Title of Invention | AN IMPROVED END SEALING DEVICE ADAPTABLE TO CENTRIFUGAL COMPRESSORS |
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Abstract | The invention relates to an improved end sealing device adaptable to centrifugal compressors, the compressor provided with at least two journal bearings (6) one at each end, the distance between the centerlines (JBCL) of the journal bearings (6) constituting a bearing span (Y+A) which accommodates the impellers mounted on a rotor; at least two sealing devices (1,2) and a plurality of nozzles (9) disposed along a nozzle center line (NCL), the suction and discharge regions of the compressor provided with a plurality of gas collection zones in the form of volutes (8) encompassed in casings (7); the impellers provided with at least one spacer (3) between each; the rotor (5) arranged with grooves corresponding to the sealing fins of the sealing device (1); and the sealing devices (1,2) constituting a two-level sealing means comprising end labyrinth seals (1) with gas ports (4) lying on the horizontal parting plane for equalizing the pressure to provide a common reference pressure at both end sealing devices, and a plurality of dry gas seals (4) to minimize the atmospheric emission, wherein the distance between a first and an intermediate centerline, and the distance between the intermediate and a second centerline respectively being 'Y' and 'A', and wherein the axial space requirement to accommodate the volute casings (7) being 'X', the improvement at least one equalizing gas port (4) is configured on the end labyrinth (1) lying on a vertical plane formed by a conical face of the casing (7) of the volute (8) and the end labyrinth (1) such that the bearing span (Y+A) is reduced by a dimension (Z) to be (Y+A-Z), the 'Z' being equal to the width of the equalizing gas port (4). |
Full Text | FIELD OF INVENTION The present invention generally relates to centrifugal compressors. More particularly, the invention relates to an improved end sealing device adaptable to centrifugal compressors. BACKGROUND OF INVENTION Centrifugal compressors are used to compress any gas medium to a higher discharge pressure. This is achieved by the high-speed rotation of the rotor supported by journal bearings. Traditional configuration of end sealing device in centrifugal compressors consists of labyrinth with an intermediate equalizing circumferential gas port on its outer diameter. These seals consist of a stationary ring with a number of sealing fins machined on inner diameter separated by equalizing gas ports. The corresponding rotor surface is either plane or may have a series of grooves. Required clearance is maintained between the stationary seal fins and the rotor surface such that there is no contact between those under any operating condition. The equalizing gas ports at both ends of the compressor are operably connected to maintain a common reference pressure for performance control of other downstream sealing mechanisms provided on the rotor. As described hereinabove, the centrifugal compressor is equipped with journal bearings on both ends of the compressor. Bearing span of the compressor constitutes a distance between the centerlines of the Journal bearings installed at both ends of the machine. Thus, bearing span constitutes an axial space in a compressor in which primarily three functional features are accommodated. Firstly, the impellers mounted on the rotor occupy a major space. Secondly, a space is occupied by a sealing device provided in the ends of the compressor to arrest the gas leakage to atmosphere. Within the sealing device, there are two levels of sealing. First, end labyrinth seals are provided to equalize the pressure at both ends of the compressor. Further, a secondary sealing is provided with variety of seals whose function is to minimize the emissions to atmosphere. The existing end labyrinth seal configuration occupies more axial space, which calls for provision of higher bearing span of the machine rotor. This generally results in poor rotor dynamic behaviour of the machine leading to infeasibility of machine design. OBJECTS OF INVENTION It is therefore an object of the invention to propose an improved end sealing device adaptable to centrifugal compressors which eliminates the disadvantages of the prior art. Another object of the invention is to propose an improved end sealing device adaptable to centrifugal compressors which reduces the bearing span of the compressor thereby improve rotor dynamics. A further object of the invention is to propose an improved end sealing device adaptable to centrifugal compressors which is efficient and cost-effective solution for design of compressor. SUMMARY OF INVENTION Availability of axial space in the casing between the nozzle centerline and the conical face largely depends on the selected size of the nozzle. Nozzles are the openings for the gas entry and exit. To minimize the pressure loss at entry and exit the nozzle area is required be kept adequate to maintain the flow velocities within the specified limits. Gas intake and discharge volutes are constructed in line with the size of the nozzles. Based on the selected size of the nozzle, the axial space requirement will change but cannot be lowered below a minimum value. The end labyrinth seal with equalizing port according to prior art lie on the horizontal parting plane. The invention proposes an end sealing device having equalizing gas port incorporated on the vertical plane formed by the casing conical face and the seal. Thus, the invention proposes a modification of the end sealing device which reduces the distance of the journal bearing centerline with respect to the centerline of the nozzle by a value, which is equal to the width of the annular equalizing gas port. Accordingly, there is provided an improved end sealing device adaptable to centrifugal compressors, the compressor provided with at least two journal bearings at one each end, the distance between the centerlines (JBCL) of the journal bearings constituting a bearing span (Y+A) which accommodates the impellers mounted on the rotor, the sealing devices and a plurality of nozzles disposed along a nozzle center line (NCL); the suction and discharge regions of the compressor are provided with a plurality of gas collection zones in the form of volutes encompassed in casings; the impellers provided with at least one spacer between each; the rotor arranged with grooves corresponding to the sealing fins of the sealing device; and the sealing device constituting a two-level sealing means comprising end labyrinth seals with gas ports lying on the horizontal parting plane for equalizing the pressure to provide a common reference pressure at both end sealing devices, and a plurality of dry gas seals to minimize atmospheric emission, wherein the distance between the first and intermediate centerline, and the distance between the intermediate and the second centerline respectively being 'Y' and 'A', and wherein the axial space requirement to accommodate the volute casings being 'X', the improvement is characterized in that at least one equalizing gas port is configured on the end labyrinth lying on a vertical plane formed by a conical face of the casing of the volute and the end labyrinth such that the bearing span (Y+A) is reduced by a dimension (Z) to be (Y+A-Z), the 'Z' being equal to the width of the equalizing gas port. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 - shows a prior art end sealing device in centrifugal compressors, Figure 2 - shows an end sealing device with equalizing gas port incorporated on the vertical plane according to the invention Figure 3 - shows an arrangement of a compressor equipped with an end sealing device having a bearing span according to the prior art Figure 4 - shows the arrangement of figure-3 with the equalizing gas port incorporated according to the invention to reduce the bearing span. DETAILED DESCRIPTION OF INVENTION As shown in Figure 3, the centrifugal compressor ends are provided with end sealing device (1, 2) to minimize the leakage. The distance between the nozzle centerline (NCL) and journal bearing centerline (JBCL) is one of the critical dimensions to decide the bearing span of the machine. A compressor equipped with a particular nozzle (9) and dry gas seal (2) combination and end labyrinth arrangement (1) as shown in Figure 3, the bearing span works out to Y + A. The modification proposed on the end sealing device (1, 2) indicated in Figure 4 incorporating the equalizing gas port (4) on the vertical plane which reduces the bearing span of the compressor rotor (5). The compressor equipped with the same nozzle (9) and dry gas seal (2) combination when modified as indicated in Figure 4, the bearing span works out to (Y-Z)+A. This clearly evidences a reduction in bearing span by a value 'Z', which is equal to the width of the equaling gas port (4). This is achieved by extending the end labyrinth (1) into the volute zone (8) of the compressor, by reducing the length of the spacer (3) a component mounted on rotor as shown in figure 3 without disturbing the volute (8) requirements. As described hereinabove, the dimension 'X' is the axial space requirement of the volute (8) and basically governed by the size of the Suction and discharge nozzles (9). From the figures 3 and 4, it is evident that in both configurations dimensions 'X' remained same. However the modified configuration of the end sealing device results in considerable reduction of the bearing span that improves rotor dynamics. TECHNICAL FEATURES Nozzles (9): Projecting parts with an opening of specified geometry for directing a flow of fluid and to minimize the gas entry and exit pressure losses. Volute (8): The gas collection zones with a particular geometrical construction at suction and discharge regions of a compressor. Dry Gas Seal (2): A secondary end sealing device provided next to end sealing device to prevent toxic process gas leaking into atmosphere and to reduce the losses. Journal Bearinq(6): A hydrodynamic lubricated bearing supporting the journals to provide the required rotor dynamic stability during machine operation. Rotor Assembly (5): An assembly of shaft and impellers, which are shrunk fit on the shaft by maintaining the specified pitch. Spacer (3): The pitch between the impellers is maintained by providing a spacer of a particular geometry and length between impellers. Balancing Gas Port (4): The balancing gas port is meant to provide a common reference pressure for the end sealing device. End Labyrinth (1): A primary end labyrinth sealing device to minimize the process gas leakage from the compressor and to provide a common reference pressure for the seals at both ends. Conical Face of the Casing (7) A conical profile of the casing required to direct the flow of gas into the first impeller. WE CLAIM 1. An improved end sealing device adaptable to centrifugal compressors, the compressor provided with at least two journal bearings (6) one at each end, the distance between the centerlines (JBCL) of the journal bearings (6) constituting a bearing span (Y+A) which accommodates the impellers mounted on a rotor; at least two sealing devices (1,2) and a plurality of nozzles (9) disposed along a nozzle center line (NCL), the suction and discharge regions of the compressor provided with a plurality of gas collection zones in the form of volutes (8) encompassed in casings (7); the impellers provided with at least one spacer (3) between each; the rotor (5) arranged with grooves corresponding to the sealing fins of the sealing device (1); and the sealing devices (1,2) constituting a two-level sealing means comprising end labyrinth seals (1) with gas ports (4) lying on the horizontal parting plane for equalizing the pressure to provide a common reference pressure at both end sealing devices, and a plurality of dry gas seals (4) to minimize the atmospheric emission, wherein the distance between a first and an intermediate centerline, and the distance between the intermediate and a second centerline respectively being 'Y' and 'A', and wherein the axial space requirement to accommodate the volute casings (7) being 'X', the improvement is characterized in that: at least one equalizing gas port (4) is configured on the end labyrinth (1) lying on a vertical plane formed by a conical face of the casing (7) of the volute (8) and the end labyrinth (1) such that the bearing span (Y+A) is reduced by a dimension (Z) to be (Y+A-Z), the 'Z' being equal to the width of the equalizing gas port (4). 2. An improved end sealing device adaptable to centrifugal compressors as substantially described herein and illustrated with the accompanying drawings. The invention relates to an improved end sealing device adaptable to centrifugal compressors, the compressor provided with at least two journal bearings (6) one at each end, the distance between the centerlines (JBCL) of the journal bearings (6) constituting a bearing span (Y+A) which accommodates the impellers mounted on a rotor; at least two sealing devices (1,2) and a plurality of nozzles (9) disposed along a nozzle center line (NCL), the suction and discharge regions of the compressor provided with a plurality of gas collection zones in the form of volutes (8) encompassed in casings (7); the impellers provided with at least one spacer (3) between each; the rotor (5) arranged with grooves corresponding to the sealing fins of the sealing device (1); and the sealing devices (1,2) constituting a two-level sealing means comprising end labyrinth seals (1) with gas ports (4) lying on the horizontal parting plane for equalizing the pressure to provide a common reference pressure at both end sealing devices, and a plurality of dry gas seals (4) to minimize the atmospheric emission, wherein the distance between a first and an intermediate centerline, and the distance between the intermediate and a second centerline respectively being 'Y' and 'A', and wherein the axial space requirement to accommodate the volute casings (7) being 'X', the improvement at least one equalizing gas port (4) is configured on the end labyrinth (1) lying on a vertical plane formed by a conical face of the casing (7) of the volute (8) and the end labyrinth (1) such that the bearing span (Y+A) is reduced by a dimension (Z) to be (Y+A-Z), the 'Z' being equal to the width of the equalizing gas port (4). |
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00185-kol-2007-correspondence.pdf
0185-kol-2007-correspondence others.pdf
0185-kol-2007-description (complete).pdf
185-KOL-2007-AMANDED PAGES OF SPECIFICATION.pdf
185-kol-2007-correspondence.pdf
185-KOL-2007-DESCRIPTION (COMPLETE).pdf
185-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf
185-kol-2007-examination report.pdf
185-kol-2007-granted-abstract.pdf
185-kol-2007-granted-claims.pdf
185-kol-2007-granted-description (complete).pdf
185-kol-2007-granted-drawings.pdf
185-kol-2007-granted-form 1.pdf
185-kol-2007-granted-form 2.pdf
185-KOL-2007-GRANTED-LETTER PATENT.pdf
185-kol-2007-granted-specification.pdf
185-kol-2007-reply to examination report.pdf
Patent Number | 248334 | ||||||||
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Indian Patent Application Number | 185/KOL/2007 | ||||||||
PG Journal Number | 27/2011 | ||||||||
Publication Date | 08-Jul-2011 | ||||||||
Grant Date | 05-Jul-2011 | ||||||||
Date of Filing | 06-Feb-2007 | ||||||||
Name of Patentee | BHARAT HEAVY ELECTRICALS LIMITED | ||||||||
Applicant Address | REGIONAL OPERATIONS DIVISION(ROD), PLOT NO:9/1, DJ BLOCK, 3RD FLOOR, KARUNAMOYEE, SALTLAKE CITY, KOLKATA-700091 HAVINGS ITS REGISTERED OFFICE AT BHEL HOUSE,SIRI FORT, NEW DELHI-110049, INDIA | ||||||||
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PCT International Classification Number | F04D 29/12 | ||||||||
PCT International Application Number | N/A | ||||||||
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