Patent Description:
The invention further relates to a method of overriding a malfunctioning valve operating device.

Normally actuators are used in a variety of applications, such as in operating subsea valves. The actuators normally have all required functions necessary to operate the valve, including a system for receiving a control signal for operating the valve as well as a source of energy. The control signal may be of relatively low energy and may, at least for subsea use, be e.g. electric voltage or current, pneumatic, or hydraulic fluid pressure. The energy source may be an electric current, hydraulic pressure, or pneumatic pressure. When the energy source receives a control signal, an actuator responds by converting the source's energy into mechanical motion thereby operating the valve.

Subsea X-mas trees normally comprise a number of pressure-tight fluid-barriers ensuring that the fluid and thus the pressure in the well is kept under control. However, from time to time the X-mas trees need maintenance or need to be pulled to surface for other reasons. In such situations, the barriers formed by the X-mas trees against uncontrolled release of well fluids are removed and have to be replaced by other temporary barriers. Such temporary barriers are normally installed in pressure containing bores below the X-mas tree, and this is done by accessing the area below the X-mas tree through dedicated bores in the X-mas tree. Accessibility to the well through the dedicated bores is allowed or restricted using one or more valves arranged at different locations of the individual dedicated bores. The valves, such as e.g. gate valves, normally move between two operating positions, which two positions corresponds to a) an open position of the valve where the bore is open (i.e. the area below the valve is accessible), and b) a closed position of the valve where the bore is closed (i.e. the area below the valve is not accessible).

Prior art includes <CIT> which relates to a valve assembly. The assembly comprising a valve housing; an inlet for fluid entering the valve housing; an outlet for fluid leaving the valve housing; a flow control assembly disposed within the valve housing between the inlet and the outlet, whereby fluid entering the valve housing is caused to flow through the flow control assembly, the flow control assembly comprising a cage having apertures therethrough to provide passage for fluid passing from the inlet to the outlet.

For tree retrieval it is necessary to have access through vertical bore(s) and to be able to vent eventual pressure in annulus.

It is an objective of the invention to be able to operate a valve to an open position in case of failure of the operating mechanism in order to secure access to the area below the valve.

The invention is set forth in the independent claims, while the dependent claims define other characteristics of the invention.

The valve operating device and methods of overriding it may provide a solution for opening a valve to get access to the well below in case the valve operating device malfunctions. The override solutions provided herein are thus only used in case all other operating procedures for opening the valve fails. In other words, in case an operator is unsuccessful in opening, e.g. a valve to gain access to a well below the valve, and all attempts for normal operation of the valve operating device fails, the solution and methods described herein may be used as a final solution to open the valve. Once the valve operating device has been subject to the described methods herein, it is not able to perform its required function anymore and the tree has to be retrieved. the overriding solution is irreversible.

The override solution according to the invention provides a setup and methods for machining out a core of a rotational shaft, e.g. an operator spindle, of a valve operating device which ensures that the rotational shaft separates in two parts such that a valve connected to the shaft can be operated even if the valve operating device malfunctions.

It is described a valve operating device for operating a subsea valve, the valve operating device comprises:.

The connection parts of the thrust bearings and the rotational shaft are preferably complementary shaped. For example, the connection part of the thrust bearings may be a recess and the connection part of the rotational shaft can be a complementary shaped rib. Alternatively, the connection part of the thrust bearings may be a rib and the connection part of the rotational shaft can be a complementary shaped recess. In this latter example, the recess in the first portion of the rotational shaft may function as a weakened part of the rotational shaft.

The valve operating device is preferably connectable to an actuator, e.g. an electric actuator. The actuator typically has a rotating interface towards the external interface of the rotational shaft. The valve operating device is thus configured to convert rotational movement from a valve actuator connectable to the external interface to a linear movement of the valve stem.

The threaded connection formed by the threaded portion of the rotational shaft and the threaded portion of the linear shaft translates rotational movement of the rotational shaft to linear movement of the linear shaft. The rotational movement of the rotational shaft may be formed by rotation of the actuator.

In one aspect, the first portion of the linear shaft may encircle the second portion of the rotational shaft. The threaded portion of the linear shaft may be internal threads and the threaded portion of the rotational shaft may be external threads.

In another aspect, the second portion of the rotational shaft may encircle the first portion of the linear shaft. The threaded portion of the linear shaft may then be internal threads and the threaded portion of the rotational shaft may be external threads.

The valve operating device may operate a valve in a subsea valve tree. The subsea valve tree may be an electric tree, as well as a so-called all electric subsea valve tree. An all-electric subsea valve tree form part of an all-electric subsea well. The all-electric subsea well is defined as comprising an electric subsea valve tree (i.e. X-mas tree), electric downhole safety valve, and associated subsea control modules, where valve control is established via an electric cable.

Alternatively, the valve operating device can operate or can be connected to a subsea valve on a flow line, or a valve on a manifold.

In order to prevent rotation, the first and second part of the linear guide can form a key or spline connection.

The pre-machined hole extends from the first end of the rotational shaft, i.e. from the external interface for connection to e.g. an actuator, and along a center axis of the rotational shaft. The pre-machined hole facilitates machining of a core of the rotational shaft in that it may serve as a guide for a machining tool during machining such as drilling or milling.

The part of the axial length of the rotational shaft that the pre-machined hole extend, may preferably be the length from the first end and to or past the connection part of the rotational shaft.

The rotational shaft may form a sealing connection to the housing. The first portion of the rotational shaft may via a sealing gland on the rotational shaft be received in a groove in the housing (or vice versa).

The intermediate portion may comprise a weakened part. The weakened part may be positioned on a part of the intermediate portion which is within the inner chamber.

The weakened part may be formed by a reduction in an outer diameter of the rotational shaft. By reducing the diameter of the rotational shaft at the weakened part, i.e. by providing a "weak link" in the rotational shaft, it may be easier to break or separate the rotational shaft in case an override operation is required.

The connection part of the rotational shaft may be a recess with a reduced diameter and the weakened part may be formed by the recess. , the recess may form the weakened part.

The weakened part may be arranged at the connection part of the rotational shaft or at a position further away from the external interface than the connection part of the rotational shaft. By arranging the weakened part at any of these positions, the operator is insured, in case of an override operation, that the rotational shaft breaks or separates at a position where the connection between the connection part on the thrust bearings and the connection part on the rotational shaft no longer prevents axial movement of the rotational shaft. By ensuring that the rotational shaft separates closer to the valve than the thrust bearings, the probability of a successful override of the valve operating device is increased because the operator then knows that there are no longer any axial obstructions preventing movement of the rotational shaft, and thus, the valve stem connected to the valve can be pushed enabling override operation of the valve to a desired position. It may be advantageous to position the weakened part further away from the external interface than the connection part of the rotational shaft, but as close to the connection part of the rotational shaft for any later override machining operation to be as short as possible.

Alternatively, the rotational shaft may be formed of three separate parts, where the middle part, i.e. the intermediate portion, may be formed of a different material than the two end parts of the rotational shaft. The middle part may be of a more brittle and/or a weaker material such that upon machining through the core of the rotational shaft, the middle part breaks before the two end parts ensuring that the override functionality can be obtained. The middle part may then function as a weak link for the rotational shaft.

The intermediate portion may comprise a weakened part.

It is further described a method of overriding a malfunctioning valve operating device as defined above, wherein the method comprises the steps of:.

The desired position can be an open or closed position depending of valve configuration, i.e. normally open or normally closed valve. For example, the desired position can be an open position such as to secure access to the well below the valve tree.

In one aspect, the machining unit can be a drilling unit and the machining tool can be a drill bit. In another aspect, the machining unit can be a milling unit and the machining tool can be a milling tool.

It is further described a subsea valve tree comprising a subsea valve and a valve operating device as described above.

The term "releasing the second portion of the rotational shaft from the first portion of the rotational shaft and thus the outer housing" involves breaking the material of the rotational shaft such that the second portion physically separates from the first portion of the rotational shaft. When the second portion separates from the first portion it is consequently released from its engagement with the thrust bearings and the housing and is free to move axially relative the first portion and the thrust bearings.

The step of releasing the second portion of the rotational shaft from the first portion of the rotational shaft may comprise:.

Alternatively, the step of releasing the second portion of the rotational shaft from the first portion of the rotational shaft may comprise:.

In yet a further alternative, the step of releasing the second portion of the rotational shaft from the first portion of the rotational shaft may comprise:.

The method may comprise, prior to the step of connecting the machining unit with a machining tool to the external interface of the rotational shaft, a step of:.

The step of removing the actuator may be necessary in order to make space for connection of the machining unit to the external interface.

It is further described a subsea valve tree comprising a subsea valve and a valve operating device as defined above.

It is further described a valve operating device for operating a subsea valve, the valve operating device comprises:.

the intermediate portion comprises a weakened part.

Features of the weakened part may be similar to the features described in relation to the weakened part above.

The relative terms "upper", "lower", "below", "above", "higher" etc. shall be understood in their normal sense and as seen in a cartesian coordinate system. When mentioned in relation to seabed, "upper" or "above" shall be understood as a position closer to the water surface (relative to another component), contrary to the terms "lower" or "below" which shall be understood as a position further away from the water surface (relative another component).

It is obvious for the person skilled in the art that the different features in the different aspects or embodiments may be combined in any way.

The invention will now be described in non-limiting embodiment, with reference to the accompanying Figures wherein:.

In the following, the invention will be described in greater detail.

<FIG> shows a valve operating device <NUM> according to the invention where the rotational shaft <NUM> is an inner shaft with external threads and the linear shaft <NUM> is an outer shaft with internal threads. The valve operating device <NUM> is configured to operate a subsea valve <NUM> of a valve tree for a subsea well (valve tree and subsea well shown in <FIG>). On the left-hand side of the Figure, an electric actuator <NUM> providing energy to the valve operating device <NUM> is shown. The electric valve actuator <NUM> typically has a rotational output for connection to an external interface <NUM> of the valve operating device <NUM>. Although an electric actuator <NUM> is shown, other energy sources are also possible.

The valve operating device <NUM> comprises a housing <NUM>. The housing <NUM> comprises a chamber <NUM>. The chamber <NUM> having a longitudinal extension and comprises a linear guide <NUM>. Thrust bearings <NUM> is supported by the housing <NUM> and comprises a connection part <NUM>. The connection part <NUM> in <FIG> is shown as a recess <NUM>'.

The valve operating device <NUM> further comprises a rotational shaft <NUM> comprising a first end with an external interface <NUM> outside the chamber <NUM>. The actuator <NUM> is disclosed connected to the external interface <NUM>. A second end of the rotational shaft <NUM> is arranged inside the chamber <NUM>. The rotational shaft <NUM> is disclosed with a first portion <NUM> forming a sealing connection with the housing <NUM> via sealing gland <NUM> on the rotational shaft <NUM> received in groove <NUM> in the housing <NUM>.

The rotational shaft <NUM> comprises a first portion <NUM> that comprises a connection part <NUM> in the form of a radial rib <NUM>' which is connected to the connection part <NUM> in the form of a recess <NUM>' of the thrust bearings <NUM> forming a connection therebetween. The connection allows rotational movement of the rotational shaft <NUM> while preventing axial movement of the rotational shaft <NUM> relative to the thrust bearings <NUM> and the housing <NUM>. The rotational shaft <NUM> further comprises a second portion <NUM> comprising a threaded portion <NUM>, and an intermediate portion between the first portion <NUM> and the second portion <NUM>. The threaded portion <NUM> is exterior threads <NUM>. The second portion <NUM> is disclosed within the chamber <NUM>.

The intermediate portion is disclosed with a weakened part <NUM>. The rotational shaft <NUM> is shown with a main outer diameter having substantially the same outer diameter over the whole axial length thereof, however the weakened part <NUM> in the intermediate portion is disclosed with a smaller outer diameter compared to the main outer diameter. Section A in <FIG> indicates the area where the weakened part <NUM> may be provided on the rotational shaft <NUM> in order to ease separation of the rotational shaft <NUM> in the event of an override operation. The weakened part <NUM> thus enables release of the second portion <NUM> of the rotational shaft <NUM> relative the first portion <NUM> of the rotational shaft <NUM>. As seen, section A represents the possible area of the weakened part <NUM> extending from the engagement of the first portion <NUM> to the thrust bearings <NUM> and to the threaded portion <NUM> of the rotational shaft <NUM>.

The valve operating device <NUM> further comprises a linear shaft <NUM> arranged within the chamber <NUM>. The linear shaft <NUM> is guided by the linear guide <NUM> in the chamber <NUM>. The linear guide <NUM> prevents rotation of the linear shaft <NUM> relative the housing <NUM>, e.g. the linear guide <NUM> may form a spline connection with the linear shaft <NUM>. The linear shaft <NUM> comprising a first portion <NUM> and a second portion <NUM>. The first portion <NUM> comprises a threaded portion <NUM>. The threaded portion <NUM> may be interior threads <NUM> connected to the exterior threads <NUM> on the second portion <NUM> of the rotational shaft <NUM> forming a threaded connection translating rotational movement of the rotational shaft <NUM> to linear movement of the linear shaft <NUM>. The second portion <NUM> of the linear shaft <NUM> is shown connected to a valve stem <NUM> operating the valve <NUM>.

In order to function as a guide for a machining unit <NUM> with a machining tool <NUM> in case using the override functionality (see e.g. <FIG> and <FIG>) is required, the rotational shaft <NUM> is provided with a pre-machined hole <NUM> extending from the first end (i.e. the external interface <NUM>) of the rotational shaft <NUM> and along a center axis of the rotational shaft <NUM> over a part of an axial length of the rotational shaft <NUM>. As seen in <FIG>, the pre-machined hole <NUM> may extend to the weakened part <NUM>.

In order to compensate for hydrostatic pressure of the seawater experienced on the valve <NUM>, the disclosed valve operating device <NUM> is shown with a system for pressure equalizing the chamber <NUM> such that the valve operating device <NUM> does not have to work against force formed by the weight of the hydrostatic column of seawater. This system may comprise one or more bellows chambers <NUM> in pressure communication with the surrounding seawater via outer drainage holes <NUM> and with the chamber <NUM> via inner drainage holes <NUM>. The bellows <NUM> inside the bellows chambers <NUM> ensures that seawater is prevented from entering into the chamber <NUM>. If seawater enters the inner chamber <NUM>, the valve operating device <NUM> will probably decrease its operational life due to corrosion of the components inside chamber <NUM>.

<FIG> shows a first method of overriding the valve operating device <NUM> in <FIG> by releasing the second portion <NUM> of the rotational shaft <NUM> from a first portion <NUM> of the rotational shaft <NUM> using the same machining unit <NUM> for machining out a core of the rotational shaft <NUM> and stroking of the rotational shaft <NUM>. When comparing <FIG> with <FIG>, it is seen that a machining tool <NUM> in the form of a drill bit <NUM> connected to the machining unit <NUM> in the form of a drilling unit <NUM> has drilled out a core of the rotational shaft <NUM> forming a machined hole <NUM> in the form of a drilled hole <NUM> in the rotational shaft <NUM>. The drilled hole <NUM> extends from the external interface <NUM> towards the weakened part <NUM>. As shown in <FIG>, the drilled hole <NUM> is drilled to the position of the weakened part <NUM>. Drilling or milling the machined hole <NUM> at least to the position of the weakened part <NUM> (and possibly past the weakened part), enables easier release of the second portion <NUM> of the rotational shaft from the first portion <NUM> of the rotational shaft <NUM>. The final separation of the rotational shaft could be done by breaking the material left after machining during the first part of the stroke.

When the depth of the machined hole <NUM> is sufficient, the machining tool <NUM> can be stroked onto the bottom of the machined hole <NUM> in the core of the rotational shaft <NUM> until the rotational shaft <NUM> breaks at the weakened part <NUM> separating the second portion <NUM> from the first portion <NUM> of the rotational shaft <NUM>.

Once the second portion <NUM> and the first portion <NUM> have been released or separated from each other, the machining unit <NUM> can be used in pushing the machining tool <NUM> onto a bottom of the machined hole <NUM> in the core of the rotational shaft <NUM>. Since the valve stem <NUM> is connected to the linear shaft <NUM>, which again is connected to the second portion <NUM> of the rotational shaft <NUM>, the valve stem <NUM> will also be moved thereby operating the valve <NUM> upon pushing the machining tool <NUM> towards the bottom of the machined hole <NUM>. As such, the valve <NUM> can be operated to a desired position.

<FIG> shows a second method of overriding the valve operating device <NUM> in <FIG> by releasing a second portion <NUM> of a rotational shaft <NUM> from a first portion <NUM> of the rotational shaft <NUM> using a machining unit <NUM> for machining out a core of the rotational shaft <NUM> and a hydraulic override tool <NUM> for stroking of the rotational shaft <NUM>. The method for machining out the core of the rotational shaft <NUM> is similar to the method described in relation to <FIG> and will not be repeated herein. However, instead of stroking the machining tool <NUM> onto the bottom of the machined hole <NUM> in the core as in <FIG>, the machining unit <NUM> with machining tool <NUM> is replaced by a hydraulic override tool <NUM>. The hydraulic override tool <NUM> comprises a stroke piston <NUM>. The stroke piston <NUM> is positioned into the machined hole <NUM> and the hydraulic override tool <NUM> is used to stroke the stroke piston <NUM> against the bottom of the machined hole <NUM> until the second portion <NUM> of the rotational shaft <NUM> separates from the first portion <NUM> of the rotational shaft <NUM> by separating or breaking at the weakened part <NUM>.

Once the second portion <NUM> and the first portion <NUM> have been released or separated from each other, the machining unit <NUM> can be used in pushing the stroke piston <NUM> onto the bottom of the machined hole <NUM> in the core of the rotational shaft <NUM>. Since the valve stem <NUM> is connected to the linear shaft <NUM>, which again is connected to the second portion <NUM> of the rotational shaft <NUM>, the valve stem <NUM> will also be moved thereby operating the valve <NUM> upon pushing the stroke piston <NUM> towards the bottom of the machined hole <NUM>. As such, the valve <NUM> can be operated to a desired position.

<FIG> shows a third method of overriding the valve operating device <NUM> in <FIG> by releasing a second portion <NUM> of a rotational shaft <NUM> from a first portion <NUM> of the rotational shaft <NUM> using a machining unit <NUM> with a machining tool <NUM> for machining out a core of the rotational shaft <NUM> until the second portion <NUM> releases from the first portion <NUM>.

Arrows B indicate that the second portion <NUM> and the first portion <NUM> of the rotational shaft <NUM> have been released or separated from each other at the weakened part <NUM>, i.e. the rotational shaft <NUM> has been cut or machined into two parts.

In order to be able to machine out, such as by e.g. using a drill bit <NUM> or milling tool <NUM>, the second portion <NUM> from the first portion <NUM>, the diameter of the machining tool <NUM> used in the method of <FIG> is larger than the machining tool <NUM> in <FIG>. The diameter of the machining tool <NUM> can for example be at least of the same size as an outer diameter of the weakened part <NUM>, or it can be larger or slightly smaller.

Similarly as for the method in <FIG>, once the second portion <NUM> and the first portion <NUM> have been released or separated from each other, the machining unit <NUM> can be used in pushing the machining tool <NUM> onto a bottom of the machined hole <NUM> in the core of the rotational shaft <NUM>. Since the valve stem <NUM> is connected to the linear shaft <NUM>, which again is connected to the second portion <NUM> of the rotational shaft <NUM>, the valve stem <NUM> will also be moved operating the valve <NUM> upon pushing the machining tool <NUM> towards the bottom of the machined hole <NUM>. As such, the valve <NUM> can be operated to a desired position.

<FIG> shows the situation after the second portion <NUM> of the rotational shaft <NUM> has been released or separated from the first portion <NUM> of the rotational shaft <NUM> independently of using the method disclosed in <FIG>, <FIG> or <FIG>. The arrows B indicate that the second portion <NUM> and the first portion <NUM> of the rotational shaft <NUM> have been released or separated from each other at the weakened part <NUM> over a distance L, i.e. the rotational shaft <NUM> has broken into two parts and the valve <NUM> (not shown in <FIG>) can be opened.

<FIG> is a schematic overview of a subsea valve tree <NUM> comprising a number of subsea valves <NUM>, where each of the valves <NUM> are connected to a valve operating device <NUM>. The subsea valve tree <NUM> is arranged on a seabed <NUM> below a body of water. A floating vessel FV floats on a surface <NUM> of the body of water. The valve tree <NUM> is arranged above a subsea well <NUM>.

<FIG> is an example of a valve operating device <NUM> with an alternative connection between the rotational shaft <NUM> and the housing <NUM> compared to <FIG>. All of the elements of the valve operating device <NUM> are identical to the valve operating device <NUM> in <FIG>, except that the radial rib and recess are on the opposite parts. , as seen in <FIG>, the thrust bearings <NUM> comprises a connection part in the form of a rib <NUM>'' and the first portion <NUM> of the rotational shaft <NUM> comprises a connection part in the form of a recess <NUM>" for receiving or accommodating the rib <NUM>". In this example, the recess <NUM>" in the first portion of the rotational shaft <NUM> may function as a weakened part and thus a dedicated weakened part may be superfluous.

<FIG> shows an example of a valve operating device <NUM> as shown in <FIG> but where the rotational shaft <NUM> is an outer shaft with internal threads <NUM> and the linear shaft <NUM> is an inner shaft with external threads <NUM>. Some of the components of the valve operating device <NUM> in <FIG> have been omitted in <FIG> in order to better illustrate the difference between the example of <FIG> and the example in <FIG>, including e.g. the valve <NUM>, parts of the valve stem <NUM>, the connection between the rotational shaft <NUM> and the housing <NUM>, as well as the system for pressure equalizing the chamber <NUM>.

As seen in <FIG>, the threaded portion <NUM> of the rotational shaft <NUM> encircle the threaded portion <NUM> of the linear shaft <NUM>. threaded portion <NUM> of the rotational shaft <NUM> is internal threads <NUM> and the threaded portion <NUM> of the linear shaft <NUM> is external threads <NUM>. For this to be possible, the second portion <NUM> of the rotational shaft <NUM> is arranged radially outside the first portion <NUM> of the linear shaft <NUM>. The linear guide <NUM> which prevents rotation of the linear shaft <NUM> relative the housing <NUM> is arranged to the right of where the rotational shaft <NUM> ends.

It should be recognized that, while the present invention has been described in relation to the preferred embodiments thereof, those skilled in the art may develop a wide variation of structural and operational details without departing from the principles of the invention as defined in the attached claims.

Claim 1:
A valve operating device (<NUM>) for operating a subsea valve (<NUM>), the valve operating device (<NUM>) comprises:
- a housing (<NUM>);
- thrust bearings (<NUM>) supported by the housing (<NUM>), wherein the thrust bearings (<NUM>) comprises a connection part (<NUM>,<NUM>';<NUM>");
- a chamber (<NUM>) within the housing (<NUM>), wherein the chamber (<NUM>) comprises a first part of a linear guide (<NUM>);
- a rotational shaft (<NUM>) comprising a first end with an external interface (<NUM>) which is outside the chamber (<NUM>) and the housing (<NUM>) and a second end inside the chamber (<NUM>), the rotational shaft (<NUM>) comprises a first portion (<NUM>) that comprises a connection part (<NUM>,<NUM>';<NUM>") which is connected to the connection part (<NUM>) of the thrust bearings (<NUM>) forming a connection therebetween which allows rotational movement of the rotational shaft (<NUM>) while preventing axial movement of the rotational shaft (<NUM>) relative to the housing (<NUM>), a second portion (<NUM>) comprising a threaded portion (<NUM>), and an intermediate portion between the first portion (<NUM>) and the second portion (<NUM>), and wherein the second portion (<NUM>) is arranged inside the chamber (<NUM>);
- a linear shaft (<NUM>) arranged within the chamber (<NUM>), the linear shaft (<NUM>) comprising a first portion (<NUM>) and a second portion (<NUM>), wherein the first portion (<NUM>) comprises threaded portion (<NUM>) interacting with the threaded portion (<NUM>) of the rotational shaft (<NUM>) forming a threaded connection translating rotational movement of the rotational shaft (<NUM>) to linear movement of the linear shaft (<NUM>), and the second portion (<NUM>) is connectable to a valve stem (<NUM>) operating the valve (<NUM>), wherein the linear shaft (<NUM>) also comprises a second part of the linear guide (<NUM>), the first part and the second part of the linear guide (<NUM>) prevent rotation of the linear shaft (<NUM>) relative to the housing (<NUM>), and wherein
- the rotational shaft (<NUM>) comprises a pre-machined hole (<NUM>) extending from the first end of the rotational shaft (<NUM>) and along a center axis of the rotational shaft (<NUM>) over a part of an axial length of the rotational shaft (<NUM>).