Electromechanical actuator for use under water

An electromechanical actuator with a through-going center passage for use under water, wherein the motor and transmission elements are arranged in parallel with and are via dog elements mechanically coupled to the axially displaceable elements through a scaling partition. A hydraulic axially displaceable piston ring facilitates secondary release of locking segments in a coupling device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage application of International Application PCT/NO2021/050161, filed Jul. 5, 2021, which international application was published on Jan. 13, 2022, as International Publication WO 2022/010360 in the English language. The International Application claims priority of Norwegian Patent Application Nos. 20210760, filed Jun. 11, 2021 and 20200771, filed Jul. 6, 2020. The international application and Norwegian applications are all incorporated herein by reference, in entirety.

FIELD

The invention concerns an electromechanical actuator for use under water, more specifically wherein an annulus is formed between an actuator housing and a partition, the annulus being delimited in a fluid-sealing manner against a centre passage in the actuator, an electric ring motor is arranged enclosed in the annulus, an axially displaceable actuator element that is enveloped by the partition is displaceable along an internal partition portion between a first position and a second position, and a transmission element is arranged in the annulus axially displaceable along an external partition portion and is connected to the electric ring motor via an assembly of further transmission elements. The invention concerns means for transferring the actuator element's axial displacement to actuate one or more elements that surround a centre passage of the actuator.

BACKGROUND

In connection with petroleum extraction at sea it is necessary to be able to manoeuvre actuators that are provided with a centre passage to facilitate through-flow of fluid as well as to allow passage of equipment in connection with various work operations. These are included in other types of subsea equipment like well barrier equipment such as blow-out preventers for drilling and well completion and in subsea production trees for oil and gas production. For these uses, coupling devices are used to lock the equipment in a sealing manner to a subsea well head or for sealing connection of equipment modules. Ring piston actuators are also used for radial compression of a sealing element that can for example grip around a drill string in a sealing manner.

Subsea well barrier equipment and related coupling devices have traditionally been operated hydraulically. Hydraulic operation usually requires hydraulic lines to be fed from the surface. To reduce system complexity and weight, eliminate hydraulic distribution and leakage issues, eliminate the need for hydraulic fluid and obtain increased control functionality, efforts are being made to replace hydraulic actuation with electromechanical actuation of the equipment.

Due to said and other disadvantages of hydraulic systems, electromechanical actuators for use under water have been developed. Such actuators are typically characterised by the fact that they are supplied with several drive systems and are arranged to be manoeuvrable by means of an external rotation unit, for example by a rotation actuator on a remote operated vehicle (ROV).

WO2013/119127 A1 describes an electromechanical actuator that via an actuation element respectively locks or releases a coupling device or compresses or unloads a flexible sealing element. The actuated locking segments, alternatively the sealing element, are placed at an end of an outer housing, while a ring motor and transmission elements are axially displaced in relation to these. Several guide bolts are attached to the actuation element at its one end portion, and extend in the actuator's axial direction through respective bores in an end portion of the actuator housing, the guide bolts being coupled to a locking ring at their opposite end portion. Such a construction is not optimal for minimising the total length of the assembly.

SUMMARY

The object of the present invention is to facilitate a geometry where a locking device, alternatively a ring piston, is arranged in parallel with the engine and the transmission elements, as well as provide a hydraulic function for an alternative release of the locking device.

The object is fulfilled by features specified in the description below and subsequent patent claims.

An electromechanical actuator for use under water is provided with an electric ring motor that comprises an annular stator and an annular rotor and related transmission elements arranged in a tight, oil-filled annulus in an actuator housing. The transmission elements may comprise a rolling nut that is directly coupled to the ring motor and is in threaded engagement with an actuation ring. Alternatively the transmission elements may include a planetary gear between the engine and a rolling nut in threaded engagement with an actuation ring.

The annulus is delimited by the actuator housing and a partition that seals against a centre passage in the actuator, where actuatable elements are arranged. In an embodiment, the actuatable elements are made up of a number of locking segments that are enclosed by a locking ring that sealingly abuts an inside of the partition and can be moved axially via a mechanical connection through the partition of the actuation ring, which in turn sealingly abuts an outside of the partition. In an alternative embodiment, the locking ring can if necessary be pushed back by means of a hydraulic axially displaceable piston ring arranged at an end portion of the actuator housing. In an alternative embodiment of the actuator, a ring piston sealingly abuts the inside of the partition and is arranged to be able to compress a flexible, annular sealing element as the ring piston is moved axially via a mechanical connection through the partition of the actuation ring.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

More specifically, the invention concerns an electromechanical actuator for use under water, whereinan annulus is formed between an actuator housing and a partition, the annulus being delimited in a fluid-sealing manner against a centre passage in the actuator,an electric ring motor is arranged enclosed in the annulus,an axially displaceable actuator element that is enveloped by the partition is dis-placeable along an internal partition portion between a first position and a second position,a transmission element is arranged in the annulus axially displaceable along an external partition portion and is connected to the electric ring motor via an assembly of further transmission elements,
characterised in thatthe axially displaceable actuator element is connected to the axially dis-placeable transmission element by one or more dog elements that extend in the radial direction of the actuator through respective slits in the partition,each slit having an extent in the axial direction of the actuator that facilitates a displacement of the respective dog element in the axial direction of the actuator in accordance with the axially displaceable actuator element's said first and second position.

A first end portion of the at least one dog element may be in engagement with a recess in the actuation ring, and a second end portion of the at least one dog element may be in engagement with an assembly channel in the axially displaceable actuator element. An advantage of this is that the at least one dog element can be guided to engagement with the actuation ring and the axially displaceable actuator element from the centre passage.

The second end portion of the at least one dog element may be arranged to be held in a recess in the assembly channel by a plug being inserted into the assembly channel for locking engagement with the assembly channel and the second end portion of the dog element. An advantage of this is that the at least one dog element is locked from the centre passage.

The axially displaceable actuator element may be a locking ring arranged for radial movement by locking segments that are arranged in the centre passage of the actuator. An advantage of this is that the actuator can be used to grip, hold and release an element that has been inserted into the centre passage of the actuator.

The locking ring may be provided with radially inward-protruding, heightened first and second end collar portions that are arranged to abut in a supporting manner radially outward-facing side faces and end portions of the locking segments, said end collar portions, in the locking ring's first, locking end position, being arranged to abut against the locking segments' outward-facing side face and the locking segments' heightened second end portion, the locking elements being pushed radially inwards to a gripping position, and said end collar portions, in the locking ring's second, releasing end position, are arranged to abut against the locking segments' tapered first end portion and the outward-facing side face, the locking elements being pulled radially outwards to a non-gripping position. An advantage of this is that the gripping and releasing function of the actuator is directly and unequivocally related to the two end positions of the locking ring.

A hydraulic, axially displaceable piston ring that surrounds a cylindrical end portion of a neck on a coupling flange may be arranged to push a locking ring in the axial direction of the actuator to release the locking segments' locking grip on an element disposed in the centre passage of the actuator. An advantage of this is that the actuator is set more quickly into its releasing state.

The axially displaceable actuator element may be a ring piston arranged to compress an annular sealing element against an end cover at an end portion of the centre passage of the actuator. An advantage of this is that the actuator can be arranged for alternative use.

DETAILED DESCRIPTION OF THE DRAWINGS

All position indicators refer to the position shown on the figures.

Similar or corresponding elements are specified with the same reference number on the figures. For the sake of clarity some elements may be shown without reference numbers on some of the figures.

A skilled person will understand that the drawings are only principle drawings. The relative sizes of the different elements may be distorted.

On the drawings the reference number1indicates an annular actuator arranged in a cylindrical actuator housing2.

Reference is first made toFIGS.1,2,3aand3b, which show axial sections, respectively radial sections through the actuator1, wherein the actuator housing2is formed of a cylindrical external wall2a, which at a first end portion is releasably coupled to an assembly flange2band at a second end portion is releasably coupled to a coupling flange2f. The assembly flange2bis provided with an assembly flange neck2cthat protrudes inwards in the actuator housing2. The coupling flange2fis provided with a coupling flange neck2gwith an external cylindrical end portion2h. The coupling flange neck2gprotrudes inward in the actuator housing2. The assembly flange2bis arranged for connection with a subsea equipment module that is not shown here. The coupling flange2fis arranged for connection with a well head that is not shown here. The actuator1is provided with a through-going, axial centre passage8.

A number of locking segments10are distributed about the assembly flange neck2c. The locking segments10are provided with radially inward-facing locking portions10ethat are in engagement with corresponding engagement portions2don the periphery of the assembly flange neck2cand are kept in place by a first axially displaceable element, herein shown as a locking ring14. Each locking segment10has a first end portion10bwith an outward-facing side face10a, wherein the end portion10bis tapered in a radial direction, and opposite the first end portion10b, a second end portion10cthat is heightened in a radial direction. A locking segment portion that freely faces the centre passage8between the necks2c,2gof the assembly flange4and the coupling flange6, forms gripping surfaces10dthat are toothed or in some other way formed to abut in a locking manner an element that is to be held in a fixed grip.

The locking ring14has an external cylindrical shape and is provided internally with radially inward-protruding, heightened first and second end collar portions14a,14bthat are arranged to supportingly abut against the locking segments'10outward-facing side faces10aand end portions10b,10c. In a first, locking end position, as shown onFIG.1, said end collar portions14a,14babut against the locking segments'10outward-facing side face10aand the heightened second end portion10c. In a second, releasing end position said end collar portions14a,14babut against the locking segments'10tapered first end portion10band the outward-facing side face10aand allow the locking elements10with its gripping surfaces10dto pull radially outwards to a non-locking position.

In an annulus2idelimited by the actuator housing2and a cylindrical partition16that in a fluid-sealing manner delimits the actuator housing2against the actuator's1centre passage8, an electric ring motor18with an external, annular stator20and an internal, annular rotor22is arranged. The partition16can be demountable. The stator20is attached to the actuator housing2. An electromagnetic brake (not shown) with a brake coil is supplied with energy when the motor18is started up, whereby a friction ring that normally abuts the rotor22is released and frees the rotor22for rotation.

The annulus2iis filled with a fluid, typically a silicone oil, and is pressure-compensated against an actuator-surrounding water pressure by means of an elastic pressure compensator24that communicates with the annulus2ivia a channel26through the assembly flange2b.

A first transmission element in the form of a rolling nut28is arranged radially inside the rotor22and is attached to it. The rotor22is together with the rolling nut28supported in a radial and axial direction by means of rotor bearings30arranged at the end portions of the rotor22and the rolling nut28. The rolling nut28rotates together with the rotor22.

The rolling nut28is provided with second transmission elements in the form of axially arranged, supported thread rollers36. The thread rollers36that are arranged to be able to rotate freely about their own length axis in the rolling nut28, are distributed about and are engaged with external threads on an actuation ring38. The actuation ring38surrounds a portion of the partition16and is displaceable in the axial direction of the partition16. The rolling nut28, the thread rollers36and the actuation ring38, possibly in combination with the planetary gear32(seeFIG.2), thereby comprises transmission elements for conversion of a torque provided by the ring motor18to axial displacement of the actuation ring38.

As shown inFIG.2, a third transmission element in the form of a planetary gear32can be disposed between the rotor22and the rolling nut28, which in this embodiment is supported in a radial and axial direction by means of thereto appropriate rotor bearings34.

The actuation ring38, which abuts in a sealing manner the outside of the partition16, is coupled to the locking ring14that abuts in a sealing manner the inside of the partition16and surrounds the locking segments10. The connection between the locking ring14and the actuation ring38is formed by dog elements40that extend through slits42in the partition16to a locking engagement in the actuation ring38and the locking ring14. The dog elements40are shown herein with a plate shape with a width extent in the axial direction of the actuator1and a length extent in the radial direction of the actuator1. The slits42have an axial extent (height) that is greater than the width of the dog elements40and thereby allow the dog elements40to be displaceable in the axial direction of the actuator1, the peripheral extent (width) of the slits42exceeding the thickness of the dog elements40. The support of the dog elements40against the side edges of the slits42prevent rotation of the actuation ring38. When the actuation ring38is displaced in the axial direction of the actuator1by the ring motor18putting the rolling nut28into rotation, the axial displacement of the actuation ring38is transferred to the locking ring14via the dog elements40. The locking ring14thereby causes a radial displacement of the locking segments10between a gripping and a releasing position, the gripping surfaces10dbeing pushed radially towards or pulled radially away from a correspondingly designed portion of a well head profile (not shown) in the centre passage8.

FIG.3bshows in greater detail the connection of the actuation ring38and the locking ring14by means of the dog element40. When openings in assembly channels48in the locking ring14, respective slits42in the partition16and respective recesses50in the actuation ring38are lined up, the dog elements40are pushed in through these until a first end portion40abottoms out in the recesses50. Each assembly channel48in the locking ring14is designed with a recess48anext to the through-going opening. The purpose is for a second end portion40bof the dog elements40to be able to be brought into the respective recesses48aby rotating the locking ring14until it stops against a side face40cof each dog element40. The open side of each assembly channel48is then closed by a plug52. The dog elements40are thereby locked inside the recesses50in the actuation ring38and the recesses48ain the assembly channel48of the locking ring14respectively.

The locking segments10may hinder assembly of the dog elements40. This can be solved by at least one of the locking segments10being provided with an opening (not shown) for insertion of the dog elements40and the plugs52through said at least one locking segment10. The locking segments10hang in loose engagement with the engagement portion2don the inward-protruding assembly flange neck2c, and can be displaced along the engagement portion2dto provide access for assembly of the dog elements40via the opening in said at least one locking segment10. As an alternative to providing said at least one locking segment10with the through-going opening that is not shown, the locking segments10can be arranged with a certain clearance so that the locking segments10can be pushed together during assembly so as to form an adequate opening between two locking segments10for access to assembly of the dog elements40in the coincident openings formed by the assembly channel48in the locking ring14, the slit42in the partition16and the recess50in the actuation ring38, as well as insertion of the plugs52for locking the dog elements40.

Reference is now made toFIG.4, which shows an alternative embodiment example of the actuator1for cooperation with a sealing device in a blow-out preventer. The actuator housing2is here shown in an alternative embodiment, wherein the assembly flange2baccording toFIGS.1and2is replaced with an end cover2jthat forms an end portion of the centre passage8. The ring motor18and the transmission elements28,36and38as well as the dog elements40are arranged as described above, while the locking ring14according toFIGS.1-3bis replaced with a ring piston44that sealingly abuts the partition16.

The ring piston44is arranged to be axially displaceable by the dog elements40to compress, respectively unload a flexible, annular sealing element46that abuts in a supporting manner the end cover2j. Like the arrangement described above, the dog elements40are pushed in through assembly channels44ain the ring piston44, through the slits42in the partition16and into the recesses50in the actuation ring38. The dog elements40are locked in the cavities in the actuation ring38and the ring piston44respectively by a ring54that is fixed to and sealingly abuts an inside of the ring piston44.

Reference is again made toFIGS.1and2. A hydraulic axially displaceable piston ring56is arranged between the inside of the partition16and the external cylindrical end portion2hof the coupling flange neck2g. When an underside56aof the piston ring56is pressurised, the piston ring56pushes the locking ring14to the releasing second end position relative to the locking segments10and at the same time drives the transmission elements28,36,38, respectively28,32,36,38, and the ring motor18in reverse, while the motor brake that is not shown is overcome.

Reference is then made toFIGS.1and2, which show rotatable coupling devices58for coupling to an external rotation actuator that is not shown, for example a motor on a remote operated vehicle (not shown). The coupling devices58can, when needed, drive the transmission elements28,36,38, respectively28,32,36,38. The rotatable coupling devices58can optionally be operated in parallel with the hydraulic piston ring56being pressurised to push the locking ring14to a releasing position relative to the locking segments10.

Necessary seals are not described, but are known to a skilled person.

It should be noted that all embodiments mentioned above illustrate the invention, but do not delimit it, and experts on the area will be able to design many alternative embodiments without deviating from the scope of the attached claims. In the claims, the reference numbers in parenthesis shall not be considered delimiting.

The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles “a” or “an” before an element do not exclude the presence of more such elements.

The fact that some features are specified in mutually different dependent claims does not indicate that a combination of these features cannot be used advantageously.