DESCRIPTION

Embodiments of the subject matter disclosed herein relates to turbo -machines, methods for fixing bundles of a turbo -machines, and covers for the openings of barrel casings.

A centrifugal compressor or pump comprise an external pressure barrel casing that accommodates a diaphragm bundle. Typically, the barrel casing defines a cylindrical cavity and the diaphragm bundle has a cylindrical shape. Said diaphragm bundle typically comprises at least rotor and stator with their impellers, seals and fluid channels.

The cylindrical cavity, defined by the barrel casing, has an open at one side, typically the circular lateral side. This open allow the insertion of the bundle. Said open is closed after insertion of the bundle by mean of a cover, which typically has the form of an end wall structure. The barrel casing contains stationary and rotatable components. Stationary components are in general rigidly fastened to the barrel casing; whilst rotatable components are generally held up by bearings positioned in the cover.

The barrel casing of a turbo-machine in operation tends to expand radially, due to the rise of temperature and pressure at its inside; whilst the cover tends to shift axially. This can bring to a misalignment of stationary components with respect to rotatable components, affecting the working conditions of the machine. In fact, it is essential that the center axis of the cover is kept at all times in alignment with the central axis of the barrel casing.

Figure 1 shows a solution known from the prior art, where barrel casing 10 is firmly fixed to the cover 20 (after insertion of the bundle 5) by mean of shear ring 30. Said shear ring 30 is a ring composed by two, or four (or even more) symmetrical portion, that when joined together in contiguous way form the whole ring. The inner surface of the barrel casing 10 (namely on the surface facing the volume containing the bundle 5) is provided with a circumferential groove 70 adapted to receive the portions composing the shear ring 30. The outer surface 20a of the cover 20 is provided with a similar circumferential groove 40, which is adapted to receive partially the shear ring, when the turbo-machine is assembled. The outer surface of the barrel casing 10 is provided with a plurality of screws 80 (typically one screw per portion composing the shear ring), to move (partially) the shear ring from the groove 70 - on the barrel casing 10 - to the groove 40 - on the cover 20. It worth noting that the groove 40 on the cover 20 has a depth adapted to receive only part of the cross section of the shear ring 30. Thus the steps for assembling a turbo-machine of this kind are: insert the various portion of the shear ring on the groove 70; insert the bundle 5; mount the casing 20 on the open side of the barrel casing 10; fix the barrel casing 10 to the cover 20 by mean of the shear ring 30, threading the screws emerging from the outer surface of the barrel casing 10. The shear ring 30 is thus partially engaged in the groove 40 and partially engaged in the groove 70, blocking, in this way, the axial movement of the bundle 5 and the cover 20.

In this configuration, the depth of the groove 70 has to be dimensioned to contain completely the cross section of the shear ring 3, in order to perform the insertion of the bundle 5 and the successive fixing. Furthermore, un-engaging screws must be provided (not shown in figure 1) to raise up the shear ring 30 on the groove 70 on the barrel casing 10, for dismounting the bundle 5 to perform the maintenance operations.

Thus, the wall of the barrel casing 10 must have a certain minimum thickness to realize the groove 70 of the proper dimension. This solution increases the overall dimension of the turbo machine, the amount of material required to produce the barrel casing 10 and impacts with dimensional constraints of the turbo -machine.

Therefore there is a need for a system for fixing a cover in a turbo machine barrel casing that is easier to mount and dismount, thus allowing saving on maintenance, and does not require an increase in size at the mouth of the barrel casing. SUMMARY

According to first exemplary embodiments, there is a turbo machine comprising: a. a barrel casing having a cylindrical internal surface defining an internal containment volume,

b. a bundle having a cylindrical shape, adapted to be accommodated into said internal containment volume,

c. a cylindrical cover connected to the bundle to close said internal containment volume and hold the bundle inside the barrel casing,

d. a split shear ring adapted to fix said barrel casing with said cylindrical cover wherein the external cylindrical surface of the cylindrical cover and the cylindrical internal surface of the barrel casing are provided with a first circumferential groove and a second circumferential groove adapted to accommodate said shear ring and wherein said first grooves is adapted to completely accommodate the cross section of said split shear ring. According to second exemplary embodiments, there is a method for fixing a bundle of a turbo machine inside a barrel casing.

Specifically, before the insertion of the bundle into the barrel casing, a split shear ring is completely inserted within a first groove machined in the external surface of a cover for an opening of a barrel casing of a turbo machine. More in general, before insertion of the bundle into the barrel casing, one or more shear action devices are completely inserted within one or more recesses of the bundle; furthermore, after insertion of the bundle into the barrel casing, said one or more shear action devices are partially inserted within said one or more recesses of the bundle and partially inserted within one or more recesses of the barrel casing; the implicit movement of these devices is at least partially in the radial direction; such general principle is applicable for example to covers for openings of a barrel casing of a turbo machine. Advantageously, said one or more shear action devices are held within said one or more recesses of the bundle by one or more springs. Advantageously, said one or more shear action devices are pulled out of said one or more recesses of the bundle by one or more mechanical devices acting on said one or more shear action devices; the movement of these devices is at least partially in the radial direction. According to third exemplary embodiments, there is system for holding a cover connected to a bundle in a barrel casing of a turbo machine by means of a shear ring that engage partly said first groove and partly said second groove, said first groove machined in the external cylindrical surface of the cover and said second groove machined in the inner surface of the barrel casing wherein said first groove is adapted to accommodate completely the cross section of said shear ring and wherein said shear ring is maneuverable from outside the barrel casing, by mean of screwing means.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent from the following description of exemplary embodiments to be considered in conjunction with accompanying drawings wherein:

Figure 1 shows a section view of a turbo-machine with the barrel casing and the cover fixed according the state of the art;

Figure 2 shows a partial section view of a turbo-machine with the barrel casing and the cover fixed according to an exemplary embodiment;

Figure 3 shows a tridimensional view of a turbo-machine according to an exemplary embodiment in a first mounting condition;

Figure 4 shows a tridimensional view of the turbo-machine of figure 3 in a second successive mounting condition; Figure 5 shows a tridimensional view of the turbo-machine of figure 3 and 4 in a final mounted condition; Figure 6 shows a partial and enlarged tridimensional view, with focus on the zone in which the fixing between the barrel casing and cover occurs.

DETAILED DESCRIPTION

The following description of exemplary embodiments refer to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. Figure 2 shows a cross section of a part of a turbo-machine 100. Said turbo-machine 100 comprises a barrel casing 1 having a cylindrical internal surface defining an internal containment volume. In said internal cavity is accommodated a bundle 5 having a cylindrical external surface. The bundle 5 is inserted into the barrel casing 1 in the axial direction (according to the axis 50 of the turbo -machine) through a lateral opening on the barrel casing 1. Furthermore the turbo-machine 100 comprises a cylindrical cover 2 connected to the bundle 5 that closes said opening on the barrel and holds the bundle 5 inside the barrel casing 1. Thus, in a mounted configuration of the turbo-machine 100 the containment volume of the bundle 5 is a volume closed by mean of the barrel casing 1 and the cover 2. The fixing between the barrel casing 1 and the cover 2 occurs by mean of a shear ring 3. For this scope, a first groove 6 is provided on the outer surface of the cover 2, to accommodate the cross section of the shear ring 3. In particular, the first groove 6 is adapted to accommodate the whole cross section of the shear ring 3. A second groove 4 is provided on inner surface of the barrel casing 1 to accommodate the cross section of the shear ring 3. In particular, the second groove 4 is adapted to accommodate a part of the whole cross section of the shear ring 3.

The shear ring 3 is adapted to fix barrel casing 1 and the cover 2 and consequently avoid axial movement of the bundle 5. Thus, the ring 3 is subject to shear forces; for this scope the cross section of the shear ring 3 has a rectangular shape; the grooves 6 and 4 have the same (complementary) shape.

Figure 2 shows a mounted configuration of the turbo-machine 100. In said configuration, the barrel casing 1 and the cover 2 are in contact and the shear ring 3 is partially accommodated on the first groove 6 and partially accommodated on the second groove 4. In this way, axial movements, with respect to the axis 50, of the cover 2 and the bundle 5 are avoided. The first groove 6 is a circumferential groove on the cover 2. The second groove 4 is a is a circumferential groove on the barrel casing 1. The shear 3 is composed of two (or more) portions. These portions, when reciprocally fixed in contiguous way, form the whole shear ring 3. For example, if a shear ring 3 is formed by two equal portions, a first one and a second one; the first portion will engage the first half of the two circumferential grooves 4 and 6; the second portion will engage the second half of the two circumferential grooves 4 and 6. In the description, the term "shear ring 3" thus comprise the various portions that form the shear ring 3. The shear ring 3 is associated to a screw 10 to move the ring 3 from and to the axis 50, in order to realize the mounting and dismounting phases. This aspect will be clearer afterwards, in particular with reference to figures 3, 4 and 5.

Figures 3 shows a turbo-machine during a mounting phase. In said phase the bundle 5 is inserted in the barrel casing 1 through the opening 15 of the barrel casing 1 itself. In one embodiment, the shear ring 3 comprise two portion. A first portion 3 a engages the part of the groove 6 at higher portion of the cover 2, a second portion 3b engages the part of the groove 6 at the lower portion of the cover 2. In one embodiment are provided holding means to maintain the shear ring 3 completed engaged on the groove 6 during mounting phase. The shear ring 3 is movable in a first mounting position (shown in figure 3), in which said ring completely engages in the groove 6, namely the cross section of the ring 3 is wholly contained in the groove 6; and in a second mounted position (shown in figure 5) in which said ring partially engages the groove 6 and partially engages the groove 4, namely the cross section of the ring 3 is partially contained in the groove 6 and partially contained in the groove 4; and a third demounting position coinciding with the first mounting position.

The clearance between the bundle 5 and barrel casing 1 is very limited and designed in relation with the thermodynamic cycle of the turbo -machine. The outer surface 2a of the cover 2 and the inner surface la of the barrel casing 1 are in contact in mounted configuration. Thus to insert the bundle 5 and close the open 15 no part can protrude from the outer surface 2a of the cover 2. In fact, during the mounting phase, the shear ring 3 is completely engaged in the groove 6. The portions 3a and 3b could slip off from their position in the groove 6 during the mounting phase. In particular second portion 3b, at the lower portion of the cover 2, due to gravity force could very easily slip off. To the end, the shear ring is provided with holding means (not show in figure, but visible in figure 6) adapted to maintain the ring 3 in the mounting position during the mounting phase.

Figure 4 shows the shear ring 3 in a still first mounting position, but with the bundle 5 inserted in the barrel casing 1 and the open of the same closed by the cover 2.

In this position, the operator can move the shear ring 3 in the second mounted position and thus realize the fixing of the barrel casing 1 with the cover 2. The screw 10 allows the movement of the shear ring 3 from the first to the second position. In one embodiment, barrel casing 1 comprises a first through hole from the surface of the outer surface of the barrel casing 1 to the seat defined by the groove 4. In this way, the screw 10 can enter in contact with the ring 3. In particular, the threaded portion of the screw 10 engage with a threaded hole on the ring 3. The screwing action imposed raise the ring 3 outwardly with respect to the axis 50, according to the radial direction R. Thus the ring 3 engages the groove 4. In one embodiment, the thread on the ring 3 and the screw 10 are configured to raise the ring 3 so as that in the mounted configuration it fully engages the groove 6. In another embodiment, the thread on the ring 3 and the screw 10 are configured to raise the ring 3 so that in the mounted configuration it partially engages the groove 6.

In one embodiment, one screw 10 per portion of ring 3 is provided. Furthermore, are provided reference means adapted to put the ring 3 in one predetermined angular position. In said predetermined angular position, the first through hole on the barrel casing 1 collimate with the threaded hole on the ring 3. The operator can thus performs the mounting procedure.

Figure 5 show a turbo-machine with a ring 3, according to an embodiment, in a mounted position. As shown in the enlarged view A, the ring 3 fully engages the first groove 6 and partially engages the second groove 4. In this way, the fixing between the cover 2 and the barrel casing 1 is realized. As said, the ring 3 is raised up to engage the groove 6 toward radial direction R. This movement is performed by mean of the screw 10. In one embodiment, the same screw 10 is adapted to move the ring 3 to the third demounting position, coinciding with the first mounting position, namely the groove cross section of the ring 3 wholly contained in the first groove 6.

According to this embodiment, a first screwing sense of the screw 10, i.e. the clockwise sense, realize the raising of the ring 3 from the first mounting position to the second mounted position. A second screwing sense of the screw 10, i.e. the counterclockwise sense, realize the lowering of the ring 3 from the second mounted position to the third demounting position (coinciding with the first mounting position).

As shown in figure 6, in one embodiment, shear ring 3 is provided with holding means (not shown in figure 5, but visible in figure 6). Said means maintain the shear ring 3 completed engaged on the groove 6 in the mounting position. In one embodiment, these means comprise resilient means. Said resilient means have an annular configuration and are realized on the outer surface 31 of the ring 3. The outer surface 31 of ring 3 is the surface that face the groove 4.

In one embodiment the resilient means comprise an annular spring that surround the ring 3. According to another embodiment, the resilient means comprise a first helical spring 35 on a first groove realized on the surface 31 of the ring 3, and a second helical spring 36 on a second groove realized on the surface 31 of the ring 3. The first groove and the second groove are parallel and accommodate the whole cross section of the spring 35 and 36. Thus, the springs 35 and 36 are flush with the surface 31 of the ring 3. It worth saying that the first helical spring 35 is a unique spring that surround the portions composing the ring 3, as the second helical spring 36 that, in turn, surround the portions composing the ring 3.

The resilient means thus impress a radial force to the ring 3 toward the axis 50. In figure 6, the ring 3 is in a mounting position, namely his cross section is completely contained in the groove 6. In this mounting position, the two helical springs 35 and 36 are in a first normal position, impressing a certain radial force to the ring 3 toward the axis 50. In the passage from the first mounting position to the second mounted position, the operator by mean of the screw 10 impose a radial force to the ring 3 (directed according to the sense of the arrow R, as shown in figures 4 and 5) higher and contrary to the force imposed by the two helical springs 35 and 36. The screw 10 engages with the threaded hole on the ring 3, and keep the same on the mounted position.

In the mounted position the ring 3 is raised as shown in figure 5. The helical springs 35 and 36 are integral with the ring 3. Thus, in the mounted position the helical springs 35 and 36 are in a second expanded position. In case of maintenance of the barrel 5, is necessary dismount the cover 2 and extract it from the containment volume in which is inserted. According to one embodiment, the operator thread the screw in the proper sense. Thus the screwlO disengage the ring 3. The helical spring 35 and 36, in the expanded position, tend to return in their normal position exercising a radial force on the surface 31 of the ring 3 directed to the central axis 50. Said force bring back the ring 3 on the groove 6, in the third demounting position. Thus, according to these embodiments, mustn't provided second different means other than screw 10 to bring the ring 3 in a demounting position to carry out maintenance operations.

Embodiments are also directed to a method for fixing a bundle 5 of a turbo machine 100 inside a barrel casing 1 of said machine, wherein before the insertion of the bundle 5 into the barrel casing 1 , said split ring 3 is completely inserted within said first groove 6 machined in the external surface of the cover 2. In one embodiment, after the insertion of the bundle 5 into the barrel casing 1, the portions forming the split shear ring 3 are pull up using the screw 10 inserted into the wall of the barrel casing 1 so that, seen in cross section, the segments forming the split shear ring 3 remain engaged partly said first groove 6 and partly said second groove 4.

System for holding a cover 2 connected to a bundle 5 in a barrel casing 1 of a turbo machine 100 by means of a shear ring 3 that engage partly said first groove 6 and partly said second groove 4, said first groove 6 machined in the external cylindrical surface of the cover 2 and said second groove 4 machined in the inner surface of the barrel casing 1 wherein said first groove 6 is adapted to accommodate completely the cross section of said shear ring 3 and wherein said shear ring 3 is maneuverable from outside the barrel casing 1, by mean of screwing means 10.