Plug for plugging a line and a method for installing a plug in a line

Abstract

A plug for plugging a line includes a seal, a first end assembly and a second end assembly. The first end assembly includes a gripping member. An actuator is configured to draw the first and second end assemblies together when there is a relative motion between the actuator and the first end assembly. The actuator is configured to actuate the gripping member. An initial part of a motion of the actuator actuates the gripping member to grip an inner surface of the line, thus inhibiting a motion of the first end assembly, and a subsequent part of the motion of the actuator, relative to the thus motion-inhibited first end assembly, draws the second end assembly toward the first end assembly so as to compress the seal such that the seal may seal against the inner surface of the line thus plugging the line.

Claims

1. A plug for plugging a line, the plug comprising: a seal; a first end assembly located at a first end of the seal and a second end assembly located at an opposite second end of the seal, the first end assembly comprising at least one gripping member that is configured to grip an inner surface of the line; and an actuator configured to draw the first and second end assemblies together when there is a relative motion between the actuator and the first end assembly, wherein the actuator is configured to actuate the gripping member, and the plug is arranged such that: an initial part of a motion of the actuator actuates the gripping member to grip the inner surface of the line, thus inhibiting motion of the first end assembly, and a subsequent part of the motion of the actuator, relative to the thus motion-inhibited first end assembly, draws the second end assembly toward the first end assembly so as to compress the seal such that the seal may seal against the inner surface of the line thus plugging the line, wherein the actuator comprises a gripping member-contacting portion that is located adjacent the gripping member, the plug being configured such that motion of the actuator causes rotation of the gripping member-contacting portion, which in turn causes the gripping member to be actuated; and wherein the gripping member-contacting portion comprises threads that are engaged with a threaded elongated member of the actuator.

2. A plug as claimed in claim 1, wherein the actuator is configured such that the motion of the actuator actuates the gripping member directly.

3. A plug as claimed in claim 1, wherein the motion is a first motion and the plug is arranged such that: a second motion of the actuator moves the first and second end assemblies away from each other so as to decompress the seal, and the second motion of the actuator causes the gripping member to release the inner surface of the line.

4. A plug as claimed in claim 1, wherein the motion of the actuator is a rotation.

5. A plug as claimed in claim 1, wherein the gripping member is pivotable between its non-gripping and its gripping positions.

6. A plug as claimed in claim 1, wherein the gripping member is slidable between its non-gripping and its gripping positions.

7. A plug as claimed in claim 1, wherein the gripping member has a generally elongated shape, such as a crescent-shape.

8. A plug as claimed in claim 1, wherein the gripping member has a B-shape.

9. A plug as claimed in claim 1, wherein the gripping member is substantially incompressible and/or inelastic.

10. A plug as claimed in claim 1, wherein the first end assembly comprises at least one stop, the stop being arranged so as to limit the movement of the gripping member, and wherein the gripping member comprises a channel through which the stop is configured to pass.

11. A plug as claimed in claim 1, wherein the first end assembly comprises a plurality of gripping members.

12. A plug a claimed in claim 1, wherein the actuator comprises an elongated member that passes through the seal and the first end assembly, the elongated member comprising threads that engage threads on the first end assembly, and wherein the actuator comprises a stop attached to the end of the elongate member configured to prevent the elongate member from being withdrawn entirely from the first end assembly.

13. A plug as claimed in claim 1, wherein the actuator comprises a torque transmission bar extending generally perpendicular to the longitudinal axis of the plug proximate the second end of the seal.

14. A plug as claimed in claim 1, wherein the first end assembly comprises a raised member having a width greater than the width of the seal or remainder of the plug, the raised member being configured to cooperate with the inner surface of the line to provide the first end assembly with some initial resistance to movement during the initial part of the motion of the actuator.

15. A method of installing a plug inside a line, the plug comprising: a seal; a first end assembly located at a first end of the seal and a second end assembly located at an opposite second end of the seal, the first end assembly comprising at least one gripping member that is configured to grip an inner surface of the line; and an actuator configured to draw the first and second end assemblies together when there is a relative motion between the actuator and the first end assembly and to actuate the gripping member, the method comprising: moving the actuator with an initial part of a motion that actuates the gripping member to grip the inner surface of the line, thus inhibiting motion of the first end assembly, further moving the actuator with a subsequent part of the motion, relative to the thus motion-inhibited first end assembly, to draw the second end assembly toward the first end assembly, thus compressing the seal, thus sealing the seal against the inner surface of the line, and thus plugging the line, and wherein the actuator comprises a gripping membercontactinq portion that is located adjacent the gripping member, the plug being configured such that the motion of the actuator causes rotation of the gripping membercontactinq portion, which in turn causes the gripping member to be actuated and the gripping membercontacting portion comprises threads that are engaged with a threaded elongated member of the actuator.

16. A method as claimed in claim 15, wherein the motion is a first motion, and the method comprises: moving the actuator with a second motion, thus moving the first and second end assemblies away from each other so as to decompress the seal, and causing the gripping member to release the inner surface of the line.

17. A method as claimed in claim 15, wherein the line is a lateral side line pipe to a well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 shows an exploded view of a plug according an embodiment of the invention;

(3) FIG. 2 shows a perspective view of the plug in its relaxed state;

(4) FIG. 3 shows an end view of the plug in its relaxed state;

(5) FIG. 4 shows a perspective view of the plug in its compressed state;

(6) FIG. 5 shows an end view of the plug in its compressed state;

(7) FIGS. 6-9 show a method of installing the plug;

(8) FIGS. 10 and 11 show an alternative embodiment of the plug;

(9) FIGS. 12 and 13 show a side view of an exemplary prior art plug.

DETAILED DESCRIPTION

(10) FIG. 1 shows an exploded view of a plug 1 and FIG. 2 shows a perspective view of the plug 1. The plug 1 comprises a cylindrical seal 2 with a central bore 3 extending in a longitudinal direction through the centre of the seal 2 from a first end 4 to a second end 5 of the seal. The seal 2 is made from a resilient material, such as rubber, such as polyurethane rubber. The central bore 3 is sized so that the actuator 50 can pass through it. The seal 2 may have a relaxed length of between 30 to 200 mm. The seal 2 may have a compressed length of between 25-180 mm. The diameter of the seal 2 when relaxed may be between 30-55 mm. The diameter of the seal 2 when compressed may be between 32-61 mm. The diameter of the remainder of the plug 1 may be between 30-55 mm. The length of the plug 1 (i.e. including the first end assembly, the second assembly, the seal and the actuator) may be between 90 and 270 mm.

(11) Adjacent and in contact with the first end 4 of the seal 2 is a first end assembly 10.

(12) First end assembly 10 comprises a first end plate 11 in contact with the first end 4 of the seal 2. The first end plate 11 is made from a metal, such as stainless steel.

(13) A resilient raised member 12 is in contact with the first end plate 11. The resilient raised member 12 has a radius greater than of the other components of the plug 1. The resilient raised member comprises blades 13 that extend generally radially from a cylindrical body 14 of the resilient raised member 12. The blades 13 also run extend generally longitudinally. The cylindrical body 14 may have a radius substantially equal to that of the other components of the plug 1. The resilient raised member 14 is made from a resilient material such as rubber, such as polyurethane rubber.

(14) A second end plate 15 is in contact with the resilient raised portion 12, such that the resilient raised portion is sandwiched between the first 11 and second 15 plates. The second end plate 15 is made from a metal, such as stainless steel.

(15) The first end assembly 10 also comprises a first gripping member 16 and a second gripping member 17. These gripping members 16, 17 are substantially identical to each other. Each gripping member 16, 17 is substantially crescent-shaped and comprises a countersunk bore 18 through a midpoint of the crescent. The countersunk bore 18 is designed so as to cooperate with an elongated member 19 so as to hold the gripping member 16, 17 to the remainder of the first end assembly. Specifically, the elongated member 19 is held in and passes through the countersunk bore 18. The elongated member 19 also passes through bore 20 in the second end plate 15 and bore 21 in the resilient raised member 12. The elongated member 19 may be a bolt that is threadedly attached to first end plate 11 via threaded bore 22. Alternatively, it may not be threaded and instead may be press fit into the bores. Thus, the elongated member 19 not only holds the gripping member 18 to the second end plate 15, it also is used to secure the first end assembly 10 together, and to prevent relative longitudinal and rotational movement of the different components of the first end assembly. The elongate member 19 may pass entirely through the first end assembly 10 and protrude therefrom such that the elongate members 19 may press into the first end 4 of the seal 2. This may at least partially hold the first end assembly 10 relative to the seal 2 (against relative rotation).

(16) The elongated member 19 and the counter bore 18 are configured to allow the gripping member 16, 17 to pivot around the elongated member 19.

(17) The elongated member 19 may preferably be made from high-tensile steel, and may preferably be a commercially available socket head bolt.

(18) The crescent-shaped gripping members 16, 17 are arranged such that (when in the non-gripping state as shown in FIG. 2) the outer radial edges/surfaces 23 of the crescent-shaped members may form two arc portions of the same circle, said circle being concentric with the remainder of the plug 1. Thus, the two crescent-shaped gripping members 16, 17, when in the non-actuated position, may not extend beyond the radial outer extent of the plug 1 or first end assembly 10 or second end plate 15. However, when the gripping members 16, 17 pivot about the elongated member 19, an end portion 24 may extend beyond the outer periphery of the remainder of plug 1. This is explained in more detail below.

(19) The crescent-shaped gripping members 16, 17 are also shaped/arranged so that an elongated gripping member-contacting portion 70 can be located in between the gripping members 16, 17 adjacent a radially central location of the first end assembly 10. Again, this is explained in more detail below. The gripping member-contacting portion 70 is part of the actuator 50 and rotates with the remainder of the actuator 50 when the actuator 50 rotates. Thus, the actuator 50 (through the gripping member-contacting portion 70, which is part of the actuator) directly actuates the gripping members 16, 17. There is no intermediate portion moved by the actuator 50, in a different motion to the actuator 50 (such as linear motion), which in turn actuates the gripping members 16, 17, as occurs in the prior art.

(20) The gripping members 16, 17 also comprise a gripping surface 25. The gripping surface 25 is located on the outer radial surface 23 of the gripping members 16, 17 and is located on the end portion 24 that may extend beyond the periphery of the plug 1. The gripping surface 25 may comprise grooves and ridges extending radially and in the longitudinal direction. Preferably, grooves and ridges also extend circumferentially.

(21) The gripping member 16, 17 may comprise a nickel-chrome alloy, hi-tensile steel alloy or tungsten carbide and the gripping surface 25 may comprise a tungsten carbide alloy.

(22) The first end assembly 10 also comprises two stops 26. These comprise a portion that protrudes from the second end plate 15 and a portion that extends through a bore 27 in the second end plate 15, extends through a bore 28 in the raised resilient member 12 and engages with bore 29 in the first end plate 11. The stop 26 may be attached to the first end assembly 10 via threads or via a press fit. Thus, the stop 26 also acts to secure the first end assembly 10 together, preventing relative longitudinal and rotational movement of the first end plate 11, the resilient raised member 12 and the second end plate 15.

(23) The stops 26 may pass entirely through the first end assembly 10 and protrude therefrom such that the stops 26 press into the first end 4 of the seal 2. This may at least partially hold the first end assembly 10 relative to the seal 2 (against relative rotation).

(24) The stop 26 thus protrudes from the second end plate 15. The gripping member 16, 17 comprises a channel 30 through which the stop 26 may pass when the gripping member pivots. The channel 30 extends from an opening in the outer radial edge/surface 23 into a central portion of the gripping member 16, 17 and comprises an end portion within the central portion. The pivoting of the gripping member 16, 17 may be limited by contact between the end portion of the channel 30 and the stop 26, as is discussed further below.

(25) The first end assembly 10 is generally cylindrical and is generally concentric with the seal 2. For instance, the first end plate 11, the raised resilient member 12 and the second end plate 15 are concentric with the seal. Further, the first end assembly 10 comprises a threaded bore that may receive the actuator 50. The first end plate 11 comprises a bore 31 that may be threaded so as to cooperate with a threaded portion of the actuator 50. The second end plate 15 comprises a bore 32 that may be threaded so as to cooperate with a threaded portion of the actuator 50. Due to this threaded connection, as the actuator 50 is turned relative to the first end assembly 10, there is longitudinal relative movement between the actuator 50 and the first end assembly 10 as discussed below. The raised resilient member 12 also comprises a central bore 33.

(26) The first end plate 11, the raised resilient member 12 and the second end plate 15 are generally disk-shaped, i.e. cylindrical. They all have substantial equal radii (except for the raised resilient member 12, which is slightly larger), which are substantially equal to the radius of the seal 2.

(27) The first end assembly 10 has a 180 rotational symmetry about its central longitudinal axis. Thus, the two bores 20, 21, 22, 27, 28, 29 are separated by 180 from each other, and the two gripping members 16, 17 are arranged similarly separated by 180 from each other. Between the end 24 of one gripping member 16, 17 and the opposite end 34 of the other gripping member 17, 16 there may be a gap.

(28) The plug 1 also comprises a second end assembly 40 adjacent to and in contact with the second end 5 of the seal 2.

(29) The second end assembly 40 comprises a first end plate 41 in contact with the second end 5 of the seal 2. The first end plate 41 is made from a metal, such as stainless steel. The first end plate 41 comprises a central bore 42 through which the actuator 50 passes. This bore 42 is not threaded to the actuator 50. Thus, the actuator 50 may rotate relative to the first end plate 41 without causing any relative longitudinal motion therebetween.

(30) A washer 43 is provided adjacent to and in contact with the first end plate 41. This washer is preferably made of bronze, such as high tensile bronze (such as AMPCO M4 Bronze or similar), which prevents lugging. The washer 43 comprises a central bore 44 through which the actuator 50 may pass. Again, there is no threaded connection between bore 44 and the actuator 50 so that the actuator 50 may rotate relative to the washer 44 without causing any relative longitudinal motion therebetween. The washer 43 is provided between the first end plate 41 (which is generally held stationary by friction with the seal 2) and the actuator 50 (which rotates), so as to allow the rotation of the actuator 50 relative to the first end plate 41.

(31) The first end plate 41 and the washer 43 are disk shaped (e.g. cylindrical). The first end plate 41 has a radius substantially similar to that of the seal 2. The washer has a radius substantially smaller than the seal 2. The first end plate 41 and the washer 43 are concentric with the seal 2, and the first end assembly 10.

(32) The plug 1 also comprises an actuator 50. Proximate the second end 5 of the seal 2, the actuator 50 comprises a radially extending torque bar 51 and a torque transmitter 52. The torque transmitter 52 is generally cylindrical and hollow with an open end 53 facing away from seal 2 and a generally closed end 54 facing toward the seal 2. The generally closed end 54 comprises a bore 55 through which the elongated actuator member 57 passes. The outer surface of the generally closed end 54 abuts the washer 44.

(33) In the torque transmitter 52 comprises two bore holes 56 extending radially through the walls of the torque transmitter 56 at 180 to each other. These holes 56 accept the torque bar 51. These holes 56 are located near the open end 53.

(34) On the inner side of the generally closed end 54 (i.e. the side of the closed end 54 further from seal 2), there is a socket (not shown) that accepts and cooperates with the bolt head 58, in a manner similar to how a spanner or wrench socket accepts a bolt head.

(35) The actuator 50 also comprises a bolt 57 (the elongated actuator member) that comprises a threaded elongated shaft 59 and a bolt head 58. The bolt 57 may preferably be a standard bolt. The bolt 57 may be comprised of metal, such as stainless steel. Preferably the bolt 57 is a commercially available bolt 57 with threads matching the threads of the bore 71 and the threads of the first end assembly 10. The threads on the bolt 57 may extend along substantially the entirety of the length of the bolt 57, or may only extend over a length in the region of the first end assembly 10 and nut 70.

(36) Thus, when bolt 58 is inserted into the torque transmitter 52, the bolt head 58 engages with the socket, locking the bolt head 58 to the torque transmitter 52 in the rotational direction. The torque bar 51 may then be inserted through the holes 56 such that the torque bar extends radially outward from the torque transmitter 52. The torque bar 51 may be secured by a press-fit to the holes 56. It is these radially extending portions of the torque bar 51 that torque may be applied to by a user/tool.

(37) Due to this simple design, the overall length of the plug 1 may straightforwardly be adjusted to suit a specific situation by replacing the bolt 57 and the seal 2 with another bolt 57 and seal 2 of different length.

(38) In order for the radially extending portions of the torque bar 51 to not extend beyond the diameter of the plug 1 as a whole, the radius of the torque transmitter 52 may be substantially smaller than the radius of the plug 1 (e.g. at least two thirds, or at least one half).

(39) The elongated threaded shaft 59 of the bolt 57 pass through the bore holes 55, 44, 42, 3, 31, 33, 32 and emerges in between the gripping members 16, 17. The bolt 57 is in threaded contact with the first end assembly 10 (via bore hole 31 and/or 32).

(40) At the first end 4 of the seal 2 the actuator 50 also comprises an elongated nut 70 which comprises a threaded bore 71 that connects to the threads on the shaft 59 of the bolt 57 in the vicinity adjacent to the first end assembly 10, preferably in the space in between the two gripping members 16, 17.

(41) The actuator 50 comprises a washer 61 that is placed between the end of bolt 57 and an end bolt 62. The end bolt 62 comprises a threaded portion 63 that threads into internal threads 60 in the bolt. Thus, the end bolt 62 and the bolt 57 clamp the washer 61 in place. Since the washer has a diameter greater than that of the bolt 57, the washer 61 acts as a stop when it contacts the elongated nut 70, so as to prevent the bolt being fully unscrewed from the elongated nut 70 and the first end assembly 10.

(42) The elongated nut 70 is elongated in a direction perpendicular to the longitudinal direction (i.e. in the radial direction). The elongated nut 70 may comprise two elongated end portions 72 that are used to contact the gripping members 16, 17 to actuate the gripping members 16, 17 as is discussed in more detail below.

(43) A tool head 80 may be provided to provide torque to the plug 1. The tool head 80 may comprise a spring 81 and a gripping slot 82 that are used to releasable grip the torque bar 51. The tool head 80 may be connected to a motor or any torque-providing means, such as a manual spanner/wrench. The tool head 80 is cylindrical with a diameter less than or equal to the diameter of the plug (in its relaxed state). The tool head may be generally hollow so that its inner radial surface can cooperate with the outer radial surface of the torque transmitter 52.

(44) Below, the function of the plug 1 is set out.

(45) Regarding FIGS. 2 and 3, the plug 1 is shown in a non-actuated relaxed state. In this state, the plug 1 the entirety of the plug 1 has radius substantially equal to the radius of the non-compressed seal 2, except for the resilient raised portion 12 which has a slightly greater radius so that its blades 13 protrude radially.

(46) The gripping members 16, 17 are thus within the profile of the plug 1, and are held in position by elongated nut 70. The elongated nut 70 is in contact with ends 34 of the gripping members and holds the gripping members 16, 17 against the stops 26. The outer edges of the gripping members 23 follow arc sections of the same circle in this non-actuated state.

(47) In the non-actuated state, the plug 1 may be inserted inside a line 101. The diameter of the line 101 may be slightly larger than that of the plug 1 or seal 2. The insertion of the plug may be carried out via a tool connected to the plug 1 via cooperation between the torque bar 51 and the torque transmitter 52 of the actuator 50 and the spring 81 and hollow tool head 80.

(48) Once in the correct position relative to the line 101, the insertion of the plug can be ceased (see FIG. 6). The tool head 80 provides clockwise torque (clockwise when looking from the tool head 80 toward the plug 1). This provides a clockwise torque to the torque bar 51, which is transmitted the clockwise torque 51 to the torque transmitter, which transmits the torque (via the socket and bolt head 58) the bolt 57.

(49) Due to friction between the bolt 57 and first end assembly 10 (e.g. via threads), this torque may also be transmitted to the first end assembly 10. To ensure that this torque rotates the bolt 57 relative to the first end assembly, the resilient raised portion 12 is provided. The resilient raised portion 12 contacts the inner surface of the line 101 and initially resists rotation of the first end assembly 10 (which may otherwise have been caused by the torque) due to friction between the resilient raised portion 12 and the inner surface of the line 101.

(50) This allows the bolt 57 to turn relative to the first end assembly 10. Due to friction between the threads of the elongated nut 70 and the bolt 57 and between the washer 61 and the elongated nut 70, this causes rotation of the elongated nut relative to the gripping members 16, 17. Thus, the torque may be transferred from the bolt 57 to the elongated nut via friction in the threads and/or via washer 61. This rotation would be anti-clockwise in FIG. 3.

(51) As can be seen from FIGS. 4 and 5, when the elongated nut 70 rotates in this manner, it contacts ends 24 of the gripping members 16, 17 causing them to pivot about elongated member 19. Continued rotation of the elongated nut 70 causes ends 24 of the gripping members 16, 17 to protrude beyond the periphery of the remainder of the plug and causes the gripping surfaces 25 to grip the inside of the line, as can be seen in FIG. 7.

(52) The movement of the gripping members 16, 17 is limited either by the contact between the gripping members 16, 17 and the inside wall of the line 101, or by contact between the other end 34 of the gripping members 16, 17 with the other end 72 of the elongate members.

(53) Once the gripping members 16, 17 reach the limit of their movement, they stop pivoting. This in turn stops the rotation of elongated nut 70. The actuated gripping members 16, 17 grip the inside of the line 101 and inhibit the rotation of the first end assembly.

(54) With continued rotation of the tool 80, the bolt 57 continues to rotate. Since the first end assembly 10 is held, the elongated nut 70 is also held. Thus, the bolt 57 rotates relative to both the first end assembly 10 and the elongated nut 70. Due to the threaded connection of the first end assembly 10 and the bolt 57, this relative rotation draws the first end assembly 10 toward the second end assembly 40, thus compressing the seal 2 and expanding the seal's radius such that it causes the seal to plug the line 101 as can be seen in FIGS. 4, 5 and 8. Also, due to the threaded connection of the elongated nut 70 and the bolt 57, this relative rotation keeps the elongated nut 70 adjacent the first end assembly.

(55) The tool 80 may then be removed and the plug 1 remains inside the line 101 plugging the line 101, as can be seen in FIG. 9.

(56) In order to retrieve the plug 1, essentially the opposite process is done. Thus, the tool 80 is inserted into the line and contacts/grips the torque bar 51. The tool 80 then applies torque in the opposite direction (e.g. anticlockwise). This causes the bolt 57 to move the second end assembly 40 away from the still held first end assembly 10, thus allowing the seal 2 to expand in the longitudinal direction and to shrink in the radial direction so that the seal is broken.

(57) Once the seal has returned to its natural state (or has nearly returned to its natural state), the first end assembly 10 is released from the inner surface of the line 101. This is done by further rotation of bolt 57 anticlockwise. This further rotation (preferably when the washer 61 contacts the elongated nut 72) causes the elongated nut 72 to rotate in the opposite direction to the actuating direction (clockwise in FIGS. 3 and 5). The torque may be transferred from the bolt 57 to the elongated nut via friction in the threads and/or via washer 61.

(58) This rotation causes the ends of elongated nut 72 to push against ends 34 of the gripping members 16, 17, which causes the gripping members to pivot back to the non-actuated position (shown in FIGS. 2 and 3). The gripping members 16, 17 come to rest against respective stops 26, which limit their movement in this direction.

(59) Thus, in this way, the plug 1 is detached from the line 101. The plug 1 is then removed from the line using the tool 80.

(60) Regarding FIGS. 10 and 11, and alternative embodiment of the plug 301 is shown. All details of this plug 301 may be the same as plug 1, except where discussed below.

(61) Thus, shown is the first end assembly 310, comprising a first gripping member 316 and a second gripping member 317. These gripping members 316, 317 are substantially identical to each other. Each gripping member 316, 317 is substantially B-shaped (i.e. comprises two bulges at opposite ends 324, 334) and comprises a means 318 for retaining the gripping member 316, 317 to the remainder of the first end assembly 310. This means may comprise a guide that extends in the direction of sliding, preferably two such guides, preferably along a segment of the circle defined by the periphery of the plug 301. There are preferably two such guides extending parallel with one another, and holding the gripping members 316, 317 inbetween. The gripping member 316, 317 may have edge portion(s) 318 extending parallel with the guides 318, preferably at each end 324, 334 of the gripping member 316, 317. These edge portions 318 may be configured to cooperate with the guides 318 to allow the gripping member 316, 317 to slide relative to and along the guides 318 and to retain the gripping member 316, 317 adjacent the first end assembly 310 (e.g. via a tongue and groove arrangement).

(62) The guide 318 and the gripping member 316, 317 are configured to allow the gripping member 16, 17 to slide along the guide 318.

(63) The guide 318 may be made integral with the second end plate 315 or may be attached thereto. The guide may be stainless steel, preferably high tensile stainless steel.

(64) The B-shaped gripping members 316, 317 are arranged such that (when in the non-gripping state as shown in FIG. 10) the outer radial edges/surfaces 323 of the B-shaped gripping members 316, 317 do not extend beyond the radial outer extent of the plug 301 or first end assembly 310 or second end plate 315. However, when the gripping members 316, 317 slide along the guides 318, the end portions 324, 325 (e.g. the bulge portions of the B-shaped) may extend beyond the outer periphery of the remainder of plug 301. This is explained in more detail below.

(65) The gripping members 316, 317 are also shaped/arranged so that an elongated gripping member-contacting portion 370 can be located in between the gripping members 316, 317 adjacent a radially central location of the first end assembly 310. Again, this is explained in more detail below. The gripping member-contacting portion 370 is part of the actuator 50 and rotates with the remainder of the actuator 50 when the actuator 50 rotates. Thus, the actuator 50 (through the gripping member-contacting portion 370, which is part of the actuator) directly actuates the gripping members 316, 317. There is no intermediate portion actuated by the actuator 50, in a different motion to the actuator 50 (such as linear motion), which in turn actuates the gripping members 316, 317, as occurs in the prior art.

(66) The gripping members 316, 317 also comprise a gripping surface 325. The gripping surface 325 is located on the outer radial surface 323 of the gripping members 316, 317 and is located on the end portions 324 and 325 that may extend beyond the periphery of the plug 301. The gripping surface 325 may comprise grooves and ridges extending radially and in the longitudinal direction. Preferably, grooves and ridges also extend circumferentially.

(67) The gripping member 316, 317 may comprise a nickel-chrome alloy, hi-tensile steel alloy or tungsten carbide and the gripping surface 325 may comprise a tungsten carbide alloy.

(68) The first end assembly 310 also comprises two stops 326. These comprise a portion that protrudes from the second end plate 315. The stop 326 may be fastened to the first end assembly 310, and may function, similarly to how the stop 26 is fastened to the first end assembly 10, and functions.

(69) The rotation of the elongated nut 370 in the second rotation direction may be limited by the stops 26.

(70) Below, the function of the plug 301 is set out.

(71) Regarding FIG. 10, the plug 301 is shown in a non-actuated relaxed state. In this state, the entirety of the plug 301 has a radius substantially equal to the radius of the non-compressed seal, except possible for the resilient raised portion (not shown).

(72) The gripping members 316, 317 are thus within the profile of the plug 301, and are held in position by elongated nut resilient members 340 (e.g. springs) that are attached between the two gripping members 316, 317 thus urging them toward each other and hence toward the centre of the plug 301. The elongated nut 370 is in contact with the gripping members 316, 317 and holds the gripping members 316, 317 in position (against the urging of the resilient members 340) due to stops 326.

(73) Anticlockwise rotation of the bolt 357 (as viewed in FIG. 10 at least), due to friction between the elongated nut 370 and the bolt 357 and washer (not shown), this causes rotation of the elongated nut 357 relative to the gripping members 316, 317. Thus, the torque may be transferred from the bolt 357 to the elongated nut 370 via friction.

(74) As can be seen from FIG. 11, when the elongated nut 370 rotates in this manner, it contacts radial inner edges 341 of the gripping members 316, 317 causing them to slide along guides 318, against the urging of the resilient members 340. Continued rotation of the elongated nut 370 causes ends 324, 325 of the gripping members 316, 317 to protrude beyond the periphery of the remainder of the plug and causes the gripping surfaces 325 to grip the inside of the line.

(75) The movement of the gripping members 316, 317 is limited either by the contact between the gripping members 316, 317 and the inside wall of the line 101, or by extension of the resilient members 340 overcoming the friction force between the nut 370 and the bolt 357.

(76) Once the gripping members 316, 317 reach the limit of their movement, they stop sliding. This in turn stops the rotation of elongated nut 370. The actuated gripping members 316, 317 grip the inside of the line 101 and inhibit the rotation of the first end assembly.

(77) With continued rotation of the bolt 357 relative to the elongated nut 370, the plug 301 may plug the line.

(78) In order to retrieve the plug 301, essentially the opposite process is done. Thus, once the seal has returned to its natural state (or has nearly returned to its natural state), the first end assembly 310 is released from the inner surface of the line 101. This is done by further rotation of bolt 357 (clockwise in FIGS. 10 and 11). This rotation causes the elongated nut 370 to rotate in the opposite direction to the actuating direction (clockwise in FIGS. 10 and 11). The torque may be transferred from the bolt 357 to the elongated nut via friction.

(79) This rotation causes the ends of elongated nut 370 to turn anticlockwise, which in turn allows the resilient members (340) to urge the gripping members 316, 317 toward each other, toward the centre of the plug 301, and hence toward the non-gripping position. The gripping members 316, 317 come to rest when the elongated nut 370 comes to rest against the stops 326, which limit its movement in this direction.