Sealing system, machine and method with special pressure protection

Abstract

A sealing system (100) for a rotating shaft (190) of a machine is configured to separate a first zone (110) surrounding a first portion (191) of the rotating shaft (190) from a second zone (120) surrounding a second portion (192) of the rotating shaft (190). The sealing system (100) comprises a sealing member (130) disposed between the first portion (191) of the rotating shaft (190) and the second portion (192) of the rotating shaft (190), and a support member (135) supporting the sealing member (130). The support member (135) is configured to move at least in the axial direction due to a pressure differential between the first zone (110) and the second zone (120) and to close a gap (150) defined between the sealing system (100), in particular between the sealing member (130) and the rotating shaft (190), when the pressure differential is higher than a predetermined value.

Description

[Technical field]

[0001] The subject matter disclosed herein relates to a sealing system having extra pressure protection, a machine equipped with such a sealing system, and a protection method that operates even in the event of failure of a sealing device on the shaft of the machine. [Background technology]

[0002] In the oil, chemical and gas industries, it is known to equip turbomachines with dry gas seals, which are dry-operating mechanical seals, to prevent leakage of process fluids (which are particularly dirty and polluting in these applications) and to avoid the use of lubricating oils. Dry gas seals are used in harsh environments such as oil exploration, extraction and refining, petrochemical industry, gas transportation and chemical processing, and handle dirty fluids, so that a possible seal failure can cause uncontrolled amounts of process fluid to escape outside the turbomachine, which is very dangerous for the environment.

[0003] Therefore, in June 2018, the American Petroleum Institute published the first edition of API692 "Dry Gas Sealing Systems for Axial, Centrifugal, Rotary Screw Compressors and Expanders" to set minimum requirements for dry gas sealing systems to limit the amount of uncontrolled gas to the atmosphere. To avoid environmental contamination, the correct operation of dry gas sealing systems requires precise control of the pressure and flow rate of the process gas and / or sealing gas supplied to them to ensure the required level of reliability of the system. Summary of the Invention [Problem to be solved by the invention]

[0004] However, if a dry gas seal, or more generally a sealing device, fails, the process fluid can escape in an uncontrolled manner outside the turbomachine.

[0005] It would be desirable to have a system that significantly reduces (or even avoids) process gas flow outside of a turbomachine in the event of a seal failure, particularly a dry gas seal failure, and in particular, it would be desirable for such a system to have limited impact on the machine design.

[0006] According to one aspect, the subject matter disclosed herein relates to a sealing system for a rotating shaft of a machine, the system being configured to separate a first zone surrounding a first portion of the rotating shaft and a second zone surrounding a second portion of the rotating shaft, the first zone being at a higher pressure than the second zone during operation of the machine. The sealing system includes a sealing member configured to face a lateral surface of the rotating shaft at an intermediate portion of the rotating shaft located between the first and second portions, and a support member supporting the sealing member configured to move due to a pressure difference between the first and second zones. A gap is defined between the sealing system and the rotating shaft, the support member being further configured to close the gap when the pressure difference is higher than a predetermined value. [Brief description of the drawings]

[0007] A complete understanding of the disclosed embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which: [Figure 1] FIG. 1 is a highly simplified cross-sectional view of an embodiment of a machine provided with an innovative sealing system with extra pressure protection. [Diagram 2] FIG. 2 is a simplified cross-sectional view of a first embodiment of an innovative sealing system whose movement is an axial translation. [Diagram 3] FIG. 3 is a simplified cross-sectional view of a second embodiment of the innovative sealing system, the movement of which can be considered as a rotation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] According to one aspect, the subject matter disclosed herein relates to an innovative sealing system that can be equipped on a machine (e.g., a compressor or expander) to reduce (or even avoid) gas flow outside the machine on the rotating shaft of the machine. The innovative sealing system can also operate in the event that a standard seal, such as a dry gas seal, already equipped on the turbomachine fails. The innovative sealing system is placed on the machine shaft between the turbomachine and the standard seal.

[0009] In particular, the innovative sealing system seals the passage of gas (which is the process gas) in the machine shaft when a standard seal failure occurs during the operation of the machine by modifying its position on the machine shaft (at least axially translating and possibly also rotating) in order to reduce (or even eliminate) the clearance between the sealing system and the machine shaft. It is noted that when a standard seal failure occurs during the operation of the machine, the pressure upstream of the standard seal increases very rapidly, and therefore the pressure differential across the innovative sealing system increases very rapidly. Thus, the innovative sealing system is operable when the pressure differential across the system is higher than the pressure differential during normal operation of the machine (normal operation being when no seal failure occurs).

[0010] Next, the embodiments of the present disclosure will be described in detail, and examples thereof will be illustrated in the drawings. The embodiments and drawings are provided as explanations of the present disclosure and should not be construed as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope or spirit of the present disclosure. In the following description, similar reference numbers are used in the illustrations of the embodiment figures to indicate elements that perform the same or similar functions. Moreover, for clarity of illustration, some reference numbers may not be repeated in all figures.

[0011] In Fig. 1, a (partial) simplified cross-sectional view of an embodiment of a machine provided with an innovative sealing system with special pressure protection is shown. The sealing system is generally indicated with the reference number 100. The sealing system 100 comprises a sealing member 130, preferably a labyrinth seal, for example with a plurality of teeth, and a support member 135 supporting the sealing member 130. In other words, the sealing member 130 is mechanically coupled to the support member 135. Preferably, the sealing member 130 is made of or includes steel or an abradable material or a phenolic resin. It should be noted that the support member 135 may be manufactured from the same material as the sealing member 130 or from a different material. According to some embodiments, the sealing member and the support member may be realized in a single (suitably molded) part.

[0012] According to a preferred embodiment, the support member 135 is mechanically coupled to a body which may in particular be part of the machine casing 140. In particular, the body surrounds a rotating shaft 190 of the machine. The sealing system 100 defines two zones of the machine, namely a first zone 110 on a first side of the sealing system 100 and a second zone 120 on a second side of the sealing system 100. It should be noted that Figure 1 shows (very diagrammatically) a partial cross-section of only half of the machine with respect to a plane defined by the A-axis of the machine itself.

[0013] 1, the first zone 110 is fluidly coupled to a turbomachine, e.g., a compressor or expander 181, and the second zone 120 is fluidly coupled to a sealing device, e.g., a dry gas sealing device 182, that is specifically configured to limit gas leakage from the turbomachine (particularly around a rotatable shaft 190 thereof) during normal operation of the machine. Instead, the sealing system 100 is configured to separate the first zone 110, which surrounds a first portion 191 of the rotatable shaft 190, and the second zone 120, which surrounds a second portion 192 of the rotatable shaft 190, and specifically to fluidly isolate them upon failure of the sealing device 182, as better described below.

[0014] As partially and diagrammatically shown in Fig. 1, the sealing member 130 is configured to face a lateral surface, in particular a cylindrical lateral surface, of the rotating shaft 190 in an intermediate portion 193 of the rotating shaft 190 located between a first portion 191 and a second portion 192 of the rotating shaft. In other words, the sealing system 100 is arranged between a first zone 110 and a second zone 120, the first zone 110 being at a higher pressure than the second zone 120 during operation of the machine. A gap 150 is defined between the sealing system 100, in particular the sealing member 130, and the rotating shaft 190 of the machine. It is noted that the gap that is closed when necessary may be arranged differently from the gap 150 of Fig. 1, as will be better explained below.

[0015] When a seal failure occurs, in particular when a failure of the dry gas seal device 182 occurs, the pressure difference between the first zone 110 and the second zone 120 increases and may exceed a predetermined value, for example a safe predetermined value, which may be higher than 100 bar for a high pressure machine (however, the safe predetermined value depends on the machine rating). Indeed, when the seal device fails, the pressure drop across the seal device is zero or very small, for example 1-5 bar. As will become clear from the following, the support member 135 is configured to perform a movement at least in the axial direction due to the pressure difference between the first zone 110 and the second zone 120 and to close the gap 150 when the pressure difference is higher than a predetermined value. It is noted that although FIG. 1 does not show how and why the support member 135 moves (because this figure is very simplified), this can be understood from FIG. 2 and FIG. 3 taking into account the arrangement of the corresponding support members 235 and 335. In particular, the sealing system 100 is configured to reduce, and in particular eliminate, the gap 150 when the pressure differential is above a predetermined value.

[0016] For example, when a seal failure occurs, in particular when a failure of the dry gas seal device 182 occurs, the pressure difference between the first zone 110 and the second zone 120 may reach and even exceed a predetermined value, for example in less than one second, so that the machine is typically automatically switched off (the speed of the rotating shaft reaches 0 in a variable time range, for example 5-15 minutes). As mentioned above, when the pressure difference reaches a predetermined value, the support member 135 closes the gap 150. Advantageously, the sealing member 130 is configured to be able to close the gap 150 and to keep it closed from the time when the seal failure is detected until the machine is switched off and the machine no longer rotates, i.e. for a period of time of, for example, 5-15 minutes.

[0017] It is noted that the machine may be equipped with one or more innovative sealing systems. It is also noted that the sealing member may have a cylindrical inner surface that continuously surrounds and faces the outer surface of the rotating shaft, or may have one or more cuts that extend along the axial direction and interrupt the cylindrical development of the inner surface. Advantageously, such cuts do not extend along the entire axial length of the sealing member, for example, the cuts may extend along 80% of the axial length of the sealing member, leaving a portion of the inner surface of the sealing member with a continuous cylindrical development. Such cuts may allow different and / or independent movements of separate parts of the sealing member.

[0018] Figures 2 and 3 show two different embodiments of a sealing system with different movement possibilities (see in particular the large black arrows in each).

[0019] According to the embodiment of Fig. 2, a sealing system 200 is shown having a support member 235 that can perform a movement (particularly a translation) only in the axial direction, i.e. parallel to the direction of the axis A of the rotating shaft 290. For example, the support member 235 may be coupled to the body 240 by an elastic element 236, in particular a spring. Advantageously, the support member 235 performs an axial movement (particularly a translation) due to a force caused by a pressure difference between the first zone 210 and the second zone 220 above a predefined value, thus closing the gap 250. The force due to the pressure difference is countered by the elastic element 236.

[0020] 2, the sealing system 200 is configured to separate, in particular fluidly separate, a first zone 210 surrounding a first portion 291 of the rotating shaft 290 and a second zone 220 surrounding a second portion 292 of the rotating shaft 290. It is noted that the rotating shaft 290 may be mechanically coupled to an additional element 295 surrounding the rotating shaft 290 and rotating together therewith, the additional element 295 being considered as part of the rotating shaft. In particular, the gap 250 is defined in the second zone 220 between the body 240 and the rotating shaft 290, in particular between the body 240 and the additional element 295, more particularly the portion of the additional element 295 that projects radially relative to the shaft 290.

[0021] Advantageously, when the support member 235 performs an axial movement, it translates relative to the body 240 until it abuts against the additional element 295, in particular against an annular radially projecting portion of the additional element 295. In this way, the support member 235 closes the gap 250 and prevents the passage of fluid across the gap 250. Advantageously, the body 240 can be provided with an additional mechanical gasket 241, for example an O-ring, to improve the sealing between the body 240 and the support member 235 during the movement of the support member 235.

[0022] According to the embodiment of FIG. 3, a sealing system 300 is shown having a support member 335 that is capable of performing rotational movement about an axis (i.e., movement having axial and radial components) due in particular to deformation of the support member 335, as will be better explained below.

[0023] With non-limiting reference to Fig. 3, the sealing system 300 comprises a sealing member 330 mechanically coupled (for example welded or glued or bolted) to a support member 335. Advantageously, the support member 335 comprises an annular groove 339. Preferably, the groove 339 is arranged on the support member 335 on the side facing the first zone 310 and in particular fluidly coupled to the first zone 310. The groove 339 is configured such that at least a portion of the support member 335 undergoes a rotational movement when the pressure difference between the first zone 310 and the second zone 320 is equal to or greater than a predetermined value. In particular, at least a portion of the support member 335 may rotate (in particular by deformation) with respect to an area or point located on a portion of the support member 335 near the groove 339, in particular with respect to an area or point of the support member 335 located near the second zone 320 (see for example the black dot in Fig. 3). It should be noted that according to an embodiment similar to that of Fig. 3, the support member may include at least two separate portions, a first portion being capable of rotating relative to a second portion, such rotation may result from deformation of the first portion and / or the second portion and / or another portion of the support member.

[0024] Advantageously, the support member 335 is mechanically coupled to the body 340. It is noted that the support member 335 is configured to rotate relative to the body 340 and close the gap 350 due to forces acting on the groove 339, in particular forces resulting from a pressure difference between the first zone 310 and the second zone 320 being equal to or greater than a predetermined value. It is noted that due to a certain movement of the support member 335, the closing of the gap 350 may result from only partial contact of the sealing member 330 with the shaft 390 (or alternatively an additional element 395 as described in the following paragraph), for example some teeth of the sealing member 330.

[0025] With non-limiting reference to FIG. 3, the support member 335 can be conceptually separated into three zones: a first zone mechanically coupled to the body 340, a second zone mechanically coupled to the sealing member 330, and a third zone between the first and second zones, in which the groove 339 is located. As will be readily apparent to a person skilled in the art, the third zone of the support member 335 is the zone that is mainly affected by the deformation and where the point / area around which the rotational movement of the support member 335 is located (see, for example, the black dots in FIG. 3). Advantageously, the sealing member 330 may have one or more cuts extending along the axial direction so as to be able to define two or more sectors of the sealing member 330. According to a first embodiment, the cuts do not extend along the entire axial length of the sealing member 330, for example the cuts may extend along 80% of the axial length leaving a portion of the inner surface of the sealing member 330 with a continuous cylindrical development. According to another embodiment, the notches extend along the entire axial length of the sealing member 330. Such notches may allow different and / or independent movements of separate sectors of the sealing member 330. More advantageously, even the second zone of the support member 335 may have one or more notches extending along the axial direction, in particular in the sealing member notches.

[0026] As mentioned above, the sealing system 300 is configured to separate, in particular fluidically separate, a first zone 310 surrounding a first portion 391 of the rotating shaft 390 and a second zone 320 surrounding a second portion 392 of the rotating shaft 390. It is noted that the rotating shaft 390 may be mechanically coupled to an additional element 395 surrounding the rotating shaft 390 and rotating together therewith, the additional element 395 being considered as part of the rotating shaft. Advantageously, a gap 350 is defined between the sealing member 330 and the rotating shaft 390, in particular between the sealing member 330 and the additional element 395.

[0027] According to other embodiments (not shown in any of the figures), the support member can translate both axially and radially with respect to the axis A of the rotating shaft. For example, the body of the sealing system can have an inclined surface facing the rotating shaft, on which the support member can slide, for example by means of an elastic element. In particular, the support member can translate both axially and radially with respect to the body until the sealing member abuts the rotating shaft, closing the gap between the sealing member and the rotating shaft and preventing the passage of fluid across the gap.

[0028] According to another aspect (see, e.g., FIG. 1 ), the subject matter disclosed herein is a machine having a rotating shaft 190, a compressor or expander 181 arranged on a first portion 191 of a rotating shaft 190; a sealing device 182, in particular a dry gas sealing device, arranged on the second part 192 of the rotating shaft 190; - a sealing system 100 arranged between a compressor or expander 181 and a sealing device 182 and facing a third portion 193 of a rotating shaft 190, configured to separate a first zone 110 surrounding a first portion 191 of the rotating shaft 190 and a second zone 120 surrounding a second portion 192 of the rotating shaft 190, the sealing system 100 moving due to a pressure difference between the first zone 110 and the second zone 120 and closing a gap 150 between the sealing system 100 and the rotating shaft 190 when the pressure difference is higher than a predetermined value.

[0029] According to yet another aspect, the subject matter disclosed herein relates to a method of protection in the event of failure of a sealing device (e.g., seal 182, FIG. 1 ) of a shaft (e.g., rotating shaft 190, FIG. 1 ) of a machine (e.g., compressor or expander 181, FIG. 1 ). A sealing system (e.g., system 100, FIG. 1 ) is provided on the shaft upstream of the sealing device. The sealing system is specifically configured to completely seal the shaft when a pressure difference across the sealing system is higher than a predetermined value.

Claims

1. A sealing system (100) for a rotating shaft (190) of a machine, configured to separate a first zone (110) surrounding a first portion (191) of the rotating shaft (190) from a second zone (120) surrounding a second portion (192) of the rotating shaft (190), the first zone (110) being at a higher pressure than the second zone (120) during operation of the machine, the system comprising: a sealing member (130) configured to face a lateral surface of the rotating shaft (190) at an intermediate portion (193) of the rotating shaft (190), the intermediate portion (193) of the rotating shaft (190) being located between the first portion (191) of the rotating shaft (190) and the second portion (192) of the rotating shaft (190); a support member (135) for supporting the sealing member (130); A gap (150) is formed between the sealing system (100) and the rotating shaft (190); the support member (135) is configured to effect movement due to a pressure differential between the first zone (110) and the second zone (120) and to close the gap (150) when the pressure differential is higher than a predetermined value; The sealing system (100), wherein said movement is at least in an axial direction.

2. The sealing system (100) of claim 1, wherein the movement is axial and radial.

3. The sealing system (100) of claim 1, wherein the movement is a portion of a deformation of the support member (135) due to the pressure differential.

4. The sealing system (100, 300, 400) of claim 1, wherein the gap is defined between the sealing member (130) and the rotating shaft (190, 395, 495).

5. The sealing system (100, 200) of claim 1, wherein the gap (250) is defined between the body (140, 240) and the rotating shaft (190, 290).

6. 2. The sealing system (100, 200) of claim 1, wherein the gap is defined between the support member (135, 235) and the rotating shaft (190, 295), in particular an annular radially protruding portion (295) integral with or fixed to the rotating shaft (290).

7. The system further includes a body (140, 240); The support member (135, 235) is configured to translate axially relative to the body (140, 240). The sealing system (100, 200) of claim 1.

8. The system further includes a body (140, 340); The support member (135, 335) is configured to rotate relative to the body (140, 340). The sealing system (100, 300) of claim 1.

9. The sealing system (100) of claim 1, wherein the sealing member (130) is made of or includes steel or an abradable material or a phenolic resin.

10. the sealing member (130) is arranged to deform and / or wear when the support member (135) moves to close the gap (150); The sealing system (100) of claim 1.

11. A machine having a rotating shaft (190), A sealing system (100) according to claim 1; a compressor or expander (181) mechanically coupled to the rotating shaft (190); a seal device (182), in particular a dry gas seal device, The sealing system (100) is disposed between the compressor and / or the expander (181) and the sealing device (182).

12. 1. A method of protecting a machine in the event of failure of a sealing device (182) of a rotating shaft (190) of said machine during operation, comprising the steps of: a sealing system (100) is provided on the rotating shaft (190) upstream of the seal device (182); The method of claim 1, wherein the sealing system (100) is configured to seal against the rotating shaft (190) when a pressure differential across the sealing system (100) is greater than a predetermined value.

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