Abstract: A downhole dynamic compressor comprises an electric motor having a stator 6 with stationary windings and an armature with permanent magnets 7 supported on gas bearings 9, 10 for rotation relative to the stator. The gas bearings 9 and 10 are arranged at the upstream and downstream opposite ends of the motor, respectively. The dynamic compressor has a bladed wheel 12 mounted on an overhanging end of the motor armature 7 that projects beyond the gas bearing 9 at the upstream end of the motor, whereby all the gas bearings of the compressor and the electric motor are arranged on the downstream side of the dynamic compressor.

Abstract: A tandem gas seal assembly is described for sealing between the rotor and the casing of a rotary machine. The assembly comprises two sealing stages 10, 12 mounted axially adjacent to one another on the machine rotor. In the invention, wherein the two stages 10 and 12 are totally separable from one another and each is capable of functioning as a seal when separated from the other.

Abstract: A gas seal assembly comprises a pair of mutually rotatable sealing members A, B, each of which has a face adjacent a gap between the two members. One of the members B is urged in a direction attempting to close the gap h which constitutes a leakage path through the seal assembly. A gas bleed arrangement 7 allows gas from a high pressure side P3 of the seal assembly to bleed into the gap at a position radially spaced between an inner diameter of the members and an outer diameter of the members A,B so as to apply a force tending to separate the members, the force decreasing as the size of the gap increases.

Abstract: A rotary electric machine is disclosed having stator windings and a rotor incorporating permanent magnets distributed about the axis of the rotor to create a magnetic field having circumferentially alternating north and south poles. In the invention, the principal structural member is an external sleeve, this providing resistance to bending and to centrifugally induced stresses due to rotation. The direction of polarization of the permanent magnets 214 is such that the parts of the magnetic circuits that lie within the outer circumference of the rotor pass predominantly through the bodies of the permanent magnets 214, thereby avoiding the need for a central ferromagnetic core to complete the magnetic circuit of the magnets.

Abstract: A multi-stage compressor comprises a variable speed electrically driven rotodynamic compressor stage connected in series with and upstream of a water lubricated screw compressor stage and an intercooler arranged between the two compressors to reduce the temperature of gas entering the screw compressor stage. In the invention, the intercooler is a water spray intercooler, the water supply of which is shared with that of the water lubricated screw compressor.

Abstract: A downhole compressor system is disclosed for assisting in extracting gas from the well. The system comprises a compressor 14, an electric motor 10 for driving the compressor 14 which motor has a stator winding and a rotor 12 and, in use, is lowered into the well together with the compressor. A control system 18, which when in use is disposed outside the well, is connected to the stator winding for controlling the current supply to the motor 10. The control system 18 receiving a signal indicative of the speed and phase of the rotor from a feedback sensor 16 mounted for rotation with the rotor 12. In the invention, the feedback sensor is a current generator having a permanent magnet 16a mounted for rotation with the rotor 12 and a second stator winding 16b connected to the control system 18.

Abstract: A gas lubricated axial thrust bearing for resisting axial forces acting on a machine rotor, comprises at least one pad mounted on a stationary machine surface and axially spaced from a surface of the rotor by a lubricating gas film. The bearing further includes a temperature sensor for sensing the temperature of the pad to provide an output signal indicative of the axial load on the bearing.

Abstract: A rotary electric machine is disclosed having stator windings and a rotor incorporating permanent magnets distributed about the axis of the rotor to create a magnetic field having circumferentially alternating north and south poles. In the invention, the principal structural member is an external sleeve, this providing resistance to bending and to centrifugally induced stresses due to rotation. The direction of polarization of the permanent magnets 214 is such that the parts of the magnetic circuits that lie within the outer circumference of the rotor pass predominantly through the bodies of the permanent magnets 214, thereby avoiding the need for a central ferromagnetic core to complete the magnetic circuit of the magnets.

Abstract: A tandem gas seal assembly is described for sealing between the rotor and the casing of a rotary machine. The assembly comprises two sealing stages 10, 12 mounted axially adjacent to one another on the machine rotor. In the invention, wherein the two stages 10 and 12 are totally separable from one another and each is capable of functioning as a seal when separated from the other.

Abstract: A converter system is described having an AC-to-DC first converter stage connectable to an AC supply and operative to produce a DC output on a DC link and a DC-to-AC second converter stage directly connected to the DC link and producing an AC output for driving an AC load at a frequency and amplitude that may differ from the frequency and amplitude of the input AC supply. In the invention, the first converter stage comprises a bridge of bi-directional electronic switching elements connected between the input AC supply and the DC link and control means for activating the electronic switching elements of the bridge with variable phase relative to the input AC supply in order to vary the DC output on the DC link to the second converter stage.

Abstract: A downhole compressor system is disclosed for assisting in extracting gas from the well. The system comprises a compressor 14, an electric motor 10 for driving the compressor 14 which motor has a stator winding and a rotor 12 and, in use, is lowered into the well together with the compressor. A control system 18, which when in use is disposed outside the well, is connected to the stator winding for controlling the current supply to the motor 10. The control system 18 receiving a signal indicative of the speed and phase of the rotor from a feedback sensor 16 mounted for rotation with the rotor 12. In the invention, the feedback sensor is a current generator having a permanent magnet 16a mounted for rotation with the rotor 12 and a second stator winding 16b connected to the control system 18.

Abstract: A tilting pad journal bearing (2) comprises a bearing shell (4) having a substantially cylindrical inner surface and at least three bearing pads (5, 6, 7) extending around the inner surface of the bearing shell in a substantially circumferential direction. Each of the pads (5, 6, 7) is arranged for pivotal movement relative to the bearing shell (4) by a substantially spherically-extending surface (8, 9, 10) on the pad engaging a mating substantially spherically-extending surface (11, 12, 13) associated with the bearing shell. At least one of the substantially spherically-extending surfaces (11) associated with the shell (4) is provided on a member (14) so mounted in or on the bearing shell as to be capable of radial movement relative to the shell and a spring is provided for urging the member radially inwards.

Abstract: A bearing assembly (2) comprises an outer shell (3) providing a pair of coaxial annular surfaces (4a, 5a) spaced apart-and facing inwardly towards each other, and an inner shell (7) within the outer shell, the inner shell providing a pair of coaxial annular surfaces (8a, 9a), each of which faces outwardly towards one of the inwardly-facing annular surfaces of the outer shell and is arranged substantially coaxially with, and adjacent to, its associated inwardly-facing annular surface. The inner shell (7) is capable of movement relative to the outer shell (3) in an axial direction and by inclination to the outer shell. Each of the said inwardly-facing annular surfaces (4a, 5a) and/or its associated outwardly-facing annular surface (8a, 9a) has one or more channels (13, 14) arranged to extend around the surface. The bearing assembly (2) also comprises means (17-21) for supplying a fluid from a high pressure source to each of the said channels (13, 14) through flow resistance means (15, 16).

Abstract: A composite shaft comprising at least two axial segments of dissimilar materials, the segments being held together by a central tie-bar, wherein a segment of material least subject to radial expansion is provided with a coaxial male member extending axially from its end, and the cooperating segment subject to greater radial expansion is provided with a female skirt shrunk onto the male member in the assembly of the shaft and also being provided with an annular upstand, at or towards its peripheral edge and directed towards the cooperating segment, the upstand being held by the compressive force of the tie-bar always in full annular contact with its cooperating segment. The male member is of smallest practicable diameter and the upstand is of largest practicable diameter.

Abstract: An oil free high speed gas compressor driven by a high frequently electric motor with a soft magnetic armature which holds permanent magnets arranged peripherally and a centrifugal impeller overhung at one or at each end of the shaft of the armature of the motor, wherein the temperature of the armature is held within the characteristic temperature of its permanent magnets by a flow of cooling liquid through a central bore in the armature or by a flow of cooling liquid through a central drilling through a tie-bolt in thermal contact with a bore in the armature.