FR2706192A1 - Valve device for cutting off a fluid circuit in the event of fire - Google Patents

Abstract

The device (D) includes a valve (1) with a rotary shutter comprising a valve body (3) in which there is mounted so that it can rotate a shaft (6) projecting outside the body. The device (D) further includes a mechanical system (S) for causing the valve (1) to close, this system being capable of acting on that part of the shaft (6) which is outside the valve body (3) and which is set off by fusible means (M) sensitive to the external temperature. The mechanical system (S) comprises, on the one hand, an elastic torsion means (T) situated outside the valve body (3) and tensioned so that it urges the shaft (6) and the shutter in rotation in the closure direction and, on the other hand, a connecting member (27) keyed onto the shaft (6) in terms of rotation and including holes (27a) which can be brought to face corresponding holes (23) provided in a component (21) integral with the valve body (3), the fusible means (M) consist of at least one member (38) for immobilisation in terms of rotation, engaged in a hole (27a) of the connecting member and in a hole (23) of the component (21).

Description

FLAP VALVE FOR CUTTING A CIRCUIT OF
FLUID IN CASE OF FIRE
The invention relates to a device for cutting a fluid circuit in the event of a fire, of the type which includes a rotary flap valve, this valve comprising a valve body in which a shaft protruding inside is rotatably mounted. of the body, the assembly being such that when the leaf is in the open position the flow of fluid is fully released, the device further comprising a mechanical system for controlling the closing of the valve, this mechanical system being able to act on the part of the shaft outside the valve body, the mechanical system being triggered by fusible means sensitive to the outside temperature.

 US-A-3 860 024 relates to a device of this kind comprising an arm, retained by a fusible element outside the valve body, against the action of a spring located inside the body valve.

 The mechanism constituted by the arm and the fusible element is relatively bulky and fragile because it is not protected against accidental tripping caused, for example, by unwanted impacts from objects handled in the immediate environment of the device.

 It is further desirable that the maintenance and verification operations of the mechanical control system can be carried out simply, and as frequently as desired, with the least possible interference with the operation of the installation equipped with such a device.

 The invention aims, above all, to provide a device, as defined above, which no longer has, or to a lesser degree, the drawbacks mentioned above.

 We particularly want the device to be safe, robust, reliable, easy to maintain and calibrate.

We also want this device to be of an acceptable cost price.

 According to the invention, a device for cutting a fluid circuit in the event of a fire, of the type defined above, is characterized in that the mechanical system comprises, on the one hand, an elastic torsion means located outside of the valve body and tensioned so as to urge the shaft and the wing in rotation in the closing direction, and on the other hand, a connecting member wedged in rotation on the shaft and having holes suitable for being brought opposite corresponding holes provided in a part integral with the valve body, the fusible means being constituted by at least one member for locking in rotation, engaged in a hole in the connecting member and in a hole in the part.

 Advantageously, the elastic torsion means is housed in a housing secured to the valve body.

 Preferably, the elastic torsion means is constituted by a helical torsion spring, arranged coaxially with the shaft, one end of the spring being locked in rotation relative to the valve body while the other end of the spring is linked in rotation to the end of the tree.

 The connecting member can be constituted by an intermediate piece or clutch connected in rotation with the end of the extension of the shaft by a removable driving member, while the piece integral with the valve body is constituted by a flange fixed so removable on a crown secured to a tubular part of the housing, the last internal turn of the torsion spring extending radially by an extension engaged in a hole in the housing while the other end turn of the spring is extended by a radial extension engaged and blocked in a housing of a pin secured to the dog.

 Advantageously, the end of the shaft has a polygonal contour, in particular square, and the driving member consists of a bushing having an internal housing of cross section conjugate with that of the end of the shaft.

 Preferably, the dog clutch has, on the inside, a collar on which is fixed a tube around which the spring is disposed.

 The housing may comprise, in the vicinity of its attachment to a sleeve, fixed to the valve body, two diametrically opposite windows, while the shaft has two diametrically opposite flats to which the windows allow access from the outside, with a appropriate key.

 Advantageously, the rotation locking members consist of cylindrical pins of metal or of a fusible alloy at low temperature.

 An indicator disc can be mounted at the end of the shaft, fixed in rotation on this shaft, this indicator disc comprising indication zones, in particular of different colors, while a plate provided with a window is fixed at the end of the crown, the window allowing to see from the outside an area of the indicator disc and to know if the valve is open or closed.

 Advantageously, the mechanical system comprises heating means placed near the fusible means, and control means controlling the starting of the heating means, the latter being designed so as to allow a rise in temperature sufficient to cause, at will. , in particular by remote control, the melting of the fusible means and the closing of the valve.

 In the case of a proximity fire, when the temperature around the valve is insufficient to cause it to close, it is possible, thanks to this arrangement, to close the valve and prevent preventively that the contents of a storage bin fitted with this valve does not fuel the fire.

 Preferably, the above heating means comprise an electrical resistance disposed in a housing, in particular explosion-proof, placed at the end of the valve shaft, this housing being linked to the valve body.

 The heating means control means may include a temperature sensor in the housing, connected to thermostatic control means arranged in a control box fixed to the outside of the housing.

 The above control means may include a source of electrical energy, in particular a battery, capable of supplying the electrical resistance to cause the closure of the valve.

 The valve device may include means for remotely transferring the position indication (open or closed) of the valve.

 The shutter of the valve is advantageously equipped with a pressure relief valve capable of eliminating an excessive excess pressure of the fluid upstream of the shutter, when the latter is closed.

 The invention consists, apart from the arrangements set out above, in a certain number of other arrangements which will be more explicitly discussed below in connection with a particular embodiment described with reference to the attached drawings, but which is in no way limiting.

 Figure 1 of these drawings is an axial vertical section of a valve device according to the invention.

Figure 2 is a section, on a larger scale, along the line
II-II of Figure 1.

 FIG. 3 is a partial view from the right with respect to FIG. 1.

 Figure 4 is an end view of the end of the housing, plate and indicator disc removed.

 Figure 5 is a view similar to Figure 4 of the end of the housing provided with the plate and the indicator disc.

 Figure 6 is a partial section, similar to that of Figure 2, illustrating an alternative embodiment of the valve device equipped with heating means placed near the fusible means.

 Figure 7 is an end view of the end of the housing of Figure 6, cover removed.

 FIG. 8 is a partial view, similar to FIG. 3, of the valve device equipped with means for remotely transferring the position indication of the valve.

 Figure 9, finally, is a view, on a larger scale, with parts cut away and cut, along the line Ix-Ix, Figure 6, means of remote reporting of the position indication.

 Referring to the drawings, in particular Figures 1 and 2, one can see a device D for cutting a fluid circuit, in the event of fire.

Such a device is intended, in particular, to be installed in a
pipeline at the bottom of the oil tank so as to cut all
circulation of hydrocarbons in the event of fire.

 The device D comprises a check valve 1 with wing 2, arranged in the opposite direction to the flow of fluid which normally takes place in the direction of the arrow F. In other words, the wing 2 closes in a direction such that the fluid tends to keep it closed. This valve is of the full passage type, that is to say that in the fully open position (shown in phantom), the closure means are completely erased from the fluid stream.

 The valve 1 comprises a valve body 3 in the form of a portion of tubing, provided at each end with a connection flange allowing the body 3 to be inserted between two parts of tubing. This body 3 is provided, in the upper part, with a circular opening 4 closed by a bolted cover 5. The dismantling of this cover allows examination of the valve and its maintenance.

 A shaft 6, of circular section, is rotatably mounted in bearings carried by the valve body as clearly visible in FIG. 2.

This shaft 6 is orthogonal to the plane passing through the axis A of the valve body 3 and through the axis of the opening 4, and protrudes outside the body 3.

 The leaf 2 is keyed onto the shaft 6. This leaf 2 comprises a shutter 7, constituted by a sort of disc, suitable for applying in leaktight manner against a seat 8 of the valve body; in the closed position, the shutter 7 has its mean plane orthogonal to the axis A.

The shutter 7 is fixed, at its center, to the end of a radial arm 9 locked in rotation on the shaft 6 by a system of keys 10, combined with grooves provided respectively in a bore of the arm 9 and on the shaft 6. The arm 9 is provided, on the side opposite the seat 8, with a rib 11 with a contour substantially at right angles, which is capable of coming to bear against the internal wall of the valve body 3 to form the stop leaf 2.

 The shutter 7 is advantageously crossed by a hole 7a equipped with a decompression valve 7b. The hole 7a is provided, for example, in the vicinity of the edge of the shutter remote from the shaft 6. The pressure relief valve 7b is capable of opening in the direction of the arrow F, that is to say to let the liquid flow from upstream to downstream when the pressure upstream exceeds a predetermined value by the calibration of the valve 7b. The presence of this valve 7b is advantageous because, when the shutter 7 is closed, a volume of liquid is trapped upstream of this shutter 7 in a pipe located at the bottom of the tank. The rise in temperature produced in the event of a fire causes thermal expansion of the trapped volume upstream of the shutter 7. This could result in a significant increase in pressure, with risk of leakage at the fittings or seals, if none evacuation was not planned for the liquid. The valve 7b makes it possible to avoid such a drawback. This valve 7b is advantageously of the ball and spring type.

 As shown in Figure 1, the shaft 6 is located outside, in the radial direction, of the cylindrical part of the body 3 intended to be in alignment with the pipe. This makes it possible to place the shutter 2 in the open position in a space located radially outside the fluid stream, under the cover 5.

 The fixing of the shutter 7 on the arm 9 is advantageously carried out using a spherical ball joint 12 mounted in a cylindrical bore 13 of the end of the arm 9. The shutter 7 is stopped, in the direction perpendicular to the arm 9, with a certain play by a washer 13a and a nut 15. The shutter 7 thus has a certain freedom allowing it to be applied correctly against the seat 8.

 The closing of the valve 1 is controlled by a mechanical system S capable of acting on the part of the shaft 6 located outside of the valve body.

 As can be seen in FIG. 2, the extension of the shaft 6 passes through a sleeve 14 fixed to the valve body 3 and equipped, at its outer end, with external seals 15 constituted by several superimposed washers, and a stuffing box 16. The outer extension of the shaft 6 is surrounded by a coaxial cylindrical housing 17, fixed in a removable manner, for example by screws, on an end flange of the sleeve 14. In the vicinity of its fixing on said flange, the housing 17 comprises two diametrically opposite windows 18 allowing access, from the outside, with an appropriate key, to two diametrically opposite flats 19, provided on the shaft 6.

 The tubular part of the housing 17 is integral, at its end remote from the sleeve 14, with a crown 20, the central opening of which is closed, towards the outside, by a flange 21 fixed removably by screws 22 on this crown 20. The transverse end face 21a of the flange 20 is set back relative to the transverse end face 20a of the crown 20.

 The flange 21 has regularly distributed holes 23, for example three in number, angularly spaced 1200 as visible in FIG. 4. A central opening 21b is provided in this flange 21.

 The end 24 of the extension of the shaft 6 arrives at the flange 21. This end 24 has a polygonal contour, preferably square (see FIG. 4) with flat faces of sufficient length to ensure a connection in rotation with a driving member 25.

 The driving member 25 is constituted by a bushing having an internal housing of square section combined with that of the end 24 and whose cylindrical external surface is engaged in a bore 26 of an intermediate part 27.

 This intermediate piece 27 or dog clutch has the shape of a circular plate mounted to rotate freely in a bore of the crown 20, this dog clutch being held, without any axial tightening, between a shoulder 28 of the crown and the flange 21. The dog clutch 27 comprises, around its bore 26, on the inside, a flange 29 on which is fixed a tube 30 which extends to the vicinity of the windows 18.

 The driving member 25 is fixed to the dog clutch 27 by screws 31 cooperating with corresponding tapped holes provided in the dog clutch 27. Additional extraction holes 32 are further provided in the collar of the coach member 25 to allow, using screws bearing against the face of the dog clutch 27, to extract the driving member from said dog clutch.

 An elastic torsion means T, advantageously constituted by a helical torsion spring 33, is provided to return the leaf 2 to the closed position, by exerting a return torque at the end of the shaft 6. This spring 33 is disposed at the inside the housing 17, coaxial with the shaft 6, around the tube 30 whose outside diameter is only slightly less than the internal diameter of the turns of the spring 33. The spring 33 extends over an axial length substantially equal to that of tube 30.

 The last inward turn of the spring 33 is extended radially by an extension 34 engaged in a hole 35 in the housing 17.

 The other extreme turn of the spring 33, located towards the outside, is extended by a radial extension 36 engaged and locked in a housing of a pin 37 secured to the dog clutch 27.

 The torsion spring 33 is tensioned so as to apply the shutter 7 against its seat 8 according to a determined pressure, for example of the order of S bars, which is thus perfectly controlled, independently of the hydrostatic pressure which the fluid can exert. located upstream of the closed shutter 7. It should be noted, as will be explained later, that in the event of closure of the shutter 7 due to a fire, it remains possible to inject in the opposite direction, using sufficient pumping means to overcome the torque of spring 33, water or foam to extinguish a fire.

 The leaf 2 is kept in the normal open position, against the torque exerted by the spring 33, using fusible means M constituted by members 38 for locking the dog clutch 27 in rotation relative to the flange 21. The members blocking 38 are constituted by cylindrical pins of fusible alloy, at a predetermined temperature, for example of the order of 70 "C. Of course, the admissible temperature limit is chosen according to normal operating conditions and the ambient temperature .

 These pins 38 work in shear and are engaged in the holes 23 of the flange 21 and in holes 2-, of the same diameter, of the dog clutch 27 which are opposite the holes 23 when the dog clutch 27 occupies an angular position corresponding to the leaf opening 2.

In the example considered, as visible in FIG. 4, three pins 38 of fusible material are provided.

 An indicator disc 39 is detachably fixed, using a screw 40, at the end of the shaft 6; the disc 39 is locked in rotation relative to the shaft 6, for example using a sleeve of reduced length provided on the inner side and whose cross section is square so as to cover the end of the shaft 6 The screw 40 has the function only of an axial holding of the disc 39 relative to the shaft 6. The disc 39 can rotate freely, with the shaft 6, relative to the flange 21.

 The disc 39 may include areas of different colors, for example a green area to indicate that the valve 1 is "open" and a red area to indicate that the valve 1 is "closed". In addition, indications such as "O" (open) (see Figure 5) or "F" (closed) can be entered in these areas.

 A circular plate 41 (see also FIG. 5) is fixed at the end of the crown 20 by screws, this plate comprising a window 42 (FIG. 5) of substantially trapezoidal shape, making it possible to see the indication zones of the disc 39.

 A seal 43 can be provided on two of the fixing screws of the plate 41, which makes it possible, in the event of a break, to know immediately that an unauthorized person has intervened at the level of the housing 17 and, possibly, of the calibration of the spring. 33.

 That said, the operation of the device of the invention and its maintenance are as follows.

 In normal operation, the valve 1 is in the open position, the leaf 2 being raised.

 When an external fire appears and the temperature at the level of the housing 17 and the fuses 38 reaches a predetermined temperature, for example of the order of 70 "C / 800 C, the fuses 38 melt and release in rotation the dog clutch 27 and therefore the shaft 6 linked in rotation to this dog clutch 27, relative to the flange 21.

 The torque of the torsion spring 33 which is exerted between the housing 17, and therefore the body 3 of the valve to which this housing 17 is fixed, and the dog clutch 27, causes this dog clutch 27 and the shaft 6 to rotate in the closing direction of the valve 1. The shutter 7 is applied against the seat 8 at a pressure determined by the setting of the spring 33.

 It is possible to reinject into the fluid tank, at the foot of which the device 1 is mounted, foam under sufficient pressure or water depending on the nature of the fluid stored in the tank, insofar as the injection pressure is sufficient to overcome the known torque exerted by the spring 33.

 Maintenance and operational control operations, the frequency of which is to be agreed, are carried out as follows.

 First of all, the plate 41 and the indicator disc 39 are removed.

 A first operation consists in controlling the maneuverability of the shutter 2.

 For this operation, the shaft 6 is disengaged in rotation from the dog clutch 27 in order to be able to maneuver the shaft 6 using a torque wrench, to check the conditions of rotation of the leaf 2, in particular the absence of any jamming. .

 We begin by introducing an appropriate key through one of the windows 18 to exert a grip on the flats 19 of the shaft 6, in the vicinity of the stuffing box 16, in order to keep the leaf 2 in the open position.

 The driving member 25 is then removed by removing the screws 31 and using the extraction threads 32.

 The shaft 6 is then free to rotate relative to the dog clutch 27.

 A torque wrench is then engaged with the square end of the shaft 6.

 After removing the key which was in engagement with the flats 19, a few maneuvers are carried out using the torque wrench, for example two "open / close" maneuvers of the shutter 2, ensuring that the necessary torque by these maneuvers is not greater than normal values.

 When this control is finished, the leaf 2 is replaced in its open position and the driving member 25 is replaced to restore the connection in rotation between the shaft 6 and the dog clutch 27.

 A second maintenance operation consists in checking the safety device and more particularly the restoring torque exerted by the spring 33.

 Still after dismantling the plate 41 and the disc 39, a torque wrench is engaged with the square end of the shaft 6.

 We unscrew and remove the fixing screws 22 from the flange 21, retaining the shaft 6, using the torque wrench, against the restoring torque exerted by the spring 33.

 The shaft 6 and the spring 33 are gradually released using the torque wrench to the closed position of the shutter 7. During this maneuver, it is checked that the restoring torque exerted by the spring 33 remains equal to or less than the announced torque.

 Still using the torque wrench, by acting on the end of the shaft 6, the leaf 7 is repositioned in the open position, controlling the torque developed during this maneuver. These closing / opening operations are repeated a second time, checking the torque exerted.

 After returning the shutter 7 to the open position, the flange 21 is immobilized again, relative to the crown 20, using the four screws 22 replaced.

 We can then remove the metric dynamo key and replace the indicator disc 39 in a position such that the area, for example green and possibly assigned the letter O, appears through the window 42 of the cover plate 41 when it is put back into place.

 The device of the invention is particularly compact with the coaxial arrangement of the spring 33 and of the box 17. I1 offers great reliability and good security since the spring 33 is sheltered, completely enclosed in a box which can be sealed with so that the calibration of this spring 33 cannot be modified by an unauthorized person, without being aware of it.

 Maintenance and control operations are simple and quick to perform.

 The application of the shutter 7 on its seat 8 is carried out under controlled pressure. The shear work of the fusible elements 38 makes it possible, under a reduced bulk, to benefit from great operational safety.

 Referring to Figure 6, we can see an alternative embodiment of the valve device which allows an operator, monitoring a facility in which the valve is installed, to control, in particular remotely, the closing of the valve in a given time, even before a proximity fire has spread to the valve device.

 The elements of the device of Figure 6 identical or playing roles similar to elements already described with respect to the previous figures, are designated by the same reference numerals without their description being repeated, or with a brief description.

 The mechanical system S comprises heating means C placed near the fuse means M formed by the cylindrical pins 38 made of metal or of a fusible alloy at low temperature.

 The heating means C comprise an electrical resistor 44 disposed in an explosion-proof housing 45 placed at the end of the shaft 6 of the valve, coaxial with the assembly. The housing 45 can be filled with an electrically insulating material in which the resistor 44 is embedded. A central hole 46 is provided in the housing 45 to allow the free passage of the end of the shaft 6. The housing 45 is fixed , removably by screws 47, on the crown 20, itself linked to the valve body. The cover 41 is fixed by screws to the front end of the housing 45. The latter has a peripheral rim projecting in the axial direction and against which the cover 41 is fixed. A free space 48 is thus reserved between the cover 41 and the transverse face of the housing 45. The indicator disc 39 is fixed to the end of the shaft 6 so as to be able to rotate in the free space 48. As explained with reference to FIG. 5, the cover 41 has a window allowing to observe the position of the disc 39. The terminals of the electrical resistance 44 are connected, by a cable 44a to control means K comprising a cylindrical box 49, also explosion-proof, fixed laterally outside the housing 45, by lugs 50 (see Figure 7).

 The control means K comprise a temperature measurement probe 51 in the housing 45 connected by a cable 51a to thermostatic control means 52 arranged in the box K. These thermostatic control means 52, include, for example, a thermal relay to limit the heating temperature of the housing 45 to a predetermined value, for example of the order of 200 "C, however sufficient to cause the pins 38 to merge in a limited time, for example a few tens of seconds.

 The control means K may comprise a source of electrical energy constituted in particular by a battery 53 suitable for supplying the electrical resistance 44 when the thermostatic control means 52 close the supply circuit of this resistance, and when the operator remotely operates the control means.

 As a variant, the electrical supply can be ensured from an external source connected to the box 49 by a cable 54.

 It is possible to provide both an external power supply and a battery power supply 53, the latter only intervening, for example, in the event of a failure of the external power supply.

 The control means K are connected by an electric cable 55 to a control station (not shown) from where an operator can cause the actuation of the control means K and the electrical supply of the resistor 44, to cause the closure of valve 1.

 The valve device further comprises means 56 for remotely transferring the "open" or "closed" position indication of the valve. These means of remote reporting, or of remote indication, 56 are provided at the level of the windows 18 of the tubular part 17, and include a plate 57 (see FIG. 9), substantially in the form of an isosceles right triangle, the mean plane of which is orthogonal. to the axis of the shaft 6. This plate 57 has, on one of its edges, a semi-circular notch 58, in which the shaft 6 is engaged. The latter comprises on the side opposite to the bottom of the notch 58, a flat 59, located in the vicinity of one of the flat 19, outwardly relative to the valve body. A key 60 (Figure 9) bears against this flat 59 and blocks the plate 57 on the shaft 6 by tightening screws 61 provided at each end of the key 60 and engaged in tapped holes provided on the edge of the plate 57.

 A support 62 passes diametrically through the element 17 passing through the windows 18 and projecting on either side of the element 17. The support 62 is fixed by lugs 63 (FIG. 6) on the outer surface of the element 17. Two end-of-travel contacts 64, 65, diametrically opposed, are fixed on the support 62. Each contact comprises a mechanical arm 64a 65a intended to cooperate with the wafer 57 to actuate an electrical contact connected by a corresponding cable 64k, 65b to signaling devices located, for example, in a control room where an operator is located.

 One of the limit switch contacts, for example the contact 64 is actuated by the plate 57 when the valve is in the open position, while the other contact, for example 65, is actuated when the valve is in the closed position. The operator, at a distance, can therefore know the position of the valve at any time and, in particular, know whether this valve has closed properly when the heating means 45 have been triggered.

 That said, the operation of the device of Figures 6 to 9 is as follows.

 An operator, remotely monitoring the installation in which

Claims (17)

 1. Device for cutting a fluid circuit in the event of fire, comprising a valve (1) with a rotary leaf (2), this valve comprising a valve body (3) in which a projecting shaft (6) is rotatably mounted outside the body, the assembly being such that when the leaf (2) is in the open position the flow of fluid is completely released, the device further comprising a mechanical system (S) for controlling the closing of the valve (1), this mechanical system (S) being able to act on the part of the shaft (6) external to the valve body (3), the mechanical system (S) being triggered by fusible means (M) sensitive to the outside temperature, characterized in that the mechanical system (S) comprises, on the one hand, an elastic torsion means (T) located outside the valve body (3) and tensioned so as to stress the shaft (6) and the leaf (2) rotating in the closing direction, and on the other hand, a connection (27) wedged in rotation on the shaft (6) and comprising holes (27fui) suitable for being brought opposite corresponding holes (23) provided in a part (21) integral with the valve body (3), the fuse means (M) being constituted by at least one member (38) for locking in rotation, engaged in a hole (27a) of the connecting member and in a hole (23) of the part (21).  2. Device according to claim 1, characterized in that the elastic torsion means (T) is housed in a housing (17) integral with the valve body (3).  3. Device according to claim 1 or 2, characterized in that the elastic torsion means (T) is constituted by a helical torsion spring (33), arranged coaxially with the shaft (6), one end of the spring ( 33) being locked in rotation relative to the valve body (3) while the other end of the spring (33) is linked in rotation to the end of the shaft (6).  4. Device according to claim 3, characterized in that the connecting member is constituted by an intermediate piece or clutch (27) connected in rotation to the end (24) of the extension of the shaft (6) by a removable drive member (25), while the part integral with the valve body consists of a flange (21) removably fixed on a crown (20) integral with a tubular part of the housing (17), the last inner turn of the torsion spring (33) extending radially by an extension (34) engaged in a hole (35) of the housing (17), while the other end turn of the spring (33) is extended by a radial extension (36) engaged and locked in a housing of a pin (37) integral with the dog clutch (27).  5. Device according to claim 4, characterized in that the end (24) of the shaft (6) has a polygonal contour, in particular square, and the driving member (25) consists of a sleeve having a internal housing of cross-section of that of the end (24) of the shaft.  6. Device according to claim 4 or 5, characterized in that the dog clutch (27) comprises, on the inner side, a flange (29) on which is fixed a tube (30) around which the spring (33) is arranged.  7. Device according to claim 2, characterized in that the housing (17) comprises, in the vicinity of its attachment to a sleeve (14), fixed to the body (3) of the valve, two windows (18) diametrically opposite, while the shaft (6) has two diametrically opposite flats (19) to which the windows (18) allow access from the outside, with an appropriate key.  8. Device according to any one of the preceding claims, characterized in that the members (38) for blocking rotation consist of cylindrical pins of metal or of a fusible alloy at low temperature.  9. Device according to one of claims 4 to 6, characterized in that an indicator disc (39) is mounted at the end of the shaft (6), fixed in rotation on this shaft, this indicator disc comprising zones d indication, in particular of different colors, while a plate (41) provided with a window (42) is fixed at the end of the crown (20), the window (42) making it possible to see an area from the outside indicator disc (39) and whether the valve (1) is open or closed.  10. Device according to any one of the preceding claims, characterized in that the elastic torsion means (T) is calibrated to apply the leaf (2) of the valve on its seat according to a predetermined pressure.  11. Device according to one of the preceding claims, characterized in that the mechanical system (S) comprises heating means (C) placed near the fusible means (M, 18), and control means (K) controlling the starting of the heating means (C), the latter being designed so as to allow a rise in temperature sufficient to cause, at will, in particular by remote control, the melting of the fusible means (38) and the closing of the valve.  12. Device according to claim 11, characterized in that the heating means (C) comprise an electrical resistance (44) disposed in a housing (45), in particular explosion-proof, placed at the end of the shaft (6) of the valve, this housing (45) being linked to the valve body.  13. Device according to claim 12, characterized in that the control means (K) comprise a probe (51) for taking the temperature in the housing (45), connected to thermostatic control means (52) arranged in a control box (49) attached to the outside of the housing (45).  14. Device according to claim 12 or 13, characterized in that the control means (K) comprise a source of electrical energy (53), in particular a battery, suitable for supplying the electrical resistance (44 ) to cause the valve to close.  15. Device according to any one of claims 1 1 to 14, characterized in that it comprises means (56) for remote reporting of the position indication (open or closed) of the valve.  16. Device according to claim 15, characterized in that the means (56) of remote transfer comprise a plate (57) fixed on the shaft (6) of the valve and two limit switch contacts (64, 65), linked to the valve body, corresponding to the open position and the closed position of the valve, the plate (57) cooperating with one of these contacts when the valve is in the corresponding position.  17. Device according to any one of the preceding claims, characterized in that the shutter (7) of the valve is equipped with a pressure relief valve (7b) capable of eliminating an excessive excess pressure of the fluid upstream of the shutter , when the latter is closed.