FIELD OF INVENTION
The present invention relates to an improved centrifugal compressor casing with
thicker solid end wall and with separately bolted lube oil chamber. More
particularly the invention relates to an improved centrifugal compressor casing
with thicker solid end wall and separately bolted lube oil chamber for
accommodating seal gas and oil holes and adequate lube oil holding space.
BACKGROUND OF THE INVENTION
Centrifugal compressors as shown in Fig. 3 are used to compress any gas
medium to a higher discharge pressure as per the process requirement. The
compression work is done by a high speed rotor mounted with radial impellers
and bounded by stationery diaphragms having diffuser and return channel gas
paths. The rotor and diaphragms are covered by a leak tight pressure vessel
called casing. It is having as cast Volutes and nozzlesfor intake and discharge of
process gas from the compressor. Rotor is supported by two journal bearings
and one thrust bearing which are located at both ends of the casing. For low
pressure applications the compressor castings are normally horizontally split
steel castings and they are finish machined to accommodate all internal parts. At
parting plane the upper half casing and lower half casings are tightly bolted
around the parting plane area to prevent any gas leakage. To prevent gas
emission from compressor through annular interface clearance of casing and
rotor at both ends, labyrinth seals& dry gas seals are prOVided.
casing end walls are drilled with number of holes for the purpose of equalizing
the pressure at both ends of compressor and then to provide seal gas connection
for dry gas seals. Also conventionally the cast casing are configured with built in
as cast bosses and chambers to supply lube oil and collect the discharged oil
from the bearings and then route to drain pipe lines.
The conventional casing (A) end walls (4) as shown in Fig. leA) and 1(8) of prior
art, thickness is relatively small and many gas holes (5) are drilled in close
proximity in upper part casing and connections are hanging out. Likewise some
more gas and oil inlet connection are provided in the lower part casing and they
are drilled through the local bosses embedded in the lube oil discharge
chambers. Lube oil discharge chambers (6) at both ends of casing are
accommodated as cast and integral to the main casing. This configuration is
complex in nature as it involves highly intricate shapes that are to be formed
during foundry process and it shall be free of casting defects. Any casting defect
or dislocation of these chambers will lead to puncturing / wall thinning of
connection holes drilled during machining. Oil chambers formed improperly and
inadequately will hinder the performance of lube oil discharge system leading to
other reliability issues of compressor.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved centrifugal
compressor casing with thicker solid end wall and with separately bolted lube oil
chamber which eliminates the vulnerability of gas and oil holes puncture and wall
thinning, by increasing the end wall thickness thereby reducing gas leakage.
Another object of the invention is to propose an improved centrifugal compressor
casing with thicker solid end wall and with a separately bolted lube oil chamber
which improves the performance of bearings lube oil discharge system providing
adequate lube oil holding space.
A still another object of the invention is to propose an improved centrifugal
compressor casing with thicker solid end wall and with a separately bolted lube
oil chamber which makes the casting shape simpler.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l(A) - shows the compression casing end wall, seal gas holes and drain
oil collection chamber at one end of casing of prior art.
Fig.l(B) - shows the compressor casing end wall, seal gas holes and drain
oil collection chamber at the other end of casing of prior art.
Fig. 2(A) - shows the compressor casing end wall, bolted drain oil chamber,
oil and seal gas connections at one end of casing of present
invention.
Fig. 2(B) - shows the compressor casing end wall, bolted drain oil chamber,
oil and seal gas connections at the other end of the casing of
present invention.
Fig. 3 A photograph of a compressor showing two ends of the casing.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Conventionally casings are made of casting process with thin walls and built in oil
drain chambers of intricate shapes. The thin walls lead to puncturing of the
casing oil chambers frequently while drilling, which leads to gas leakage. In
order to make the casting and gas holes drilling processes simpler, the wall
thickness is increased and to allow free discharge of lube oil, the drain chambers
(side covers) are separately cast and bolted.
In the present invention a casing casting with higher end wall thickness is
developed eliminating wall thinning/puncturing of gas & oil holes during
machining and to facilitate easy discharge of lube oil from the bearings. This
improvement also reduces the complexity in casting process.
As shown in Fig. 2(A) and 2(B) casting with thick walls (1) facilitates easy drilling
of the gas & oil holes (2) circumferentially without any wall thinning and
puncturing. The lube oil discharge chambers 3 (Side Cover) are separately cast
and fitted to the casing by bolting. This configuration provides more hold up area
for drain oil and easy discharge of oil from bearings.
The modified casing (B) end walls (1) as shown in Fig. 2(A) and 2(B) of the
invention, thickness has been increased so that enough space is available for
housing dry gas seals and for drilling gas connection holes liberally in size and
number. Also the Lube oil chamber (3) is separated from the main casing.and
this function is served by another side cover which is attached to the main casing
by bolting. This helps to have adequate lube oil holding space and free discharge
of oil from the bearings. The modified casing end wall (1) is simpler with respect
to foundry process as the intricate shapes are eliminated. This meets the
functional requirement of dry gas seal and lube oil discharge system.
WE CLAIM:
1. An improved centrifugal compressor casing with thicker solid end wall
and with separately bolted lube oil chamber comprising:
a casing (8) with thicker end wall (1) for housing dry gas seals and drilling
gas connection holes (2); characterized in that a plurality of side covers
performing as lube oil discharge chambers (3) are bolted to main casing
(8) for providing adequate lube oil holding space.
2. An improved compressor casing (8) as claimed in claim 1, wherein the
said casing is made of casting.
3. An improved compressor casing (8) as claimed in claim 1, wherein the
lube oil discharge chambers (3) are separately cast.
4. An improved compressor casing (8), as claimed in claim 1, wherein the
side covers (3) are casting of simpler shape.