Subsea high voltage terminal assembly

A system and method are provided for a terminal assembly of a subsea motor-compressor. The terminal assembly may include a plurality of terminal ports extending through a hollow spherical body to a cavity defined therein. The terminal assembly may also include a penetrator detachably coupled with the spherical body about each of the plurality of terminal ports. The terminal assembly may further include a mounting port extending through the spherical body to the cavity defined therein. The mounting port may be configured to couple the terminal assembly with a housing of the motor-compressor.

BACKGROUND

Reliable and efficient compression systems have been developed and are used in a myriad of industrial processes (e.g., petroleum refineries, offshore oil production platforms, and subsea process control systems). There is, however, an ever-increasing demand for smaller, lighter, and more compact compression systems. Accordingly, compact motor-compressors that incorporate compressors directly coupled to high-speed electric motors have been developed. Conventional compact motor-compressors may combine a high-speed electric motor with a compressor, such as a centrifugal compressor, in a single, hermetically sealed housing. In compact motor-compressors, the high-speed electric motor may operate in a process fluid contained in the housing, which may be maintained at a pressure from about 1 megapascal (MPa) to about 30 MPa. To deliver an electrical current across the pressure boundary of the housing and power the high-speed electric motor, high voltage penetrators (HVPs) are often utilized. In topside or terrestrial (e.g., ground based) environments with ambient air external conditions, the HVPs may be contained in a pipe section extending from the sealed housing. These pipe sections, however, are neither practical nor adequate for the larger and more complex HVPs required in subsea environments.

In view of the foregoing, compact motor-compressors used in subsea environments may often include a terminal assembly in lieu of the pipe section to engage or couple with the HVPs.FIG. 1illustrates a partial, cross-sectional view of a conventional compact motor-compressor100including a conventional terminal assembly102. The motor-compressor100may combine a pressurized, high-speed motor120with a compressor130in a hermetically sealed housing112. The motor-compressor100may further include a terminal assembly102disposed about the housing112and configured to couple with one or more HVPs106,108,110. The HVPs106,108,110may be configured to receive an electrical current from a sea- or land-based power source and deliver the electrical current to the motor120via the terminal assembly102. To limit power losses resulting from induced eddy currents, the terminal assembly102may be cast with costly non-magnetic metals. However, in conventional motor-compressors100, the terminal assembly102may often be cast integral with the housing112, thereby hindering the ability to fabricate the terminal assembly102and the housing112from different materials. As such, the housing112and the terminal assembly102are often cast with the same cost effective metallic materials and the resulting power losses from induced eddy currents are accepted. Further, in conventional motor-compressors100, the HVPs106,108,110are often coupled with the terminal assembly102in a co-linear orientation, which results in an increased distance and an increased amount of metallic material interposed between each of the HVPs106,108,110. The increased amount of metallic material may also contribute to the overall power losses from induced eddy currents.

What is needed, then, is an improved, cost-effective motor-compressor system and method of operating thereof, including a terminal assembly capable of minimizing induced power losses.

SUMMARY

Embodiments of the disclosure may provide a terminal assembly for a subsea motor-compressor. The terminal assembly may include a plurality of terminal ports extending through a hollow spherical body to a cavity defined therein. The terminal assembly may also include a penetrator detachably coupled with the spherical body about each of the plurality of terminal ports. The terminal assembly may further include a mounting port extending through the spherical body to the cavity defined therein. The mounting port may be configured to couple the terminal assembly with a housing of the motor-compressor.

Embodiments of the disclosure may further provide another terminal assembly for a subsea motor-compressor. The terminal assembly may include a plurality of terminal ports extending through a hollow body to a cavity defined therein. The plurality of terminal ports may be helically arranged about a longitudinal axis of the hollow body. A penetrator may be detachably coupled with the hollow body about each of the plurality of terminal ports. The terminal assembly may also include a mounting port extending through the hollow body to the cavity defined therein. The mounting port may be configured to couple the terminal assembly with a housing of the motor-compressor.

Embodiments of the disclosure may further provide a method for operating a subsea motor-compressor. The method may include coupling a terminal assembly to a housing of the motor-compressor. The terminal assembly may include a plurality of terminal ports extending through a hollow spherical body to a cavity defined therein. The terminal assembly may also include a penetrator detachably coupled with the hollow spherical body about each of the plurality of terminal ports. The terminal assembly may further include a mounting port extending through the hollow spherical body to the cavity defined therein. The mounting port may be configured to couple the terminal assembly with the housing of the motor-compressor. The method may also include receiving an electrical current from a power source via the penetrator of the terminal assembly. The method may further include delivering the electrical current from the terminal assembly to a motor of the motor-compressor.

DETAILED DESCRIPTION

As described herein, the expression spherical or substantially spherical shall be understood in a broader sense to include rotationally rounded shapes such as egg-shapes, ovoid shapes, ellipses, spheroids, substantially true spheres and true spheres. The rotationally rounded shapes may be symmetrical or asymmetrical. For example, a radius of curvature of a first portion of the rounded shape may be the same or different than a radius of curvature of a second portion of the rounded shape.

FIG. 2Aillustrates a partial, cross-sectional view of an exemplary compact motor-compressor200including an exemplary terminal assembly210coupled thereto, according to one or more embodiments. The motor-compressor200may include a housing212having a compressor end214and a motor end216. The housing212may contain and hermetically seal a motor202, a compressor204, an integrated separator208, or any combination thereof. The motor202may be disposed near the motor end216of the housing212and the compressor204may be disposed near the compressor end214of the housing212. The motor202may be coupled with the compressor204via a rotary shaft206extending substantially from the motor end216to the compressor end214.

The motor202may be an electric motor, such as a permanent magnet motor, and may include a stator221and a rotor217. It may be appreciated, however, that other embodiments may employ other types of electric motors including, but not limited to, synchronous motors, induction motors, brushed DC motors, or the like. The compressor204may be a multi-stage centrifugal compressor with one or more compressor stage impellers205. It may be appreciated, however, that any number of impellers205may be implemented or used without departing from the scope of the disclosure.

In at least one embodiment, the motor-compressor200may include the integrated separator208coupled with the motor202via the rotary shaft206. In another embodiment, the integrated separator208may be omitted from the motor-compressor200. The integrated separator208may be configured to separate and remove higher-density components from lower-density components contained within a process gas introduced thereto. The higher-density components (i.e., liquids and/or solids) removed from the process gas may be discharged from the integrated separator208via a discharge line (not shown), thereby providing a relatively dry process gas to be introduced into the compressor204. Especially in subsea applications where the process gas may commonly be multiphase, any separated liquids discharged via the discharge line may accumulate in a collection vessel (not shown) and be subsequently pumped back into the process gas at a pipeline (not shown) located downstream of the compressor204. Otherwise, separated liquids may alternatively be drained into the collection vessel for subsequent disposal.

An aperture218may be defined in the housing212to provide communication or access to the motor202disposed therein. The terminal assembly210may be coupled to the housing212about the aperture218to provide electrical current or power from a power source (not shown) outside the housing212to the motor202, as further discussed below.

FIGS. 2B and 2Cillustrate an isometric view of the exemplary terminal assembly210ofFIG. 2A, according to one or more embodiments. The terminal assembly210may include a body302having an exterior surface304defining a shape thereof. The shape of the body302may be substantially spherical, spherical, polyhedral, or ovoid. As shown inFIGS. 2B and 2C, the terminal assembly210may include a hollow body302including an interior surface306defining a cavity308therein. The cavity308may be substantially spherical, spherical, polyhedral, ovoid, or any other geometric shape capable of being defined within the body302. The cavity308may have the same or substantially the same shape as the body302. For example, as shown inFIGS. 2B and 2C, the terminal assembly210may include a spherical body302having a spherical cavity308defined therein. The spherical body302may be centered about a longitudinal axis310of the terminal assembly210. The longitudinal axis310may extend through a lower end or hemisphere352and an upper end or hemisphere354of the body302. As used herein, “lower hemisphere” may refer to the lower half of the body302and “upper hemisphere” may refer to the upper half of the body302, whether the body302is spherical, substantially spherical, polyhedral, or ovoid.

As shown inFIGS. 2B and 2C, the terminal assembly210may further include one or more terminal ports320,322,324defined by the exterior surface304of the body302and extending from the exterior surface304to the cavity308defined therein. In at least one embodiment, one or more high-voltage penetrators331,332,333may be coupled to the body302about each of the terminal ports320,322,324. In another embodiment, as shown inFIGS. 2B and 2C, each of the penetrators331,332,333may be coupled with conduit members340,342,344extending from each of the terminal ports320,322,324.

The terminal ports320,322,324and/or the conduit members340,342,344extending therefrom may be positioned in or near the upper hemisphere354of the body302. The terminal ports320,322,324and/or the conduit members340,342,344may be helically arranged about the body302. For example, as shown inFIGS. 2B and 2C, the terminal ports320,322,324and/or the conduit members340,342,344may be helically arranged about the longitudinal axis310of the terminal assembly210. The helical arrangement of the terminal ports320,322,324and/or the conduit members340,342,344may improve nesting of the penetrators331,332,333coupled therewith. The helical arrangement may allow the terminal ports320,322,324and/or the conduit members340,342,344to be positioned about the body302such that the distance therebetween may be minimized, thereby minimizing the amount of material interposed between each of the penetrators331,332,333. Minimizing the amount of material interposed between each of the penetrators331,332,333may minimize the occurrence of induced eddy currents and improve the efficiency of the penetrators331,332,333. For example, the terminal assembly210may be fabricated from one or more metallic materials that may promote induced eddy currents and reduce efficiency. Minimizing the amount of the metallic materials interposed between the penetrators331,332,333may reduce the magnitude of induced eddy currents, thereby minimizing the reduction in efficiency. Reducing the induced eddy currents may also minimize eddy current heating, thereby decreasing an overall operational temperature of the penetrators331,332,333and minimizing premature failure of the penetrators331,332,333resulting from high temperature operation.

The penetrators331,332,333coupled with the body302of the terminal assembly210about the terminal ports320,322,324and/or the conduit members340,342,344may be configured to receive an electrical current from a power source (not shown) and deliver the electrical current to the motor-compressor200and/or components thereof. For example, the penetrators331,332,333may receive an electrical current from a sea- or land-based power source (not shown) and deliver the electrical current through the terminal assembly210to the motor202of the motor-compressor200. It may be appreciated that each of the penetrators331,332,333, terminal ports320,322,324, and/or the conduit members340,342,344disclosed herein may comprise similar components and parts. Consequently, discussions herein regarding a single penetrator331, terminal port320, and/or conduit member340are equally applicable to the remaining penetrators332,333, terminal ports322,324, and/or the conduit members342,344.

FIG. 2Cillustrates an isometric view of the exemplary terminal assembly210ofFIG. 2Aincluding the penetrator331decoupled from the terminal assembly210, according to one or more embodiments. As shown inFIG. 2C, the penetrator331may include a housing end334, a power source end337, and an annular collar351interposed therebetween. The power source end337may be coupled with a power source (not shown) and may be configured to receive an electrical current or power therefrom. The housing end334may be coupled with the motor102of the motor-compressor200and may be configured to deliver the electrical current from the power source to the motor202, as further discussed below.

The annular collar351may be configured to couple the penetrator331with terminal assembly210about the terminal port320and/or with the conduit member340. For example, as shown inFIG. 2B, the annular collar351may couple the penetrator331with the conduit member340. As shown inFIG. 2C, the annular collar351may define one or more circumferentially-arrayed perforations350extending therethrough. The perforations350may be configured to receive one or more mechanical fasteners (not shown) to facilitate the coupling of the penetrator331with the conduit member340. Illustrative mechanical fasteners may include, but are not limited to, a series of bolts, studs, nuts, and/or any other known mechanical fasteners. Coupling the annular collar351of the penetrator331with the conduit member340may provide a fluid tight seal therebetween.

One or more cables360may be coupled with the housing end334of the penetrator331and may extend from the housing end334of the penetrator331into the cavity308. The cables360may be at least partially stored or contained within the cavity308of the terminal assembly210. In at least one embodiment, illustrated inFIG. 2B, the cables360may be at least partially stored in the cavity308such that at least a portion or length of the cables360are spirally or helically arranged therein. The helical arrangement of the terminal port320and/or the conduit member340may facilitate the spiral or helical arrangement of the cables360within the cavity308. The helical arrangement of the cables360may allow an excess length of the cables360to be stored within the cavity308. The excess length may allow the penetrator331to be separated from the terminal assembly210without disturbing or disconnecting the cables360from the penetrator331. In at least one embodiment, the excess length of the cables may allow the penetrator331to be separated from the terminal assembly210a length (L) sufficient to allow access to and/or installation of the cables360and/or the penetrator331. For example, the length (L) that the penetrator331may be separated from the terminal assembly210may be from a low of about 12.7 cm (5 in.) to a high of about 76.2 cm (30 in.) or greater.

In at least one embodiment, the cables360may extend from the cavity308and couple with the motor202of the motor-compressor200to provide power thereto. In another embodiment, the cables360may further extend from the cavity308and couple with one or more sensors (not shown) of the motor-compressor200, the terminal assembly210, and/or components thereof. Illustrative sensors may include, but are not limited to, motor-based sensors, pressure sensors, temperature sensors, or any combination thereof.

As shown inFIG. 2C, the terminal assembly210may further include an access port372defined by the body302. The access port372may extend from the exterior surface304of the body302to the cavity308defined therein, thereby providing access to the cavity308and the cables360stored therein. The access port372may be any size and/or shape suitable to allow maintenance of the cables360stored in the cavity308. In at least one embodiment, illustrated inFIG. 2C, the access port372may be circular or substantially circular.

As shown inFIG. 2B, the terminal assembly210may further include a cover376configured to seal the access port372. The cover376may be detachably coupled to the body302about the access port372to provide a fluid tight seal therebetween. As illustrated inFIG. 2B, the cover376may be cylindrical to sufficiently seal the circular access port372. As shown inFIG. 2B, the cover376may define one or more circumferentially-arrayed perforations378extending therethrough. The perforations378may be configured to receive one or more mechanical fasteners (not shown) to facilitate the coupling of the cover376to the body302. Illustrative mechanical fasteners may include, but are not limited to, a series of bolts, studs, nuts, and/or any other known mechanical fasteners.

As shown inFIGS. 2B and 2C, the terminal assembly210may further include a mounting port312defined by the exterior surface304of the body302. The mounting port312may extend from the exterior surface304of the body302to the cavity308to provide communication therethrough. In at least one embodiment, the mounting port312may be positioned in the lower hemisphere352of the body302such that the mounting port312is centered about the longitudinal axis310of the terminal assembly210. The size and shape of the mounting port312may be determined, at least in part, by the size and shape of the aperture218defined by the housing212of the motor-compressor200. For example, as illustrated inFIGS. 2B and 2C, with continued reference toFIG. 2A, the mounting port312may be circular to correspond with the circular aperture218of the motor-compressor200.

The terminal assembly210may further include a mounting flange314extending from the mounting port312to detachably couple the terminal assembly210to the housing212of the motor-compressor200. As illustrated inFIGS. 2B and 2C, the mounting flange314may define one or more circumferentially-arrayed perforations316extending therethrough. The perforations316may be configured to receive one or more mechanical fasteners, illustrated as bolts318inFIGS. 2B and 2C, to facilitate the coupling of the terminal assembly210to the housing. In addition to, or in substitution of the bolts318, the mechanical fasteners may include one or more studs, nuts, and/or any other known mechanical fasteners.

Having the terminal assembly210detachably coupled to the housing212may allow the terminal assembly210and the housing212to be cast or fabricated from different materials. For example, the terminal assembly210may be cast with a non-magnetic metal to reduce induced eddy currents and the housing212may be cast with a cost effective metallic material such as carbon steel, thereby reducing the overall cost of fabricating and manufacturing the motor-compressor200. Illustrative materials from which the terminal assembly210and/or components thereof may be fabricated may include, but are not limited to, INCONEL®, titanium, a titanium alloy, materials with similar operational properties to titanium, non-magnetic stainless steel, preferably of the 200 or 400 series, or any combination thereof. INCONEL® may include a nickel chromium alloy having oxidation and corrosion resistance.

The motor-compressor200including the terminal assembly210described herein may be used for subsea applications at substantial sea depths (e.g., about 200-3000 meters). As such, it may be appreciated that the external pressures (e.g., hydrostatic ambient pressures) at such depths may be elevated with respect to topside or terrestrial (e.g., ground based) applications. Accordingly, the terminal assembly210described herein may be configured to withstand such elevated pressures. For example, in addition to reducing induced eddy currents, the materials used in fabricating the terminal assembly210and/or components thereof may provide a pressure-resistance thereto. The terminal assembly210and/or components thereof may be fabricated with a material configured to withstand pressures from a low of about 0.5 MPa to a high of about 35 MPa or greater.

FIG. 3is a flowchart illustrating a method300for operating a subsea motor-compressor, according to one or more embodiments. The method300may include coupling a terminal assembly to a housing of the motor-compressor, as shown at302. The terminal assembly may include a plurality of terminal ports extending through a hollow spherical body to a cavity defined therein, a penetrator detachably coupled with the hollow spherical body about each of the plurality of terminal ports, and a mounting port extending through the hollow spherical body to the cavity disposed therein, where the mounting port may be configured to couple the terminal assembly with the housing of the motor-compressor. The method300may also include receiving an electrical current from a power source via the penetrator of the terminal assembly, as shown at304. The method300may further include delivering the electrical current from the terminal assembly to a motor of the motor-compressor, as shown at306.