CASING INCLUDING A TURBOMACHINE EXHAUST DRAIN

Abstract

CASING COMPRISING A TURBOMACHINE EXHAUST DRAIN One aspect of the invention relates to a casing comprising a drain (D) for discharging liquids through a discharge orifice (60) in a wall (6), the drain comprising a base (1) comprising a receiving channel (110), a frustoconical external mounting surface (111). The drain comprises a first nut (2) cooperating with the threaded external surface (112) of the base (1) to compress the frustoconical external mounting surface (111) against a corresponding frustoconical-shaped portion (601) of the wall (6) delimiting the discharge orifice (60). The drain further comprises a drainage tube (3) comprising a discharge conduit (30) and a connecting head (31) connected to one end of the discharge conduit (30). The drain further comprises a second nut (4) for connecting the connecting head (31) of the drainage tube (3) to the base (1) by compressing them to connect the channel (110) to the discharge conduit (30).Figure to be published with the abstract: Figure 1A.

Description

Title of the invention: CASING COMPRISING A TURBOMACHINE EXHAUST DRAIN TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the evacuation of liquids from the exhaust casings of a turbomachine via drains and a turbomachine comprising such an exhaust casing equipped with drains.

[0002] The present invention relates to a turbomachine casing comprising a drain and a turbomachine comprising such a casing. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] As described in document FR2913725, it is common for liquids such as water, fuel or oil to be retained in the exhaust casing of a turbomachine. Stagnation of the liquids is not desirable, particularly given the risks of fire and those associated with freezing. To overcome this problem, the casings of the prior art generally comprise an orifice provided with a drain which allows the liquids retained in the exhaust casing to be evacuated. This drain is generally formed of a cylindrical body comprising a zone integrally welded to the casing at the level of the evacuation orifice and a drainage tube extending from the body. However, carrying out this welding requires the addition of material which can obstruct the evacuation orifice. It is then necessary for an operator to manually remove the excess material in the drain orifice in order to unblock it.In addition, when opening the engine hood, the vein drainage tube is exposed to many risks of damage due to various environmental reasons resulting in a total change of the drain.

[0004] Such an operation is long and delicate for the operator. Document FR2913725 therefore proposed to remedy this problem a new type of drain which has a skirt crimped into the orifice of the exhaust casing. Such a drain makes it possible to simplify the mounting of the drain in the exhaust casing since the operation of unblocking the drain orifice is no longer necessary. However, as described in document FR303761, the fixing of this drain by crimping is less effective than fixings by welding. Document FR303761 also proposes a drain comprising a first part welded to one face of a wall of the casing by passing through it and a second part screwed to the first part then welded to the second surface of the wall opposite the first surface.Such a drain makes it possible to simplify the assembly of the drain, however for disassembly it is necessary to break the welding points and then unscrew the second part from the first part to be able to remove the . drain. Without these welds, the first part needs to be held in place during disassembly, making disassembly more complex since it is necessary to have a tool inside the cylinder head to hold it in place.

[0005] Other fluid recovery solutions exist, such as in documents FR3098242 and FR3098243, requiring a plate comprising a collector part pressed against an opening in the cylinder head and fixing means on either side of the plate requiring the use of means for fixing a flange of the wall to fix a liquid collector. Thus, in the event of changing this plate or mounting this plate, it is necessary to dismantle and reassemble the flange. In addition, this solution may pose a sealing problem between the plating of the surface of the cylinder head and the plate.

[0006] Document FR3106613 describes yet another solution comprising two drains linked together by a connecting piece on one side of the wall of the casing screwed on either side to the two drains and secured by an anti-rotation wire. Such an assembly is complex to put in place, in particular due to the insertion of the connecting piece inside the cylinder head.

[0007] There is therefore a need to replace a drainage tube easily without having to have a complex assembly or disassembly of the drain at the cylinder head and without the need to use means of fixing a flange. Summary of the invention

[0008] The invention offers a solution to the problems mentioned above, by making it possible to have fixing means only on the outside without adding fixing means to the cylinder head while still being able to dismantle the drainage tube.

[0009] One aspect of the invention relates to a turbomachine casing comprising: • An annular wall comprising: • a radially internal surface, • a radially external surface opposite the radially internal surface, • a discharge orifice passing from the radially inner surface to the outer surface, the discharge orifice comprising a frustoconical portion extending from the radially inner surface to the radially outer surface, • a drain comprising a base comprising: • an inlet end and an outlet end opposite the inlet end, • a channel opening at the inlet end and at the outlet end, • a frustoconical external mounting surface mounted on the frustoconical part from the drain hole, • a threaded external surface between the frustoconical external mounting surface and the outlet end, • an internal connecting surface delimiting a part of the channel up to the outlet end. The drain of the part according to the first aspect of the invention further comprises: • a first connecting nut which extends around and cooperates with the threaded external surface of the base to compress the frustoconical external mounting surface against the frustoconical-shaped part of the discharge orifice, • a drainage tube comprising a discharge conduit and a connection head connected to one end of the discharge conduit, the connection head comprising an external connection surface which cooperates with the internal connection surface of the base, • a second nut for connecting the connection head of the drainage tube to the base by compressing the internal connection surface of the base against the external connection surface so as to fluidly connect the channel of the base to the discharge conduit of the drainage tube.

[0010] Thanks to the invention, it is possible to change the drain tube or the evacuation conduit without using a tool inside the cylinder head. During a drainage tube or conduit change operation, the operator can maintain from the outside the clamping between the base and the wall of the cylinder head by this first nut while allowing the tube to be removed from the base by its connection. In addition, the external truncated cone-shaped mounting surface fixed to the wall using the first nut makes it possible to simplify the assembly while having a good seal between the wall and the base.

[0011] By "truncated cone-shaped portion of the discharge orifice" is meant the truncated cone-shaped surface of the annular wall delimiting (around) a portion of the volume of the discharge orifice. In other words, the annular wall comprises a surface of revolution defining the orifice, the surface of revolution comprising at least one portion of truncated cone shape having a diameter which increases as it approaches the first end.

[0012] In addition to the characteristics which have just been mentioned in the preceding paragraph, the casing according to one aspect of the invention may have one or more complementary characteristics among those described in the following paragraphs, considered individually or according to all technically possible combinations.

[0013] According to one embodiment, the base comprises an axial stop and the connection head of the drainage tube comprises a threaded external surface, the second nut comprising a stop surface abutting against the axial stop and being screwed onto a threaded external surface of the connection head. This makes it possible to change the drainage tube. without risk of losing the second nut.

[0014] According to an example of this embodiment, the base comprises a stop groove located between the threaded external surface and an external surface of a portion comprising the internal connection surface of the base, the base further comprising a removable ring mounted in the stop groove, forming the axial stop.

[0015] According to a variant, the connection head of the drainage tube comprises an axial stop and the base comprises a threaded external surface, the second nut connecting the drainage tube to the base by abutting against the axial stop and being screwed onto the threaded external surface.

[0016] According to one embodiment, the internal connection surface of the base is frustoconical, and in which the channel of the base comprises an outlet opening comprising the largest diameter of the frustoconical internal surface, and in which the external connection surface of the connection head is a curved frustoconical surface which cooperates with the internal connection surface to form a seal.

[0017] According to one embodiment, the base comprises a shoulder forming a cylindrical external surface extending from the internal connection surface of the base and the first nut comprises a cylindrical internal surface cooperating with the cylindrical external surface.

[0018] According to one embodiment, the casing is a turbine exhaust casing and the annular wall is a downstream annular wall, and in which the casing comprises an upstream annular wall which is intended to surround a ring of rotating blades, the upstream annular wall being frustoconical along the axis and comprising at its upstream end an upstream flange fixed to a downstream flange arranged at the downstream end of the downstream annular wall.

[0019] A second aspect of the invention relates to a turbomachine comprising a casing according to the first aspect of the invention and a ring of rotating turbine blades mounted to rotate around the axis, the ring of rotating blades being surrounded by the upstream annular wall.

[0020] A third aspect of the invention relates to a method of mounting a drain on an annular wall of a casing of a turbomachine according to the first aspect of the invention comprising: • a step of inserting a body of the base into the evacuation orifice from the inside to the outside of the wall, • a step of inserting the first nut, around the body of the base, after the step of inserting the body of the base, • a waterproof assembly step including: • a sub-step of screwing the first nut to the external surface threaded until the first nut rests against the wall, then • a tightening sub-step compressing the external truncated mounting surface against a corresponding truncated part of the wall, • a connection step by screwing the second nut onto a surface threaded part of the fitting head or base to compress the internal connecting surface to the external connecting surface so as to connect the channel of the base to the discharge conduit of the drainage tube.

[0021] According to an embodiment of this mounting method, in which the base of the drain comprises a body comprising a groove, the method comprises a step of inserting the second nut around a body of the base and then a step of inserting the ring into the groove to form the axial stop by having the stop surface of the second nut closer to the wall than the groove.

[0022] According to an example of this embodiment of this mounting method, the second nut comprises an internal groove and a deformation orifice opening onto the head and onto the internal groove, the method comprising a step of positioning the second nut on the body of the base so that the groove for forming the axial stop is opposite the internal groove.

[0023] A fourth aspect of the invention relates to a method of changing a drainage tube of a fluid recovery assembly of a turbomachine according to the first aspect of the invention, comprising:

[0024] • a step of unscrewing the second nut, a step of changing the drainage tube with a new drainage tube and a step of connecting by screwing the second nut onto a threaded surface of the connection head or the base body to compress the internal connection surface to the external connection surface of the new drainage tube connecting the channel to the evacuation conduit.

[0025] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0026] The figures are presented for information purposes only and in no way limit the invention.

[0027] [Fig.lA] shows a schematic representation of a section of a drain according to an example of an embodiment of the invention for the evacuation of liquids through a discharge orifice of a wall of a turbomachine casing.

[0028] [Fig. IB] shows a portion of a wall of the cylinder head of [Fig. 1 A].

[0029] [Fig.2] shows a three-dimensional schematic representation of a body of a drain base of [Fig.lA].

[0030] [Fig.3] shows a three-dimensional schematic representation of a first nut of the drain of [Fig.lA].

[0031] [Fig.4] shows a three-dimensional schematic representation of a drainage tube of the drain of [Fig.1A].

[0032] [Fig.5a] shows a three-dimensional schematic representation of a second base nut of the drain of [Fig.1A].

[0033] [Fig.5b] shows a section of the second drain base nut of [Fig.5a].

[0034] [Fig.5c] shows a section of a part of the drain including the second nut of [Fig.5a], part of the base 1 including a ring. DETAILED DESCRIPTION

[0035] The figures are presented for information purposes only and in no way limit the invention.

[0036] [Fig.lA] shows a schematic representation of a section of a part of a turbomachine at a casing 1 comprising an annular wall 6 and a drain D, according to an example of an embodiment of the invention for discharging liquids through a discharge orifice 60 of the annular wall 6 by means of the drain D. In this example, the drain D makes it possible to recover a low-pressure turbine fluid from the turbomachine. [Fig.lB] represents a section of a part of the annular wall 6 at the discharge orifice 60.

[0037] The annular wall 6 extends around an axis and comprises a first orifice 60, passing between a volume, called the inner volume hereinafter, in the casing 1 protecting the blades 9 and an outer volume. The annular wall 6 may comprise other orifices spaced angularly from each other (spaced circumferentially around the axis X). The annular wall 6 therefore has a radially inner surface 6i (also called the inner surface 6i) on the side of the inner volume and a radially outer surface 6e (also called the outer surface 6e) opposite the radially inner surface as well as a surface of revolution 600 (referenced in [Fig.lB]) delimiting the discharge orifice 60 formed in the thickness of the wall joining the inner surface to the outer surface.In particular, the discharge orifice 60 comprises a frustoconical portion 601, that is to say that the surface of revolution comprises a frustoconical portion extending from the internal surface 6i and a cylindrical portion extending from the frustoconical portion to the external surface 6e.

[0038] The annular wall 6 is frustoconical and extends along the axis of revolution, and comprises at the upstream end a flange portion 61 connected to a flange portion 71 of an external ring 7 of the casing 1 of the turbomachine, here in this case the exhaust casing of a low-pressure turbine of which a blade 9 can be seen in the interior volume of a last annular row. The blades 9 of the turbine are surrounded by the external ring 7 of the casing 1. The flange portion 61 and the flange portion 71 each comprise an orifice opposite each other and are connected by a bolt whose screw passes through this orifice. Furthermore, it can be seen that the wall comprises a retention spout 62 whose end is further from the axis of revolution than a part of the discharge orifice 60 so that the liquid flows into the drain D through this discharge orifice 60.

[0039] The drain D comprises a base 1 comprising a body 11 inserted from downstream (the inside of the annular wall 60) into the orifice 60. The base 1 is shown in a three-dimensional view in [Fig.2].

[0040] The body 11 comprises an inlet end on the inner side of the annular wall 60 and an outlet end opposite the inlet end on the outer side of the annular wall. The body 11 comprises a frustoconical external mounting surface 111 having a diameter which increases as it approaches the first end. This frustoconical external mounting surface 111 is in contact with the frustoconical part of the surface of revolution of the wall 6 delimiting the discharge orifice 60.

[0041] The body 11 comprises a channel 110 comprising an inlet opening 110i opening at the inlet end and an outlet opening 110o opening at the outlet end. The body 11 comprises a radially internal connection surface 113 delimiting a portion of the channel up to the outlet 110o.

[0042] The body 11 further comprises a threaded external surface 112 between the frustoconical external mounting surface 111 and the second end.

[0043] The drain D further comprises a first nut 2 shown in [Fig.3] according to a three-dimensional view and shown in [Fig.1A] in section by being screwed tightly onto the threaded external surface 112 of the body 11 of the base 1. The first nut 2 thus exerts a force against the external surface 6e and by the thread moves the base 1 by compressing the frustoconical external mounting surface 111 against the frustoconical-shaped part of the surface of revolution 601 of the wall 6 delimiting the evacuation orifice 60. The first nut 2 therefore comprises an orifice 20 crossed by the body 11 of the base 1 and a threaded internal surface 22 cooperating with the threaded external surface 112 of the body 11 of the base 1. The first nut 2 further comprises a head 21 comprising an external gripping surface 319 by a tool such as pliers or a wrench and the internal threaded surface 22.In this example, the nut 22 comprises a stop and guide ring 26 comprising an external surface 26e, a cylindrical internal surface 26i delimiting a portion of the orifice 20 and a radial surface 26r abutting against the external surface 6e of the wall 6. The body 11 of the base 1 comprises a shoulder forming a cylindrical external surface 116 extending from the frustoconical external mounting surface 111 to a radial surface 116r of the shoulder from which the threaded external surface 112 extends having a diameter smaller than that of the cylindrical external surface 116. The cylindrical external surface 116 comprises a portion surrounded by the discharge orifice 60 and a portion . surrounded by the cylindrical inner surface 26i. The cylindrical inner surface 26i comprises a longer axial length than the portion of the cylindrical outer surface 116 surrounded by the cylindrical inner surface 26i. Thus, the cylindrical outer surface 116 and the cylindrical inner surface 26i make it possible to align the discharge orifice 60 with the channel 110 by means of the support of the radial surface 26r of the first nut 2 bearing against the wall 6. This makes it possible to improve the seal between the frustoconical outer mounting surface 111 and the frustoconical-shaped portion 601 of the wall 6.

[0044] The drain D further comprises a drainage tube 3 shown in a three-dimensional view in [Fig.4]. The drainage tube 3 comprises a discharge conduit 30 and a connecting head 31 connected to one end of the discharge conduit 30, the connecting head 31 comprising an external connecting surface 313 corresponding to the shape of the internal connecting surface 113 to cooperate. The drainage tube 3 shown in [Fig.1A] in section is connected to the shape of the internal connecting surface 113. In this example, the internal connecting surface 113 is in contact with the external connecting surface 313.

[0045] The drain D further comprises a second nut 4 shown in a three-dimensional view in [Fig.5a] for connecting the connecting head 31 of the drainage tube 3 to the base 1. [Fig.5b] represents a section along an axial plane of the second nut 4 and [Fig.5c] also represents a section along an axial plane of a part of the base 1 comprising a downstream part of the body 11 and a ring 14j surrounded by the second nut 4. As visible in [Fig.1A], the second nut 4 makes it possible to compress the internal connecting surface 113 against the external connecting surface 313, thus connecting the channel 110 to the channel of the evacuation conduit 30.

[0046] Either the connecting head 31 or an element among the body 11 or the first nut 2 comprises a thread cooperating with the second nut 4 and respectively either one of the two elements or the connecting head 31 comprises an axial stop abutting against the second nut 4. In this embodiment, the connecting head 31 comprises a threaded external surface 314 cooperating with the second nut 4 and the base 1 further comprises an axial stop 14 abutting against the second nut 4. The second nut 4 is also represented by a section along an axial plane in [Fig.5b]. The second nut 4 comprises a head 41 having an external gripping surface of gripping shape 419 by pliers or a wrench and a cylindrical internal surface 411 around an axis X delimiting a part of an orifice 40. The second nut 4 further comprises a threaded internal surface 46 delimiting the other part of the orifice 40. In [Fig.lA], the threaded internal surface 46 is screwed with the threaded external surface 314. The cylindrical internal surface 411 comprises an internal stop abutting against the ring 14j in the direction towards the drainage tube 3. The ring 14j. of the base thus makes it possible to make the body 11 and the second nut 4 integral in translation by coming into abutment against these two parts. [Fig.5c] represents a section along an axial plane of an assembly comprising the second nut 4 and a part of the base 1 comprising the snap ring 14j and the downstream part of the body 11. In this example, the internal stop is formed in this case by an internal groove 414 referenced in [Fig.5b], located opposite the external groove 115, visible in [Fig.5c]. The internal groove 414 and the external groove 115 form a housing for the ring 14j, thus making it possible to limit the axial displacement of the second nut 4 relative to the body 11 of the base 1 while allowing it to pivot along the axis of rotation X around this part of the body 11. The cylindrical surface has a smaller diameter than that of the threaded external surface 314 and as visible in [Fig.[lA], the internal groove and the external groove form a stop surface against the axial stop 14 thus allowing, during screwing, the internal connection surface 113 to be compressed against the external connection surface 313.

[0047] In this example, the body 11 of the base 1 comprises a stop groove 115, also called an external groove, located between the threaded external surface 112 and the internal connecting surface 113, the base 1 further comprising a removable snap ring 14j mounted in the stop groove 115, one of the surfaces delimiting the groove of which forms with the snap ring 14j the axial stop 14. The snap ring 14j can be mounted in the stop groove 115 after insertion of the body 11 of the base 1 into the opening 40 of the second nut 4. The second nut 4 comprises an internal groove 414 complementary to the stop groove 115 housing together the snap ring 14j. In this example, the second nut 4 comprises at least one deformation orifice 414j opening onto the head 41 and onto the internal groove 414. This allows the insertion of a rod into this deformation orifice 414j to form the ring 14j by deformation and is housed in the housing formed by the internal groove 414j and the stop groove 115.The surfaces delimiting the internal groove 414j and the stop groove 115 are each in axial abutment against the ring sandwiching the ring 14j. According to another example, the body 11 of the base 1 comprises the axial stop 14 and the second nut 4 is bayonet-mounted by inserting its shoulder into a notch of the axial stop 14 and then turning the second nut 4 such that the shoulder is in abutment against the axial stop 14.

[0048] The connecting head 31 further comprises an external gripping surface 319 for a tool such as pliers or a wrench.

[0049] In this example, the internal connecting surface 113 is frustoconical, such that the discharge outlet 113o comprises the largest diameter of the frustoconical internal surface 113. The external connecting surface 313 is a curved frustoconical surface in contact with the internal connecting surface 113 to form a seal. Thus, when tightening by a tool on each external gripping surface 419, 319 of the second nut 4 and of the connecting head 31, the internal shoulder of the nut in abutment against the axial stop 14 moves the connecting head 4 towards the base 1 by compressing the internal connecting surface 113 against the external connecting surface 313 in order to form a seal (a plastic or elastic deformation can be produced during this deformation).

[0050] In this example, the body 11 of the base 1 comprises a second groove 118 between the threaded external surface 112 and a collar 117 formed between this second groove 118 and the stop groove 115.

[0051] The external gripping surfaces 219, 319, 419 are all in this example surfaces having a hexagonal section for mounting by key.

[0052] In this example, the maximum diameter of the second nut 4, here in this case measured at the level of the external gripping surface 419, is greater than the smallest diameter of the discharge orifice 60 (here in the cylindrical part) as well as that of the smallest diameter of the first nut 2, here measured at the level of the internal threaded surface 22. Thus, it is necessary to mount the second nut 4 after mounting the body of the base 1 and the first nut 2 as explained below.

[0053] The method of mounting the drain D therefore comprises: • a step of inserting the body 11 of the base 1 into the evacuation orifice 60, from the inside to the outside of the wall 6, • a step of inserting the first nut 2, around the body 11 of the base 11, after the step of inserting the body 11, • a sealed mounting step comprising a sub-step of screwing the first nut 2 to the threaded external surface 112 until the first nut 2 rests against the wall 6 then a tightening sub-step compressing the frustoconical external mounting surface 111 against a corresponding frustoconical-shaped part 601 of the wall 6 delimiting the evacuation orifice 60, • a connection step by screwing the second nut 4 onto a threaded surface of the connection head 31 or of the base 11 (according to the other example not shown) to compress the internal connection surface 113 to the external connection surface 313 connecting the receiving channel 110 to the channel of the evacuation conduit 30 in a sealed manner.

[0054] The connecting step may be by screwing the second nut 4 onto a threaded surface of the connecting head or the base body and by abutting against an axial stop respectively of the base or the connecting. In this example shown, the connecting step is carried out by screwing the second nut 4 onto the threaded external surface 314 of the connecting head 31 until the second nut is pressed against the axial stop 14, thus compressing by tightening the radially internal connecting surface 113 against the external connecting surface 313.

[0055] Having a base 1 fixed by a first nut 2 to the outside of the wall 4 makes it possible to simplify the assembly. Furthermore, having a drainage tube 3 connected by the second nut 4 to the base 1 makes it possible to simplify an assembly operation.

[0056] The method further comprises, before the screwing step, a step of inserting the second nut 4 around the body 11 of the base 11 and then a step of inserting a snap ring 14j into the groove 115 to form (by the surfaces forming the groove with the snap ring 14j) the axial stop 14 by having the stop surface of the second nut 4 closer to the wall 4 than the groove 115.

[0057] Finally, the fact in this example of having this second nut 4 mounted on the base 1 makes it possible to avoid losing the second nut 4 in the event of changing the drain pipe 3.

[0058] The method may include in particular a step of inserting a rod into the deformation orifice 414j to form the ring 14j housed in the housing formed by the internal groove 414j and the stop groove 115. The method according to the example shown further includes a step of positioning the second nut 4 on the body 11 of the base 1 so that the groove 115 is opposite the internal groove 414.

[0059] The method for changing the drainage tube 3 therefore comprises unscrewing the second nut 4 by applying a force using a tool to the external gripping surface 319 and an opposite force to the external gripping surface 419.

[0060] Then the method comprises a step of changing the drainage tube 3 with another drainage tube 3 and a connection step by screwing the second nut 4 in this case onto the threaded surface of the connection head 31 until it presses against the axial stop 14 to compress the internal connection surface 113 to the external connection surface 313 of the new drainage tube 3 connecting the channel 110 to the evacuation conduit 30.

[0061] Unless otherwise specified, the same element appearing in different figures has a single reference.

Claims

Claims

1. Turbomachine casing (1) comprising: an annular wall (6) which extends around an axis (X) and comprises: • a radially internal surface (6i), • a radially external surface (6th) opposite the radially inner surface (6i), • an evacuation orifice (60) passing from the radially internal surface (6i) to the radially external surface (6e), the evacuation orifice (60) comprising a frustoconical part (601) extending from the radially internal surface (6i) towards the radially external surface (6e), a drain (D) comprising: • a base (1) comprising:

1. an inlet end and an outlet end opposite the inlet end, 2. a channel (110) opening at the inlet end and at the outlet end, 3. a frustoconical external mounting surface (111) mounted on the frustoconical portion (601) of the discharge port (60), 4. a threaded external surface (112) between the frustoconical external mounting surface (111) and the outlet end, 5. an internal connecting surface (113) delimiting a part of the channel (110) up to the outlet end, • a first nut (2) which extends around and cooperates with the threaded external surface (112) of the base (1) to compress the frustoconical external mounting surface (111) against the frustoconical part (601) of the discharge orifice (60), • a drainage tube (3) comprising a discharge conduit (30) and a connection head (31) connected to one end of the discharge conduit (30), the connection head (31) comprising a surface external connecting surface (313) which cooperates with the internal connecting surface (113) of the base (1), • a second nut (4) for connecting the connecting head (31) of the drainage tube (3) to the base (1) by compressing the internal connecting surface (113) of the base (1) against the external connecting surface (313) so as to fluidically connect the channel (110) of the base (1) to the evacuation conduit (30) of the drainage tube (3).

2. Turbomachine casing (1) according to the preceding claim, in which the base (1) comprises an axial stop (14) and the connection head (31) of the drainage tube (3) comprises a threaded external surface (314), the second nut (4) comprising a stop surface (414) in abutment against the axial stop (14) and being screwed onto a threaded external surface (314) of the connection head (31).

3. Turbomachine casing (1) according to the preceding claim, in which the base (1) comprises a stop groove (115) located between the threaded external surface (112) and an external surface (119) of a portion comprising the internal connection surface (113) of the base (1), the base (1) further comprising a removable snap ring (14j) mounted in the stop groove (115) forming the axial stop (14).

4. Turbomachine casing (1) according to one of the preceding claims, in which the internal connection surface (113) of the base (1) is frustoconical, and in which the channel (110) of the base (1) comprises an outlet opening (1100) comprising the largest diameter of the frustoconical internal surface (113), and in which the external connection surface (313) of the connection head (31) is a curved frustoconical surface which cooperates with the internal connection surface (113) to form a seal.

5. Turbomachine casing (1) according to any one of the preceding claims, in which the base (1) comprises a shoulder forming a cylindrical external surface (116) extending from the internal connection surface (113) of the base (1) and the first nut (2) comprises a cylindrical internal surface (26i) cooperating with the cylindrical external surface (116).

6. Turbomachine casing (1) according to one of the preceding claims, in which the casing (1) is a turbine exhaust casing and the annular wall is a downstream annular wall (6), and in which the casing (1) comprises an upstream annular wall (7) which is intended to surround a ring of rotating blades (7), the upstream annular wall (6) being frustoconical along the axis (X) and comprising at its upstream end an upstream flange (61) fixed to a downstream flange (71) arranged at the downstream end of the downstream annular wall (7).

7. Turbomachine comprising a casing (1) according to the preceding claim and a ring of rotating turbine blades (9), mounted in rotation around the axis (X), the ring of rotating blades (9) being surrounded by the upstream annular wall (7).

8. Method for mounting a drain on an annular wall of a casing of a turbomachine according to one of claims 1 to 6, comprising: - a step of inserting a body (11) of the base (1) into the discharge orifice (60) from the inside to the outside of the wall (6), - a step of inserting the first nut (2), around the body (11) of the base (11), after the step of inserting the body (11) of the base (1), - a sealed mounting step comprising: • a sub-step of screwing the first nut (2) to the threaded external surface (112) until the first nut (2) rests against the wall (6) then, • a tightening sub-step compressing the frustoconical external mounting surface (111) against a corresponding frustoconical part (601) of the wall (6),- a connecting step by screwing the second nut (4) onto a threaded surface of the connecting head (31) or the base (11) to compress the internal connecting surface (13) to the external connecting surface (31) so as to connect the channel (110) of the base (1) to the discharge conduit (30) of the drainage tube (3).,

9. Mounting method according to the preceding claim, in which the base (1) of the drain (D) comprises a body (11) comprising a groove (115), the method comprising a step of inserting the second nut (4) around the body (11) of the base (11) and then a step of inserting a snap ring (14j) into the groove (115) to form the axial stop (14) by having the stop surface of the second nut (4) closer to the wall (4) than the groove (115).

10. Mounting method according to the preceding claim, in which the second nut (4) comprises an internal groove (414) and a deformation orifice (414j) opening onto the head (41) and onto the internal groove (414), the method comprising a step of positioning the second nut (4) on the body (11) of the base (1) so that the groove (115) for forming the axial stop (14) is opposite the internal groove (414).

11. A method of changing a drainage tube (3) of a casing according to one of claims 1 to 6, comprising a step of unscrewing the second nut (4), a step of changing the drainage tube (3) with another drainage tube (3) and a step of connecting by screwing the second nut (4) onto a threaded surface of the connecting head (31) or the body (11) of the base (1) to compress the internal connecting surface (13) to the external connecting surface (313) of the other drainage tube (3) connecting the channel (110) of the base (1) to the discharge conduit (30) of the other drainage tube (3).

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