Compressor unit

This application is the US National Stage of International Application No. PCT/EP2007/051474, filed Feb. 15, 2007 and claims the benefit thereof. The International Application claims the benefits of European application No. 06006059.7 filed Mar. 24, 2006, both of the applications are incorporated by reference herein in their entirety.

The invention relates to a compressor unit, in particular for underwater operation, comprising a compressor with a rotation axis and an electric motor, which compressor unit has a housing which has an inlet and an outlet for a pumping medium, having an automation unit which is designed such that it carries out open-loop and closed-loop control tasks for the compressor unit.

Recent developments in the field of compressor design have also been concentrated on undersea arrangements of large compressors which are intended to be used for the pumping of natural gases.

Because of the particular operating conditions, in particular because of the greatly restricted accessibility both for maintenance purposes and by means of supply lines, the specialists are confronted with major requirements. The relevant environmental regulations forbid any exchange of substances between the equipment to be installed and the surrounding seawater. Furthermore, seawater is an aggressive medium and extreme pressure and temperature conditions can be found at the various depths in the sea. A further requirement is that the equipment should on the one hand have an extremely long life and on the other hand must be designed to be virtually free of maintenance. An additional exacerbating factor is not-inconsiderable contamination of the medium to be pumped which in some cases is chemically aggressive.

Compressor units normally require numerous electrical connections for their operation, in particular for the power supply and for transmission of control signals between a higher-level automation unit and the compressor unit. The higher-level automation units are in this case arranged separately from the compressor unit, at some distance away, on the one hand in order to achieve a high level of modularity of design, and on the other hand to ensure optimum operating conditions for the electronics of the automation unit. Particularly when using active magnetic bearings, numerous signal lines are required between the automation unit and the compressor unit, and transmit various measured values to the automation unit, and transmit corresponding control parameters to the magnetic bearings.

The transmission of the power for operation of the compressor unit and of the signals between the compressor unit and the automation unit necessitates a considerable amount of complexity since the numerous lines must be designed, inter alia, to be disconnectable by means of a very costly plug connection. The cost aspect becomes many times more important when this relates to an installation which is suitable for undersea operation, since the plug connection has to comply with particular requirements for this purpose.

Furthermore, the automation unit must be provided with a cooling system by means of which the not-inconsiderable lost power from the components, some of which are in the form of power electronics, must be dissipated.

The document WO-A-2005/003512 has already disclosed a compressor unit for underwater operation in which the compressor together with an electric motor is accommodated in a common, gas-tight housing. An automation unit, which controls the operation of magnetic bearings, is connected for signal transmission purposes to these bearings.

Against the background of the problems of the prior art, the object of the invention is to provide a better interaction between the automation unit and the compressor unit and, in particular, to reduce the complexity for cooling the automation unit and of the signal and power transmission.

A compressor unit is proposed in order to achieve the object according to the invention.

The arrangement of an additional housing, in which the automation unit is arranged, on the housing of the compressor unit has, in particular, the advantage that appropriate power supply lines and signal lines between the automation unit and the compressor unit need no longer be designed to comply with a standard which is suitable for direct contact with the environmental conditions. In fact, these lines can be designed such that they merely satisfy the always reproducible and exactly predictable operating conditions in the interior of the additional housing and of the housing of the compressor unit. Furthermore, no special plug connections are required for disconnection of lines between the automation unit and the compressor unit. Surprisingly, it was also found that some areas on the housing of the compressor unit satisfy the thermal constraints required for operation of the automation unit, without any additional modification. This major advantage means that there is no longer any need for a separate cooling system for the automation unit. This advantage is particularly evident when the additional housing for the automation unit is thermally conductively fitted to the housing in the area of an intake connecting stub of the inlet such that the power lost from the automation unit is dissipated by means of thermal conduction to the housing. Although this advantage is fundamentally relevant for compressor units, it is additionally important in the field of underwater operation since, in this case, the accessibility to the compressor unit is very greatly restricted and, for this reason, additional cooling media are available only with difficulty, if at all. It is virtually impossible to use seawater as a cooling medium, because of the aggressive chemical characteristics. When pumping natural gas, the lost power can be absorbed without any problems by the cold pumping medium. However, one problem in this case is the introduction of the heat into the pumped flow.

Particularly when a compressor unit is of a single-shaft design with a motor and a compressor unit along a single rotation axis, it is normally in an elongated form thus resulting in a temperature profile in the longitudinal extent during operation. The temperature in the axial area of the inlet or of the intake connecting stub is particularly advantageous for thermally conductive fitting of the additional housing for the automation unit. According to the invention, the heat is dissipated from the automation unit by means of thermal conduction in the area of the intake connecting stub of the housing, and introduced into the pumping medium flowing through the compressor unit. A person skilled in the art can decide the circumferential position in the axial area of the intake connecting stub at which the additional housing is fitted, depending on the thermal-conduction conditions between the housing of the compressor unit and the additional housing.

In this case, the automation unit is expediently connected to components of the compressor unit by means of internal signal lines and/or internal power supply lines. These internal lines can expediently be designed to be disconnectable by means of a plug connection, such that elements can be replaced without any problems even during the course of maintenance tasks. The plug connections need be designed only to satisfy the always reproducible and predictable operating conditions in the housing interior. The components which are connected to the automation unit are, in particular, magnetic bearings for the rotor of the compressor and of the motor, and the electric motor. In addition, various temperature measurements and pressure measurements can be provided.

The automation unit is expediently connected to a base station by means of an external signal line or an external power supply line, or by means of both.

One advantageous development of the invention provides for the additional housing to be connected to the housing of the compressor unit by means of welding, which on the one hand ensures good thermal conduction between the housings and on the other hand provides the required gas-tightness, in particular for underwater operation. In order to ensure that the components in the additional housing are nevertheless accessible for maintenance tasks, it is advantageous for the additional housing to have an opening which can be closed. This opening which can be closed can be sealed by means of a conventional seal. For relatively long underwater operation phases, it is also feasible for this additional opening to be sealed by means of a weld seam, which in any case withstands the adverse operating conditions.

In order to reliably dissipate on the one hand the lost power from the automation unit and on the other hand that from the operation of the compressor unit, it is expedient for the compressor unit itself to have a high-performance cooling system. This cooling system may, in particular during the pumping of natural gas during underwater operation, be designed such that the pumping medium flows around various components of the compressor unit, and the lost heat is in this way emitted to the pumping medium.