ARRANGEMENT IN TIE BOLT

[0001] BACKGROUND

[0002] 1. FIELD

[0003] Disclosed embodiments relate generally to the field of turbomachinery, and, more particularly, to a rotor structure for a turbomachine, and, even more particularly, to a venting/sealing arrangement in a tie bolt.

[0004] 2. Description of the Related Art

[0005] Turbomachinery is used extensively in the oil and gas industry, such as for performing compression of a process fluid, conversion of thermal energy into mechanical energy, fluid liquefaction, etc. One example of such turbomachinery is a compressor, such as a centrifugal compressor.

[0006] BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 illustrates a fragmentary cross-sectional view of one non-limiting embodiment of a disclosed rotor structure, as may be used in industrial applications involving turbomachinery, such as without limitation, centrifugal compressors.

[0008] FIGs. 2 through 5 respectively illustrate zoomed-in views of a portion of the cross-sectional view shown in FIG. 1 that may be used for illustrating and describing certain non-limiting structural and/or operational relationships of features in the disclosed rotor structure. [0009] DETAILED DESCRIPTION

[0010] As would be appreciated by those skilled in the art, turbomachinery involving rotors of tie bolt construction (also known in the art as thru bolt or tie rod construction) need to be sealed so that a process fluid (which could be flammable or otherwise hazardous) and which is pressurized by a turbomachine (e.g., a compressor) is inhibited from escaping to the atmosphere. In certain known rotor structures, this sealing is typically done using one or more seals (e.g., O-rings) disposed between the tie-bolt and the bore of a shaft section of the rotor. A respective O-ring may thus be subject to the process fluid internal pressure on one side and to atmospheric pressure on the other side. The present inventors have recognized that such known rotor structures lack features that would allow monitoring an incipient leakage of the process fluid about the tie bolt. Additionally, such known rotor structures lack features that would allow conveying a sealing fluid (such as a dry sealing fluid) about the tie bolt.

[0011] Disclosed embodiments make use of an innovative venting/sealing arrangement providing reliable and cost-effective venting/sealing backups and/or venting/sealing redundancies, such as with features that may be effective for venting about the tie bolt so that, for example, an incipient leakage of the process fluid can be monitored and in turn malfunctioning seals can be appropriately and timely replaced before escalating to an undesirable condition. The venting may be carried out by way of a conduit —drilled or otherwise constructed through a stub shaft— that under certain operational conditions effectively functions as a vent. Additionally, such features may be effective for conveying an appropriately pressurized sealing fluid about the tie bolt effective for reducing the likelihood of the process fluid escaping to the atmosphere. The conveying of the sealing fluid to the tie bolt may be carried out by way of another conduit — similarly drilled or otherwise constructed through the stub shaft— that under certain operational conditions effectively permits conveying the sealing fluid to the tie bolt. [0012] In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that disclosed embodiments may be practiced without these specific details that the aspects of the present invention are not limited to the disclosed embodiments, and that aspects of the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well- understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.

[0013] Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application.

[0014] FIG. 1 illustrates a fragmentary cross-sectional view of one non-limiting embodiment of a disclosed rotor structure 100, as may be used in industrial applications involving turbomachinery, such as without limitation, compressors (e.g., centrifugal compressors, etc.).

[0015] In one disclosed embodiment, a tie bolt 102 extends axially between a pressurized (e.g., relatively high pressure) process side and an atmospheric pressure side of the turbomachine. As would be readily appreciated by one skilled in the art, a stub shaft 104i is fixed to a first end of tie bolt 102.

A second stub shaft 104 ₂ is fixed to a second end of tie bolt 102. Second end of tie bolt 102 is axially opposite the first end of tie bolt 102. [0016] The description will proceed in connection with a first venting/sealing arrangement arranged proximate the first end of tie bolt 102, as illustrated in FIG. 1. As would be appreciated by one skilled in the art, a second venting/sealing arrangement is arranged proximate the second end of tie bolt 102. Since the first and second venting/sealing arrangements comprise identical structural and/or operational relationships in order to avoid pedantic and burdensome repetition the description will proceed in connection with just the first venting/sealing arrangement arranged proximate the first end of tie bolt 102, as illustrated in FIG. 1. Essentially, the first and second venting/sealing arrangements would exhibit structural symmetry with respect to one another about a radial plane 101 that cuts the longitudinal axis of the turbomachine.

[0017] In one disclosed embodiment, a plurality of axially spaced apart annular seals 106, such as annular seals 106i, IO6 ₂ through 106 _n (e.g., 0-rings)may be arranged about a segment of tie bolt 102 in correspondence with a radially- inward segment 108 of respective stub shaft 102. In FIG. 2, the number of illustrated annular seals is equal to 5 and so in this example n=5. It will be appreciated that the foregoing should be construed as one non-limiting example.

[0018] It will be further appreciated that each respective neighboring seal pair of the plurality of axially spaced apart annular seals 106 defines sealing sides of a respective chamber 109 of a plurality of axially sequential chambers, such as chambers 109i, 109 ₂ , as seen in FIG. 2, disposed between the process side and the atmospheric pressure side of the turbomachine. In the foregoing example, four axially sequential chambers would be defined by annular seals IO6 ₁ , IO6 ₂ through IO6 ₅ . For the sake of simplicity of illustration just two of such chambers are shown in FIGs. 2-5.

[0019] In the general case, the relationship that defines the number of chambers formed by an n number of annular seals is n-1. Accordingly, if the number of annular seals is 5, then the number of chambers is n — 1 = 4. [0020] A plurality of conduits 107, such as conduits 107i, 107 ₂ through 107 _n -i (e.g., drilled or otherwise constructed through the tie bolt) extend from a radially- outward segment 111 of the respective stub shaft 102 through the stub shaft to communicate with the plurality of axially sequential chambers 109 disposed between the process side and the atmospheric side of the turbomachine. In the foregoing example, four conduits would communicate with the four chambers defined by annular seals 106i, IO6 ₂ through IO6 _5.

[0021] In one disclosed embodiment, the plurality of conduits 107 may alternate between a first conduit 107i fluidly coupled at the radially-outward segment of the respective stub shaft 102 to receive a sealing fluid and a second conduit 107 ₂ fluidly connected at the radially-outward segment of the respective stub shaft to a venting outlet. It will be appreciated that the source of the sealing fluid and the venting outlet may be obtained by way of a dry fluid seal system 130, such as is commonly used in process gas centrifugal compressors.

Without limitation, dry fluid seal system 130 may involve a tandem seal configuration involving stationary and rotatable sealing elements. As would be appreciated by one skilled in the art, dry fluid seal system 130 may be disposed about the radially-outward segment 111 of the respective stub shaft 102 and, as noted above, may be used as the source of the sealing fluid and may be further used to provide a venting mechanism to a flow that may comprise the incipient leakage of the process fluid.

[0022] In one non-limiting embodiment, a plurality of impeller stages 140 (just one is illustrated in FIG. 1) may be disposed between stub shafts 104i and 104 _2. The plurality of impeller stages being supported by tie bolt 102 using any affixing technique appropriate for a given application. In one non-limiting embodiment, respective joint structures 150 may be arranged to couple contiguous impeller stages to one another. In one non-limiting embodiment, the respective joint structures 150 may, without limitation, comprise joining/stacking rotating elements, such as Hirth joint structures, Gleason curvic joints, and piloted rabbet or spigot-fit joints, each of which, as would be appreciated by one skilled in the art may center parts and transmit load but may also leak gas through the joint area. [0023] In one non-limiting embodiment, a computerized leakage monitor 160 may be coupled to second conduit/s (e.g., venting conduits 107 _2, 107 _3, etc.) to monitor a presence of any incipient leakage of process fluid in any of such venting conduits.

[0024] FIGs. 2 through 5 respectively illustrate zoomed-in views of a portion of the cross-sectional view shown in FIG. 1 that may be used for illustrating and describing certain non-limiting structural and/or operational relationships of features in the disclosed rotor structure.

[0025] FIG. 2 illustrates an example where annular seals 106i, 100 ₂ and IO6 ₃ are intact. That is, no seal malfunction is present in any of the annular seals. In this case, no fluid flow would develop in conduits 107i and 107 _2. This is essentially a static condition.

[0026] FIG. 3. illustrates an example where annular seal IO6 ₁ is broken and annular seals IO6 ₂ and IO6 ₃ are intact. That is, a seal malfunction is present in annular seal IO6 _1. In this case, pressurized process fluid would pass through malfunctioning annular seal IO6 ₁ into chamber 109i; pressurized sealing fluid would flow into chamber 109i and this would be effective to inhibit further progress of the pressurized process fluid in chamber 109i, provided the internal pressure of the sealing fluid is relatively larger compared to the internal pressure of the process fluid passing into chamber 109i.

[0027] FIG. 4. illustrates an example where annular seal IO6 ₂ is broken and annular seals IO6 ₁ and IO6 ₃ are intact. That is, a seal malfunction is present in annular seal IO6 _2. In this case, sealing fluid would pass through malfunctioning annular seal IO6 ₂ and into chamber 109 ₂ , effectively forming a fluid buffer zone overlapping chambers 109i and 109 ₂ with venting through conduit 107 _2. [0028] FIG. 5. illustrates an example where annular seals 106i and IO6 ₂ are broken and annular seal IO6 ₃ is intact. That is, seal malfunctions are present in annular seals IO6 ₁ and IO6 _2. In this case, sealing fluid mixed with pressurized process fluid would pass through malfunctioning annular seal IO6 ₂ and this mixture would be vented through conduit 107 _2. In this example, this mixture would not advance beyond chamber 109 _2.

[0029] In one non-limiting embodiment, the alternating chambers 109i, 109 ₂ through 109 _n -i include at least one backup first chamber (e.g., the chamber connected to first conduit 107 ₄ fluidly coupled to receive the sealing fluid) relative to the first chamber 109i, which is disposed downstream of the backup chamber connected to first conduit 107 _4. (The term downstream is indicative of the direction of process fluid flow between the pressurized process side and the atmospheric pressure side of the turbomachine). Similarly, the alternating chambers 109i, 109 ₂ through 109 _n -i includes at least one backup second chamber (e.g., the chamber connected to second conduit 107 ₃ fluidly coupled for venting) relative to a second chamber 109 ₂ disposed downstream of the chamber connected to second conduit 107 _3. It will be appreciated that the first chamber (e.g., chamber 109i) and the backup first chamber (e.g., chamber IO9 ₄ ) is each independently arranged to receive sealing fluid, and the second chamber (e.g., chamber 109 ₂ ) and the backup chamber (e.g., chamber 109 ₃ ) is each independently arranged to permit venting, such as discussed in the context of the foregoing examples.

[0030] In operation, for example, when one or more annular seals malfunctions in a respective neighboring seal pair of the plurality of annular seals IO6 ₁ , IO6 ₂ through 106 _n , and the malfunction of the one or more annular seals leads to incipient leakage of process fluid, a first fluid flow may be established through the first conduit/s (e.g., conduits 107i,107 ₄ )to convey sealing fluid into the respective chamber in communication with the first conduit/s, and/or a second fluid flow is established through the second conduit/s (e.g., conduits 107 ₂ , IO7 ₃ ) to permit venting of the respective chamber in communication with the second conduit/s. [0031] In operation, disclosed embodiments make use of innovative venting/sealing arrangements effective for venting the tie bolt rotor so that, for example, an incipient leakage of the process fluid can be monitored. Additionally, in operation disclosed embodiments are effective to, for example, convey to the tie bolt rotor a pressurized sealing fluid effective for reducing the likelihood of process fluid escaping to the atmosphere.

[0032] While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the scope of the invention and its equivalents, as set forth in the following claims.