Claims:We claim:
1) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine, said arrangement (200) comprising :
a) a top half high pressure casing (42) and a bottom half high pressure casing (44) provided with a projection (P) dividing a vertical mating surface in to an exterior step (ES) and an interior step (IS), said exterior step (ES) of said top half high pressure casing (42) and said bottom half high pressure casing (44) provided with a plurality of holes (H2) leaving a space (S2) at their diametrically opposite ends, said interior step (IS) of said top half high pressure casing (42) and said bottom half high pressure casing (44) provided with at least one hole (H3) at their diametrically opposite ends, said top half high pressure casing (42) and said bottom half high pressure casing (44) provided with a plurality of holes at a horizontal mating surface;
b) a plurality of mating plates (54) of arcuate shape provided with at least one hole (H5) complementary to the hole (H3) of said top half high pressure casing (42) and said bottom half high pressure casing (44) and at least one rib (R) on their top end; and
c) a top half intermediate pressure casing (46) and a bottom half intermediate pressure casing (48) coupled with the plurality of mating plates (54) on their inner surface at diametrically opposite ends leaving a space therein to accommodate the circumference of the projection (P) of said top half high pressure casing (42) and said bottom half high pressure casing (44), said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) provided with a plurality of holes and a plurality of slots (S3) at a horizontal mating surface, said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) provided with a plurality of holes (H4) complementary to the holes (H2) of said top half high pressure casing (42) and said bottom half high pressure casing (44) at a vertical mating surface, said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) adapted to mate with said top half high pressure casing (42) and said bottom half high pressure casing (44) respectively across the vertical mating surface and locked in position by means of a plurality of fasteners (56), said top half intermediate pressure casing (46) integral with said top half high pressure casing (42) adapted to mate with said bottom half intermediate pressure casing (48) integral with said bottom half high pressure casing (44) across the horizontal mating surface and locked in position by means of said plurality of fasteners (56).

2) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine as claimed in claim 1, wherein locking of said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) to said top half high pressure casing (42) and said bottom half high pressure casing (44) by means of the plurality of fasteners (56) exerts a force on the vertical mating surface of said top half high pressure casing (42) and said bottom half high pressure casing (44) and provides effective sealing.

3) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine as claimed in claim 1, wherein said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) are mated across the horizontal mating surface by encompassing a plurality of keys in the plurality of slots (S3).

4) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine as claimed in claim 2 or 3, wherein the exertion of the force on the vertical mating surface of said top half high pressure casing (42) and said bottom half high pressure casing (44) results in the creation of an axial thrust on the vertical mating surface of said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) which tries to move said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) across the horizontal mating surface which in turn is arrested by said key and said plurality of fasteners (56).

5) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine as claimed in claim 1, wherein said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) are locked to said top half high pressure casing (42) and said bottom half high pressure casing (44) respectively at four extreme locations on said interior step (IS) of said vertical mating surface.

6) An arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine as claimed in claim 1 or 5, wherein locking of said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) with said top half high pressure casing (42) and said bottom half high pressure casing (44) respectively at four extreme locations on said interior step (IS) of said vertical mating surface prevents the leakage of working fluid between the casings due to non provision of the fasteners (56) at said space (S2) on said exterior step (ES).

7) A method of locking casings of a fluid flow machine to prevent leakage of working fluid, said method comprising the steps of :
a) mounting a bottom half high pressure casing (44) at one end on a pedestal;
b) mounting a bottom half intermediate pressure casing (48) at one end on casing supporting stools;
c) adapting to mate the other end of said bottom half intermediate pressure casing (48) with the circumference of a projection (P) of said bottom half high pressure casing (44) in such a way that a plurality of holes (H2 and H3) of the bottom half high pressure casing (44) are in line to a plurality of holes (H4 and H5) of the bottom half intermediate pressure casing (48) and locked in position;
d) projecting out of a plurality of guide rods (GR) by passing through a plurality of holes provided across a horizontal mating surface of said bottom half high pressure casing (44) and said bottom half intermediate pressure casing (48);
e) holding of a top half high pressure casing (42) and a top half intermediate pressure casing (46) with the help of ropes extending from cranes and adapted to pass said top half high pressure casing (42) and said top half intermediate pressure casing (46) through a plurality of guide rods (GR) by means of a plurality of holes provided across a horizontal mating surface;
f) adapting to mate said top half intermediate pressure casing (46) with the circumference of a projection (P) of said top half high pressure casing (42) in such a way that a plurality of holes (H2 and H3) of the top half high pressure casing (42) are in line to a plurality of holes (H4 and H5) of the top half intermediate pressure casing (46) and locked in position; and
g) dropping and mating of said top half high pressure casing (42) and said top half intermediate pressure casing (46) across the horizontal mating surface of said bottom half high pressure casing (44) and said bottom half intermediate pressure casing (48) respectively and locked in position.

8) A method of locking casings of a fluid flow machine to prevent leakage of working fluid as claimed in claim 7, wherein the locking of the plurality of holes (H5) of said top half intermediate pressure casing (46) to the plurality of holes (H3) of said top half high pressure casing (42) is done keeping said top half intermediate pressure casing (46) and said top half high pressure casing (42) hanging in the air and with the help of workmen viewing from the bottom of said top half intermediate pressure casing (46).

9) A method of locking casings of a fluid flow machine to prevent leakage of working fluid as claimed in claim 7, wherein said top half intermediate pressure casing (46) adapted to mate with said bottom half intermediate pressure casing (48) across the horizontal mating surface by encompassing a plurality of keys in a plurality of slots (S3) provided therein.

10) A method of locking casings of a fluid flow machine to prevent leakage of working fluid as claimed in claim 7, wherein the locking of the plurality of holes (H5) of said top half intermediate pressure casing (46) and said bottom half intermediate pressure casing (48) to the plurality of holes (H3) of said top half high pressure casing (42) and said bottom half high pressure casing (44) prevents the leakage of working fluid between the casings.
, Description:FIELD OF THE INVENTION:
The present invention relates to the field of an arrangement for prevention of leakage of working fluid from casings of a fluid flow machine. Particularly, the present invention relates to an arrangement for prevention of leakage of steam from casings of a steam turbine.

BACKGROUND OF THE INVENTION:
Generally, Steam Turbine Casings are manufactured through the process of casting or fabrication depending on the temperature and pressure they need to withstand. Hence, typically, high pressure casings are manufactured through casting and intermediate pressure and low pressure casings are manufactured through fabrication. Typically, Steam Turbine Casings are manufactured in partitions and assembled over the horizontal plane or vertical plane with the help of a plurality of fasteners.

In steam turbines with low pressure ratio, the high pressure casings are directly bolted to the low pressure casings and due to low pressure of steam at the interface of high pressure casings and low pressure casings, the chances of leakage of steam between the casings is very less whereas in steam turbines with high pressure ratio, the high pressure casings are bolted to the intermediate pressure casings and due to high pressure of steam at the interface of high pressure casings and intermediate pressure casings, the chances of leakage of steam between the casings is considerably high.

Figure 1 illustrates a back perspective view of a casing arrangement of a steam turbine.
The casing arrangement 100 of a steam turbine comprises a top half high pressure casing 12, a bottom half high pressure casing 14, a top half intermediate pressure casing 16, a bottom half intermediate pressure casing 18, a top half low pressure casing 20, a bottom half low pressure casing 22 and a plurality of fasteners 24.

Figure 2 illustrates a mating junction of a top half intermediate pressure casing with a bottom half intermediate pressure casing and a top half high pressure casing across horizontal plane and vertical plane respectively.
It is obvious from the marked portion ‘A’ that a space S1 is left at extreme ends of the top half high pressure casing 12 and the bottom half high pressure casing 14 without provision of holes H1 for accommodating the fasteners 24 thereby avoiding the intersection of the fasteners 24 passing through the horizontal plane and the vertical plane. But, the space S1 left at extreme ends of the top half high pressure casing 12 and the bottom half high pressure casing 14 may increase the chances of leakage of steam.

Therefore, there is felt a need for development of an arrangement between the casings of a steam turbine to overcome the drawbacks of the prior art and thereby provide an effective sealing arrangement.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a simple arrangement between the casings of a steam turbine to arrest the leakage of steam.

Another object of the present invention is to provide an effective sealing arrangement between the casings of a steam turbine.

One more object of the present invention is to provide an effective mating interface between the casings of a steam turbine.

Still another object of the present invention is to provide a robust sealing arrangement between the casings of a steam turbine.

Further another object of the present invention is to provide a better locking arrangement between the casings of a steam turbine.

SUMMARY OF THE INVENTION:
In accordance with the present invention an arrangement (200) to prevent leakage of working fluid between casings of a fluid flow machine is provided, the arrangement (200) comprising:

(i) a top half high pressure casing (42) and a bottom half high pressure casing (44) provided with a projection (P) dividing a vertical mating surface in to an exterior step (ES) and an interior step (IS), the exterior step (ES) of the top half high pressure casing (42) and the bottom half high pressure casing (44) provided with a plurality of holes (H2) leaving a space (S2) at their diametrically opposite ends, the interior step (IS) of the top half high pressure casing (42) and the bottom half high pressure casing (44) provided with at least one hole (H3) at their diametrically opposite ends, the top half high pressure casing (42) and the bottom half high pressure casing (44) provided with a plurality of holes at a horizontal mating surface;
(ii) a plurality of mating plates (54) of arcuate shape provided with at least one hole (H5) complementary to the hole (H3) of the top half high pressure casing (42) and the bottom half high pressure casing (44) and at least one rib (R) on their top end; and
(iii) a top half intermediate pressure casing (46) and a bottom half intermediate pressure casing (48) coupled with the plurality of mating plates (54) on their inner surface at diametrically opposite ends leaving a space therein to accommodate the circumference of the projection (P) of the top half high pressure casing (42) and the bottom half high pressure casing (44), the top half intermediate pressure casing (46) and the bottom half intermediate pressure casing (48) provided with a plurality of holes and a plurality of slots (S3) at a horizontal mating surface, the top half intermediate pressure casing (46) and the bottom half intermediate pressure casing (48) provided with a plurality of holes (H4) complementary to the holes (H2) of the top half high pressure casing (42) and the bottom half high pressure casing (44) at a vertical mating surface, the top half intermediate pressure casing (46) and the bottom half intermediate pressure casing (48) adapted to mate with the top half high pressure casing (42) and the bottom half high pressure casing (44) respectively across the vertical mating surface and locked in position by means of a plurality of fasteners (56), the top half intermediate pressure casing (46) integral with the top half high pressure casing (42) adapted to mate with the bottom half intermediate pressure casing (48) integral with the bottom half high pressure casing (44) across the horizontal mating surface and locked in position by means of the plurality of fasteners (56).

Typically, the locking of the top half intermediate pressure casing (46) and the bottom half intermediate pressure casing (48) to the top half high pressure casing (42) and the bottom half high pressure casing (44) by means of the plurality of fasteners (56) exerts a force on the vertical mating surface of the top half high pressure casing (42) and the bottom half high pressure casing (44) and provides effective sealing.

BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in which:
Figure 1 illustrates a back perspective view of a casing of a steam turbine according to the prior art;

Figure 2 illustrates a mating junction of a top half intermediate pressure casing with a bottom half intermediate pressure casing and a top half high pressure casing across horizontal plane and vertical plane respectively according to the prior art;

Figure 3(a) illustrates a mating junction of a top half intermediate pressure casing with a bottom half intermediate pressure casing and a top half high pressure casing across horizontal plane and vertical plane respectively in accordance with the present invention;

Figure 3(b) illustrates an enlarged view of marked portion ‘B’ of figure 3(a); and

Figure 4 illustrates a method of assembling casings of a steam turbine in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.

Figure 3(a) illustrates a mating junction of a top half intermediate pressure casing with a bottom half intermediate pressure casing and a top half high pressure casing across horizontal plane and vertical plane respectively.

Figure 3(b) illustrates an enlarged view of marked portion ‘B’ of figure 3(a).

In accordance with the present invention, there is provided an arrangement 200 comprising a top half high pressure casing 42, a bottom half high pressure casing 44, a top half intermediate pressure casing 46, a bottom half intermediate pressure casing 48, a top half low pressure casing 50, a bottom half low pressure casing 52, a plurality of mating plates 54 and a plurality of fasteners 56.

The top half high pressure casing 42 and the bottom half high pressure casing 44 are provided with a projection P dividing a vertical mating surface in to an exterior step ES and an interior step IS. The exterior step ES of the top half high pressure casing 42 and the bottom half high pressure casing 44 are provided with a plurality of holes H2 leaving a space S2 at their extreme ends. The interior step IS of the top half high pressure casing 42 and the bottom half high pressure casing 44 are provided with two holes H3 at their extreme ends.

The top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 are coupled to the top half low pressure casing 50 and the bottom half low pressure casing 52 respectively by means of welding. The top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 are provided with complementary slots S3 at a horizontal mating surface to accommodate keys for locking. The top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 are provided with a plurality of holes H4
on their exterior edge complementary to the plurality of holes H2 of the top half high pressure casing 42 and the bottom half high pressure casing 44.

The plurality of mating plates 54 are of arcuate shape and provided with two holes H5
complementary to the two holes H3 of the top half high pressure casing 42 and the bottom half high pressure casing 44. The plurality of mating plates 54 are attached with three ribs R on their top end.

The plurality of mating plates 54 are coupled to the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 at their extreme ends by leaving a space to mate with the circumference of the projection P of the top half high pressure casing 42 and the bottom half high pressure casing 44. The three ribs R of the plurality of mating plates 54 are welded to the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 for structural rigidity of the plurality of mating plates 54 during and after locking with the top half high pressure casing 42 and the bottom half high pressure casing 44.

Typically, the locking of the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 with the top half high pressure casing 42 and the bottom half high pressure casing 44 respectively by means of the plurality of fasteners 56 exerts a force on the vertical mating surface of the top half high pressure casing 42 and the bottom half high pressure casing 44 which ultimately results in providing effective sealing arrangement.

Typically, the exertion of force on the vertical mating surface of the top half high pressure casing 42 and the bottom half high pressure casing 44 results in the development of an axial thrust on a vertical mating surface of the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 which ultimately tries to move the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 across a horizontal plane.

Typically, the movement of the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 across the horizontal plane is arrested by means of keys provided in the slots S3 at the horizontal mating surface.

Typically, the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 are locked to the top half high pressure casing 42 and the bottom half high pressure casing 44 at four extreme locations on the interior step IS of the vertical mating surface.

Typically, the locking of the top half intermediate pressure casing 46 and the bottom half intermediate pressure casing 48 with the top half high pressure casing 42 and the bottom half high pressure casing 44 at four extreme locations on the interior step IS of the vertical mating surface facilitates in preventing the leakage of steam due to non provision of the fasteners at the space S2 of the exterior step ES of the top half high pressure casing 42 and the bottom half high pressure casing 44.

Figure 4 illustrates a method of assembling casings of a steam turbine.
The method of locking the casings of a steam turbine to prevent leakage of working fluid in accordance with the present invention is as follows:

The bottom half high pressure casing 44 is supported at one extreme end by a pedestal. The bottom half intermediate pressure casing 48 along with the bottom half low pressure casing 52 is supported at other extreme end by casing supporting stools on either side. The free end of the bottom half intermediate pressure casing 48 is adapted to mate with the circumference of the projection P of the bottom half high pressure casing 44 in such a way that the plurality of holes H4 and H5 of the bottom half intermediate pressure casing 48 are in line to the plurality of holes H2 and H3 of the bottom half high pressure casing 44 and locked in position by means of the plurality of fasteners 56.

Guide rods GR are passed through the holes provided on either side of the horizontal plane of the bottom half high pressure casing 44 and the bottom half intermediate pressure casing 48. The top half high pressure casing 42 and the top half intermediate pressure casing 46 tied with ropes extending from cranes, slowly moved over the bottom half high pressure casing 44 and the bottom half intermediate pressure casing 48, adapted to pass over the guide rods GR with the help of complementary holes provided across the horizontal mating surface and adapted to mate at the vertical mating surface with the help of workmen in such a way that the plurality of holes H4 and H5 of the top half intermediate pressure casing 48 are in line to the plurality of holes H2 and H3 of the top half high pressure casing 44.

Typically, the top half high pressure casing 44 and the top half intermediate pressure casing 48 are held in air with the help of ropes extending from cranes while locking the plurality of holes H3 and H5 through the plurality of fasteners 56 with the help of workmen viewing from the bottom of the top half intermediate pressure casing 48.

Typically, the plurality of holes H2 and H4 of the top half high pressure casing 44 and the top half intermediate pressure casing 48 respectively are locked in position by means of the plurality of fasteners 56.

Typically, the coupled top half high pressure casing 44 and the top half intermediate pressure casing 48 is dropped slowly from the cranes along the guide rods GR and adapted to mate across the horizontal mating surface encompassing the keys and locked in position.

In this method, prevention of leakage of steam across the horizontal plane and vertical plane of the casings is achieved.

TECHNICAL ADVANCEMENTS:

An arrangement to prevent leakage of working fluid between casings of a fluid flow machine and a method of locking the casings thereof has several technical advantages including but not limited to the realization of:
• a simple arrangement between the casings of a steam turbine to arrest the leakage of steam ;
• an effective sealing arrangement between the casings of a steam turbine ;
• an effective mating interface between the casings of a steam turbine ;
• a robust sealing arrangement between the casings of a steam turbine ; and
• a better locking arrangement between the casings of a steam turbine.

Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the invention.