MOTOR COMPRESSOR WITH A DRAINAGE ARRANGEMENT

Description

[0001] The subject matter of the present disclosure relates to a turbomachine.

[0002] 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.

[0003] 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.

[0004] 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. WO 2009 / 111616 A2 discloses a compressor assembly including a separator and an ejector pump. The separator separates a multiphase fluid stream into a substantially liquid portion which is then sent to a liquid reservoir and a substantially gaseous stream. An inlet of a compressor is fluidly coupled with an outlet of the separator to receive and pressurize the substantially gaseous portion of the multiphase fluid stream and an outlet of the compressor is configured to discharge a pressurized gas. An ejector pump receives a portion of the pressurized gas from the compressor to draw in a flow of the substantially liquid portion of the multiphase fluid stream from the liquid reservoir and discharge a combined stream of liquid and pressurized gas. A fluid discharge line is fluidly coupled to the compressor outlet and receives the pressurized gas from the compressor and the combined stream of liquid and pressurized gas from the ejector pump to form a pressurized multiphase fluid stream.

[0005] 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

[0006] The present invention is defined in the accompanying claims.

[0007] Further details and specific embodiments will refer to the attached drawings,

[0008] 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 not forming part of the present invention but representing background art that is useful for understanding invention; and Figure 3 is a side sectional view of a detail of the drainage apparatuses of figures 1 and 2. DETAILED DESCRIPTION

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] According to the embodiment of figure 1 and the example of figure 2, the stages 3 are assembled in a vertical orientation. In other words, the shaft 8 is oriented vertically.

[0014] 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.

[0015] The motorcompressor 2 also comprises a droplet / solid particles separator 11 upstream of the first stage 3.

[0016] 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.

[0017] According to the invention, 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.

[0018] According to the invention, the first pipe 10 is also enclosed by the casing 12 of the motorcompressor.

[0019] 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.

[0020] In this way, the liquid is suctioned from the drainage sump 9 and delivered into the process fluid inside the motorcompressor 2.

[0021] According to the embodiment of figure 1 and the example of figure 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.

[0022] The second pipe 14 also has a second end 14b, which is fluidly connected to said first pipe 10 at an intermediate point between said first and second ends 10a, 10b.

[0023] Therefore, the second pipe takes a portion of the process fluid from inside the motorcompressor 2 and delivers it inside the first pipe 10.

[0024] 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.

[0025] 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.

[0026] Advantageously, and similarly to the first pipe 10, also the second pipe 14 is placed inside the casing 12 of the motorcompressor 2.

Claims

1. A motorcompressor (2) comprising a drainage sump (9); a plurality of stages each having a duct (4) with an intake section (5) and a discharge section (6) for a process fluid; a drainage apparatus (1) placed in fluid communication with said drainage sump (9) and with a duct of one of said stages (3), the drainage apparatus (1) comprising a first pipe (10) being placed inside an external casing (12) and having a first end (10a) inserted in a drainage sump (9) of the motorcompressor (2) and a second end (10b) in fluid communication with the intake section (5) of a duct (4) of a stage (3) of said motorcompressor (2); wherein the intake section (5) is upstream of a rotating element (7) inside the duct (4) of the stage (3) for a process fluid to be directed towards the rotating element (7), and said apparatus (1) comprises a device (13) for generating a pressure difference between said second end (10b) and said first end (10a) so that the process fluid is taken from said drainage sump (9) and delivered into the intake section (5) of said duct (4).

2. The motorcompressor (2) according to the previous claim, wherein said device (13) for generating a pressure difference comprises a second pipe (14) having a first end (14a) configured to be fluidly connected to the discharge section (6) of the duct (4) of a stage (3) of said motorcompressor (2); and a second end (14b) fluidly connected to said first pipe (10) at an intermediate point between said first and second ends (10a, 10b).

3. The motorcompressor (2) according to the previous claim, wherein said second end (14b) of the second pipe (14) has a convergent portion (16) to decrease the pressure of the process fluid discharged by the second end (14b) of the second pipe (14).

4. The motorcompressor (2) according to claim 2 or claim 3, wherein said discharge section (6) to which the first end (14a) of the second pipe (14) is configured to be fluidly connected is downstream of the rotating element (7) of the stage (3) of said motorcompressor (2).

5. The motorcompressor (2) according to any one of claims 2 or 3, wherein said discharge section (6) to which the first end (14a) of the second pipe (14) is configured to be fluidly connected is a downward section of compression suction.

6. The motorcompressor (2) according to any claim from 2 to 5, wherein said second end (14b) of the second pipe (14) is directed towards the second end (10b) of the first pipe (10).

7. The motorcompressor (2) according to any one of the previous claims, wherein said intake section (5) is the intake section (5) of the first stage (3).

8. The motorcompressor (2) according to claim 2 or any claims dependent on claim 2, wherein said second pipe (14) is placed inside said casing (12).