MOTORCOMPRESSOR THEREWITH

DESCRIPTION

The subject matter of the present disclosure relates to a turbomachine.

Preferably, the embodiments of the invention will be described specifically as applied to a subsea motorcompressor, however this will be done without losing the general approach.

According to the state of the art, a subsea motorcompressor comprises an electric motor and an operating portion, itself comprising a rotor. For example, the operating portion can be a centrifugal compressor. A shaft is connected to both the electric motor and the rotor. The rotor comprises a plurality of compression stages connected to the shaft. Each stage has an intake and a discharge duct for a process fluid. The motorcompressor stages are also placed in fluid communication with each other serially, so that the discharge of each stage feeds the intake of the next.

In a known subsea motorcompressor, the stages are assembled in a vertical configuration, meaning that the shaft itself is arranged vertically. A drainage sump is placed at the bottom, so that it can collect all of the liquids entering in the machine during the installation or operation. In another configuration, the shaft can be arranged horizontally, with the sump arranged below the stages.

The sump can then be drained through a flange on the bottom connected to an external pumping device through a valve. Disadvantageously, the drainage operation is not automatized, as it requires the intervention of the operator. Also, the current system requires that the motorcompressor be taken offline for drainage.

SUMMARY

A first embodiment of the invention therefore relates to a drainage apparatus for a subsea motorcompressor. The apparatus comprises a first pipe having a first end and a second end. The first end is configured to be inserted in a drainage sump of a subsea motorcompressor. The second end is configured to be connected to an intake duct of a stage of the motorcompressor. The apparatus comprises a device for generating a pressure difference between the second and the first end, so that liquid is taken from the drainage sump and delivered into the intake.

A second embodiment relates to a motorcompressor comprises a drainage sump. The motorcompressor also comprises a plurality of stages, each having an intake and a discharge duct for a process fluid. An apparatus as the one described above is placed in fluid communication with the drainage sump and with an intake of one of the stages.

Further details and specific embodiments will refer to the attached drawings, In which:

Figure 1 is a side sectional view of a drainage apparatus for a motorcompressor according to a first embodiment of the present invention;

Figure 2 is a side sectional view of a drainage apparatus for a motorcompressor according to a second embodiment of the present invention; and Figure 3 is a side sectional view of a detail of the drainage apparatuses of figures 1 and 2.

DETAILED DESCRIPTION

The following description of exemplary embodiments refer to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

With reference to the attached drawings, with the number 1 is indicated a drainage apparatus for a motorcompressor according to an embodiment of the present invention. Similarly, with the number 2 is indicated a motorcompressor according to a further embodiment of the present invention.

The motorcompressor 2 comprises a plurality of stages 3. Each stage 3 has a duct 4 for a process fluid. The duct 4 has an intake 5 and a discharge section 6 for the process fluid. Inside the duct 4, each stage 3 is provided with a rotating element 7, which can be, depending on the kind of machine, either a rotor of a turbine or an impeller of a compressor.

As it is usual in these machines, the stages 3 are arranged serially. In other words, the discharge section 6 of the duct 4 of each stage 3 is placed in direct fluid communication with the intake section 5 of the duct 4 of the next stage 3. Therefore, each stage 3 compresses the process fluid which is discharged by the previous stage 3 in the sequence. As shown in figures 1 and 2, the rotating elements 7 of all the stages 3 are attached onto a single shaft 8. The shaft 8 has a rotation axis "A". Also, in order to provide and/or extract energy to the rotating elements 7, the shaft 8 is connected to an engine or to a generator (both are not shown in the drawings). According to another embodiment, not shown in the drawings, there is no shaft and the stages 3 are attached to one another.

According to the embodiments shown in figures 1 and 2, the stages 3 are assembled in a vertical orientation. In other words, the shaft 8 is oriented vertically.

The motorcompressor 2 also comprises a drainage sump 9. The drainage sump 9 is placed at the bottom, below all the stages 3. In the configuration of the motorcompressor 2 shown in the figures, the sump 9 is placed below the lowest stage 3, in which is the process fluid has the highest pressure. The motorcompressor 2 also comprises a droplet/solid particles separator 11 upstream of the first stage 3.

Also, the motorcompressor 2 is provided with an external casing 12, which encloses all the above mentioned components and protects them from the outside environment. As shown in the figures, the apparatus 1 is installed inside the motorcompressor 2 just described. Specifically, the apparatus 1 comprises a first pipe 10. The first pipe 10 has a first end 10a, which is configured to be inserted in the drainage sump 9 of the motorcompressor 2. The first pipe 10 also has a second end 10b, which is configured to be connected to the stage 3 or to the inlet duct of the motorcompressor 2. Preferably, the second end 10b of the first pipe 10 is attached to the intake section 5 of the stage 3. More preferably, the second end 10b of the first pipe 10 is attached to the intake section 5 of the duct 4 of the first stage of the motorcompressor 2.

Advantageously, the first pipe 10 is also enclosed by the casing 12 of the motorcompressor. The apparatus 1 also comprises a device 13 for generating a pressure difference between the second 10b and the first end 10a of the first pipe 10.

In this way, the liquid is suctioned from the drainage sump 9 and delivered into the process fluid inside the motorcompressor 2.

According to the embodiments shown in figures 1 and 2, the device 13 comprises a second pipe 14. Such second pipe 14 has a first end 14a, which is configured to be connected to a high pressure zone 15 of the motorcompressor 2. Specifically, a "high pressure zone" is defined as any part of the motorcompressor 2 in which the process fluid has a pressure higher than the compressor suction pressure. For example, the high pressure zone 15 can be a discharge section 6 of a duct 4 of any stage 3. Alternatively, the high pressure zone 15 can be a downward section of compression suction, for example just downstream the droplet separator 11.

The second pipe 14 also has a second end 14b, which is fluidly connected to say first pipe 10 at an intermediate point between said first and second ends 10a, 10b. Therefore, the second pipe takes a portion of the process fluid from inside the motorcompressor 2 and delivers it inside the first pipe 10.

With more detail, in the detail shown in figure 3 the second end 14b of the second pipe 14 has a convergent portion 16, so that it can accelerate the process fluid which is delivered into the first pipe 10. Furthermore, the second end 14b of the second pipe 14 is arranged so that the process fluid discharged from it is directed towards the second end 10b of the first pipe 10. In this way, the acceleration creates a suction effect inside the first pipe 10, thus allowing the extraction of discharged liquid from the sump 9. This approach allows to create a pressure difference between the two ends of the first pipe 10 that is up to half of the pressure in the high pressure zone.

Should any further increase be necessary, it is advantageously possible to connect any number of devices 13 for creating a pressure difference as described above.

Advantageously, and similarly to the first pipe 10, also the second pipe 14 is placed inside the casing 12 of the motorcompressor 2.