FR2571092A1 - ANTI-ERUPTION DEVICE LODGED IN A DRILL ROD TRAIN. - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS AN INTERNAL ANTI-ERUPTION DEVICE INTENDED TO BE USED IN A DRILL ROD TRAIN. THIS DEVICE IS CHARACTERIZED IN THAT IT INCLUDES IN COMBINATION, A VALVE BODY13 PRESENTING A PASSAGE21 FOR THE FLUID FLUID FLOW, A SEAT31 FOR A BALL WHICH IS LOCKED IN THE LONGITUDINAL PASSAGE21, A BALL RECEPTION LOCATION LOCATED BELOW SEAT31 AND A BALL41 BROUGHT TO ITS RECEPTION LOCATION39 DURING THE DOWNWARD FLUID FLOW AND WHICH CAN BE MOVED, IN THE CASE OF UPPER FLOW WITH SUFFICIENT SPEED, IN THE LONGITUDINAL PASSAGE21 IN CONTACT WITH THE SEAT 31 AND INTERRUPT THE FLUID FLOW TO THE UPPER.

Description

71092

  The present invention relates generally to

  Safety valves and more particularly a device of the type used to prevent uncontrolled or excessive upward flow of a fluid in drill pipe trains from the ground. Oil and gas wells are drilled in the usual manner by rotating a drill string and drill bits that support a drill bit. The drilling fluid, that is, the drilling "mud", is pumped down into the internal bore of the drill string through the drill bit and back into the annular passage between the drill bit. wall of the drilled hole and the drill string. The mud ensures the entrainment of the debris from the borehole to the surface and the cooling of the drill bit.

  drilling. Moreover, the weight of the drilling mud is

  to create, in the bottom of the drilled hole, a pressure

  hydrostatic pressure greater than the pressure of the formation,

to prevent an eruption.

  If the mud pressure becomes too low when the surface pump is disconnected from the drill string (such as occurs when the stem joint is being added or a stem is removed or

  replaced during a movement of the drill string) of the fluid

  formation flows into the drilled hole and may result in uncontrolled upward flow both inside the drillstring and in the annular passage. This over-repression can result in a

  rash if not controlled quickly. In addition

  their heavier fluids made up of

  can not be pumped quickly through the

  to prevent a blowout, since the surface pump is disconnected from the drill string. "External" anti-rupturing devices that have been on the market and have been in use for several years are currently being used to seal the drill string to the surface and to quench the annular space between the drill string. drilling and the wall of the drilled hole. Such devices do not prevent upward flow of drilling mud within the drill string during an eruption. "Inner" anti-eruption devices are also known. An internal anti-eruption device

  typical is kept on the deck of the derrick. Lors-

  that an upward flow begins to appear in the

  the drill string, the device is screwed

  tive internal eruption at the top of the drill string and closes a valve. Then the mud pipe is reconnected to drown the well. Since the upward flow starts before the anti-blowout device such type is plugged in, the use of such a device

  can be messy and dangerous.

  Various solutions have already been considered in

  patented patent, to use internal anti-blowout devices that remain inside the drill string during drilling. Examples of such anti-eruption devices are described in US Patents 3,850,191, 3,850,194, 4,040,441, 4,049,015, 4,088,298, 4,108,203 and 4,263.

  936. In these patents the device includes a subassembly

  intended to be mounted inside the drill string. This subassembly has a longitudinal passageway with a recess or side pocket on one side and a

  flap seat in the passage above the side pocket

  rale. A ball is housed in the side pocket during the

  normal drilling. This ball moves in the long passage

  and applies to the seat if a flow

  Precise appears during an eruption. A passage of

  the base of the lateral pocket to the longitudinal passage, below the lateral pocket, determines the

  flow rate upwards which causes the displacement

  ball in the longitudinal passage. The area of the cross section of the equalization passage prevents the bile from being applied to the seat during the normal upward flow that occurs during the descent of the train.

drill rods in the well.

  Erosion is an ongoing problem for

  internal anti-eruption positives of the type described in

  aforementioned patents. High flows and solid particles

  or sand contained in the drilling mud causes erosion of the valve seat and passage within the anti-blowout device, thus preventing a long effective service life. Experience has shown that

  ball tends to move partially in the long passage.

  even during the flow of the fluid downwards.

  In this position the ball causes a restriction of

  the flow will have a variable area as a result of the oscilla-

  the ball, which translates into excessive speeds.

  of the fluid around the ball-and in the long passage

  gitudinal. This inevitably results in a tur-

  bulent and erosion of the passage and the ball.

  The subject of the invention is an anti-

  internal eruption of the type mounted in a drill string during drilling operations. This internal anti-eruption device includes a ball that remains in one

  reception area on one side, during a

  down. This ball moves-up for

  come into contact with a valve seat during the

  flow upwards - sufficiently large.

  The ball receiving location is located

  part of the subset that has a passenger section

  significantly larger than the passage section through the valve seat. This larger section of passage results in a reduction of the speed of the fluid compared to

  the marble. The downward flow comes directly

  part of the ball. The part of the longitudinal passage

  which extends downwards from the flap seat and

  towards the ball may be a broadcaster or a passenger.

  ge diverge in order to decelerate the fluid uniformly. To additionally contribute to maintaining the ball at its receiving location 39, a communication passage extends from a point below the ball to a point where the rate of flow is much higher. and the area of the cross-section is

  much smaller than where the ball is.

  Preferably, the longitudinal passage for the main flow extends from the ball receiving location to a smaller diameter cylindrical section. This communication passage ends at a point adjacent to the cylindrical section to create a pressure drop

  helping to keep the ball at its location.

  reception. Longitudinal passage allows tool passage

through the subset.

  An embodiment of the present invention will be described hereinafter by way of nonlimiting example, with reference to the appended drawing in which:

  FIG. 1 is a vertical sectional and axially

  of an internal anti-eruption device follow the invention.

tion.

  FIG. 2 is a sectional view, on a larger scale, taken along the line II-II of FIG.

  anti-eruption device of FIG.

  FIG. 3 is a sectional view, on a larger scale, taken along line III-1II of FIG.

  snti-eruption device of Figure 1.

  FIG. 4 is a sectional view, on a larger scale, taken along the line IV-IV of FIG.

  anti-blowout device of Figure 1.

  Figure 5 is a sectional view, to larger

  scale, taken along the line V-V of Figure 1, of the

  positive anti-eruption of Figure 1.

  FIG. 6 is a sectional view, on a larger scale, taken along the line VI-VI of FIG.

  anti-blowout device of Figure 1.

  Figure 7 is an axial and vertical sectional view

  partial, on a larger scale, of part of the

  tif eruption of Figure 1, the ball has not been shown. FIG. 8 is an elevational view, on a larger scale, of a portion of the lower insert, which is a

  element of the anti-blowout device of Figure 1.

  If we refer to Figure 1, we see that a

  The anti-eruption device 11 comprises a tubular casing 13.

  This casing 13 has a thread 15 at its end

  superior, with a view to its connection with a stem, not

  felt, of a drill string. An adapter 17 is

  attached to the lower end of the envelope 13. This

  tubular tubular 17 has an external thread 19 to ensure its connection with another rod, not shown, the drill string. A longitudinal passage 21 extends through the envelope 13 and the adapter 17 for the passage

drilling fluid.

  An upper insert 23 is housed in the envelope 13

  near its upper end. This superior insert

  23 is a tubular member having a co-bored bore

  25 which is part of the longitudinal passage 21 for the passage of the drilling fluid. The conical bore 25 has a lower end which is smaller than its upper end and the axis 24 of this bore 23 is offset with respect to the axis 26 of the casing 13. The axis 24 of the bore

  conical 25 intersects the axis 26 of the envelope 13.

  A seat 31 for a flap or a ball is housed

  in a recess provided at the lower end of the bore

  25. An insert 27 for maintaining the seat is applied.

  The insert 27 is a tubular member having a cylindrical bore 29 which is aligned with the lower end of the tapered bore 25. The valve seat 31 is held in recesses

formed in the inserts 23 and 27.

  An intermediate insert 33 is applied against the former

  lower end of the insert 27. This insert 33 is a tubular member having a bore 35 which has the same diameter, at its upper end, than that of the cylindrical bore 29 to which it is connected. The bore 35 has a conical shape, as well as the bore 25, its axis 34 is inclined with respect to the longitudinal axis 26 of the casing 13 but is in an inverted position with respect to

  The axis of the conical bore 25. FIG.

  wise conical 35 seen upward towards the seat 31.

  The conical bore 35 opens into a central section

  enlarged tread 37, as shown in Figures 2 and 7, which has a generally cylindrical shape. The area of the cross section or section of the flow at the location of the central section 37 is greater than that of the passage section through the seat 31. The axis of the central section is shifted with respect to the axis 26 but in an opposite direction to the direction of the

seat offset 31.

  Referring to FIG. 7, it can be seen that a location for receiving a ball 39 is located in the central section 37. This reception location of a

  ball 39 supports a ball 41 (Figure 1) during the flow.

  fluid flow downwards. Figure 2 is a sectional view

  showing the ball 41 lying on its location

  reception. The axis of the location of receiving a ball 39 is offset with respect to the axis 26 in a direction opposite to that of the offset of the axis of the seat 31 for the

  ball (Figure 1). The section of passage at the level of the

  receiving placement of a ball 39 is equal to the area of the cross-section of the central section 37 minus the

  dimension of the cross-section of the receiving location

  This section of passage is considerably higher than

  than the passage section of seat 31 (Figure 1) la-

  which is smaller than the straight section of ball 41.

  As shown in Figure 2, the location

  ball receiving member 39 has a circular cross-section of a diameter smaller than that of the central section 37, and its axis is offset with respect to the axis of the central section 37. The outer side of this location of The receiving section is tangent to the outer side of the central section 37. The u-section of the central section 37 may be described as having the shape of a crescent having one side (left side in FIG.

  concave while the other side is convex.

2 5 7 1092

  The receiving location 39 of ball 41 con-

  the top end of a ball-receiving member 43. This ball-receiving member 43 is a cylindrical member, as shown in Figures 2,3 and 6, having a diameter slightly greater than This ball receiving element 43 is fitted into a cylindrical hole 44 (FIGS. 3 and 6), which is formed in a lower insert 45. This lower insert is a tubular member whose upper end is

  in contact with the lower end of the insert

  33. The lower insert 45 is fitted into the housing.

  13 and has a conical bore 47 which extends downwardly from its upper end, forming part of the longitudinal passage 21. The conical bore 47 is

  shown in Figures 2 and 3 and Figure 7.

  The conical bore 47, converging downwards, has an axis 46

  (Figure 7) which is inclined with respect to the axis 26, its ex-

  lower end with a diameter smaller than that of

its upper end.

  The lower end of the conical bore 47 de-

  mouth in a cylindrical section 49 provided in the lower insert 45 and which has a passage section smaller than the passage section at the location of the central section 37. The axis of the cylindrical section 49 coincides

  25. with the axis of the valve seat 31, these two axes being disconnected

  with respect to the axis 26 of the envelope 13. The section

  cylindrical 49 opens into a conical bore 51 which is

  tends towards the lower end of the lower insert 45.

  The conical bore 51 has, as shown in Figure 4, an axis 52 (Figure 7) which intersects the axis 26, as well as the

  other bores 25,35 and 47. The lower end of the

  conical damage 51 has a diameter greater than that of its

  upper end. Bores 47, 49 and 51 form

jointing a Venturi.

  Part of the lower insert 45 is shown removed from the casing 13 in FIG. 8. This insert has a cylindrical wall which fits tightly into the casing

  13. On the one side a notch 55 is cut in the wall.

257109Z

  This notch is also shown in FIG.

  The notch 55 makes part of the outer side of the receiving element of a ball 43 appear. This makes it possible to weld

  the element for receiving a ball 43 at the insert 45. The

  55 does not extend over the entire length of the hole 44 or the receiving element of a ball 43. The line

  The indent 57 shown in Figure 7 indicates how

  It would be apparent that the conical bore 47 has the ball-receiving member 43 not welded in place and the bore 44 does not exist. The outlet of the conical bore 47 in the cylindrical section 49 can be seen by comparing Figures 2,3 and 6. In Figure 6 the conical bore 47 does not appear.

  Moreover, this figure showing only the cylindrical section

that 49.

  Referring to FIG. 7, it can be seen that a communication passage 59 extends through the receiving element of a ball 43. while being inclined with respect to the axis 26. This

  communication passage 59 has a wide upper end

  61 which is circular but has a smaller diameter

  to the diameter of the ball 41. The upper end 61 defines

  a circular sealing surface which is located in a plane perpendicular to the axis 26 (FIG.

  bring the ball 41 to be applied in a sealed manner

  against the upper end of the passage 59 during the

  drilling fluid downward. During this flow

  the ball 41 prevents the fluid from

  flows down through the passageway 59.

  The tapered section 65 extends from the lower end 63 of the passage 59 to the lower end 67 of the ball-receiving member. 43. This tapered section 65 is a flattened section on the side wall of the ball receiving member 43. The lower end 67 extends slightly toward and

in the cylindrical section 49.

  An open channel 69 extends upward from a point near the lower end of the insert 45, to the lower end of the receiving member.

  of a ball 43. This channel 69 is formed in the wall of the

  51. The channel 69 is aligned with a channel 70 which extends upward from the lower end

  67 of the receiving element of a ball 43, to the ex-

  lower end 63 of the communication passage 59. As shown in FIG. 4, the channel 69 joins the

  channel 70 to provide a flow path for the flow of

  upwardly to and in the lower end 63 of the passage 59. The channels 69 and 70 are inclined relative to each other.

to the axis 26 (Figure 1).

  An additional structure for the anti-blowout device includes a tooth-shaped guide member 71 which is located on the inner side of the

  receiving a ball 39. As can be seen in the figure

  8, this guide member 71 forms a ridge above

  the upper end 61 of the passage 59. This guide member

  Dage 71 serves as a guiding means for contributing to the placement of the ball 41 at its receiving location 39 during the downward flow. Figure 1 shows

  Belleville washers 73 which are arranged between the adapter

  17 and the lower end of the lower insert 45 to firmly hold the inserts 23,27,33 and 45 to

the inside of the envelope 13.

  In operation the anti-blowout device 11 is attached to the drill string during the drilling operation. The drilling mud is pumped down through the drill string and passes through the blowout device 11. The drilling fluid passes through the longitudinal passage 21, the tapered bore 25 and the seat 31. drilling fluid then passes through the section

  cylindrical 29 and then enters the conical bore 35.

  As shown in FIGS. 1 and 5,

  the area of the cross-section or the crossing section increases

  so gradually in the conical bore 35, this results in the existence of a diffuser in the case of a flow downwards. The fluid velocity decreases to a minimum in the vicinity of the central section 37. The fluid flows around the receiving member of a ball 43 and enters the conical bore 47. Part of the fluid stream The downwardly flowing down stroke directly hits the ball 41. In the conical bore 47 the fluid velocity increases and reaches a maximum velocity in the cylindrical section 49. The pressure at the location of the cylindrical section 49 is less than the pressure in the section

Central 37.

  The location of receiving a ball 39 is in

  communication, through the passage of communica-

  59, with the adjacent cylindrical section 49 at low pressure. This creates a pressure difference on the ball 41. Normally, in the case of a downward flow, the

  ball 41 does not move out of its receiving location.

  39 in the main passage section of the other

  side of the guide member 71. Even if the ball 41 is

  place somewhat in relation to its location of reception

  39, the distance between the receiving element of a ball 43 and the opposite side of the conical bore 47 is smaller than the dimension of the ball 41 and therefore it can not move downwards. . Likewise, as can be seen in FIG. 2, even if the ball 41 is able to move away from its receiving location 39 and come into contact with the opposite wall of the conical bore 47, it does not significantly restrict the flow because of the importance of the crescent-shaped crossing section

  surrounding the ball receiving element 43. The earpiece

  fluid, after leaving the cylindrical section 49, enters the conical bore 51 and passes through

the adapter 17.

  If the formation pressure in the well becomes greater than the hydrostatic pressure due to the drilling mud column, and the fluid begins to flow to the

  high, the drilling fluid can begin to rise to the

  interior of the entire drill string. The neck-

  The upward movement is effected through the conical bore 47 which then acts as a divergent. Part of the flow passes upward through the communication passage 59. The fluid flowing through this passage

7 1092

  -of communication 599 if it is sufficient, spreads the ball 41 from its seat and pushes it back into the main course of Ae flow upward tapered lsConnection 350 Ball 41 eet and then upward to come s2apo pliquer center 319 then interrupting everything else! to the height of the rash in the heart can then be stopped by pumping into it of the heavier mud. The ball 41 remains pressed against the seat 31 until the pressure above the ball 41 becomes greater than that below the ball When the pressure above the ball 41 becomes greater than the pressure below of the ball, it falls and returns to its receiving location 39. The guide member 71 guides the ball to bring it back to its eaplap

receiving cement 39.

  The dimensions of the components of the anti-Orress device 11 are chosen such that a minimum upward flow is achieved before the ball 45 is driven upwards and comes to bear against the seat 31. For the Ball 41 comes into contact with the seat 31, a minimum upward speed is required so that the ball 41 is not normally brought into contact with the seat 31 during the normal descent of the drill string. During the descent of the drill string, mud in the bore enters the drill string to equalize the pressure inside and outside the drill string. The ball 41 and the sections of the various bores are dimensioned in such a way that the ball 41 comes into contact with the seat 31 of

  preference when one reaches a flow upwards of

  It is used for a drilling fluid having a specific gravity of 1.9 g / cm 3 and a flow rate of 757 l per minute for pure water. The maximum upward flow that may occur during the normal descent of the train of

  drill pipes, even with large nozzles and heavy mud

  of, is about 508 liters per minute.

  The minimum clearances between the valve seat 31 and the cylindrical section 39 are chosen so as to allow the removal of normal tools suspended from a cable in

  the drill string during certain operations.

  The distance between the extreme internal dimension of the ball-receiving element 43 and the opposite side of the conical bore 47 is calculated so as to allow the passage of

these same tools.

  The dimensions of the bore sections are chosen

  in order to reduce erosion during normal downward flow. A flow rate of about 30.5 meters per second is considered a value from which erosion occurs with most sludge. The smallest section of passage in the device

  anti-eruption 11 is that of the valve seat 31 obappa-

  lower speeds of 30.5 meters per second for a flow rate of 2840 liters per minute, assuming an internal diameter of 44.5 cm for seat 31. A speed of 30.5

  meters per second through the seat 31 is brought back to

  about 13.1 meters per second in center section 37 around ball 41. This reduced speed is

  below the threshold of appearance of erosion.

  The lower end 63 of the communication passage

  tion 59 is preferably located in a portion of the

  conical wrap 47 having a passage section smaller than the passage section around the receiving location

  39. This translates into a difference of pres-

  sion on the ball 41 during the downward flow, the magnitude of this pressure difference dependent

  the fluid velocity and the weight of the drilling fluid.

  For example, for a flow rate of 757 liters per minute the estimated pressure difference is from 0.16 bar for water to 3.1 bar for a drilling mud with a specific gravity of 1.9 g / cm3. In the preferred embodiment of the invention,

  the diameter of the seat 31 is 44.5 cm, which gives a sec-

  passage of 155cm2. The nominal passage section of the central section 37 is approximately 35.5 cm 2. The distance, along the axis 26, between the lower edge of the seat 31 and the top of the ball 41 being at its location. receiving 39 is about 28 cm. The ball is preferably

  made of steel and has a diameter of 5.4cm.

  wise of the cylindrical section 49 is about 19 cm2. The distance between the center of the ball 41, being at its receiving location 39, and the upper edge of the cylindrical section 49 is about 1.3 cm. The diameter of the

  communication passage 59 is 0.8cm.

  The diameter of the section 35 at its junction with the central section 37 is about 6.6cm. The diameter of the

  central section 37 is about 9.8cm. The flow of

  the main point at the top of the central section

  trale 37 is conical. The edge of this tapered current hits the ball 41 about 3.8 cm from the inner side (right side of FIG. 1) of the ball 41. Thus, about three-quarters of the ball becomes. find directly in the main stream down in the embodiment of the invention.

  The invention offers appreciable advantages. DIETS

  of convergent and divergent passages and the provision of

  Positioning of the receiving location 39 of the ball 41 at a point where the speed is significantly reduced results in an appreciable reduction in erosion. The use of the

  pressure difference caused by the passage of

  cation 59 below the ball 41 maintains this ball in the location provided for it, so as to prevent oscillation and turbulence. The offset axes of the converging and diverging sections at the seat 31 of the ball allow the tools to pass easily through the

anti-eruption device.

Claims (7)

  1.- internal anti-eruption device for use in a drill string characterized in that it comprises in combination, a valve body (13) having a passage (21) for the flow of drilling fluid and upper and lower ends (15, 19) for connection to the drill string, a seat   (31) for a ball which is housed in the longitudinal passage   dinal (21), a ball receiving location (39) beneath the seat (31), and a ball (41) provided at its receiving location (39) during the flow of fluid downwardly and displaceable, in the case of upward flow with sufficient velocity, in the longitudinal passage (21) for contacting the seat (31) and interrupting the flow of fluid upwards, the location receiving (39) the ball (41)   protruding at least partially in the long passage   gitudinal (21) by exposing at least a portion of the ball   (41) to at least a portion of the direct contact of the fluid flowing down.   2.- internal anti-eruption device according to claim 1 characterized in that it comprises a section (35) forming a diffuser in the longitudinal passage (21), this   diffuser (35) starting with a passage section halfway   at the point of the ball valve seat (31) and having a passage section progressively increasing towards the   down to ensure a lower fluid velocity at the ex-   lower end of the diffuser (35) lower than at its upper end, the receiving location (39) of the ball (41) being arranged at the lower end of the diffuser section (35) the ball (41) which is carried by its receiving location (39) during the downward flow, movable out of its upward receiving position to engage the seat (31) if an upward flow having a speed selected occurs.   3. * Internal anti-rupturing device according to claim 1 erocté1ius in that the longitudinal passage (21) includes sectlons superior and infr @ aian paoag sectio 2n p3uo small that the passing passa300 of a secion centaeGeP the sibga ( 31) paeor the ball (41) is 8itu in the supârieauroe section, Iep oe n% receiving (39) of the ball (41) is located in the central section of the longitudinal passage (21), and a passage ocamunicesion ( 59) extends from the location of receiving the ball (41) downwards, towards the smallest section of passage 9 of the intermediate section, so as to return a difference in pressure to the ball (41). ) during the downward flow in order to move the ball on its reception amplification (39), and to move the island (41) towards the aperture (31) during a flow to the hsut having a pre-determined speed Co Internal anti-eruption device following   claim 3 characterized in that the location of   ception (39) of the ball (41) has a cross section of general circular frearne, with an axis offset from the axis (26) of the central section which is also circular in cross section, thereby defining a passage section generally having a crescent at the ball receiving location (39), the crescent shape of the passage section at the receiving location of a crescent   ball (39) preventing the ball (41) from interrupting the ear   downwardly if this ball (41) is spaced from its receiving location (39) during the flow down.   5.- Internal anti-eruption device according to one   any of the preceding claims characterized   it comprises a guide member (71) extending upwardly from the receiving location of a ball (39) to guide the ball (41) towards its receiving location (39). -   6.- Internal anti-eruption device according to the   claim 1 characterized in that the longitudinal passage   Nal (21) has an upper section, a central section (37) and a lower section having a reduced diameter portion (49) having a smaller passage section than that of the central section (37), the seat (313 for the ball (41) has a passage section smaller than that of the central section (37) and is located in the upper section, being coaxial with the reduced diameter portion (49) and offset from the axis longitudinal (26), the ball receiving location (39) is located in the central section (37) and offset from the axis (26) of the envelope (13) in a direction opposite to the direction of the shift of the seat (31) of the ball (41), and a   communication channel (59) extends from the   receiving cement of a ball (39) towards the reduced diameter portion (49) to apply to the ball (41) a pressure lower than that prevailing in the section   central (37), during. the flow down and hand-   thereby holding the ball (41) at its receiving location (39), and for deriving a portion of the flow towards the   top to the underside of the ball (41) to   to move the ball outward in the direction of   flowing upwards in the middle section and against the   seat (31) if a predetermined upward flow rate   completed, the coaxial arrangement of the seat (31) and the reduced diameter portion (37) and the shift of the ball receiving location (39) allowing the   - passage of tools through the longitudinal passage (21).   7.- Internal anti-eruption device according to the   claim 1 characterized in that the longitudinal passage   Nal (21) has an upper section, a central section (37) and a lower section having a reduced diameter portion (49) having a smaller passage section than that of the central section (37), the seat (31) for the   ball (41) is located in the upper section, the   receiving member (39) is located in the central section (37) and a communication passage (59) extends from the ball receiving location (39)   direction of the reduced diameter portion (49) in order to   to apply to the ball (41) a pressure lower than that prevailing in the central section (37), during the downward flow, to contribute to the displacement of the ball towards the seat (31) 8.- internal anti-eruption device according to the Claim 3 characterized in that the upper section comprises a diffuser section (35) starting with a minimum passage section at the seat (31) for   the ball (41), this section of passage increasing progressively   down to give the fluid a speed   weaker, at the lower end of the cross-section of   fuser, only at its upper end.   9.- Internal anti-eruption device according to the   Claim 7, characterized in that the location of   ception (39) of the ball (41) has a cross-section of generally circular shape, with an axis offset from the axis (26) of the central section which is also circular in cross section, thereby defining a section of passage   having the general shape of a crescent at the level of the   receiving placement of a ball (39), 10.- Internal anti-blowout device according to the   claim 1 characterized in that the longitudinal passage   nai (21) extends through the casing (13) for the passage of the fluid, this passage having an upper section (35)   conical shape of a section gradually increasing   than a central section (37) having a larger passage section, and a conical lower section (47) progressively extending downwards from the central section to   a zone with a smaller passage section.