Abstract:
This valve is integrated into a fluid distribution network and enables selective interruption or authorization of the circulation of a fluid. The valve includes a fluid blocking member driven in rotation by an actuator device of the valve and at least one journal, a hollow body inside which the blocking member is mobile and which defines at least one bore for receiving the journal, and a bearing disposed around each journal and inside the bore of the body enabling support of the journal and guidance thereof in rotation relative to the bore, thereby centering the journal. The valve further includes a device for immobilizing and sealing for maintenance the journal relative to the body of the valve. This immobilization device is disposed on the same side of the bearing as the internal volume of the hollow body and is maneuverable via the bearing to go from a non-clamped first configuration to a clamped second configuration in which it immobilizes the journal in the bore and vice versa.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to French application 1350143 filed Jan. 8, 2013, the contents of which are hereby incorporated in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention concerns a valve integrated, in a configuration of use, into a fluid distribution network, notably on the upstream side of a hydraulic machine, and enabling, in controlled manner, interruption or authorization of the flow of a fluid in a pipe. By hydraulic machine is meant a turbine, a pump or a turbine-pump. Such a valve includes a member known as the obturator for blocking the fluid that is driven in rotation by an actuator device of the valve alternately to block or to authorize the passage of the fluid. The valves may be of the spherical type, in which the blocking member, referred to as the obturator, has the shape of a sphere, or of the butterfly type, in which the obturator is a simple disk. The obturator is connected to the actuator device of the valve by journals, enabling transmission of the rotation movement. The journals are therefore situated inside a receiving bore located in the body of the valve. Moreover, a smooth bearing is used to support, guide and center each journal in rotation relative to the bore in the body of the valve. 
       BACKGROUND 
       [0003]    Moreover, it is known that a hydraulic installation may include a plurality of hydraulic machines all fed in parallel by a pipe on the upstream side. Accordingly, during maintenance operations on a valve, it is necessary to work on the valve dry, i.e. without fluid inside it. This has the disadvantage that the arrival of fluid on the upstream side of the valve, in the pipe, must be shut off and therefore feeding of the other hydraulic machines of the installation must be stopped. This drawback is moreover exactly the same for valves installed on other fluid distribution networks. This is economically disadvantageous because the production or the distribution of fluid is stopped during maintenance operations on the valve. The smooth bearing, disposed around the journal, is subjected to friction forces by the journal that are generated by the force of the water on the obturator and by the weights. It is therefore necessary to repair it or to replace it several times over the service life of the hydraulic installation. The same problem arises for valves used in other fluid distribution networks. 
         [0004]    EP-A-0 834 032 describes a valve designed so that, during maintenance operations, it is possible to access some components supporting the journal such as the smooth bearing. The above document describes a valve in which it is possible to replace the bearing parts without evacuating all of the water on the upstream side. To this end, the valve described uses upstream and downstream sealing rings, these rings providing the seal between the obturator and the body of the valve. These sealing rings are movable axially in the direction of flow of the fluid inside the valve by pressurizing the space between the body of the valve and the blocking member, which pushes the sealing rings into contact both with the blocking member and with the body of the valve. This technology is applicable only if the blocking member is a ball, i.e. only for a valve of spherical type. Moreover, in the method described in this document, in order to remove the parts supporting the journal and the journal itself, it is obligatory to demount the downstream sealing ring in order to install a cover on the downstream side of the valve, as this makes it possible to balance the pressure of the fluid on the upstream and downstream sides of the valve and therefore to prevent the journal or the parts supporting the journal being subjected to the thrust force on the obturator caused by the pressure of the fluid. The problem with this device is that if the upstream sealing ring is not tight enough, i.e. if the pressurization of this ring is not sufficient, fluid invades the interior of the body and maintenance operations are impossible. Moreover, dismantling the parts supporting the journal and/or the journal necessitates decompression of the space between the body of the valve and the obturator, which can lead to the upstream sealing ring moving and causing a leak. Moreover, this valve does not include any mechanical device enabling the journal to be kept perfectly centered in the bore. This can lead to the journal being off-center and therefore a fortiori the obturator being off-center and can therefore cause leaks placing personnel in danger during the maintenance operation. 
         [0005]    It is these drawbacks that the invention is more particularly intended to remedy by proposing a system integrated into the valve whereby maintenance operations on the bearing are facilitated, more reliable, and applicable to any type of obturator. 
       SUMMARY 
       [0006]    To this end, the invention concerns a valve integrated into a fluid distribution network and enabling selective interruption or authorization of the circulation of a fluid in a feed pipe, this valve including:
       a fluid blocking member driven in rotation by an actuator device of the valve alternately to block or to authorize the passage of the fluid and which includes at least one journal,   a hollow body inside which the blocking member is mobile and which defines at least one bore for receiving the journal,   a bearing disposed around the journal and inside the bore of the body to support the journal and guide its rotation relative to the bore, thereby centering the journal.
           This valve is characterized in that it further includes a device for immobilizing the journal relative to the body of the valve, this immobilization device being on the same side of the bearing as the internal volume of the hollow body and being movable via a lining that is part of the bearing to go from a non-clamped first configuration in which it does not oppose the rotation of the journal in the bore to a clamped second configuration in which it immobilizes the journal in the bore and to go from the second configuration to the first configuration.   
               
 
         [0011]    Thanks to the invention, it is possible to remove the bearing disposed between the journal and the body of the valve in any type of valve without having to demount supporting parts on the downstream side of the valve and without having to recenter the journal after replacing the bearing. 
         [0012]    According to advantageous but not obligatory aspects of the invention, a valve may incorporate one or more of the following features in any technically permissible combination:
       The immobilization device includes at least one elastically deformable sleeve and a ring controlling the elastic deformable of the sleeve, the sleeve and the ring being disposed around the journal and inside the bore, while the ring includes a cam surface adapted to exert on the sleeve a deformation force that locks the sleeve against an element defining the bore or against the journal in the second configuration of the immobilization device.   The cam surface of the ring is frustoconical and the surface of the sleeve radially facing the ring is frustoconical and inclined in a manner complementary to the frustoconical surface of the ring.   The immobilization device includes two elastically deformable sleeves respectively disposed radially inside and outside the actuator ring.   The actuator ring is movable axially along an axis parallel to the rotation axis of the journal and pushes each sleeve radially against the element defining the bore and against the journal, respectively, when the immobilization device goes from its first configuration to its second configuration.   The actuator ring is moved by means of a plurality of screw-nut systems, the ring including screwthreads for receiving threaded members rotation of which is commanded via the lining, the screwthreads and the threaded members being distributed around the rotation axis of the journal.   The valve further includes a sealing mechanism including a seal-support disposed on the same side of the actuator ring and the sleeves as the internal volume of the hollow body and that supports a seal and in that the seal-support is movable axially along an axis parallel to the rotation axis of the journal from an open first position in which the fluid can flow inside the immobilization device to a closed second position in which the seal abuts against the shoulder of the journal, sealing the immobilization device, and, conversely, the seal-support is movable from the second position to the first.   The seal-support is moved by means of a plurality of clamping screws that are axially fastened to the seal-support.   The valve includes at least one indicator disposed externally of the valve and enabling indication of the immobilization device being in its first configuration.   The body of the valve is equipped with passages and at least one needle valve enabling balancing of the pressure of the fluid on either side of the immobilization device.   In the first configuration of the immobilization device, a radial clearance between the or each extensible sleeve and the journal or the element defining the bore, respectively, is strictly greater than the radial clearance of the bearing and is less than one millimeter.   The immobilization device is maneuverable to go from its first configuration to its second configuration and vice versa by at least one maneuvering member that passes axially through a lining that is part of the bearing. This maneuvering member may be permanently mounted on the valve. Alternatively, the maneuvering member is a rod that is inserted when necessary into an axial bore in a lining of the bearing secured to the bore.       
 
         [0024]    The invention also concerns a fluid distribution network including at least one valve as described above installed on a pipe. 
         [0025]    The invention further concerns an installation for converting hydraulic energy into electrical or mechanical energy or vice versa characterized in that it includes a fluid distribution network as described above in which the pipe is a pipe feeding a hydraulic machine that is part of the installation. 
         [0026]    The invention finally concerns a method for partial dismounting of a valve as described above, this method including the steps of: 
         [0027]    a)—placing a blocking member on a downstream part of the hollow body, 
         [0028]    b)—balancing the water pressure on either side of the blocking member,
       characterized in that this method further includes the steps of:       
 
         [0030]    c)—maneuvering the immobilization device so that it goes from its first configuration to its second configuration, 
         [0031]    d)—removing the bearing. 
         [0032]    In accordance with advantageous but not obligatory aspects of the invention, such a method for partial demounting of a valve may incorporate one or more of the following steps:
       The valve includes a sealing device as envisaged above and the method further includes a step e) after the step b) and before the step c) consisting in allowing the fluid to flow inside the immobilization device in order to clean it, and then stopping this flow.   The valve includes a sealing device as envisaged above and the method further includes a step f) after the step c) and before the step d) consisting in maneuvering the sealing mechanism so that it goes from its first position to its second position.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The invention will be better understood and other advantages thereof will become more clearly apparent in the light of the following description of valves in accordance with two embodiments of the invention given by way of example only and with reference with the appended drawings, in which: 
           [0036]      FIG. 1  is a diagrammatic view of a hydraulic installation including valves in accordance with the invention, 
           [0037]      FIG. 2  is a cross section of a valve in accordance with the invention that is part of the  FIG. 1  installation, 
           [0038]      FIG. 3  is a view to a larger scale of the detail III from  FIG. 2 , 
           [0039]      FIG. 4  is a view to a larger scale of the detail IV from  FIG. 3  when the valve is in a first configuration, 
           [0040]      FIGS. 5 and 6  are detail views analogous to  FIG. 4  but to a smaller scale when the valve is in other configurations during demounting, 
           [0041]      FIG. 7  is a view analogous to  FIG. 3  for a valve conforming to a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    In  FIG. 1  there is represented an example of an installation  1  according to the invention for converting hydraulic energy into electrical energy, which hydraulic installation  1  includes a dam B, an upstream pond R 1 , a plurality of hydraulic machines M 1  and M 2  and a downstream pond R 2 . Among other things, this type of hydraulic installation provides a simple way of storing electrical energy: each hydraulic machine functions as a turbine during the day, i.e. uses the hydraulic energy resulting from the height difference h between the upstream retainer R 1  and the hydraulic machine M 1  or M 2 , for example to rotate an alternator and therefore produce electricity, and to function as a pump at night, thus feeding water contained in the downstream retainer R 2  to the upstream retainer R 1 . To this end, the hydraulic installation further includes a feed pipe C connected to the upstream retainer R 1  that enables all the hydraulic machines to be fed in parallel by means of a bifurcation D situated on the upstream side of all the hydraulic machines. Two types of valves are routinely used in this case. A first valve  4  known as the pipe head valve stops or alternatively authorizes flow in the pipe C. A second valve  2  called the guard valve is situated on the downstream side of the bifurcation and on the upstream side of each hydraulic machine. It stops or feeds the hydraulic machine on the downstream side of this valve. 
         [0043]    Note a feed pipe C 1  of the hydraulic machine M 1  and a feed pipe C 2  of the hydraulic machine M 2 . The pipe C and the pipes C 1  and C 2  together form a fluid distribution network. 
         [0044]    The description given hereinafter is therefore more particularly concerned with a guard valve  2  designed to allow or to stop the feeding of the hydraulic machine M 1 . It may nevertheless be transposed to a pipe head valve to which the invention also applies. All this can also be transposed to a fluid distribution network with no hydraulic machines. 
         [0045]    The guard valve  2  is in a pipe C 1  directly feeding the hydraulic machine M 1  and water therefore passes through it in a direction defined by an axis Y-Y. There are moreover defined an axis Z-Z as the axis perpendicular to the axis Y-Y in the plane of  FIG. 1 , the axis Z-Z being vertical, and an axis X-X perpendicular to the axes Y-Y and Z-Z and to the plane of  FIG. 1 . The axes X-X, Y-Y and Z-Z intersect at the center of the valve  2 . 
         [0046]    As emerges from  FIG. 2 , which is a more detailed representation of the valve  2  seen from the downstream side, the latter valve includes a hollow cylindrical or spherical body  24  centered relative to the axis Y-Y and a blocking member  22  known as the obturator able to turn about the axis X-X through an angle of 90° to allow or interrupt the flow of the fluid toward the hydraulic machine M 1 . In  FIG. 2 , only half of the fixed part of the valve  2  is represented, on the right-hand side in that figure. A journal  20 , of cylindrical shape and also centered relative to the axis X-X, is fastened by screws  21  to an actuator device which, in the example concerned, is a lever  23  enabling application of a torque about the axis X-X to drive the journal  20  and the blocking member  22  in rotation about the axis X-X and therefore between the passing and blocking positions of the valve. 
         [0047]    The valve  2  includes a fixed body  24  that defines an internal volume V 24  in which the blocking member  22  is received. 
         [0048]    The journal  20  is accommodated in a bore A 26  defined inside a cylindrical element  26  with a circular base that is part of the body  24  of the valve  2 . The bore A 26  and the element  26  are also centered relative to the axis X-X and disposed radially around the journal  20 . 
         [0049]    The bore A 26  includes a shoulder at the forward end of the bearing  31 , i.e. on the same side as the internal volume V 24  of the body  24 . The valve  2  further includes a smooth bearing  31  inserted radially between the journal  20  and the element  26 . The bearing  31  is formed of a first facing  32  immobilized against rotation about the journal  20  and a second lining  33  immobilized against rotation in the bore A 26 , i.e. against the element  26 . The first lining  32  is a bearing ring and the second lining  33  is a bearing bush. The lining  33  surrounds a lining  32  and sliding occurs at the interface between the surfaces in contact of these linings. 
         [0050]    This bearing  31 , on the one hand, keeps the journal  20  centered relative to the axis X-X and, on the other hand, guides rotation of the journal  20  about the axis X-X. It is therefore clear that the component parts  32  and  33  of the bearing  31  have a low coefficient of mutual friction, which enables the blocking member  22  to be maneuvered easily and damage linked to friction to be prevented. The fact of maintaining the journal  20  precisely centered relative to the axis X-X is important because, if the blocking member  22 , fastened to the journal  20 , is off-center, leaks occur because the blocking member  22  no longer blocks the pipe completely. It is therefore clear that the function of the bearing  31  is of primordial importance, which is why it is important to verify that the linings  32  and  33  of the bearing  31  have not been damaged several times during the service life of the hydraulic machine, and if necessary to replace them. 
         [0051]    Now, if one of the linings of the bearing  31  were removed without taking precautions, the journal  20  would then no longer be immobilized and it would therefore be impossible to recenter it relative to the axis X-X. 
         [0052]    The valve  2  therefore includes an immobilization device  30  of globally annular shape, centered relative to the axis X-X, shown better in  FIG. 3 , and disposed radially between the journal  20  and the bore  26 . The immobilization device  30  consists of a plurality of mechanical parts and is on the same side of the bearing  31  as the internal volume V 24  of the body  24 , i.e. inside or at the front of the bore A 26 . 
         [0053]    Externally of the immobilization device  30 , and to the rear thereof, i.e. on the side opposite the internal volume V 24 , there are disposed maneuvering members  34  and  36 . Conversely, the immobilization device  30  is at the front of the maneuvering members  34  and  36 , i.e. on the same side of them as the volume V 24 . These maneuvering members  34  and  36  are rods which in this embodiment are permanently mounted on the valve  2 . In the remainder of the description one part is therefore considered in front of another if it is on the same side of it as the internal volume V 24  of the body  24 . 
         [0054]    At the rear of the rods  34  and  36  there is an indicator  38  for indicating if the journal is immobilized or not. In fact, if the maneuvering rods  34  and  36  are not fully retracted, attempting to open the obturator is prohibited because this would risk damaging the immobilization device. 
         [0055]    The first smooth lining  32  also known as the ring includes a plurality of through-bores  35  each centered on an axis X30 parallel to the axis X-X. The second lining  33  also known as the bush is therefore between the lining  32  and the bore A 26 . 
         [0056]    In order to center the journal  20  relative to the axis X-X as accurately as possible, the forces with which the immobilization device  30  presses on the journal  20  are distributed uniformly around the axis X-X by using a plurality of bores  35 . Here sixteen bores  35  in the lining  32  are distributed around the axis X-X in order to render the immobilization uniform. 
         [0057]    In order for the operation of the immobilization device  30  to be clearly understood the latter device is represented in three different configurations in  FIGS. 4 ,  5  and  6 . 
         [0058]    In  FIG. 4  the immobilization device  30  is represented in a first, so-called relaxed configuration in that it does not exert any radial pressure on the journal  20  or on the bore in the body  26 . The immobilization device  30  includes a actuator ring  304  disposed radially around the journal  20  and inside the bore A 26 , centered relative to the axis X-X, which includes sixteen screwthreads  305  axially aligned with the bores  35  in the lining  32 , i.e. each centered relative to the axis X30. 
         [0059]    The actuator ring  304  has an external radial surface  316  and an interior radial surface  312 . With respect to the axis X-X, the exterior surface  316  converges toward the front and the interior surface  312  diverges toward the front, which gives each of them a frustoconical shape. This actuator ring  304  bears radially on elastically deformable sleeves  314  and  322 . Each of the elastically deformable sleeves  314  and  322  has the overall shape of a split ring, centered relative to the axis X-X, and radially disposed in the bore A 26 , respectively inside and outside the actuator ring  304 . Moreover, the fact of using split sleeves  314  and  322  enables them to be made more elastic. These sleeves  314  and  322  are part of the device  30  and have respective interior radial surfaces  313  and  321  of complementary shape to the surfaces  312  and  316  of the actuator ring  304 . 
         [0060]    The sleeve  314  further includes an indexing flange  315  situated externally and at the front, i.e. on the same side as the internal volume V 24 . The sleeve  322  also includes an indexing flange  323 , situated internally and also at the front. The flanges  315  and  323  may be continuous or interrupted over the circumference of the sleeves  314  and  322 . 
         [0061]    These indexing flanges are engaged radially in grooves of corresponding shape provided in a ring  318  that is also part of the device  30  and is disposed at the front relative to the actuator ring  304  and is also of globally annular shape centered relative to the axis X-X. It follows from this that the indexing flanges enable axial fastening together of the ring  318  and the sleeves  314  and  322 . 
         [0062]    The sleeves  314  and  322  are therefore also immobilized axially, thanks to the flanges  315  and  323 . The ring  318  is axially immobilized in the bore A 26  in one direction by bearing on the flange  323  and in the other direction by bearing on the bearing bush  33 . 
         [0063]    On movement of the actuator ring  304  toward the left in  FIGS. 4 to 6 , the surfaces  312  and  316  slide on the surfaces  313  and  321 , respectively, while the sleeves  314  and  322  are stopped axially by the flanges  315  and  323  in the rings  318 . Accordingly, movement in translation of the ring  304 , toward the left in  FIGS. 4 to 6 , i.e. toward the volume V 24 , is converted into a radial movement of the ends of the sleeves  314  and  322  facing the flanges  315  and  323 . The surfaces  312 ,  313 ,  316  and  321  are therefore cam and sliding surfaces for the immobilization device  30 . 
         [0064]    The immobilization device  30  uses two elastically deformable sleeves  314  and  322 . In a variant that is not shown the immobilization device  30  can also function with only one sleeve  314  or  322 , this sleeve bearing externally on the bore A 26  or on the journal  20 . 
         [0065]    Inside each screwthread  305  of the actuator ring  304  there are disposed a nut  302 , a clamping screw  310  and a bolt  330  all centered relative to the axis X30 and forming part of the device  30 . The screw  310  is received in the bolt  330  which is itself received in a central screwthread of the nut  302 . The nut  302  includes a front portion threaded externally with a thread pitch complementary to that of the screwthread  305  of the actuator ring  304  and a rear portion with a polygonal external surface  334  functioning like the functional surfaces of a nut. The nut  302  is disposed inside the immobilization device  30  at the rear, axially facing each clamping key  34 . Inside this nut  302  and the bolt  330  there is positioned the screw  310  that extends longitudinally along the axis X30 and includes an external screwthread, a screwhead  311 , situated at the rear of the screw  310 , i.e. oriented axially facing each rod  36 , and a shoulder  309  situated at the front of the screw  310 . At its front end the clamping screw  310  bears along the axis X30 on a seal-support  324  that is centered relative to the axis X-X, disposed in an annular housing  319  of the ring  318  and supports a seal  326 . This seal-support  324  further defines a volume V 324  for receiving the front end or shoulder  309  of the screw  310 . The bolt  330  lies axially between the screw  310  and the nut  302  and includes an internal screwthread complementary to the screwthread of the screw  310 . Moreover, a seal  328  is disposed radially between the ring  318  and the bore A 26 . 
         [0066]    In this configuration, the radial clearance J between the elastic sleeve  314  and the journal  20  is less than 1 mm for a journal  20  of diameter D20 equal to 1000 mm. Similarly, the radial clearance J′ between the sleeve  322  and the bore A 26  is less than 1 mm for the same value of the diameter. The clearances J and J′ are greater than the radial clearance of the bearing  31 , i.e. the existing clearance between 0.2 and 1 mm. The clearances J and J′ must be identical to enable uniform forward movement of the ring  304 . In practice, the radial clearances J and J′ depend on the dimensions of the valve. They are defined so that the sleeves  314  and  322  do not impede the rotation of the journal when the immobilization device  30  is released. 
         [0067]    All the components described above, apart from the seals, are made of stainless steel, to prevent corrosion. The seals used are O-rings or lip seals and are made from a nitrile or polyurethane type elastomer material. Moreover, although in this embodiment sixteen clamping screws  310 , sixteen bolts  330  and sixteen nuts  302  are used, the number of screws, bolts and nuts used for immobilization is adapted as a function of the diameter of the pipes and the pressure of the fluid inside. Similarly, the number of bores  35  and of screwthreads  305  is also adaptable and may be different from  16 . 
         [0068]    Manipulating the clamping rod  34  enables the immobilization device to be brought into a second configuration represented in  FIG. 5 . 
         [0069]    The journal  20  is immobilized relative to the bore A 26  by the clamping rod  34  which is placed around the functional surfaces  334  of the nut  302  thanks to the tightening of the three nuts  40  and is turned about the axis X30, therefore driving rotation of the nut  302  about the axis X30. The exterior screwthread of the nut  302  cooperates with the screwthread  305  of the actuator ring  304  in order to drive the actuator ring  304  in translation in a direction F1 parallel to the axis X30. The cam surfaces  312  and  316  of the actuator ring  304  that are already in contact with the surfaces  313  and  321  of the sleeves  314  and  322  push these sleeves radially in two radial directions F2 and F3 relative to the axis X30, respectively against the element  26  and against the journal  20 . In this configuration the radial clearances J and J′ between the sleeves  314  and  322  and the journal  20  and the element  26 , respectively, is zero. It is the adhesion caused by the contact pressures between the sleeve  314  and the journal  20  and between the sleeve  322  and the element  26  that fastens together the immobilization device  30 , the element  26  and the journal  20 . 
         [0070]    To summarize, the immobilization device  30  can be maneuvered from a non-clamped first configuration in which it does not oppose rotation of the journal  20  in the bore A 26  to a clamped second configuration in which it immobilizes the journal  20  in the bore A 26  and conversely from the second configuration to the first. Because the sleeves  322  and  314  are fastened together by the indexing flanges  315  and  323  of the ring  318 , axial movement of the sleeves  314  and  322  is blocked. Accordingly, the axial force exerted by the actuator ring  304  is converted completely into a radial force exerted on the sleeves  314  and  322 . In this way, when all the nuts  302  distributed around the axis X-X are tightened the journal  20  is held immobilized and centered relative to the axis X-X. 
         [0071]    If the operation is effected on a valve with the fluid still present inside the valve  2 , it is then necessary to seal the bearing  31  in order to remove it to replace it. The immobilization device  30  therefore further includes a sealing mechanism which, when actuated, brings the immobilization device  30  into the configuration represented in  FIG. 6 . 
         [0072]    In order to go from the configuration represented in  FIG. 5  to the configuration of  FIG. 6 , it is simply necessary to rotate the second rod  36  about the axis X30. In fact, the first rod  34  having been advanced previously, the second rod  36  has moved axially with the first rod  34 . The latter is therefore in position around the functional surfaces of the head  311  of the screw  310 . This rotation results in a movement in translation of the screw  310  in a direction F4 parallel to the axis X30 because of the complementary nature of the external screwthread of the clamping screw  310  and the internal screwthread of the bolt  330 . As it moves in axial translation, the clamping screw  310  drives the seal-support  324  against a shoulder  202  of the journal  20 . The seal  326  carried at the front of the seal-support  324  is therefore compressed against the shoulder  202  of the journal  20 , thus sealing the actuator device  30 . 
         [0073]    Conversely, to release the system, i.e. to go from the  FIG. 6  configuration to that of  FIG. 4 , it is necessary to turn the rod  36  in the direction opposite that described above, in order to move the clamping screw  310  in axial translation toward the rear. In practice, this movement is accompanied by the pressure of the water exerted on the front, which tends to retract the rod  36 . As it moves in translation, the clamping screw  310  drives rearward axial movement of the seal-support  324  by virtue of the contact between the receiving volume V 324  in the seal-support  324  and the shoulder  309  of the screw  310 . The seal  326  is therefore no longer in contact with the shoulder  202  of the journal  20 . It is then necessary to turn the clamping rod  34  in the opposite direction in order to move the actuator ring  304  in axial translation toward the rear. This enables releasing of the pressure exerted radially by the actuator ring  304  of the sleeves  314  and  322 . By virtue of their elasticity, the split sleeves  314  and  322  resume the initial radial clearances J and J′. 
         [0074]    A method is explained hereinafter for removing the bearing  31  from the valve  2 . Firstly, before any other operation, it is essential to unfasten the downstream pipe from the valve  2  and to install a cover or in this particular situation a convex dome on the downstream side of the valve  2  and then to balance the upstream pressure and the downstream pressure by injecting fluid into the space between the blocking member and the cover. This operation is not shown in the figures because it is known in itself. This has the advantage that the blocking member  22  and therefore a fortiori the journal  20  do not have to be subjected to the fluid pressure force. The bearing  31  therefore supports only the weight of the blocking member  22 . If the fluid passing through the valve  2  is impure, i.e. contains mud or sand, it is then beneficial to be able to purge the impurities inside the immobilization device  30 . This prevents long-term damage to the immobilization device  30 . To be more precise, the fluid flows from the internal volume V 24  of the valve  2  through a first passage  264  and then a second passage  266  inside the immobilization device  30 . The passages  264  and  266  are formed in the element  26 . A first needle valve  262  is used that enables opening or closing of communication between the passages  264  and  266 , i.e. selective opening of communication between the internal volume V 24  and the device  30 . The water injected into the immobilization device  30  when the needle valve  262  is open is then evacuated by means of a drain passage  268  also situated in the body of the element  26 . Evacuation is effected by opening a second needle valve or small manual valve  270 . In practice, the cleaning time to evacuate the residues that have remained inside the immobilization device  30  is evaluated during the maintenance operation. Finally the valve  270  must be closed. 
         [0075]    When this operation has been effected, there follows activation of the immobilization device  30 . As described above, maneuvering the clamping rod  34  enables the screw/nut system  302 / 304  to press the two deformable sleeves  314  and  322  against the journal  20  and the element  26 , respectively. This is achieved by virtue of elastic deformation of the sleeves  314  and  322 . If it is necessary to actuate the sealing mechanism, for example in the case of a butterfly type valve in which fluid would be in contact with the smooth bearing  31 , it is necessary to maneuver the rod  36  for the screw/nut system  310 / 330  to press the seal  326  against the shoulder of the journal  202  and thus seal the bearing  31 . When this has been done, injection of the fluid into the interior of the immobilization device  30  via the needle valve  262  can be stopped and the remaining fluid purged via the drain passage  268 . In the case of a spherical type valve, the sealing mechanism need not be activated in that the fluid that has remained inside the locking member  22  is drained away. After the journal  20  has been immobilized, in order to access the bearing  31  it is necessary to remove the rods  34  and  36 , after first removing the nuts  40  and the locking indicator  38 , and then to dismantle the lever  23  by undoing the screws  21 . Finally, if no leak is seen, the bearing  31  may be freely removed from the valve  2 . Note that none of the steps leading to the removal of the bearing  31  necessitate the input of external energy, for example by compressed air or by a hydraulic power system, and can be carried out using simple tools such as a pipe torque wrench. 
         [0076]    Conversely, when fitting a new bearing  31  inside the valve  2 , it is first necessary to position this bearing  31  inside the bore A 26 , then to reposition the lever  23  by tightening the screws  21  and finally to insert the rods  34  and  36  into the bore  35  again. There follows this the fixing of the rods  34  and  36  by means of the nuts  40  and the replacement of the locking indicator  38 . 
         [0077]    Only in a second stage can the immobilization device  30  be deactivated, in order to prevent the journal  20  being off-center relative to the axis X-X. 
         [0078]    In  FIG. 7  there is represented another embodiment of the valve in which the smooth bearing  31 ′ includes a first lining  33 ′ disposed radially outside the journal  20  and a second lining  32 ′ that is disposed radially outside the first smooth lining  33 ′. To be more precise, the first lining  33 ′ is a thin self-lubricating ring and the second lining  32 ′ is a thick bush. The particular feature of this configuration is that the clamping keys  34  and  36  are no longer mounted permanently on the valve  2  but are fitted by the operative when necessary. Given that this structural feature does not influence the functioning of the immobilization device  30  specific to the invention, the foregoing description therefore covers either of these two embodiments. 
         [0079]    By way of a variant that is not represented, it is possible to insert a key into the split area of the sleeves  314  and  322  to prevent rotation thereof about the axis X-X. Similarly, using a single sleeve  314  or  322  may be envisaged that is pushed back when the actuator ring  304  advances. This solution is less effective than using two sleeves, however.