des revendications 1 à 3, comprenant en
outre un dispositif d'amélioration de frottement (24) configuré pour être disposé
sur la surface de broche (12).
5. Ensemble de couplage selon l'une quelconque des revendications 1 à 4, dans lequel
la surface de broche comprend une pluralité de surfaces étagées (12a-c) de rayon de
surface décroissant vers l'extrémité libre de broche (15).
6. Ensemble de couplage selon l'une quelconque des revendications 1 à 5, dans lequel
la surface de boîte comprend une pluralité de surfaces étagées de rayon de surface
croissant vers l'extrémité libre de boîte (17).
7. Ensemble de couplage selon l'une quelconque des revendications 1 à 6, dans lequel
une région (Rb) de la surface de boîte (13) comprend une épaisseur de paroi (ta) qui est inférieure aux épaisseurs (tb, tc) des parois de boîte adjacentes.
8. Ensemble de couplage selon l'une quelconque des revendications 1 à 7, dans lequel
une région (Rp) de la surface de broche (12) comprend une épaisseur de paroi (td) qui est inférieure aux épaisseurs (te, tf) des parois de broche adjacentes.
9. Ensemble de couplage selon l'une quelconque des revendications 1 à 8, dans lequel
une région (Rb) de la surface de boîte (13) comprend un matériau d'un module d'élasticité inférieur
à celui du matériau d'une région correspondante (Rp) de la surface de broche (12), ou vice versa.
10. Ensemble de couplage selon l'une quelconque des revendications 1 à 9, dans lequel
les éléments allongés (1,2) comprennent des éléments tubulaires tels que des tiges
de forage ou des tubages de puits de forage, ou des essieux ou des arbres.
11. Procédé d'accouplement de l'ensemble de couplage tel que défini par l'une quelconque
des revendications 1 à 10,
caractérisé par :
a) la réalisation d'une étape d'accouplement initiale jusqu'à ce qu'une cavité (V)
soit formée entre les première et deuxième surfaces d'accouplement (12, 13) ;
b) l'injection d'un fluide sous pression dans la cavité, et le maintien de la pression
de fluide tout en exerçant une force axiale pour pousser les premier et deuxième éléments
d'accouplement (5, 6) à une distance prédéterminée l'un vers l'autre ;
c) la libération de la pression de fluide.
12. Procédé selon la revendication 11, dans lequel la pression de fluide et la force axiale
dans l'étape b) sont équilibrées pour assurer une déformation élastique prédéterminée
et empêcher une déformation plastique dans les éléments d'accouplement (5, 6).
13. Procédé selon la revendication 11 ou la revendication 12, dans lequel l'étape a) est
réalisée jusqu'à ce que les joints d'étanchéité et scellements de broche et de boîte
viennent en prise, facilitant l'injection d'un fluide entre la broche et la boîte.