Title of Invention

AN IMPROVED END SEALING DEVICE ADAPTABLE TO CENTRIFUGAL COMPRESSORS

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).

Documents:

00185-kol-2007-correspondence.pdf

00185-kol-2007-form-18.pdf

0185-kol-2007-abstract.pdf

0185-kol-2007-assignment.pdf

0185-kol-2007-claims.pdf

0185-kol-2007-correspondence others.pdf

0185-kol-2007-description (complete).pdf

0185-kol-2007-drawings.pdf

0185-kol-2007-form1.pdf

0185-kol-2007-form2.pdf

0185-kol-2007-form3.pdf

185-KOL-2007-ABSTRACT.pdf

185-KOL-2007-AMANDED PAGES OF SPECIFICATION.pdf

185-KOL-2007-CLAIMS.pdf

185-kol-2007-correspondence.pdf

185-KOL-2007-DESCRIPTION (COMPLETE).pdf

185-KOL-2007-DRAWINGS.pdf

185-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

185-kol-2007-examination report.pdf

185-KOL-2007-FORM 1.pdf

185-kol-2007-form 18.pdf

185-KOL-2007-FORM 2.pdf

185-kol-2007-form 3.pdf

185-KOL-2007-FORM-27.pdf

185-kol-2007-gpa.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-OTHERS.pdf

185-kol-2007-reply to examination report.pdf

abstract-00185-kol-2007.jpg


Patent Number 248334
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
Inventors:
# Inventor's Name Inventor's Address
1 POTHINENI VAMSI CHOWDARY COMPRESSOR ENGINEERING, ENGINEERING BUILDING, 2ND FLOOR, R.C.PURAM, HYDERABAD-502 032
PCT International Classification Number F04D 29/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA