KR101210400B1 - Pump casing and pump with the pump casing - Google Patents

Abstract

The invention relates to a pump housing (2) comprising a double walled casing (3) in which the first wall (4) at least partially allows the first fluid (4) to compress the second fluid (6). In order to be able to flow around, the compression is carried out with at least two elongated rotors 7, 8. The double wall casing 3 comprises: (i) a first wall 10 forming a volume of the compression chamber 5; And (ii) a second wall 11 extending around the first wall 10 at a distance 12 from the first wall to allow the first fluid 4 to pass therethrough. The pump housing 2 consists of two subassemblies 13, 14, that is, the first subassembly 13 and the second subassembly 14, which are the longitudinal axes of the rotors 7, 8. Assembled along a sealing surface 15 substantially perpendicular to 70,80. The first subassembly 13 and the second subassembly 14 are characterized in that they consist of a rigid element 16, which is molded with a first thermally conductive material and has two opposing faces, namely a first Face 18 and second face 19. According to the invention, the above mentioned first wall 10 molded with the rigid element 16 is arranged to extend substantially perpendicularly past the first face 18, while the second wall 11 is It extends substantially perpendicularly past the first face 18 but is disposed parallel to and not bonded to the fourth face of the first wall 10. In addition, the ablation portion 23 is recessed into the first face 18 so that each ablation portion forms at least one housing for the first member 9, the first member being the rotors 7, 8. It is used to guide the rotation of one of the opposite ends 71, 72, 73, 74 of one of them.

Description

Pump casing and pump with the pump casing

The present invention relates to a pump casing.

The present invention more particularly relates to, but is not limited to, the pumping field, and such pumps are used as compressors for gaseous fluids using a rotor.

The invention clearly relates to a pump comprising such a casing.

In the simplest example, for example, in US Pat. No. 2,460,957, the pump casing consists of two assemblies, referred to as a first subassembly and a second subassembly, which are joint surfaces substantially perpendicular to the longitudinal axes of the rotor. Are joined along.

In the pump casing, the rotors are rotationally guided along the longitudinal axis by guide elements called first guide elements, which are located at the level of both ends they comprise.

Generally the casings of such pumps are obtained by casting walls from a metallic material, and the specific surfaces of these walls are machined, in particular boring, to form a chamber, referred to as a compression chamber, in which the rotors are placed. Is processed by

Manufacturing subassemblies by casting a metal material is significantly easier when the ratio between the transverse dimension (thickness) and the longitudinal dimension of each wall forming the subassembly is close to one.

Although not necessarily, the structure of the two half subassemblies in which the longitudinal dimension substantially corresponds to half of the longitudinal dimension of the pump casing is preferred, since the casting of the metal material can be facilitated.

Moreover, the reduced longitudinal dimension of each chamber portion included in the subassembly makes it possible to improve the precision of machining.

The situation is complicated when the compression chamber has to be cooled through circulation of the heat transfer medium.

In fact, the pump casing should have a double wall shell that allows circulation of the heat transfer medium around the compression chamber.

In this type of pump, the envelope of the double wall extends around the first wall on the one hand, which determines the volume of the compression chamber and on the other hand, with a specific spacing intended for circulation of the first fluid. Has a second wall.

In this type of construction, the problem of sealing occurs when operating the pump, which is caused by the different expansion of the first wall and the second wall.

The result to be obtained by the present invention is to provide a double walled pump casing having a structure that can overcome the problems of the prior art that arise during operation and manufacture of the pump.

To this end, the present invention has a pump casing according to claim 1 as a subject matter.

The present invention also has a pump comprising such a casing as the subject matter.

The invention will be well understood from the following description given by way of non-limiting example with reference to the drawings schematically shown.

1 is an exploded perspective view of a pump casing according to the present invention.

FIG. 2 is a pump comprising the pump casing of FIG. 1, shown in cross section along a plane passing through a longitudinal axis of a rotor included in the pump.

3 shows the end of one of the subassemblies consisting of a pump casing according to the invention.

FIG. 4 is a cross section of the subassembly according to FIG. 3, which is shown along an intermediate plane.

FIG. 5 shows a detailed view of the joining of two subassemblies of a pump casing, in a local section, on an enlarged scale.

Referring to the drawings, there is shown a pump casing 2 having a double walled shell 3, which shell is at least partially around a chamber 5 for compression of the second fluid 6. Permitting the circulation of (4), in particular the circulation of the heat medium, the compression being effected by at least two elongated rotors 7, 8, the rotors having longitudinal axes 70, 80 And is located in the compression chamber (5).

The second fluid 6 as well as the first fluid 4 are indicated by arrows.

The rotors 7, 8 are rotationally guided about the longitudinal axes 70, 80 by elements referred to as first guide elements 9 for rotational guidance, the first elements of which the rotor comprises; At the level of the opposite ends 71, 72, 81, 82.

The double wall sheath 3 has, on the one hand, a second wall 10 which determines the volume of the compression chamber 5 and on the other hand has a specific spacing 12 intended for the circulation of the first fluid 4. Having a second wall 11 extending around the first wall 10.

The pump casing 2 consists of two subassemblies 13, 14, which are referred to as the first subassembly 13 and the second subassembly 14, which are longitudinal axes of the rotors 7, 8. Joined along the joining surface 15 substantially orthogonal to (70, 80).

As is apparent in FIG. 1, the two basic subassemblies 13 and the rotors 7, 8 of the pump casing 2 enable the formation of the pump 1.

Notably, each of the first subassembly 13 and the second subassembly 14 has a rigid element 16, which is molded with a first thermally conductive material, which is the first side 18. ) And two opposite faces, second face 19,

As being positioned past the first side 18,

* On the one hand, the first wall 10 is cast with the rigid element 16 and extends substantially perpendicular to the first face 18,

** defined transversely between two opposing faces, referred to as third face 20 and fourth face 21, third face 20 defining compression chamber 5 laterally, and a fourth The face 21 constitutes an exchange surface with the first fluid 4,

** defined by the fifth side 22 in the longitudinal direction, the fifth side being at least one for joining with the fifth side 22 of the first subassembly 13 or the second subassembly 14. Forming a bearing area, whereby it is joined along the joining surface 15 in a manner for constructing the pump casing 2,

On the other hand, the second wall 11 extends parallel to the fourth face 21 of the first wall 10 substantially perpendicular to the first face 18, and the fourth face 21. Is not connected to

Cutouts 23 retracted with respect to the first face 18, each of which has opposite ends 71, 72, 81, 82 of one of the rotors 7, 8; It constitutes at least one receptacle for the first element 9 for guiding rotation of one of the two.

The adoption of these technical features allows a structure that radically simplifies the manufacturing process to be given to the pump casing 2, no matter what level of manufacturing process it is, especially when the manufacturing process involves casting and mechanical processes. Simplify the process.

As will become more evident later, the adoption of these technical features is a pump comprising a first subassembly 13 and a second subassembly 14 adapted to include various common features or even the same features. It can be configured as the casing 2.

As should also be noted, in at least one of the first subassembly 13 and the second subassembly 14, the first wall 10 is supported by a rigid element 16 which is supported by it via the connecting portion 24. , Which leads to displacement of the first wall 10 by elastic deformation of the connecting portion 24 in a first direction 25 substantially orthogonal to the joining surface or joining plane 15.

In a preferred embodiment, the connecting portion 24 is constituted by the area of the rigid element 16 adjacent the first wall 10.

For example, this region is constituted by a thin portion of the rigid element 16.

Advantageously, this thin region extends in the first plane 26 substantially parallel to the joining plane or joining plane 15.

The adoption of these features allows any stretch or shortening of the first wall 10 to be absorbed by the elastic deformation of the connecting portion 24.

Each cutout 23 retracted and positioned with respect to the first face 18 likewise constitutes a receptacle for the second element 27, with the second element being rigid to which the cutout 23 under consideration is located. It is intended to ensure tightness between the element 16 and the opposite ends 71, 72, 81, 82 of the elongated rotated 7, 8.

The second element ensures a closure, referred to as "dynamic", that is, a seal during the rotation of the rotor.

As is apparent from the figure, each ablation section 23 consists of a bore, which is adapted to guide the rotation of the ends 71, 72, 81, 82 of the rotors 7, 8. A bearing portion 231 for the first element and a second bearing portion 232 for the second element 27, the second element 27 having the ends 71, 72 of the rotor 7, 8. It is intended to ensure tightness between the 81 and 82 and the rigid element 16 at the level at which its ends are located.

Although not shown here, each rotor 7, 8 is rotationally driven and the rotation of the different rotors 7, 8 is synchronized.

As is evident in FIG. 2, one of the subassemblies 13, 14 of the pump casing 2 is connected to the housing 17 and the cover 28.

Although not shown here, it is considered to be the housing 17 or the cover 28 that protects the mechanism for synchronized rotational drive of the different rotors 7, 8 housed in the pump housing 2.

At least one of the first subassembly 13 and the second subassembly 14 is provided with bores that pass directly through the rigid elements they contain, to allow the rotor 7, 8 to drive. The electrons have ends that traverse the bores in a way that extends beyond the second face of the rigid element under consideration.

The means for driving the rotors 7, 8 in synchronized rotation can be connected to the ends passing through the bores in a manner extending beyond the second face of the rigid element under consideration.

Preferably, the first subassembly 13 and the second subassembly 14 are provided with bores passing through the rigid element 16 they contain, the first and second subassemblies 13, 14 The second side 19 of the rigid element 16 bears on at least one cover 28 which seals and closes the bores.

The first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are joined by third elements 29 that pull one against the other, which is each first subassembly. The fifth side 22 of the rigid element 16 of the 13 and second subassembly 14 is made in such a way that one is applied to be sealed against the other.

The adoption of these technical features ensures the assembly of the assembly of the first subassembly 13 and the second subassembly 14.

In a preferred embodiment, the first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are joined by a third element 29 consisting of tension rods:

Each tension rod extends in a second direction 30 substantially orthogonal to the joining surface 15 and at least certain of the tension rods of each of the first subassembly 13 and the second subassembly 14. Through a space located between the first wall 10 and the second wall 11,

At the level of the second face 19 of each rigid element 16 comprising one of the first and second subassemblies 13, 14.

The expression “at the level of the second face 19” here should not be interpreted to mean that the third elements 29 must be accurately supported in the plane of the second face 19.

For example, the third elements 29 are supported on bearing parts (not shown), which bearing parts are retained in the rigid element 16 as being retracted with respect to the second face 19.

The adoption of these technical features likewise allows the first subassembly 13 and the second subassembly to be applied to the rigid regions of the subassemblies in a second direction 30 tangent to the first wall 10. Ensure the bonding force of the bonding of (14).

In a notable way:

The first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are joined by third elements 29, the third element being the first and second subassemblies ( By pulling one of the 13, 14 relative to the other, the second faces 22 of the rigid elements 16 of each of the first subassembly 13 and the second subassembly 14 one against the other. It is made in such a way that it is hermetically applied.

The second wall 11 of each of the first subassembly 13 and the second subassembly 14 extends beyond the first face 18 and comprises a face referred to as a sixth face 31. The sixth face extends into a second plane 32 parallel to the fifth face 22 of the same first subassembly or second subassembly 13, 14, but on the fifth face 22. Retracted relative to the first subassembly 13 and second subassembly 14 when the fifth faces 22 of the first subassembly 13 and the second subassembly 14 seat one against the other. The six faces 31 are spaced apart by a predetermined value E such that the gap 33 remains in between.

Adoption of these technical features ensures complete isostatism of the assembly.

Preferably, the sixth faces are spaced apart by a value E in the range between several millimeters of hundredths to several millimeters of tenths.

Within the limit of the spaced value of the sixth faces 31 (thermal expansion), the extension of the second walls 11 held on the sixth faces affects the fitting with the fifth faces 22. Can't go crazy

Also noteworthy,

At least one of the first subassemblies 13 and the fifth faces 22 of the second subassembly 14, which seat one against the other, is held in at least one first gasket 35. The gasket ensures a circumferential closure of the compression chamber 5 at the level of the two fifth surfaces 22 arranged to cooperate with the other fifth surface 22 to seat one against the other.

At least one of the sixth faces 31 of the first subassembly 13 and the second subassembly 14, which are located facing each other, is connected to the other one via an intermediary of at least one second gasket 36. Rests against the space located between the first wall 10 and the second wall 11 despite the gap 33 of the predetermined value E held between the sixth faces 31. Ensure sealing.

For example, at least one of the fifth faces 22 of the first subassembly 13 and the second subassembly 14 includes a groove 34 for receiving the first gasket 35 and the other fifth Cooperate with face 22.

There are other technical solutions which allow for the acceptance of the first gasket, which are not described herein as they belong to the prior art.

The expressions "at least the first gasket 35" and "at least the second gasket 36" mean that at least one tightness element is used herein, and / or the action of each closure element. It can be reinforced or replaced by the use of a sealing material bonded by this coating.

The first gasket 35 and the second gasket 36 ensure a static tightness, that is, a seal between the fifth faces where one does not move relative to the other, or one moves relative to the other. To ensure closure between the sixth sides that are not.

In the figure, the first gasket and the second gasket have the appearance of a toric type gasket, but that is a problem of possible solutions for achieving each of the gaskets.

The first gasket 35 and the second gasket 36 may consist of flat gaskets or may be formed by strands of material placed on the faces to be joined.

The adoption of these technical features ensures a complete closure of the space in which the compression chamber 5 and the first fluid 4 circulate.

The bearing portions for joining consist of the fifth face 22 of the first subassembly and the second subassembly intended to be joined, so that relative lateral positioning of the two first and second subassemblies can be possible. To this end, it has a male element 37 and a female element 38 which are complementary elements of lateral positioning.

In an advantageous embodiment, the fifth faces 22 are flat and the complementary positioning elements are coupled to the bore 38 formed in the respective bearing regions for joining, which are constituted by the fifth faces 22. (37).

The adoption of these technical features ensures strict positioning of the first and second subassemblies 13, 14 relative to each other.

When the pump casing 2 is intended to receive at least two elongated rotors 7, 8 and the longitudinal axes 70, 80 of the rotors are located in the same third plane, each first or The bearing area for joining, consisting of the fifth face 22 of the second subassembly 13, 14, has two complementary elements for lateral positioning, the female element 37 and the male element 38. Which are located in the third plane 39.

In this way, the positioning of the two subassemblies 13, 14 of the pump casing 2 is not affected by the microscopic changes caused by the continuation of the heating and cooling cycles the pump undergoes.

In general, the first and second subassemblies 13, 14 are one-fourth to the distance of the distance between the opposing first faces 18 of the assembled first and second subassemblies 13, 14. Made in such a way that the joining surface 15 is located between three quarters.

Preferably, the first and second subassemblies 13, 14 are substantially in the middle of the distance apart from the opposing first faces 18 of the assembled first and second subassemblies 13, 14. Is made in such a way that the joining surface 15 is located.

The adoption of such technical features makes it possible to form the pump casing 2 by, for example, the same first and second subassemblies 13, 14.

In any case, the adoption of the above technical features simplifies the machining of the compression chamber 5 and also simplifies the machining of the bores, on the one hand the ends of the extending rotor 7, 8 ( First bearing portions 231 intended to receive first elements for guiding rotations 71, 72, 81, 82 and, on the other hand, rigid elements 16 and ends of the rotor 71, 72, 81. , Constitutes second bearing portions 232 intended to receive the second element 27 while ensuring a seal between them.

When the pump casing 2 has at least one first channel 40 that allows injection of the third fluid 41, referred to as dilution fluid, into the chamber and injection from outside the compression chamber, the rigid element 16. Route of the third fluid 41, which is introduced through the inlet located at and discharged into the compression chamber 5 through at least one outlet orifice 42 located at the level of the third face 20. At least a first channel intended to be defined is formed within the thickness of the first wall 10.

The third channel 41 is indicated by an arrow exiting the outlet orifice 42.

The adoption of these technical features allows the third fluid 41 to route to any good place in the compression chamber 5.

In a first embodiment, the second wall 11 of each of the first subassembly and the second subassembly 13, 14 is formed by double molding.

According to a second embodiment, the second wall 11 of each of the first and second subassemblies 13, 14 is subjected to a double molding of the same second material as the first material constituting the first wall 10. Is formed by.

According to a third embodiment, the second wall 11 of each of the first and second subassemblies 13, 14 is adapted to a double molding of a second material different from the first material constituting the first wall 10. Is formed by.

The adoption of these technical features can significantly simplify the manufacture of the pump casing 2.

Two elongations arranged in parallel in the compression chamber 5 comprising a first orifice 44 for the reception of the second fluid 6 and a second orifice 45 for the outflow of the second fluid 6. When the pump casing 2 houses the rotated rotors 7, 8, the rigid element 16 of each of the first and second subassemblies 13, 14 passes through the hole to the first face 18. An open second channel 46, the aperture constituting one of the first orifice 44 or the second orifice 45, provided with a symmetry plane 47, the symmetry plane being on the one hand Located at an intermediate distance between the longitudinal axes 70, 80 of the elongated rotor 7, 8, on the other hand comprising longitudinal axes 70, 80 of the rotor 7, 8. Perpendicular to the third plane 39.

The second channel 46 is defined by transverse portions each having a plane of symmetry 47, the plane of symmetry between the longitudinal axes 70, 80 of the rotors 7, 8 extending on the one hand. It is located at an intermediate distance and is on the other hand perpendicular to the third plane 39 comprising the longitudinal axes 70, 80 of the rotors 7, 8.

The adoption of these features ensures a symmetrical temperature distribution in each of the first and second subassemblies, in particular the same temperature distribution at the level of the first elements for rotational guidance contained within each of the first and second subassemblies. do.

Substantially, the hot fluid emptied from the compression chamber 5 carries the same amount of heat on both sides of the plane of symmetry 47.

Each of the first and second subassemblies 13, 14 has a plane of symmetry 47, the plane of symmetry between the longitudinal axes 70, 80 of the rotors 7, 8 extending on the one hand. It is located at an intermediate distance of, and on the other hand, is perpendicular to the third plane 39 comprising the longitudinal axes 70, 80 of the rotors 7, 8.

The adoption of these technical features enhances the uniformity of the temperature distribution.

In an advantageous manner, at least a second orifice 45 for the discharge of the second fluid 6 is able to gravityly remove any condensate (not shown) located in the lower part of the compression chamber 5. To be shaped and disposed within the subassembly.

The invention can be used in devices such as pumps.

Claims (20)

A pump casing (2) having a double-walled shell (3) that allows circulation of the first fluid (4) at least partially around the compression chamber (5) of the second fluid (6), the compression being at least two Two rotors 7, 8, which are located in the compression chamber 5 as having a longitudinal axis 70, 80, The rotors 7, 8 are driven by elements called first elements 9 for guiding rotation, which are located at the level of the opposite ends 71, 72, 81, 82 which these rotors comprise. , Rotationally guided about the longitudinal axis 70, 80, The double wall sheath 3 has, on the one hand, a first wall 10 which determines the volume of the compression chamber 5, and on the other hand, a specific spacing intended for circulation of the first fluid 4. 12 and has a second wall 11 extending around the first wall 10, The pump casing 2 is assembled with a first subassembly 13 and a second subassembly, which are assembled along a joining surface 15 perpendicular to the longitudinal axes 70, 80 of the rotors 7, 8. Consists of two subassemblies called 14, Each of the first subassembly 13 and the second subassembly 14 includes two elements 16 that are cast from a first thermally conductive material and are a first side 18 and a second side 19. Characterized by having opposing faces, As positioned past the first side 18, On the one hand, the first wall 10 cast with the element 16 extends at right angles to the first face 18, The first wall is laterally defined between two opposing faces, referred to as the third face 20 and the fourth face 21, with the third face 20 defining the compression chamber 5 laterally. The fourth face 21 constitutes an exchange surface with the first fluid 4, The first wall is defined in the longitudinal direction by a fifth face 22 that forms at least one bearing portion that is joined to the fifth face 22 of the first subassembly 13 or the second subassembly 14. The first subassembly and the second subassembly must be joined along the joining surface 15 in such a manner as to constitute the pump casing 2, On the other hand, the second wall 11 extends at right angles to the first face 18 and parallel to the fourth face 21 of the first wall 10, connecting to the fourth face 21. Not, Each of the abutments 23 is positioned retracted with respect to the first face 18, so that the rotation of one of the opposite ends 71, 72, 81, 82 of one of the rotors 7, 8, 9) Pump casing (2), which constitutes at least one receptacle for a first element for guiding 9). The method of claim 1, In at least one of the first subassembly 13 and the second subassembly 14, the first wall 10 is connected to the element 16 supporting it via the connecting portion 24 and the connecting portion 24. ) Is characterized in that it leads to displacement of the first wall 10 by elastic deformation of the connecting portion 24 in a first direction 25 perpendicular to the joining surface 15. . 3. The method according to claim 1 or 2, Each cutout 23 retracted and positioned with respect to the first face 18 has a respective opposite end of the element 16 on which the cutout 23 under consideration is located and the elongated rotor 7, 8. Pump casing (2), characterized in that it comprises a receiving portion for a second element (27) intended to ensure tightness between each of (71,72,81,82). 3. The method according to claim 1 or 2, The first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are joined by third elements 29 that pull one against the other, which is each first subassembly. (13) and the pump casing (2), characterized in that it is made in such a way as to firmly apply one of the fifth faces (22) of the elements (16) of the second subassembly (14) to the other. 5. The method of claim 4, The first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are joined by third elements 29 made of tension rods, Each of the tension rods extends in a second direction 30 perpendicular to the joining surface 15, at least certain of the tension rods being the first of each of the first subassembly 13 and the second subassembly 14. Through a space located between the wall 10 and the second wall 11, The tension rods are supported at the level of the second side 19 of each element 16 comprising one of the first subassembly 13 and the second subassembly 14. 2). 3. The method according to claim 1 or 2, The first subassembly 13 and the second subassembly 14 constituting the pump casing 2 are a third, in which one of the first subassembly 13 and the second subassembly 14 pulls toward the other one. Joined by an element 29, which is a manner in which the fifth faces 22 of the elements 16 of each of the first subassembly 13 and the second subassembly 14 are hermetically applied to one another. Made of The second wall 11 of each of the first subassembly 13 and the second subassembly 14 extends beyond the first face 18 and the same first subassembly 13 or second subassembly 14. Of the first subassembly 13 and the second subassembly 14, comprising a face referred to as a sixth face 31 extending in a second plane 32 parallel to the fifth face 22 of. When the fifth faces 22 are seated with respect to the other one, the sixth faces 61 of the subassemblies 13, 14 are spaced apart by a predetermined value E such that the gap 33 remains between them. Pump casing (2), characterized in that the sixth face is retracted with respect to the fifth face (22). The method of claim 6, At least one of the fifth faces 22 of the first subassembly 13 and the second subassembly 14, one of which is seated with respect to the other, cooperates with the other fifth face 22 and the second five fifths. The surfaces 22 bear at least one first gasket 35, which ensures a seal around the compression chamber 5 at a level on which one is seated relative to the other, At least one of the sixth faces 31 of the first subassembly 13 and the second subassembly 14, which are located facing each other, is one of the other ones via the intermediary of the at least one second gasket 36. The perimeter of the space seated and located between the first wall 10 and the second wall 11 despite the gap 33 of the predetermined value E, which is held between the sixth faces 31. Pump casing (2), characterized by ensuring a tight seal. 3. The method according to claim 1 or 2, The bearing site for the joining, which is constituted by two fifth faces 22 of the first subassembly 13 and the second subassembly 14, which is intended to be joined, comprises two first subassemblies and two second subassemblies. Pump casing (2), characterized in that it has complementary positioning elements, male element (37) and female element (38), in such a way that relative lateral positioning is possible. 3. The method according to claim 1 or 2, As a pump casing intended to receive at least two elongated rotors 7, 8, the longitudinal axes 70, 80 of the rotors are located in the same plane 39, the first subassembly 13 or the first subassembly 13. The bearing portion for joining, consisting of the fifth face 22 of each of the two subassemblies 14, is a male element 37 and a female, which are two complementary transverse positioning elements located in the third plane 39. Pump casing (2), characterized in that it has an element (38). 3. The method according to claim 1 or 2, The joining surface 15 is positioned between 1/4 and 3/4 of the distance apart from the opposing first faces 18 of the joined first subassembly 13 and the second subassembly 14, Pump casing (2), characterized in that the first subassembly (13) and the second subassembly (14). 3. The method according to claim 1 or 2, The first subassembly 13 such that the joining surface 15 is positioned in the middle of the distance between the opposing first faces 18 of the joined first subassembly 13 and the second subassembly 14. And a second subassembly (14). 3. The method according to claim 1 or 2, The third fluid 41, referred to as dilution fluid, has at least one first channel 40 that allows it to be injected into the chamber from the outside of the chamber and is introduced through an inlet located in the element 16 and in a third facet. At least the first channel 40 intended to route the third fluid 41 exiting the compression chamber 5 through at least one outlet orifice 42 located at the level of 20 Pump casing (2), characterized in that is made within the thickness of the first wall (10). 3. The method according to claim 1 or 2, The pump casing (2), characterized in that the second wall (11) of each of the first subassembly (13) and the second subassembly (14) is formed by molding (double molding) from the casting. 3. The method according to claim 1 or 2, The second wall 11 of each of the first subassembly 13 and the second subassembly 14 is formed by double molding with the same second material as the first material constituting the first wall 10. Pump casing (2). 3. The method according to claim 1 or 2, The second wall 11 of each of the first subassembly 13 and the second subassembly 14 is formed by double molding of a second material different from the first material constituting the first wall 10. Pump casing 2. 3. The method according to claim 1 or 2, A pump casing intended to house two elongated rotors 7, 8 arranged in parallel in the compression chamber 5, the compression chamber 5 being a first orifice for the introduction of a second fluid 6. (44) and a second orifice (45) for outflow of the second fluid (6), wherein the elements (16) of each of the first subassembly (13) and the second subassembly (14) are through a through hole. A second channel 46 is opened to the first side 18, the aperture forming the first orifice 44 or the second orifice 45, wherein the aperture is provided with a symmetry plane 47. The plane of symmetry is located at an intermediate distance between the longitudinal axes 70, 80 of the elongated rotors 7, 8, on the one hand, and on the other hand, the length of the rotors 7, 8. Pump casing (2), characterized in that it is perpendicular to a third plane (39) comprising directional axes (70, 80). 17. The method of claim 16, The second channel 46 is determined by the transverse portions, each having a plane of symmetry 47, the longitudinal axis 70 of the rotors 7, 8 on which the plane of symmetry 47 extends. Pump, characterized in that it is located at an intermediate distance between the 80 and, on the other hand, perpendicular to the third plane 39 comprising the longitudinal axes 70, 80 of the rotors 7, 8. Casing (2). 3. The method according to claim 1 or 2, Each of the first subassembly 13 and the second subassembly 14 includes a plane of symmetry 47, the longitudinal axis 70, 80 of the rotors 7, 8 on which the plane of symmetry extends, on the one hand. Pump casing, characterized in that it is located at an intermediate distance between them and on the other hand perpendicular to the third plane 39 comprising the longitudinal axes 70, 80 of the rotors 7, 8. (2). 3. The method according to claim 1 or 2, The second orifice 45 for outflow of the second fluid 6 is characterized in that it is arranged and formed in the subassembly in such a way that gravity can remove condensate located in the lower part of the compression chamber 5. Pump casing (2). A pump comprising the pump casing according to claim 1.

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