CA1300525C - Vapour plug for temporarily sealing a pipeline - Google Patents

Abstract

"VAPOUR PLUG FOR TEMPORARILY SEALING A PIPELINE"

ABSTRACT OF THE DISCLOSURE
The vapour plug can be inserted into an open end of a pipeline. It comprises a hydraulic cylinder carrying a vertically disposed, elastic, resilient seal ring. The cylinder may be hydraulically actuated to expand the ring radially to seal the bore of the line. The hydraulic lines to and from the cylinder chamber may be blocked to lock the plug in the expanded mode. A plunger valve, responsive to pipeline pressure, controls a hydraulic fluid passage connecting the ends of the cylinder chamber. When the plunger valve is in the closed mode, it prevents fluid moving between the chamber ends. When the valve is moved by pipeline pressure to the open mode, fluid can move freely between the chamber ends, thereby permitting the ring seal to contract, to unseal the bore. The plug may then be pumped down the line and recovered at a pig trap.

Description

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1 Field of the Invention 2 ~he present invention relates to a vapour plug for 3 temporarily sealing or plugging a pipeline.

When a defect manifests itself in the wall of a 6 natural gas or oil transmission pipeline, it is tAe common 7 practice to cut out a section of pipe, having the defect in 8 it, and to weld in a substitute length of new pipe~
g Before welding can occur, it is necessary to seal off each of the open ends of the pipeline, to prevent 11 migration of hydrocarbon gases into the welding area. In the 12 past, plugging has been accomplished by stuffing a charge of 13 a~ua gel into the open end of the pipeline. After the pipe 14 section substitution has been made and the line has been placed back into service, the fluid being transmitted 16 gradually removes the gel particles without damage to the 17 line equipment.
18 However, the gel plugs can slump and gas may leak 19 through to the weld area. This occurrence has led to some 20 serious accidents. In addition, the gel is viewed as an 21 unwanted contamination if a high quality fluid, such a~ jet 22 fuel, is being shipped.
23 It is therefore desirable to develop a reliable 24 expandable/contractable mechanical vapour plug for 25 temporarily sealing the bore of a pipeline. However, the 26 problem to be solved is how to collapse the expanded plug for 27 removal, once the substitute length of line has been welded 28 into place and one cannot physically get at the plug.

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1 SUNNARY OF T~E INVENTION
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2 A specific form of the vapour plug, that has been 3 developed in accordance with the present invention, combines 4 the following features:
- A cylinder, preferably hydraulic, 7 S provided.
6 The cylinder carries a pair of opposed, 7 axially movable annular wedges. The cylinder 8 is operative, when actuated, to moYe the g wedges together. An elastic resilient vertical seal ring is seated between the 11 wedges. As the wedges come together, the seal 12 ring is expanded radially until it seals 13 against the inner surface of the pipeline 14 wall. The seal ring, wedges and cylinder cooperate to seal the pipeline bore;
16 - The cylinder is associated with first and 17 second hydraulic lines or passages for the 133 supply of actuating fluid to one end of the 19 cylinder chamber and removal of fluid from the other end. These passages each incorporate 21 normally closed ralve means, such as check 22 valves, for locking the fluid in the cham~er, 23 whereby the cylinder piston (which preferably 24 actuates the wedge ~eans) may thereby be locked to fix the seal ring in the e~panded 26 mode;
27 - A third passage is provided which, when Z8 uninterrupted, enables actuating fluid to move o~

1 freely from one end of the cylinder chamber to 2 the other. A ~alYe is provided to control 3 flow through this third passage. This valve 4 is responsive to pressure applied in the pipeline bore, whereby it may open or complete 6 the third passage so that the actuating fluid 7 may move between the cylinder chamber ends, 8 thereby freeing the piston for axial movement.
9 Preferably, the valve comprises a plunger forming a transverse bore and having its outer 11 or exposed end face exposed to the pressure in 12 the pipeline bore. Prior to insertion of the 13 plug in the pipe, the plunger would have been 14 set manually to position its bore out of register ~ith the remainder of the third 16 passage, thereby interrupting the latter. ~ut when line pressure is applied to its outer end 18 face, the plunger may shift inwardly to bri~g 19 its bore into register with the remainder of the third passage, thereby completing and 21 opening the passage for fluid flow;
22 - When the third passage is so opened, the 23 elastic resilient nature of the seal ring 24 causes it to contract and retract the wedge attached to the cylinder piston, so the seal 26 ring may resume ~he initial or collapsed 27 position. The contracted plug may then be 28 pumped down the pipeline in the manner of a 29 pig and recovered and removed at a pig trap.

1 In summary then, the plug is expandable to a 2 sealing condition, it's lockable in the expanded state, and 3 it is self~contracting in response to pressure applied 4 through the pipeline bore.
S Broadly stated, the invention is a vapour plug, 6 adapted to be inserted into the open end of a pipeline and 7 actuated to expand radially to seal the bore of the pipeline, 8 said plug further being adapted to contract in response to g the application of pressure through tAe bore of the pipeline, comprising: a cylinder forming a chamber and having a fluid-11 tight piston positioned to work therein; first passage means 12 for injecting fluid into one end of the chamber and second 13 passage means for removing fluid from the other end of the 14 chamber; means forming a third passage for enabling fluid to move from one end of the cylinder chamber to the other; a 16 valve, in communication with the bore of the pipeline and 7 adapted to control fluid flow through the third passage, said 18 valve ~eing operative to be moved from a closed mode, in 19 which fluid is blocked from moving through the third passage, and an open mode, in which fluid may move through the third 21 passage, thereby freeing the piston for axial movement in the 22 chamber, said valve ~eing adapted to be moved from the closed 23 mode to the open mode in response to the application of 24 pressure in the bore of the pipeline; an elastic resilient seal ring carried by the cylinder piston and extending in a 26 generally vertical plane, said ring being adapted~ when 27 expanded radially, to seal against the inner surface of the 28 pipeline wall; means, connected with the cylinder piston, 29 for radially expanding the seal ring; and normally closed ~3~

1 valve means operative to close the ends of the first and 2 second passage means to lock fluid in the cylinder, whereby 3 the piston may be fixed in the ring-expanded mode, when the 4 valve is in the closed mode; said seal ring being operative, when the valve is in the open mode, to contract, whereby the 6 plug may be pumped down the pipeline.
7 In another broad aspect, the invention involves a 8 method comprising cutting a length of pipe out of a pipeline, g said length having a defect; inserting into each open end of the pipeline a mechanical plug comprising a hydraulic 11 cylinder, said cylinder carrying a vertically disposed, 12 elastic, resilient seal ring and being adapted, when 13 hydraulically actuated to radially expand the seal r.ing into 14 sealing engagement with the ins:ide surface of the pipeline wall, whereby the cylinder and seal ring seal the pipeline 16 bore, said cylinder further comprising means for normally 17 locking the fluid in it so that the seal ring remains 18 expanded, said cylinder further comprising means responsive 19 to pressure applied through the bore of the pipeline and operative to permit the fluid in the cylinder to move freely 21 between the ends of the cylinder chamber, whereby the seal 22 ring may contract; injecting hydraulic fluid into the 23 cylinders to expand them into sealing relation with the 24 pipeline wall; welding a length of new pipe to the open ends of the pipeline to complete the pipeline; pressuri~ing the 26 pipeline bore to contract each seal ring; and pumping the 27 contracted plugs downstream for recovery thereof.

3L3~525 DESCRIPTION OF THE DRAWINGS
2 Figures la to le are schematics illustrating the 3 utilization of the plug in connection with the installation 4 of a substitute len~th of pipe;
Figure 2 is a sectional side view showing the plug 6 in a pipeline at the start of the activating process, with 7 the plunger or valve in the retracted interrupting position;
8 Figure 3 is a sectional side view showin~ the plug g Ln the expanded or set mode with the plunger retracted so 10 that fluid cannot move from one end of the cylinder chamber ll to the other;
12 .Figure 4 is a sectional side view showing the plug 13 in the collapsed or released rnode with the plunger now driven 14 inr in response to pipeline pressure, so that the passage, between the head and rod end sections of the cylinder 16 chamber, is complete and open;
17 Figure 5 is a sectional side view showing part of 18 the plug in enlarged form; and l9 Figures 2a, 3a and 4a are simplified schematics 20 showing the hydraulic circuit of the plug when in the three 21 modes shown in Figures 2, 3 and 4 respectively.

23 The vapour plug 1 of the invention finds particular ~4 application in connection with repairs of a pipeline 2. The 25 repair normally involves removal of a pipe section 3, which 26 has a wall defect, and the subsequent insertion of a 27 replacement pipe section 4.

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1As shown in Figure 1, a pl ug 1 is inserted into 2each open end 5 of the pipeline 2 (after the defectiYe 3section 3 has been removedJ to prevent hydrocarbon ~ases 4leaking into the area where welding is to occur.
5The plug 1 comprises a hydraulic cylinder 6 having 6a fluid-tight piston 7 and rod 8 working in the cyl}nder 7chamber 9~ The body of the cylinder 6 is in three parts and 8consists of a central tube 10, a rod-end cap 11, and a head-gend cap 12. The caps 11, 12 are screw-threaded into the ends 10of the tube 10. An outer tube lOa is concentric with the 11tube 10 and extends between the caps 11, 12.
12A multiplicity of rubber 0-rings 13 (shown in 13black) and polyurethane seals 14 (indicated by "X") are provided as shown, to seal the unit.
15An annular wedge 15 is mounted around and secured 16to the outer end of the head-end cap 12. More particularly, 17the head-end cap 12 forms an annular shoulder 16. The wedge 1815 is counterbored as shown to form a shoulder 17 for locking 19with the cap shoulder 16. An end ring 18 abuts both the end 20surfaces of the wedge 15 and the head-end cap 12 and is 21secured to the wedge 15 by a bolt 19, so that the three parts 22form a solid unit.
23A sleeve 20 is positioned around and is contiguous 24to the inner end of the tube lOa. The sleeve 20 can slide 25along the tube lOa and is connected to the piston rod 8 by a 26sleeve cap 21 and bolts 22. The sleeve cap 21 is affixed to 27the piston rod 8 by washers 23, 24 and nut 2~. In summary 28then, the sleeve 20 is connected with the piston rod 8 for 29lineal movement therewith.

13C~S25 l An axially movable second annular wedge 26 is 2 positioned on the tu~e lOa at the outer end of the sleeve 20.
3 The wedge 26 is bolted to a lug 27 affixed to the sleeve 20.
4 Thus the second wedge 26 is connected with the slee~e 20 and piston rod ~ and is linearly or axially movable with them.
6 The slanted faces 28, 29 of the first and second 7 wedges 15, 26 are opposed, as shown.
8 An elastic resilient seal ring 30 is seated on the 9 slanted faces 28, 29 of the spaced-apart wedges 15, 26.
Lineal movement together of the wedges 15, 26 will cause the ll faces 28, 29 to expand the seal ring 30 outwardly and l2 zadially into abutting sealing relationship with the inner l3 surface 31 of the pipeline 2. When the seal ring 30 is so l4 expanded~ it combines with the stationary wedge 15 and cylinder 6 to seal the bore 32 of the pipeline 2.
16 A plurality of flexible pig rubber rings 33 are l7 secured to the outer surface of the sleeve 20 by welded 18 brackets 34, bolts 35 and nuts 36. WAen the seal ring 30 is l9 in the collapsed or released mode shown in Figure 4, upstream fluid pressure acting against the cylinder 6 and the pig 2l rubber rings 33 will move the plug l along through the 22 pipeline bore 32 to a pig trap (not shown) where the unit may 23 be removed from the line.
24 The cylinder 6 is activated by injection of hydraulic fluid introduced through an inlet ~uick coupling 26 37. Excess fluid is returned through an outlet quick 27 coupling 38. Hoses tnot shownJ connected to a hydraulic pump 28 and reservoir (also not shown) may be attached to the 29 couplings 37, 3~, provided that the pipe line end ~ is open.

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1 A first check valve 39 is connected with the inlet 2 quick coupling 37. This check valve 39 in turn is ~onnected 3 with a first passage 40 formed through the body of the 4 cylinder 6. The passage 40 communicates with the rod end section 41 of the cylinder chamber 9.
6 A second check valve 42 is connected with the 7 outlet quick coupling 38. ~his check valve 42 in turn is 8 connected with a second passage 4~ formed through the body of g the cylinder 6. The second passage 43 communicates with the 10 head end section 44 of the cylinder chamber 9.
11 Thus hydraulic fluid may be pumped into the rod end 12 section 41 of the chamber 9 through the first check valve 39 13 and passage 40 and may be returned from the head end section 4 44 through the passage 43 and second check valve 42. When the hydraulic fluid hoses are disconnected and there is no 16 longer fluid pressure being applied, the check valves 39, 42 17 close and lock in the fluid in the cylinder 6. As a result, 18 the piston 7, rod 8, sleeve 20 and travelling wedge 26 are 19 locked and the seal ring 30 is retained in the expanded mode.
A pair of branch passages 45a, 45b extend toward 21 each other from the first and second passages 40, 43. There 22 is a gap between the ends of the branch passages formed ~y an 23 axial bore 46 extending into the head-end cap 12.
24 A cylindrical plunger or valve 47 is positioned in the axial bore 46. This valve 47 forms a passaye 45c 26 extending through its body. The outer end face 4~ of the 27 valve 47 is exposed to the pipeline hore 32. The valve 47 can 28 be manually pulled to a "closedl' position (shown in Figure 2) 29 wherein the valve passage 45c is out of register with the 1 branch passages 45a, 45~. In this mode, the valve 47 blocks 2 fluid flow betwe~n the head and rod end sections 44, 41 of 3 the cylinder cham~er 9. If pressure is applied through the 4 pipeline bore 32 against the exposed end face 48 of the valve 47, the va~ve will be biased to the ~open~ position (shown in 6 Figure 43, wherein the passages 45a, h, c are in register and 7 fluid may flow freely between the rod and head ends 41, 44 of 8 the cylinder chamber 9.
g In operation, a plug 1 is inserted into each open end 5 of a pipeline 2 after the defective pipe section 3 has 11 been removed. The pig rubber rings 33 center each plug 1 in 12 the pipeline bore 32. The pig rubber rings 33 are reversed 13 beforehand for the left plug 1 (having reference to ~igure 14 1), so that the rings 33 of the two plugs 1 are similarly slanted. The description of operation will now be continued 16 with respect only to the right hand plug shown in Figure 1.
17 With the plug 1 in place, hydraulic fluid supply and return 18 hoses are attached to the quick couplings 37, 38. The fluid 19 passages 40, 43, and 45a, b, c and the rod and head-ends 41, 44 of the chamber 9 will have previously been filled with 21 hydraulic fluid, at time of assembly, with the valre 47 in 22 the open position. The valve 47 will have previously been 23 retracted to the closed position. Hydraulic fluid is now 24 pumped through the first passage 40 to drive the piston 7 to the left or upstream end of the chamber 9. The sleeve 20, 26 being attached to the piston rod 7, is also moved to the 27 left. This brings together the stationary and travelling 28 wedges 15, 26 and radially expands the ring seal 30 into 29 sealing engagement with the inner surface 31 of the pipeline ~3~0525 1 2. The hoses are then uncoupled and the check valYes 39, 42 2 function to lock the cylinder 6 in the set or expanded mode.
3 In this mode, the seal 30, stationary wedge 15 and cylinder 4 6 cooperate to seal the pipeline ~ore 32. With the two plugs 1 in the expanded state, installation and welding of the new 6 section 4 of pipe is carried out. The bore 32 is then 7 pressurized and, for each plug 1, the ralve 47 is shifted to 8 the ope~ position, thereby creating fluid communication 9 between the rod and head end sections 41, 44 of the chamber 9. The elastic seal ring 30 for each plug 1 then contracts, 1l driving the travelling wedge 26, sleeve 20 and piston 7 to 12 the collapsed position. The plugs 1 may then be pumped down 13 the pipeline 2 to a pig trap and removed.
14 The scope of the invention is set fortll in the claims now following.

Claims (4)

1. A vapour plug, adapted to be inserted into the open end of a pipeline and actuated to expand radially to seal the bore of the pipeline, said plug further being adapted to contract in response to the application of pressure through the bore of the pipeline, comprising:
a cylinder forming a chamber and having a fluid-tight piston positioned to work therein;
first passage means for injecting fluid into one end of the chamber and second passage means for removing fluid from the other end of the chamber;
means forming a third passage for enabling fluid to move from one end of the cylinder chamber to the other;
a valve, in communication with the bore of the pipeline and adapted to control fluid low through the third passage, said valve being operative to be moved from a closed mode, in which fluid is blocked from moving through the third passage, and an open mode, in which fluid may move through the third passage, thereby freeing the piston for axial movement in the chamber, said valve being adapted to be moved from the closed mode to the open mode in response to the application of pressure in the bore of the pipeline;
an elastic resilient seal ring carried by the cylinder and extending in a generally vertical plane, said ring being adapted, when expanded radially, to seal against the inner surface of the pipeline wall;

means, connected with the cylinder piston, for radially expanding the seal ring; and normally closed valve means operative to close the ends of the first and second passage means to lock fluid in the cylinder, whereby the piston may be fixed in the ring-expanded mode, when the valve is in the closed mode;
said seal ring being operative, when the valve is in the open mode, to contract, whereby the plug may be pumped down the pipeline.

2. A vapour plug, adapted to be inserted into the open end of a pipeline and actuated to expand radially to seal the bore of the pipeline, said plug further being adapted to contract in response to the application of pressure through the bore of the pipeline, comprising:
a cylinder forming a chamber and having a fluid-tight piston positioned to work therein;
first passage means for injecting fluid into one end of the chamber and second passage means for removing fluid from the other end of the chamber;
means forming a third passage for enabling fluid to move from one end of the cylinder chamber to the other;
a valve, in communication with the bore of the pipeline and adapted to control fluid flow through the third passage, said valve being operative to be moved from a closed mode,in which fluid is blocked from moving through the third passage, and an open mode, in which fluid may move through the third passage, thereby freeing the piston for axial movement in the chamber, said valve being adapted to be moved from the closed mode to the open mode in response to the application of pressure in the bore of the pipeline;
an elastic resilient seal ring carried by the cylinder and extending in a generally vertical plane, said ring being adapted, when expanded radially, to seal against the inner surface of the pipeline wall;
a first annular wedge associated with the cylinder and extending in a generally vertical plane;
an axially movable second annular wedge associated with the cylinder and extending in a generally vertical plane, said second annular wedge being connected with the piston rod and being operable, when moved toward the first annular wedge, to co-act with said latter wedge to radially expand the seal ring;
said seal ring cooperating with one of the wedges and the cylinder to seal the pipeline bore, when expanded;
and check valve means operative to normally close the ends of the first and second passage means to lock fluid in the cylinder whereby the piston may be fixed in the ring-expanded mode, when the valve is in the closed mode;
said seal ring being operative, when the valve is in the open mode, to contract, whereby the plug may be pumped down the pipeline.

3. A vapour plug, adapted to be inserted into the open end of a pipeline and hydraulically actuated to expand radially and seal the bore of the pipeline, said plug further being adapted to contract in response to the application of pressure through the bore of the pipeline, comprising:
a double-acting hydraulic cylinder forming a chamber and adapted to be inserted into the open end of the pipeline, whereby one end of the cylinder is the inner end and the other is the outer end, said cylinder having a piston in its chamber whose rod is at the inner end, said cylinder forming a first passage extending from its outer end and communicating with the rod end of the chamber, said cylinder forming a second passage extending from its outer end and communicating with the head end of the chamber, said cylinder forming a third passage which extends partway from each of the first and second passages toward the other;
the cylinder forming a plunger bore extending from its outer end and intersecting the third passage;
a plunger positioned in the plunger bore and forming a fourth passage extending transversely therethrough, said plunger being shiftable along the bore between closed and open positions whereby the fourth passage when in the open position connects the two ends of the third passage and completes communication between the rod and head ends of the chamber, said plunger being operative to interrupt the third passage when in the closed position, whereby fluid is prevented from moving between the first and second passages;
i a sleeve surrounding the inner end of the cylinder and being connected to the rod;
a first annular wedge carried by the cylinder;
a second annular wedge also carried by the cylinder;

an elastic resilient seal ring carried by the wedges, whereby, when the piston and rod are shifted outwardly, the first wedge moves toward the second wedge and the seal ring is expanded radially into sealing contact with the pipeline, said cylinder, wedges, and seal ring being operative to close off the pipeline bore;
first and second couplings connecting with the cylinder, for introducing hydraulic fluid into the first passage and returning it from the second passage; and normally closed check valve means controlling each of the first and second passages at their outer ends whereby, when the cylinder has been hydraulically actuated and the seal ring expanded, the hydraulic fluid in the assembly is locked in place and the assembly remains expanded, whereby, when pipeline pressure is applied to the outer end of the expanded assembly the plunger will shift from the closed to the open position and allow the fluid pressure to equalize in the head and rod end sections of the chamber so that the seal ring may contract out of sealing relation with the pipeline.

4. A method for repairing a pipeline having a defect in the pipe wall, comprising:
cutting a length of pipe out of the pipeline, said length having the defect;
inserting into each open end of the pipeline a mechanical plug comprising a hydraulic cylinder, said cylinder being adapted when hydraulically actuated to radially expand a vertically disposed, elastic, resilient seal ring into sealing engagement with the inside surface of the pipeline wall, whereby the cylinder and seal ring seal the pipeline bore, said cylinder further comprising means for normally locking the fluid in it so that the seal ring remains expanded, said cylinder further comprising means, responsive to pressure applied through the bore of the pipeline, operative to enable the fluid in the cylinder to move freely between the ends of the cylinder chamber, whereby the seal ring may contract;
injecting hydraulic fluid into the cylinders to expand them into sealing relation with the pipeline wall;
welding a length of new pipe to the open ends of the pipeline to complete the pipeline;
pressurizing the pipeline bore to contract the seal rings; and pumping the contracted plugs downstream for recovery thereof.