Safety valves for wells

A safety valve for installation in a well to close the passage for effluent therefrom comprises a valve body of generally cylindrical shape, shut-off element in a lower part of this body, and a cylindrical slideblock which is slidable longitudinally in the body and adapted to cause, in its descending movement, the opening of the shut-off element. A locking system for locking the valve in the well is located in a radially outer portion of the body and comprises a radially expandable attachment component for engaging, when expanded, in a stop groove provided in the receiving connection of the well surrounding the body. Upper and lower sealing elements for sealing against the receiving connection are arranged on radially outer regions of the body for forming between them a space for receiving a control fluid for the valve, the two sealing elements being arranged longitudinally one on each side of the locking system.

BACKGROUND OF THE INVENTION 
The present invention relates to a safety valve particularly but not 
exclusively for installation in a receiving connection (called a "nipple") 
of a production tube of a well, to shut off in this tube the passage of 
the effluent produced, e.g. oil or gas. 
The safety valves used at the present time are provided with a locking 
system mounted on the upper part of the valve body to lock the latter in a 
stop groove in the receiving connection of the production tube, and with 
two sealing linings which are located underneath the locking system and 
which come up against two inner smooth bearing surfaces of the receiving 
connection, between which opens an inlet for the fluid for controlling the 
valve. 
The disadvantage of this arrangement is that the safety valves constitute 
somewhat long components and that they substantially reduce the passage 
cross-section for the effluent, because their active part is located 
entirely under the stop groove of the receiving connection, that is to say 
in a narrowed portion of the latter. This results in considerable load 
losses. Additionally, the locking system is subjected to the corrosive 
action of the effluent. 
SUMMARY OF THE INVENTION 
One object of the invention is therefore to propose a safety valve which 
can be made of reduced length, which can provide an increased 
cross-section for the passage of the effluent produced, so that the load 
losses caused by the presence of the valve and the cost of this valve are 
reduced. Another object of the invention is to provide a safety valve in 
which the locking system can be protected from any corrosive action. 
According to the invention there is provided a safety valve which comprises 
a valve body of generally cylindrical shape, shut-off means in the lower 
part of the body, a cylindrical slide-block longitudinally slidable within 
said body and adapted to cause, in its descending movement, opening of the 
shut-off means, locking means located in radially outer portions of said 
body and comprising a radially expandable attachment component for 
engaging, when expanded, in a stop groove outside said body, upper and 
lower sealing means, which are arranged on radially outer portions of said 
body and which provide between them a space for receiving a control fluid, 
wherein the two sealing means are arranged longitudinally one on each side 
of the locking means. 
The locking means may therefore be washed by the control fluid, usually 
hydraulic oil, and the valve may be arranged only partially in the 
narrower part of the production tube located below the stop groove. 
The cylindrical block may be fixed, on the one hand, to a piston which 
bears in a leak-proof manner against the valve body and is located above 
the locking means and on which the control fluid acts for causing descent 
of the cylindrical block, and, on the other hand, to a bearing ring which 
is likewise located above the locking means and on which acts a restoring 
spring tending to cause the cylindrical block to rise. This arrangement 
makes it possible to gain even greater advantage from the installation of 
the locking means between the two sealing means as regards an increase in 
cross-section for the passage of the effluent produced. 
The restoring spring may be arranged above the upper sealing means in an 
annular space between the valve body and the cylindrical block, this space 
being delimited by an upper sealing gasket carried by the valve body and 
in contact with an upper portion of the cylindrical block and by a lower 
sealing gasket carried by the valve body and in contact with a lower 
portion of the cylindrical block along a circumference of greater diameter 
than that of the contact circumference between the upper gasket and the 
said upper portion of the cylindrical block, this annular space being 
intended to be washed by the control fluid. 
The attachment component may comprise an elastic ring with an outer profile 
matching the profile of the stop groove, into which it is to be fitted, 
and with internal toothing, whilst the valve body incorporates a first 
recess intended for receiving this attachment component in the unexpanded, 
and in the not fully active, positions, this first recess being edged at 
the lower end with a retaining means which is intended to retain the 
attachment component radially and longitudinally and which is fixed to the 
valve body, and at the upper end with an expansion means which is located 
in a second recess of the valve body and is designed to be inserted into 
the attachment component to complete the expansion of the latter and which 
is provided with external toothing for engaging with the internal toothing 
of the attachment component. 
The toothings of the attachment component and of the expansion means are 
preferably left-hand helical threads. 
The said second recess may be provided with orifices in its radially inner 
wall and through which pass keys for the radial retention of the expansion 
means, the orifices being closed by the cylindrical block against which 
the keys bear. The cylindrical block may be provided in a lower region 
with apertures designed to come opposite the said orifices when the 
cylindrical block is raised into a maximum upper recovery position, which 
it can reach only after shearing a shearable stop participating in the 
normal operation of the valve and mounted on the valve body. 
In the event that the valve is installed in a receiving connection not 
designed specially for it, and there is no inner smooth bearing surface 
above the stop groove in the receiving connection, the upper sealing means 
may be made of a solid elastic material which, when compressed, bears 
strongly against the receiving connection of the production tube. Under 
these circumstances, a spacer tube may be fixed to the valve body by means 
of a shearable pin in such a position and over such a length that it 
strikes against the attachment component when the latter is retained in a 
descending movement of the valve body, and, after the shearing of this 
pin, it compresses the upper sealing means by bearing on the attachment 
component. 
For an oil well in which the effluent rises because the column of effluent 
is lightened by means of gas and in which an inner tube is installed 
within the production tube so as to provide a passage within the inner 
tube and an annular passage between the inner tube and the production 
tube, one of these passages serving for injecting lightening gas and the 
other for the ascent of the lightened effluent, the invention is 
particularly appropriate because it is then of primary importance to have 
passage cross-sections which are as large as possible. 
In this case, if the safety valve is fastened towards the lower end of the 
inner tube and if a flap is used as a shut-off means, a coaxial tubular 
section may be connected to the valve body below the flap, and an 
intermediate tubular portion, which on the one hand is slidable 
telescopically and in a leak-proof manner at its upper end on the inner 
tube, the lower end of which is located at a certain distance above the 
flap, and which on the other hand is designed to slide telescopically and 
in a leak-proof manner at its lower end on the said tubular section, is 
driven in longitudinal displacement by the cylindrical block and has such 
a length that, depending on the position of the cylindrical block, it can 
be either located completely above the closed flap or engaged with the 
said tubular section, the flap then being open.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show in half-section a portion of a production tube 1 
comprising a series of tubular elements, such as 2, 3, 4, and a receiving 
connection 5. This production tube 1 is installed in a known way on the 
inside of an oil well (not shown). The receiving connection 5 comprises an 
inner stop groove 6 in its upper part and, beneath the stop groove 6, two 
smooth bearing surfaces, an upper one 7 and a lower one 8, (FIG. 2) which 
are separated by a recess 9 into which a control fluid, usually hydraulic 
oil, can be introduced via an orifice 10 provided in the wall of the 
receiving connection 5. 
A safety valve 11 is lowered into the production tube. It comprises a valve 
body 12, which carries in its lower part shut-off means 13 comprising a 
flap in the embodiment illustrated in FIG. 2, and two sealing means or 
linings, an upper sealing lining 14 comprising a solid element made of an 
elastomeric material, and a lower sealing lining 15 comprising an assembly 
of V-type packing. The lower sealing lining 15 bears against the lower 
smooth bearing surface 8 and the upper sealing lining 14 bears against the 
inner wall of the tubular element 3. The upper smooth bearing surface 7 of 
the receiving connection 5 is not used, in contrast to conventional 
installations of safety valves. Of course, it is possible to replace the 
conventional receiving connection 5 of the production tube 1 with a 
receiving connection designed specially for a safety valve 11 of the type 
described here and incorporating an upper smooth bearing surface located 
above the inner stop groove, thus making it possible to use sealing 
linings 14 nd 15 whih are both of V-type packing. 
The valve body 12 comprises from top to bottom the following portions 
screwed to one another: an upper radially outer portion 16, a first 
radially inner intermediate portion 17, a second radially central 
intermediate portion 18, a radially inner lower portion 19 and a portion 
20 for supporting the shut-off means. 
A cylindrical block 21 installed within the valve body 12 ends in its upper 
part in a bearing ring 22, against the lower face of which acts a 
compression or restoring spring 23, located in the annular space 24 
between the cylindrical block 21 and the upper portion 16 of the valve 
body 12 and supported on the first intermediate portion 17 of this valve 
body. The normal upper position of the bearing ring 22 and consequently of 
the cylindrical block 21 is defined by an annular stop 25 retained 
relative to the upper region of the upper portion 16 of the valve body 12 
by means of a shearable pin 26. The first intermediate portion 17 of the 
valve body 12 serves, on the one hand, as a support for the spring 23 and, 
on the other hand, as a support for the upper sealing lining 14. 
The second intermediate portion 18 of the valve body 12 delimits, together 
with the tubular element 3 of the production tube 1, an annular space 27 
in which is inserted, with a certain transverse play, a spacer tube 28 
which is retained by means of a shearable pin 29 on the valve body 12 and 
the function of which, after the shearing of the pin 29, is to compress 
the upper sealing lining 14 so as to apply it against the tubular element 
3, as will be explained below. This second intermediate portion 18 also 
delimits, together with the cylindrical block 21, an annular space 30 
which is located below the first middle portion 17 of the valve body 12 
separating it from the annular space 24 and in which a piston 31 fixed to 
the annular block 21 can move. This piston 31 separates the annular space 
20 in a leak-proof manner into an upper part, which communicates with the 
orifice 10 by means of a passage 32 provided in the second intermediate 
portion 18 of the valve body 12, and a lower part in which development of 
any counter-pressure opposing the displacement of the piston is prevented 
by the provision of at least one vent 33 in the cylindrical block 21 below 
the piston 31. The upper part of the annular space 30 constitutes a 
chamber for moving the cylindrical block 21 downwards. The leak-proofing 
of this chamber is ensured, on the one hand, by the piston 31 and, on the 
other hand, by an O-ring type sealing gasket 34 inserted between the first 
intermediate portion 17 of the valve body 12 and the cylindrical block 21. 
The lower portion 19 of the valve body 12 carries, from bottom to top, the 
lower sealing lining 15, a first recess or receptacle 35 for receiving an 
attachment component 36 comprising an expandable split ring, and a second 
recess or receptacle 37 receiving an expansion means 38 for spreading the 
attachment component 36 apart radially when it penetrates within the 
component 36. The expansion means 38 has a fixed longitudinal position in 
the second recess 37, while the expandable ring 36, initially retained 
longitudinally and radially in the lower part of the first recess 35 by 
retention means 39 in the form of a ring threaded onto the lower portion 
19 of the valve body, to which it is connected by a shearable pin 40, such 
as a screw (FIG. 3), can, if it is stopped in a descending movement of the 
safety valve 11 and after the shearing of the pin 40, move longitudinally 
so as to move into the upper part of the first recess 35 where, freed from 
the retention means 39, it can resume its natural radially expanded 
position. The attachment component 36 is, in fact, stopped during the 
descending movement of the safety valve 11 by the lower edge of the stop 
groove 6, and as soon as it is freed from the retention means 39 it 
engages in the stop groove 6, as shown in FIG. 4. When the descending 
movement of the safety valve 11 continues, the expansion means 38 
penetrates within the attachment component 36 and spreads the latter apart 
even more. The attachment component 36 is thus maintained firmly against 
the receiving connection 5 in the stop groove 6. 
FIG. 5 shows in perspective the entire locking system carried by the valve 
body 12. The attachment component 36, provided with an outer profile 41 
corresponding to that of the stop groove 6, has a natural radially 
expanded position. The expansion means 38 consists of a slightly conical 
elastic split ring, the natural position of which is a radially retracted 
position, whilst keys 42, of which there are, for example, three (only one 
of which has been shown), are arranged within the expansion means 38 so as 
to keep the expansion means in its radially expanded position. The keys 42 
extend into orifices 43 in the base of the second recess 37, the orifices 
43 extending through the lower portion 19 of the valve body 12 so that the 
keys 42 bear against the cylindrical block 21. The expansion means 38 has 
a left-hand external thread, and the attachment component 36 has on the 
inside a left-hand thread corresponding to the external thread of the 
expansion means 38. These two threads are designed to penetrate within one 
another in order to maintain the attachment component 36 in a longitudinal 
position relative to the valve body 12. These threads are useful because, 
as will be seen hereafter, they allow for the possibility of disengagement 
of the attachment component 36 from the receiving connection 5 by rotation 
of the valve body 12. The attachment component 36 could alternatively be 
linked to the expansion means 38 by means of teeth not forming a thread. 
The cylindrical block 21 is provided with apertures 44 (FIG. 2) arranged so 
as to be located below the orifices 43 during the normal operation of the 
safety valve 11, an O-ring gasket 45 ensuring leak-proofing between the 
apertures 44 and the orifices 43, just as an O-ring gasket 46 ensures 
leak-proofing between the annular space 30 and the orifices 43, and an 
O-ring gasket 47 ensures leak-proofing between the second intermediate 
portion 18 and the lower portion 19 of the valve body 12. These apertures 
44 are likewise arranged so as to be located opposite the orifices 43 
when, after the pin 26 has been sheared by pulling on the annular stop 25, 
the cylindrical block 21 is raised sufficiently to bring it into its 
maximum upper recovery position, and these operations can be carried out 
by means of a cable by inserting a gripping tool into an inner groove 48 
provided within the bearing ring 22 and also used to lower the safety 
valve 11 into the receiving connection 5. 
It will be seen in FIG. 4 that when the attachment component 36 has 
penetrated into the stop groove 6, it comes up against the spacer tube 28. 
The pin 29 retaining this spacer tube 28 is sheared, and the continued 
descending movement of the valve body 12 causes the upper sealing lining 
14 to be compressed by the spacer tube 28 and this sealing lining to be 
applied in a leak-proof manner against the receiving connection 5. The 
insertion of an annular wedge 49 makes it easier for the spacer tube 28 to 
act on the sealing lining 14. 
Two advantages of the device which has just been described may be noted 
here. On the one hand, the hydraulic control oil introduced into the valve 
11 via the inlet orifice 10 contributes to applying the upper sealing 
lining 14 against the receiving connection 5, thus reinforcing the action 
of the wedge 49. On the other hand, when the safety valve is installed, it 
is possible to ensure that the anchoring of the latter in the receiving 
connection 5 has been carried out correctly by introducing fluid under 
pressure into the valve via the inlet orifice 10 and thus checking that 
the leak-proofing of the upper sealing lining 14 has in fact been 
achieved. 
The portion 20 supporting the valve body 12 is fastened to the lower 
portion 19 of the valve body by means of screwing, and this fastening is 
made leak-proof by means of an O-ring gasket 50. The supporting portion 20 
carries a hinge 51 about which the flap 13, biassed to its closed position 
by a spring 52, can pivot. A pressure-compensating passage 53 has been 
provided in the lower portion 19 of the valve body between two O-ring 
gaskets 54 and 55. An orifice 56 provided in the cylindrical block 21 
comes opposite the passage 53 when the cylindrical block 21 reaches the 
flap 13. To make it easier to open the flap, the cylindrical block 21 ends 
in a bevel 57 so that it first contacts the flap 13 in a region of the 
latter distant from the hinge 51. Below the flap 13, the supporting 
portion 20 of the valve body 12 has an inner cylindrical face 58 with a 
diameter corresponding to the outside diameter of the cylindrical block 
21, so that it can receive the cylindrical block in the lower position of 
the latter. 
The mode of operation emerges clearly from the foregoing. During the 
descent of the safety valve 11 by means of a cable, the attachment 
component 36 is retained by the lower edge of the stop groove 6, and the 
pin 40 shears, thus freeing the attachment component 36 which is engaged 
in the stop groove 6. Then, the spacer tube 28 is retained by the 
attachment component 36, and the pin 29 shears, thus allowing the spacer 
tube 28 to start to compress the sealing lining 14. At the same time, the 
expansion means 38 penetrates into the attachment component 36 and locks 
it in the stop groove 6. The sealing lining 15 is applied against the 
bearing surface 8. The valve 11 is then ready to operate. To open it, it 
is sufficient to supply hydraulic oil via the inlet orifice 10 to the 
space formed between the valve body 12 and the receiving connection 5 and 
limited by the sealing linings 14 and 15. This oil passes via the passage 
32 into the upper part of the annular space 30 and causes the piston 31 to 
descend and consequently the cylindrical block 21 to descend. The block 21 
in turn brings the orifice 56 opposite the passage 53 so as to equalise 
the pressures on either side of the flap 13, and then opens the flap. To 
close the valve 11 again, it is sufficient to relieve the pressure on the 
control oil supplied to orifice 10, the springs 23 causing the cylindrical 
block 21 to rise again. 
When it is intended to raise the safety valve 11, the bearing ring 22 is 
pulled by means of a cable, shears the pin 26 and causes the cylindrical 
block 21 to rise until the piston housing 31 comes up against the first 
intermediate portion 17 of the valve body 12, thus defining the maximum 
upper recovery position. The apertures 44 are then located opposite the 
orifices 43, thus allowing the keys 42 to free the expansion means 38 
which resumes its natural radially retracted position and is disengaged 
from the attachment component 36. The latter is then taken up by the 
retention means 39 and returns to its retracted position in the first 
recess 35. At the same time, the keys 42 secure the cylindrical block 21 
to the valve body 12. The safety valve 11 is thus disengaged and can be 
raised to the surface. 
It will be noted that the passage within the valve 11 is defined by the 
cylindrical block 21 which has no inner projecting part and which has few 
irregularities along its inner surface. This results in minimum load 
losses for the effluent which thus flows in a virtually smooth pipe. 
The valve 11 can easily be matched to different profiles of the stop groove 
6. It is sufficient, for this purpose, to change the attachment component 
36. 
If it is intended to use a shut-off means consisting of a spherical casing 
59 (FIG. 6), it is possible to replace the supporting portion 20 of the 
valve body 12 by a supporting portion 60 carrying a floating seat 61 in 
which the spherical casing 59 can pivot. The casing 59 is provided with a 
groove 62 receiving a peg 63 fixed to the portion 60. The cylindrical 
block 21, when it is displaced vertically, carries along the floating seat 
61 and thus causes the spherical casing 59 to pivot in a way known per se, 
instead of opening a flap 13. In the junction between the cylindrical 
block 21 and the floating seat, shearable pins are inserted, thus making 
it possible to raise the cylindrical block 21 when the valve is to be 
released. 
FIGS. 7, 8 and 9 show how the valve illustrated in FIGS. 1 and 2 can be 
modified so as to be suitable for circumstances in which an inner tube 64 
is to be installed within the production tube 1, so as to provide a 
passage within the inner tube and an annular passage between the inner 
tube and the production tube, for example for the purpose of lightening 
the effluent with gas. The following modifications are envisaged. 
The upper portion 16 of the valve body 12 is extended upwards by a slide 65 
which is screwed at its lower part to a thread 66 provided at the upper 
part of the portion 16 (this thread can also be seen in FIG. 1 in which it 
has been provided so as to allow for this adaptation, although it is not 
used in the embodiment of FIG. 1) and which is connected at its upper part 
to the inner tube 64 by means of a strut 67. A shearable pin 68 keeps the 
slide 65 in a closed position. The inner tube 64 ends slightly above the 
lower face of the annular stop 25 and has in its lower part at least one 
elongate aperture 69 of a length less than the travel of the slide 65 
between its closed and open positions. 
The cylindrical block 21 carries, by means of a joining strut 70, an 
intermediate tubular portion 71 which engages telescopically inside the 
inner tube 64, to which a leak-proof connection is ensured by means of a 
gasket 72 moulded from elastomeric material. The bearing ring 22 is 
modified a little and it is fixed to the joining strut 70 which is 
connected to the cylindrical block 21 by means of this bearing ring. The 
annular stop 25 is likewise modified a little, and a centering ring 73 
makes the shearing of the pin 26 easier. The intermediate tubular portion 
71 carries a peg 74 which engages in the aperture 69 and is adjacent or 
contacts the upper edge of the aperture 69 when the cylindrical block 21 
is in the normal upper position, that is to say when the bearing ring 22 
is against the annular stop 25. The intermediate tubular portion 71 
carries in its lower part a centering strut 75 which ensures that the 
intermediate tubular portion 71 is centered in the cylindrical block 21. 
The intermediate tubular portion 71 carries towards its lower end a gasket 
76 moulded from elastomeric material, and it ends in a bevel 77 which is 
located lower than the lower end of the cylindrical block 21 and which 
allows the intermediate tubular portion 71 to act on the flap 13 in a 
region distant from the hinge 51. 
The supporting portion 20 of the valve body 12 receives at its lower end an 
additional portion 78 which carries, by means of a joining strut 79, a 
coaxial tubular section 80 designed to receive telescopically the lower 
end of the intermediate tubular portion 71 to which a leak-proof 
connection is made by means of the moulded gasket 76. 
The mode of operation of the safety valve 11 is similar in the embodiment 
of FIGS. 7, 8 and 9 to that of the embodiment of FIGS. 1 and 2, the only 
difference being that it is the intermediate tubular portion 71 which 
opens the flap 13 and that the descending movement of the cylindrical 
block 21 is prolonged sufficiently to cause the lower end of the 
intermediate tubular portion 71 to fit into the coaxial tubular section 
80. 
It will thus be seen that the travel of the piston 31 is different 
depending on the type of shut-off means 13 or 59 used and depending on 
whether or not the safety valve 11 is used with an inner tube 64. 
Consequently, using a standard embodiment of the safety valve 11, the 
travel is modified by inserting, as and if appropriate, into the lower 
part of the annular space 30, a floating ring 81 of suitable length, a 
ring 81 being shown in FIG. 2 without being installed. 
The safety valve 11 of FIGS. 7, 8 and 9 is caused to descend by means of 
the inner tube 64 instead of by means of a cable, but the mode of 
operation of the locking system and of the system for compressing the 
upper sealing lining 14 is the same as that described with reference to 
FIG. 1. 
In contrast to this, the method of release and recovery is a little 
different. There is, first of all, the possibility of releasing the safety 
valve 11 by rotating the inner tube 64 to the right. This rotation causes, 
by means of the slide 65 on the one hand and by means of the peg 74 on the 
other hand, the rotation of the safety valve as a whole, with the 
exception of the attachment component 36 which normally remains wedged in 
the stop groove 6. This causes the expansion means 38 to rise and finally 
disengages it from the attachment component 36 which, no longer being held 
internally, can be taken up by the retention means 39. At the same time, 
the upper sealing lining 14 is decompressed. 
Instead of this method of releasing the safety valve 11, it is also 
possible to adopt a method of pulling and ramming upwardly on the inner 
tube 64. This action first causes the shearing of the pin 68, that is to 
say half-opening of the slide 65, thus allowing the peg 74 to come up 
against the lower edge of the aperture 69. By continuing to pull on the 
inner tube 64, the pin 26 is sheared, thus freeing the annular stop 25 and 
allowing the cylindrical block 21 to come into its maximum upper recovery 
position defined when the piston 31 contacts the first middle portion 17 
of the valve body 12. The apertures 44 are then located opposite the 
orifices 43 and the keys 42 (FIG. 5) are freed. This is the same as the 
process described above. The slide 65 is then completely open and it is 
this which supports the weight of the safety valve 11 as a whole, the peg 
74 having served merely to carry out the releasing operations, but no 
longer being involved during recovery. 
In a preferred alternative embodiment shown in FIGS. 10, 11 and 12, it will 
be seen that the restoring spring 23 is located in an annular space 82 
which is filled with hydraulic oil when the valve is opened. This annular 
space 82, provided between the valve body 12 and the cylindrical block 21, 
is delimited by an upper sealing gasket 83 carried by the valve body 12 
and being in contact with an upper portion 84 of the cylindrical block 21 
along a first circumference, and by a lower sealing gasket 85 also carried 
by the valve body 12 and being in contact with a lower portion 86 of the 
block 21 along a second circumference having a diameter greater than that 
of the first circumference, so as to create a differential surface of 
action of the hydraulic oil on the block 21. The valve can be adapted for 
various well depths simply by modifying the diameter of the first 
circumference. 
A shock-absorbing system has been provided in the space 82, thus preventing 
the flap 13 from being subjected to dangerous shocks when it is closed 
under a high differential pressure. The shock-absorbing system comprises a 
piston 87 provided with a tetrafluoroethylene ring 88 grooved in a 
vertical direction to provide throttled passages for the hydraulic oil 
contained in the space 82. The piston 87, fixed to the block 21, also 
serves as an upper support for the compression restoring spring 23. In the 
embodiment illustrated, the piston 87 is formed by a female connection 
piece carried by the upper portion 84 of the block 21 and connected by 
means of threading to the lower portion 86 of this block. In this 
connection piece, a space is occupied by a spacer wedge 89 which, in 
another embodiment, can be replaced by a strut 90 securing the block 21 to 
an inner tube 64, as can be seen in FIG. 17. 
The upper portion 84 of the block 21 carries a recovery head 91 retained 
towards its upper end by a shearable stop 92. Between the block 21 and the 
valve body 12 there is formed, above the upper sealing gasket 83 and below 
the recovery head 91, a grease chamber 93 provided in its lower part with 
calibrated orifices 94 making it possible, during the first opening of the 
valve, to inject a silicone grease into the space between the block 21 and 
the valve body 12 and thus to prevent any sedimentation, as a result of 
which the eventual withdrawal of the valve is made much easier. 
The locking system comprises an open elastic attachment ring 95 (FIG. 13) 
provided with internal toothing, spacer keys 96 provided with external 
toothing and a cylindrical retaining ring 97. The spacer keys 96 are 
arranged in orifices 98 in the valve body 12 and are retained radially by 
springs 99 surrounding all the keys. 
The cylindrical retaining ring 97 is inserted on the outside round the 
cylindrical block 21 and spaces the keys 96 radially apart. The ring 97 
ends at its upper end in a collar 100 on which the restoring spring 23 
bears by means of a washer 101. Thus, any risk of accidental release of 
the valve in the event of shocks is eliminated. 
The elastic ring 95 is maintained in a low position during the descent of 
the valve in the production tube 1, as can be seen in FIG. 14. This ring 
95 is then retained by the lower edge of the stop groove 6, as shown in 
FIG. 15, thus allowing displacement of the ring relative to the spacer 
keys 96 which engage in the ring 95 and keep it radially expanded in the 
stop groove 6, as can be seen in FIG. 11. 
A set-back portion 102 in the outer surface of the block 21 is located 
below the lower part of the cylindrical retaining ring in the upper 
position of the block, so that when the valve is to be released the block 
21 is pulled upwards, breaking the shearable stop 92, in order to raise 
the block 21 sufficiently to ensure that the cylindrical retaining ring 
97, carried along by this block, disengages from the spacer keys 96 to 
allow the spacer keys to retract radially into contact with the block 21, 
thus freeing the elastic ring 95 for radial contraction. 
The upper sealing lining 14 comprises a movable component 103 in the shape 
of a double cone, an upper sealing washer 104 located between a stop 105 
carried by the valve body 12 and a conical surface 106 of the component 
103, a lower sealing washer 107 located between the other conical surface 
108 of the component 103 and a movable compression ring 109. This ring 109 
is pushed upwards when the ring 95 engages in the stop groove 6, and it 
compresses the lower sealing washer 107 directly and the upper sealing 
washer 104 indirectly. This sytem ensures good leak-proofing between the 
valve and the production tube, and it is retracted easily without being 
jammed when the valve is released. 
To ensure that the pressures on either side of the flap 13 are equalised, 
there is located on the valve body 12, below the lower sealing lining 15, 
a pressure-compensating valve 110 which is normally closed and which is 
opened, at the moment when the cylindrical block 21 is near the position 
in which it will open the flap 13, by means of a boss 111 carried by the 
cylindrical block 21. In FIG. 12, the block 21 is in the upper position 
and the boss 111 is located above the valve 110. In FIG. 16, the block 21 
is in the lower position and the boss 111 is located below the valve 110, 
having passed the valve 110 when the flap 13 was going to open. 
FIG. 17 shows the upper part of an embodiment of a safety valve in which 
the block 21 is fixed to an inner tube 64. A recovery head 112, through 
which the inner tube 64 passes, is in its normal state connected to the 
valve body 12 by means of a connection piece 113, the lower portion 114 of 
which is screwed to the left in the valve body 12 and an intermediate 
portion 115 of which has a narrowed cross-section, whilst an upper portion 
116 has a shoulder 117 intended to engage an upper ring 118, carried by 
the block 21 at its upper end, when the connection piece 113 is broken. 
Thus, the recovery head 112 serves as an upper stop for the block 21 
during normal operation and makes it possible to carry the block 21 
upwardly, after the connection piece 113 has been broken, either by 
rotating or by pulling. 
It will be noted in FIG. 17 that the lower end of the inner tube 64 has 
been provided with a chamfer 119 which, in the low position of this inner 
tube, comes up against a metal bearing surface 120 (FIG. 18) of a lower 
suspension 121 fixed to the valve body. A lip gasket 122 is installed 
below the metal bearing surface 120. An adjusting wedge 123 makes it 
possible to compensate in terms of height for the differences between the 
relative positions of the inner tube 64 and of the block 21.