Pump shell for centrifugal pump and centrifugal pump

Abstract

The invention relates to a pump shell for a centrifugal pump and the centrifugal pump. The invention relates to a pump housing for a centrifugal pump, which pump housing extends in an axial direction, the invention relates to a housing having a first housing part, a second housing part for sealingly attaching to the first housing part, a plurality of fastening elements for connecting the first and second housing parts, and a radial sealing element for sealing between the first and second housing parts, the first housing part having a first axial end surface, the second housing part having a second axial end surface, and the second housing part having a second axial end surface. The first housing part has a first axial end surface, and the second housing part has a second axial end surface, the first and second axial end surfaces facing each other, and wherein the first axial end surface comprises an annular protrusion extending in the axial direction and the second axial end surface comprises an annular recess configured to engage with the annular protrusion, the annular projection is disposed radially inward with respect to the fastening element. In addition, a centrifugal pump is proposed.

Description

[0001] The present application is a divisional application, the parent application of which has the application number 201810628994.X, the filing date of June 19, 2018 and the title of “Pump casing for a centrifugal pump and centrifugal pump”. TECHNICAL FIELD

[0002] The present application relates to a pump casing for a centrifugal pump and to a centrifugal pump. BACKGROUND

[0003] The pump casing of a centrifugal pump typically comprises a plurality of casing parts which are fastened to each other to form the pump casing. For example, in a barrel casing pump, the casing parts comprise a barrel in which an impeller of the pump is arranged and an end cover for closing the barrel with respect to an axial direction. The end cover is usually fastened to the barrel by means of a plurality of bolts and nuts. One very important aspect with regard to the operational reliability and performance of the pump is the sealing between the individual casing parts. As an example, in a barrel casing pump, the fluid outlet pressure which can be 1000 bar or even higher likewise acts on the connection between the barrel and the end cover on the inside of the pump. On the outside of the pump, in many cases there is an ambient pressure, so that the sealing between the barrel and the end cover has to reliably seal a huge pressure difference.

[0004] Known sealing arrangements for the sealing between casing parts are for example designed as radial sealing arrangements or axial sealing arrangements. In both sealing arrangements, the sealing element for sealing between adjacent casing parts is typically designed as an annular or ring-shaped sealing element and is arranged coaxially to the shaft of the pump. In a radial sealing arrangement, the sealing element is arranged in a curved surface, in particular in a surface having a surface normal vector which is oriented in the radial direction. The curved surface is for example concentric to the shaft of the pump. In an axial sealing arrangement, the sealing element is arranged in a planar, i.e. non-curved, surface. Usually, the surface has a surface normal vector which is oriented in the axial direction. The axial direction is defined by the longitudinal axis of the shaft, i.e. by the rotational axis around which the impeller of the pump rotates during operation.

[0005] Figure 1 is a schematic illustration of a known radial sealing arrangement for the sealing between a first casing part 2’ and a second casing part 3’, wherein the first casing part 2’ is for example a barrel of a barrel casing pump and the second casing part 3’ is for example an end cover for closing the barrel with respect to an axial direction A. The axial direction which is defined by the longitudinal axis of the shaft (not shown) of the pump is indicated by the line having reference sign A. The first and second casing parts 2’, 3’ are fastened to each other by a plurality of fastening elements 4’, wherein only one fastening element is shown in Figure 1The fastening element 4' is, for example, a bolt 41'which cooperates in a known manner with a nut 42'. The centre line of the bolt 41'is identified by the reference 4C'. A sealing gap 10' is formed between the first and second housing parts 2', 3', which is annular and which is arranged coaxially with the shaft of the pump. The sealing gap 10' is sealingly closed by means of a radial sealing element 5', for example a self-sealing O-ring type seal, which is inserted into an annular sealing groove 6' provided in the second housing part 3'. Both the sealing element and the groove completely surround the shaft in the circumferential direction. During operation of the pump, the interior of the pump is exposed to very high pressure, indicated by the reference HP, whereas on the outside of the pump there is a significantly lower pressure, indicated by the reference LP. The low pressure LP can be the ambient pressure and the high pressure HP can be, for example, 500 bar or even more. Typically, the first and second housing parts 2', 3' have different stiffnesses. In the example mentioned above, the barrel (first housing part 2') is generally the weaker part, whereas the end cap (second housing part 3') is the stronger or stiffer part.

[0006] This can lead to the following problems.

[0007] Due to the high pressure HP, the first housing part 2' expands in the radial direction, indicated by the arrow M1 in Figure 1 . Since the first housing part 2' is fixed relative to the second housing part 3', the radial expansion of the first housing part 2' accordingly leads to a widening or enlargement of the sealing gap 10', in particular on the high pressure side HP. This enlargement of the sealing gap 10' can lead to a failure of the seal. In addition and in particular for a sealing arrangement with an O-ring as sealing element, there is a risk of the O-ring being extruded. This means that the O-ring deforms under pressure in such a way that a part of it is pressed into the gap 10' which widens under pressure, which can have the consequence of damage to the O-ring and a loss of the sealing effect in this way.

[0008] Two additional effects tend to support the widening or enlargement of the sealing gap 10'. Due to the radial expansion of the first housing part 2' and the rigid connection by means of the fastening element 4', the second housing part 3' can bend towards the first housing part 2', as indicated by the arrow with the reference M2 in Figure 1 . In addition, as indicated by the arrow with the reference M3 in Figure 1 , the high pressure HP acting on the central portion of the second housing part 3' supports the bending of the second housing part 3'. Both effects can increase the widening or enlargement of the sealing gap 10' and thus additionally impair the reliable sealing effect of the sealing arrangement with the radial sealing element 5'.

[0009] Similar problems can also occur for sealing elements which are not self-sealing, but require a pre-tension, such as sealing elements of metal or graphite. The operation of these sealing elements is based on a surface pressure, by which the sealing element is pressed against one or more surfaces belonging to one or more housing parts 2', 3'. The gasket factor of such an arrangement, defined by the ratio of the surface pressure to the pressure difference which has to be sealed, should generally be significantly greater than one, for example five or even more. Different expansions or deformations of the housing parts 2', 3' as described above can lead to a significant reduction of the surface pressure or even to an opening of the sealing gap, so that a reliable sealing function is no longer ensured. In addition, it is also possible that different deformations of the housing parts 2', 3' cause an uneven loading of the sealing element, meaning that different parts of the sealing element are exposed to different surface pressures. Depending on the geometry of the sealing element, this can lead to a bending or tilting or rotation of the sealing element, which jeopardizes the proper sealing function.

[0010] When pumps are used in applications in which the fluid to be pumped has a very high temperature, problems very similar to those caused by pressure can occur. Strong temperature gradients or temperature transients can cause different thermal expansions of the first and second housing parts 2', 3', respectively. These thermally induced effects can have the same consequences as already described above with regard to the pressure-induced effects, namely an opening or widening of the sealing gap 10' or a reduction of the surface pressure, respectively.

[0011] One example for such high-temperature applications are so-called ebullator pumps. These are pumps for fluidized bed processes or ebullated bed processes in the hydrocarbon processing industry. These processes are used, for example, for the purification of heavy hydrocarbons, such as heavy fuel oil, or for the purification of refinery residues, or for the decomposition of these into more easily usable, more highly volatile hydrocarbons. This is often achieved by applying hydrogen to the heavy hydrocarbons, wherein the mixed components are swirled in a reactor and the heavy hydrocarbons are decomposed there with the help of a catalyst. In order to circulate the process fluid, which typically consists mainly of heavy hydrocarbons, in the ebullated bed reactor or fluidized bed reactor, special pump drive units are used for those pumps for which the name "ebullator pump" has become common. These ebullator pumps are usually arranged directly at the reactor as circulation pumps for the process fluid and are constructed due to the process reasons such that the pump is arranged above the drive with respect to the vertical direction. Since the process fluid is typically under very high pressure, for example 200 bar or more, and additionally has a very high temperature of more than 400°C, for example 460°C, the ebullator pump must work as reliably and long-term as possible in the very challenging conditions of the long-term operation.

[0012] The high temperature of the process fluid causes strong thermal gradients and considerable temperature transients, which, as explained above, can lead to opening or widening of the sealing gap between the housing parts sealed with the radial sealing arrangement between the two housing parts.

[0013] The present invention solves these pressure and / or temperature induced problems. SUMMARY

[0014] Therefore, starting from this prior art situation, it is the object of the present invention to propose a pump housing for a centrifugal pump having at least two housing parts and a radial sealing element for sealing between the housing parts, wherein at least the pressure and / or temperature induced opening or widening of the sealing gap between the housing parts is significantly reduced. It is a further object of the present invention to propose a centrifugal pump having such a pump housing.

[0015] These objects are achieved by the pump housing for a centrifugal pump and the centrifugal pump according to the present invention.

[0016] Thus, according to the present invention, a pump housing for a centrifugal pump is proposed, which extends in axial direction and has a first housing part, a second housing part sealingly attached to the first housing part, a plurality of fastening elements for connecting the first and second housing parts, and a radial sealing element for sealing between the first and second housing parts, wherein the first housing part has a first axial end surface and the second housing part has a second axial end surface, which face each other, and wherein the first axial end surface comprises an annular protrusion extending in axial direction and the second axial end surface comprises an annular recess configured for engaging with the annular protrusion and providing an outer centering, wherein the annular protrusion is arranged radially inwardly with respect to the fastening elements.

[0017] By providing the first axial end surface of the first housing part with an annular protrusion engaging with the annular recess provided in the second axial end surface of the second housing part, an opening or widening of the sealing gap between the two adjacent radial surfaces of the first and second housing parts, between which the radial sealing element is arranged, is effectively prevented or at least significantly reduced. This applies in particular even if a pressure induced or temperature induced deformation of the first and second housing parts occurs, which is different for the first and second housing parts, respectively.

[0018] The radially outer surface of the annular protrusion abuts against the surface delimiting the annular recess, so that the sealing gap cannot open or at least cannot open to such an extent that the function of the sealing element is jeopardized. Thus, the sealing function of the radial sealing element is reliably ensured also in such applications in which the fluid to be pumped has a high pressure and / or a high temperature.

[0019] By the engagement of the annular protrusion with the annular recess, an outer centering of the annular protrusion is achieved. The radially outer wall of the annular recess functions as an external alignment clamp acting on the radially outer surface of the annular protrusion in order to center the annular protrusion from the outside, as seen in radial direction. The second housing part encloses the annular protrusion of the first axial end surface of the first housing part by means of the annular recess. Thus, there is an overlap between the radially outer wall of the annular protrusion and the radially outer wall of the annular recess with respect to the axial direction.

[0020] Furthermore, the engagement of the annular protrusion with the annular recess has a centering effect which ensures that the radial sealing element is always loaded uniformly along the entire circumference of the sealing element. This centering effect is an outer centering or outside centering effect, meaning that the centering is achieved by the engagement of the radially outer wall of the annular protrusion with the radially outer wall of the annular recess, wherein the radially outer wall of the annular recess encloses the radially outer wall of the annular protrusion around the radially outer surface of the annular protrusion. The outer centering or outside centering of the radial sealing element prevents or at least significantly reduces the opening of the sealing gap under pressure. In addition, the outside centering ensures a uniform loading of the sealing element, meaning that different parts of the sealing element are exposed to essentially the same surface pressure even when there are large pressure differences on the sealing element. Thereby, a bending or tilting or rotation of the sealing element is prevented, ensuring a proper sealing function.

[0021] According to a preferred embodiment, the annular recess is designed such that the radially outer wall of the annular recess extends beyond the radial sealing element when viewed in axial direction, such that the annular recess encloses the radial sealing element. In such an embodiment, the radial sealing element is located within the annular recess.

[0022] It is a preferred measure that the annular recess is configured as an annular groove.

[0023] It is a further preferred measure that the sealing element is arranged in the annular sealing groove.

[0024] According to a first embodiment, the annular sealing groove is arranged in the first housing part.

[0025] According to a second embodiment, the annular sealing groove is arranged in the second housing part.

[0026] According to a third embodiment, the sealing groove is formed jointly by the first and the second housing part.

[0027] Furthermore, it is preferred that the protrusion forms a part of the radially inner surface of the first housing part.

[0028] Especially, when the protrusion forms a part of the radially inner surface of the first housing part, the sealing groove is preferably arranged in the protrusion.

[0029] According to a preferred configuration, the second housing part comprises an inner section which extends into the first housing part such that the first housing part encloses the inner section of the second housing part, wherein the sealing element is arranged between the inner section of the second housing part and the first housing part.

[0030] According to a fourth embodiment, the sealing element is arranged in an annular recess of the second housing part.

[0031] Especially with regard to the fourth embodiment, it is preferred that the sealing element is a conical sealing element having a substantially T-shaped cross section. This means that the sealing element has a substantially T-shaped cross section, wherein the transition area between the long leg of the T and the short leg of the T and the bottom side of the long leg of the T which is combined with the short leg is configured to have a conical shape.

[0032] A further preferred measure which can be applied to all embodiments is that an annular gap is formed between the first axial end surface and the second axial end surface in the area which is located radially outside the fastening element. Thus, the first and second axial end surfaces only contact each other in the area which is delimited by the radially outer side of the fastening element. By this measure, the contact surface between the first and second axial end surfaces is reduced. This has the advantage that the force which is required for achieving the desired tensioning is reduced.

[0033] Preferably, the sealing element is made of a metal-containing material, or a plastic, or a rubber, or graphite.

[0034] Further, according to the present application, a centrifugal pump is proposed, the pump comprising a pump housing according to the present application.

[0035] With regard to important applications, the centrifugal pump can be designed as a boiler feed pump, or as a boiler pump for circulating a process fluid.

[0036] Further advantageous measures and embodiments of the present application will become apparent from the preferred embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0037] In the following, the present application will be explained in more detail with reference to embodiments of the present application and with reference to the enclosed drawings. Shown in a schematic illustration are: Figure 1 is a schematic illustration of a radial sealing arrangement for a sealing between a first housing part and a second housing part according to the prior art; Figure 2 is a cross-sectional view of an embodiment of a centrifugal pump according to the present application, comprising a first embodiment of a pump housing according to the present application; Figure 3 is an enlarged view illustrating details I of the first embodiment of a pump housing according to Figure 2 Figure 4 ​is a schematic illustration of a second embodiment of a pump housing according to the present application; Figure 5 is a schematic illustration of a third embodiment of a pump housing according to the present application; Figure 6 is a schematic illustration of a fourth embodiment of a pump housing according to the present application; and Figure 7 is an enlarged view of the radial sealing element of the fourth embodiment. DETAILED DESCRIPTION

[0038] Figure 1 A schematic illustration of a pump housing 1'according to the prior art is shown, having a radial sealing arrangement for sealing between a first housing part 2' and a second housing part 3' of the pump housing 1 '. Since the above has been explained in the description of the prior art, no further explanation is required. In order to distinguish the prior art arrangement from the embodiments according to the present application, the components of the pump housing 1'of the prior art are identified in the following with reference numerals which are followed by an apostrophe (single quote) in the following. Figure 1 Figure 1

[0039] In the following description of embodiments of the present application, reference will be made to a centrifugal pump as an example of an important application, namely to a boiler pump which is designed for circulating a process fluid.

[0040] Figure 2 A cross-sectional view of an embodiment of a centrifugal pump according to the present application is shown, which is identified as a whole with reference numeral 100. The centrifugal pump 100 comprises a first embodiment of a pump housing according to the present application, which is identified as a whole with reference numeral 1. Further, Figure 3 An enlarged view of detail I in Figure 2 is shown, which illustrates the first embodiment of the pump housing 1. Figure 2 The centrifugal pump 100 shown is designed as a boiler pump for circulating a process fluid.

[0041] It goes without saying that the present application is not limited to the specific type of centrifugal pump shown, but relates to a centrifugal pump 100 in general. In particular, the present application is suitable for a centrifugal pump 100 which is designed for transporting a hot fluid of at least 200 °C or even higher, for example, and / or for generating a high pressure of up to 200 bar or 500 bar or 1000 bar or even higher. As an example, the centrifugal pump 100 can be designed as a barrel pump, as a single-stage or multi-stage pump, as a single-phase or multi-phase pump. Figure 2

[0042] First, reference will be made to Figure 2 ​​​A boiler pump is described. As initially mentioned, a boiler pump is used in fluidized bed processes or boiling bed processes in the hydrocarbon processing industry. These processes are used to purify, for example, desulfurize, heavy hydrocarbons remaining in the bottom of a separation column, for example, in a petroleum refinery, and / or to decompose them into lighter hydrocarbons which can then be used more economically as distillates. Here, heavy oil remaining in petroleum refining can be referred to as an example of heavy hydrocarbons. In the known processes, the starting material, that is to say heavy hydrocarbons such as heavy oil, is heated, mixed with hydrogen and then supplied as a process fluid to a fluidized bed reactor or a boiling bed reactor. The purification or decomposition of the process fluid then takes place in the reactor with the help of a catalyst which is held suspended in the reactor to ensure the closest possible contact with the process fluid. The boiler pump, which is typically installed directly at the reactor, is used to supply the process fluid to the reactor or for the circulation of the process fluid.

[0043] The boiler pump comprises a pump housing 1 having an inlet 103 and an outlet 104 for a process fluid to be conveyed. Within the pump housing 1, an impeller 105 is arranged for acting on the fluid. The impeller 105 is mounted on a shaft 106 for rotating the impeller 105 about a shaft direction A. The shaft direction A is defined by a longitudinal axis of the shaft 106, that is to say a rotation axis about which the impeller 105 of the pump rotates during operation.

[0044] The pump housing 1 comprises a first housing part 2 and a second housing part 3 which are sealingly connected and fixed to one another by means of a plurality of fastening elements 4 Figure 3 According to the illustration of Figure 2 , the first housing part 2 is an upper housing part which accommodates the impeller 105 and comprises the inlet 103 and the outlet 104. The second housing part 3 is a lower housing part in Figure 2 and accommodates a drive unit 108 for driving the shaft 106 and thereby the impeller 105 about the shaft direction A.

[0045] With regard to the boiler pump, it is common practice to integrate the drive unit 108 into the pump housing 1 in a similar manner to a generally constructed submersible pump. Of course, the present application is not limited to a pump with a drive unit integrated into the pump housing 1.

[0046] The drive unit 108 is preferably an electric motor and, for example, is designed as a canned motor comprising an inboard rotor 118 and an outboard stator 128 surrounding the rotor 118. A can 138 is arranged between the rotor 118 and the stator 128 and sealingly seals the stator 128 from the rotor 118 in a known manner. The rotor 118 is rotationally fixedly connected to the shaft 106 which extends in the shaft direction A and is connected to the impeller 105 in a torque-proof manner on the other hand.

[0047] Figure 2 A boiler pump in its normal operating position is shown. The pump is constructed as a vertical pump, i.e., having a shaft 106 extending in the vertical direction (direction of gravity). The inlet 103 is located on the top side of the pump, and the drive unit 108 is located below the impeller 105.

[0048] Because the process fluid pumped by the boiling pump is subjected to very high pressures, such as at least 200 bar, and very high temperatures, such as exceeding 400°C, due to the process, the boiling pump must also be designed for such pressures and temperatures. In this regard, the pump casing 1 of the boiling pump, which also surrounds the drive unit 108, is designed to safely withstand these high operating pressures, such as 200 bar or higher. Furthermore, the boiling pump is designed to safely deliver hot process fluids. These process fluids typically have temperatures exceeding 400°C.

[0049] As already mentioned, the axial direction A is defined by the longitudinal axis of the pump shaft 106. The direction perpendicular to the axial direction A is referred to as the "radial direction". The terms "axial" or "axially located" are used in the general sense of "in the axial direction" or "relative to the axial direction". Similarly, the terms "radial" or "radially located" are used in the general sense of "in the radial direction" or "relative to the radial direction". For a surface, the terms "axial" or "radial" indicate the direction of the surface normal vector. For example, an axial surface is a surface having a surface normal vector oriented along the axial direction A.

[0050] Special Reference Figure 3 The first embodiment of the pump housing 1 will now be described in more detail. The pump housing 1 includes a first housing part 2 and a second housing part 3 that are sealed to each other by fastening elements 4. A radial sealing element 5 is provided between the first housing part 2 and the second housing part 3 for sealing between the first and second housing parts 2 and 3. The radial sealing element 5 is preferably designed as an annular sealing element. Figure 3 The sealing element in the process is, for example, a self-sealing O-ring seal.

[0051] The term "radial sealing element" refers to a sealing element constructed and arranged to function as a radial seal. As commonly used in the art, a radial seal is a sealing arrangement having a sealing element disposed in or on a curved surface. In particular, the curved surface is a radial surface, i.e., a surface having a surface normal vector oriented in the radial direction. Typically, the sealing element of the radial seal is disposed in or on a curved surface surrounding the shaft 106 of the pump. The radial sealing element 5 is annular and preferably arranged concentrically with the shaft 106.

[0052] In a cross-section perpendicular to the circumferential direction of the sealing element, the sealing element can have a circular cross-sectional area, or an elliptical, or a rectangular, or a D-shaped, or a T-shaped or any other cross-sectional area known in the art for annular sealing elements.

[0053] The sealing element can be made of metal or metal-containing material or plastic or rubber or graphite, for example.

[0054] The first housing part 2 has a first axial end surface 21 and the second housing part 3 has a second axial end surface 31. The first and second axial end surfaces 21, 31 face each other.

[0055] The second housing part 3 comprises an inner section 35 located radially inwardly with respect to the second axial end surface 31. The inner section 35 extends into the first housing part 2 so that the first housing part 2 encloses the inner section 35 of the second housing part 3. The inner section 35 is delimited in the radial direction by a radially outer surface 351 facing the radially inner surface 25 of the first housing part 2. The radially inner surface 25 delimits the first housing part 2 in the radial direction.

[0056] The radial sealing element 5 is arranged between the radially outer surface 351 of the inner section 35 of the second housing part 3 and the radially inner surface 25 of the first housing part 2. The radially inner surface 25 of the first housing part 2 is provided with an annular sealing groove 6 extending along the entire inner periphery of the first housing part 2. The radial sealing element 5 is inserted into the annular sealing groove 6 and seals between the first and second housing parts 2, 3.

[0057] The area of the first and second housing parts 2, 3 that overlap with respect to the axial direction A between the radially inner surface 25 of the first housing part 1 and the radially outer surface 351 of the inner section 35 of the second housing part 3 is referred to as the sealing gap 10 since the sealing element is positioned in this area for sealing between the first and second housing parts 2, 3.

[0058] More generally, the sealing gap 10 refers to the separation between those adjacent surfaces of the first housing part 2 and the second housing part 3 in which or on which the sealing element is arranged.

[0059] Typically, the sealing gap 10 has a very small extension in the radial direction that does not exceed the clearance required for inserting the inner section 35 of the second housing part 3 into the first housing part 2.

[0060] It is also possible that the sealing gap 10 is completely closed after mounting when the first and second housing parts 2, 3 are fixed to each other. Especially in some embodiments where the sealing element is not self-sealing but needs to be pre-tightened, for example when the sealing element is made of a metal-containing material or graphite, the sealing gap 10 is usually completely closed after the first and second housing parts 2, 3 are fixed to each other, so that the desired surface pressure between the sealing element and the housing parts is achieved.

[0061] With particular reference to Figure 3 In the illustrated first embodiment, the closed sealing gap 10 means that the radially outer surface 351 is in contact with the inner surface 25. However, as already referred to above with respect to the prior art, Figure 1 Illustratively, due to the deformation caused by the pressure and / or temperature of the first and / or second housing part 2, 3, there is a clear risk that the sealing gap 10 opens up or increases in the prior art arrangement, at least during operation of the pump. As will be explained in more detail later, in the pump housing 1 according to the application, this opening up or increase of the sealing gap 10 at high pressure and / or at high temperature is avoided or at least significantly reduced.

[0062] The high-pressure side inside the pump housing 1 is identified with HP in Figure 3 and the low-pressure side is identified with LP. The low pressure LP is for example the ambient pressure. In a boiler pump, the high-temperature side is the same side as the high-pressure side HP and the low-temperature side is the same side as the low-pressure side LP.

[0063] In the mounted state of the pump housing 1, the first and second axial end surfaces 21, 31 of the first and second housing parts 2, 3 are in contact and pressed against each other by means of the fastening elements 4, respectively. Preferably, each fastening element 4 comprises a bolt 41 and a nut 42 screwed onto the bolt 41. The reference 4C identifies the centre line of the respective bolt 41. In order to connect the first and second housing parts 2, 3, the bolts 41 are tensioned and locked by means of the nuts 42 to create a desired contact pressure by which the first and second housing parts 2, 3 are pressed together. Preferably, the fastening elements 4 are arranged equidistantly with respect to the axis 106.

[0064] Preferably, the first and second axial end surfaces 21, 31 are not in contact over the entire respective surface 21, 31, but an annular gap 11 is formed between the first axial end surface 21 and the second axial end surface 31 in an area located radially outside the fastening elements 4. That is, the annular gap 11 extends from an imaginary circle on which the centre lines 4C of all bolts 41 lie to the radially outer edge of the first or second housing part 2, 3 with respect to the radial direction. In other words, the first and second axial end surfaces 21, 31 are only in contact in an area located radially inwards with respect to the centre lines 4C of the fastening elements 4.

[0065] According to the present application, the first axial end surface 21 comprises a ring-shaped protrusion 22 extending in the axial direction A and the second axial end surface 31 comprises a ring-shaped recess 32 configured to engage with the ring-shaped protrusion 22 and to provide an outer centering, wherein the ring-shaped protrusion 22 is arranged radially inwardly with respect to the fastening element 4. As the opening of the sealing gap 10 is prevented by the interaction between the ring-shaped protrusion 22 and the ring-shaped recess 32 and serves as an outer centering, by these features the opening or enlargement of the sealing gap 10 at high pressure and / or at high temperatures is avoided or at least significantly reduced.

[0066] In the first embodiment, the ring-shaped recess 32 is configured as an annular groove. The annular groove has a substantially rectangular profile in a cross-section perpendicular to the circumferential direction and is delimited by a radial outer wall 322, a radial inner wall 321 and an axial bottom wall 323 extending between the radial inner wall 321 and the radial outer wall 322. In the mounted state, the annular groove surrounds the shaft 106 of the pump. The annular groove is arranged adjacent and concentrically to the inner section 35 of the second housing part 2, such that the radial inner wall 321 is aligned with or forms an integral part of the radial outer surface 351 of the inner section 35 of the second housing part 2.

[0067] It is also possible to arrange the annular groove more outwardly, i.e. closer to the fastening element 4, with respect to the radial direction, but in any case the annular groove is positioned radially inwardly with respect to the fastening element 4.

[0068] The ring-shaped protrusion 22 at the first axial end face 21 of the first housing part 2 extends along the entire inner circumference of the first housing part 2 and has a substantially rectangular profile in a cross-section perpendicular to the circumferential direction. The ring-shaped protrusion 22 is located at a radial inner edge of the first housing part 2, such that the ring-shaped protrusion 22 forms part of the radial inner surface 25 of the first housing part 2. The ring-shaped protrusion 22 is aligned with the annular groove and is configured such that it fits into the annular groove. Preferably, the ring-shaped protrusion 22 and the annular groove are designed as a clearance fit.

[0069] The radial sealing groove 6 into which the sealing element is inserted is arranged in the ring-shaped protrusion 22.

[0070] In the mounted state, the ring-shaped protrusion 22 engages with the annular groove. This engagement results in an advantageous outer centering of the radial seal. Furthermore, the cooperation of the ring-shaped protrusion 22 with the groove ensures that the sealing element and the entire sealing arrangement are always uniformly loaded, in particular with respect to the circumferential direction.

[0071] In particular, when the pressure or temperature causes a deformation, such as a radial expansion of the first housing part 2, the engagement of the annular protrusion 22 with the groove prevents or at least significantly reduces the opening or enlargement of the sealing gap, thus ensuring a reliable and safe sealing action. Since the annular protrusion 22 abuts against the radial outer wall 322 of the annular groove, even a deformation of the first housing part 2 does not cause a significant opening or enlargement of the sealing gap 10.

[0072] The engagement of the annular protrusion 22 with the groove has an additional positive effect on the openings in the pump housing 1 arranged near the border between the first and second housing parts 2, 3. By way of example, reference is made to the outlet 104 Figure 1 ) provided in the first housing part 2 and arranged near the contact area of the first and second housing parts 2, 3. The outlet 104 must comprise an opening in the wall of the first housing part 2 for discharging the fluid. From a mechanical point of view, the opening of the outlet 104 constitutes a weak point in the first housing part 2. In the prior art arrangement, a pressure- or temperature-induced expansion or deformation of the first housing part can cause a deformation of the opening, for example an initially circular opening can be deformed so as to become elliptical or any other shape. This can have a negative effect, for example on the connection of the outlet 104 with the pipe.

[0073] The design with the annular protrusion 22 engaging with the groove according to the present application prevents or at least significantly reduces such a deformation of the openings positioned near the contact area of the first and second housing parts 2, 3, and thus also ensures an even load of the sealing element with respect to the circumferential direction.

[0074] The outer or outside centering of the annular protrusion 22 and the sealing element is respectively achieved by the radial outer wall 322 of the groove acting on the radial outer wall of the annular protrusion 22.

[0075] In the following description of further embodiments of the pump housing 1 according to the present application, only the differences to the first embodiment are described in more detail. The description with respect to the first embodiment is equally valid for the other embodiments in the same way or in a similar way. Identical reference signs identify those features which have already been referred to Figure 2 and Figure 3 in the description of the same features or functionally equivalent features. Of course, it is also possible to combine specific features of the different embodiments.

[0076] Figure 4 A schematic illustration of a second embodiment of the pump housing 1 according to the present application is shown. In this embodiment, the annular protrusion 22 is arranged in the second housing part 3. The annular protrusion 22 is arranged in the second housing part 3 in the region of the contact area with the first housing part 2. The annular protrusion 22 is arranged in the second housing part 3 in the region of the contact area with the first housing part 2. Figure 4In the first embodiment of the pump housing 1, the fastening elements 4 are not shown in detail, but are only indicated by the center lines 4C of the bolts 41. In the first embodiment of the pump housing 1, the annular sealing groove 6 for receiving the radial sealing element 5 is formed by the first and second housing parts 2, 3 jointly.

[0077] As a variant of the first or second embodiment, respectively, it is also possible to provide both the radially outer surface 351 of the inner section 35 of the second housing part 3 and the radially inner surface 25 of the first housing part 1 with a respective circumferential groove, wherein these grooves face each other and jointly form the annular sealing groove 6 for receiving the radial sealing element 5.

[0078] Figure 5 A schematic illustration of a third embodiment of the pump housing 1 according to the present application is shown. In Figure 5 In the third embodiment of the pump housing 1, the annular sealing groove 6 for receiving the radial sealing element 5 is formed by the first and second housing parts 2, 3 jointly.

[0079] The sealing element is designed as a profile seal with a rectangular cross section, also referred to as a profile gasket, and is made of graphite, for example. This type of sealing element usually requires a pre-tensioning in order to generate a surface pressure between the sealing element and the surfaces of the first and second housing parts 2, 3 which are in contact with the sealing element.

[0080] In the third embodiment, the annular protrusion 22 of the first axial end surface 21 of the first housing part 2 is not aligned with the radially inner surface 25 of the first housing part 1, but is arranged more outwardly with respect to the radial direction, such that a shoulder 24 is formed between the annular protrusion 22 and the radially inner surface 25.

[0081] The annular recess 32 of the second axial end surface 31 of the second housing part 3 is arranged more outwardly with respect to the radial direction, such that the annular recess 32 is aligned with the annular protrusion 22. Thus, the radially inner wall 321 delimiting the annular recess 32 is not aligned with the radially outer surface 351 of the inner section 35 of the second housing part 2, but is staggered with respect to the radially outer surface 351, such that the second axial end surface 31 comprises an annular region 34 arranged between the annular recess 32 and the radially outer surface 351 of the inner section 35 with respect to the radial direction. As a result, the annular sealing groove 6 is delimited by the shoulder 24 and the annular region 34 with respect to the axial direction A. With respect to the radial direction, the annular sealing groove 6 is delimited by the annular protrusion 22 and the radially outer surface 351 of the inner section 35 of the second housing part 3.

[0082] In the mounted state in which the radial sealing element 5 is inserted into the annular sealing groove 6, the sealing element abuts both against the annular protrusion 22 and against the inner section 35 of the second housing part 3 with respect to the radial direction. In addition, the sealing element abuts against the annular region 34 of the second axial end surface 31 and against the shoulder 24 with respect to the axial direction A.

[0083] The sealing gap 10 comprises a step at the sealing element. On the high pressure side HP of the sealing element, the sealing gap 10 is bounded with respect to the radial direction by the radially outer surface 351 of the inner section 35 of the second housing part 3 and by the radially inner surface 25 of the first housing part 2. On the low pressure side LP of the sealing element, the sealing gap 10 is bounded with respect to the radial direction by the radially inner wall 321 bounding the annular recess 32 and by the annular protrusion 22. In this arrangement as shown in Figure 5 The more critical part of the sealing gap 10 is in this arrangement the part on the low pressure side LP of the sealing element. By the engagement of the annular protrusion 22 with the groove, an opening or a significant enlargement of the sealing gap 10 is reliably prevented, especially on the low pressure side LP of the sealing element.

[0084] Figure 6 A schematic illustration of a fourth embodiment of the pump housing 1 according to the present application is shown. In Figure 6 the fastening element 4 is not shown in detail but is only represented by the center line 4C of the bolt 41. For a better understanding, Figure 7 An enlarged view of the radial sealing element 5 of the fourth embodiment is shown.

[0085] Unlike the first three embodiments, the fourth embodiment does not comprise an inner section 35 extending into the first housing part 2. Figures 2 to 5 In addition, the annular recess 32 in the second axial end surface 31 of the second housing part 3 is open on the radially inner side, i.e. the annular recess 32 is only bounded by the radially outer wall 322 and by the axial bottom wall 323. There is no radially inner wall like the radially inner wall 321 in the first, second and third embodiments.

[0086] The annular protrusion 22 is located at the radially inner rim of the first housing part 2 such that the annular protrusion 22 forms part of the radially inner surface 25 of the first housing part 2.

[0087] The radial sealing element 5 is arranged in the annular recess 32 of the second housing part 3. In particular, the sealing element is arranged between the annular protrusion 22 and the axial bottom wall 323 bounding the annular recess 32 with respect to the axial direction A.

[0088] The radial sealing element 5 (see also Figure 7) annular sealing element designed to have a substantially T-shaped cross-sectional area perpendicular to the circumferential direction. The sealing element comprises an annular axial leg 51 extending in axial direction A and an annular radial leg 52 extending in radial direction, i.e. perpendicular to the axial leg 51. As can be best seen in Figure 7 The axial leg 51 is configured to taper towards the radial leg 52, thus forming two conical surfaces 53, 54 which provide the most important contribution to the sealing action. Due to the conical surfaces 53, 54, such a sealing element is also referred to as conical sealing element. The conical sealing element is preferably made of metal or a metal-containing material. The first conical surface 53 connects the axial leg 51 with the radial leg 52 of the sealing element on the low pressure side LP, i.e. the first conical surface 53 contacts the second housing part 3 in the mounted state. The second conical surface 54 connects the axial leg 51 with the radial leg 52 on the high pressure side HP, i.e. the second conical surface 54 contacts the first housing part 2 in the mounted state. When the sealing element is pressurized, the overall shape of the conical sealing element does not change significantly. Thus, Figure 7 The general shape, in particular the cross-section, of the shown sealing element is essentially the same before and after mounting or pressurizing of the sealing element.

[0089] Those areas of the annular protrusion 22 and the annular recess 32 which contact the conical surfaces 53, 54 in the mounted state are adapted to receive the axial leg 51 of the sealing element, i.e. said areas are likewise configured in a tapered manner for forming conical contact faces against the first and second conical surfaces 53, 54 of the sealing element, respectively.

[0090] The conical sealing element generally requires a pre-tension in order to generate a surface pressure between the conical surfaces 53, 54 of the sealing element and the conical contact faces of the annular protrusion 22 and the annular recess 32 against the conical surfaces 53, 54 of the sealing element.

[0091] For a reliable sealing action, the surface pressure between the second conical surface 54 and the first housing part 2 (here: the conical contact face of the annular protrusion 22) should be at least essentially the same as the surface pressure between the first conical surface 53 and the second housing part 3 (here: the conical contact face of the annular recess 32).

[0092] In prior art arrangements comprising such a conical sealing element (as already referred to in the introductory part of this description), the surface pressure between the second conical surface 54 and the first housing part 2 (here: the conical contact face of the annular protrusion 22) is significantly lower than the surface pressure between the first conical surface 53 and the second housing part 3 (here: the conical contact face of the annular recess 32). Figure 1Illustratively, the deformation caused by pressure and / or temperature, in particular of the first housing part 2', generally leads to a reduction of the surface pressure between the conical surface of the sealing element and the first housing part 2', whereas the surface pressure between the conical surface of the sealing element and the second, harder housing part 3' remains essentially constant or even has a tendency to increase. Thus, when the deformation of the first housing part 2' occurs, the portion of the conical surface of the sealing element contacting the second housing part 3' is subjected to a significantly stronger surface pressure than the portion of the conical surface of the sealing element contacting the first housing part 2'. This difference in surface pressure has the adverse effect that the sealing element is loaded unevenly, which can lead to tilting or bending or rotation or deformation of the sealing element. These effects can significantly impair the reliable sealing function.

[0093] In the fourth embodiment of the pump housing 1, such negative effects are prevented or at least significantly reduced. By the interaction of the annular protrusion 22 and the annular recess 32, and in particular by the outer centering, it is ensured that the surface pressure between the second conical surface 54 and the first housing part 2, here the conical contact surface of the annular protrusion 22, is always at least approximately the same as the surface pressure between the first conical surface 53 and the second housing part 3, here the conical contact surface of the annular recess 32.

[0094] With respect to the radial direction, the radial leg 52 of the sealing element does not extend to the radially outer wall 322 delimiting the annular recess 32. This has the advantage that the sealing element and in particular the radial leg 52 can expand in the radial direction without abutting against the radially outer wall 322, for example due to high temperatures.

[0095] With respect to the axial direction A, a preferred measure is that the radial leg 52 of the sealing element is not clamped between the annular protrusion 22 and the axial bottom wall 323 of the annular recess 32. Thus, the sealing element, the annular protrusion 22 and the recess 32 are configured in such a way that a gap exists between the annular protrusion 22 and the radial leg 52 and between the axial bottom wall 323 of the annular recess 32 and the radial leg 52. In particular, said gap also exists in the mounted state when the first and second housing parts 2, 3 are pressed together.

[0096] An advantage of the gap on both sides of the radial leg 52 is that the radial leg 52 can freely expand and contract in the radial direction. Thus, in particular when the sealing element and its adjacent components are exposed to high temperatures, strong temperature gradients or temperature transients, the sealing element, in particular the radial leg 52, can change its extension in the radial direction without being clamped between the annular protrusion 22 and the axial bottom wall 323 of the annular recess 32 in the axial direction A. Thus, by providing said gap in the axial direction A, the so-called stick-slip effect can be avoided. In addition, the gap ensures that the sealing element is always self-centering, evenly loaded and prevents tilting or rotation. For example, the gap is between 0.1 mm and 0.2 mm, preferably approximately 0.15 mm, on each side of the radial leg 52 of the sealing element.

[0097] Even though the application has been described with reference to specific embodiments of a pump designed as a boiler pump, it goes without saying that the application is not limited to this type of pump, but can be applied to all other types of pumps.

[0098] As an example, in the case where the centrifugal pump 100 is configured as a volute pump, the first casing part 2 of the pump casing 1 is a volute in which one or more impellers are arranged, and the second casing part 3 is an end cover that closes the casing in the axial direction.

Claims

1. A pump casing for a centrifugal pump, the pump casing extending in an axial direction (A) and having a first housing part (2), a second housing part (3) for hermetically fitting to the first housing part (2), a plurality of fastening elements (4) for connecting the first and second housing parts (2, 3), and a radial sealing element (5) for sealing between the first and second housing parts (2, 3), wherein, The first housing part (2) has a first axial end surface (21), and the second housing part (3) has a second axial end surface (31), the first and second axial end surfaces (21, 31) facing each other, characterized in that the first axial end surface (21) includes an annular protrusion (22) extending in the axial direction (A), and the second axial end surface (31) includes an annular recess (32) configured to engage with the annular protrusion (22) and provide lateral centering, wherein the annular protrusion (22) is radially inwardly arranged relative to the fastening element (4).

2. The pump casing according to claim 1, wherein, The annular recess (32) is constructed as an annular groove.

3. The pump housing according to any one of the preceding claims, wherein, The sealing element (5) is arranged in an annular sealing groove (6).

4. The pump casing according to claim 3, wherein, The annular sealing groove (6) is arranged in the first housing part (2).

5. The pump casing according to claim 3 or claim 4, wherein, The annular sealing groove (6) is arranged in the second housing part (3).

6. The pump casing according to any one of claims 3 to 5, wherein, The sealing groove (6) is formed by the first and second housing parts (2, 3).

7. The pump housing according to any one of the preceding claims, wherein, The protrusion (22) forms part of the radial inner surface (25) of the first housing part (2).

8. The pump casing according to claim 7, wherein, The sealing groove (6) is arranged in the protrusion (22).

9. The pump housing according to any one of the preceding claims, wherein, The second housing part (3) includes an inner section (35) that extends into the first housing part (2) such that the first housing part (2) surrounds the inner section (35) of the second housing part (3), and wherein the sealing element (5) is arranged between the inner section (35) of the second housing part (3) and the first housing part (2).

10. The pump housing according to any one of the preceding claims, wherein, The sealing element (5) is arranged in the annular recess (32) of the second housing part (3).

11. The pump casing according to claim 10, wherein, The sealing element (5) is a tapered sealing element (5) having a substantially T-shaped cross-section.

12. The pump housing according to any one of the preceding claims, wherein, An annular gap (11) is formed between the first axial end surface (21) and the second axial end surface (31) in the region located radially outside the fastening element (4).

13. The pump housing according to any one of the preceding claims, wherein, The sealing element (5) is made of a metal-containing material, or plastic, or rubber, or graphite.

14. A centrifugal pump, characterized in that, The pump includes a pump casing (1) according to any one of the preceding claims.

15. The centrifugal pump of claim 14, which is designed as a boiler feed pump or a boiling pump for circulating process fluids.

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