Pipes and tubular conduits – With closures and plugs – Laterally insertable
Reexamination Certificate
2002-02-01
2003-12-09
Hook, James (Department: 3752)
Pipes and tubular conduits
With closures and plugs
Laterally insertable
C138S095000, C251S168000
Reexamination Certificate
active
06659133
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates in general to a resettable plug assembly suitable for insertion into a pipeline from a transverse tee connection and through a cut window in the pipeline in order that flow may be stopped and pressure retained by the plug. More particularly, the invention relates to a remotely installable and removable line stopper plug for pipelines.
BACKGROUND OF THE INVENTION
When repairing pipelines, it is often necessary to stop flow in the pipeline and isolate the pressure by inserting a plug into the line from a hot-tapped tee connection. Various line stoppers have been developed and been widely applied, but these conventional line stoppers are generally limited both in their ability to handle high pressures and their reliability.
One means of line stopping is to insert a deflated bladder into the pipeline to one side of a hot-tapped window in the line and then inflate it to a pressure in excess of the ambient pressure. This approach is simple and does not require a fall-size window to be cut in the pipe, but it is limited in the pressure range that it can accommodate by the bursting capacity of the bladder. In order to ensure sealing, the bladder inflation pressure must be in excess of the highest pressure to which it will be exposed. If the pressure on the downstream side of the bladder is sufficiently lower than the inflation pressure, then the bladder will burst. An additional problem is that the bladder is difficult to emplace and to inflate and deflate in a flowing line.
A second means of line stopping is the T.D.W. Product “Shortstopp II”™ plugging system device, in which a disk with a peripheral cup seal is mounted on a lever which has a fulcrum at the outer tee end of the hot tap fitting. The disk is inserted through the bore of the tee and then pivoted into the line downstream of the window in the pipe. Both solid disks and hinged disks are used; the hinged disks have an additional seal between the hinged halves. The hinged disks can be inserted through a window less than the pipeline bore. The primary problem with this disk arrangement is that the seal is wiped across the periphery of the window cut in the pipe, exposing it to a high likelihood of damage from burrs. Plug insertion is prone to shock loads if the line is flowing, and withdrawal against pressure is difficult. Cup seals can also invert and fail to seal in cases where there is high flow.
Another version of a line stopper with a disk plug using a cup seal is the IPSCO “FloStopII”™ pivoting head line stop. This device has a disk with a rotation axis mounted transverse to and to one side of the disk axis and offset from the plane of the disk. The disk rotation axis is also transverse to both the pipeline axis and the insertion tee axis. Offset from the plane of the disk on the opposite side from the pivot axis is a roller with its axis parallel to the disk rotation axis. The disk is depended from an insertion head that is forced through the tee of the hot tap fitting toward the pipeline axis. When the roller of the disk contacts the pipe wall opposite the window cut in the pipe, it is forced because of the offset between the hinge axis and the roller axis to pivot into a position transverse to its axis of insertion and enter the pipeline to the side of the window. This device is more controllable during insertions and removals in flowing conditions, but it still has the problem of the seal sliding over the burrs on the interior of the window opening and the possibility of seal cup inversion.
IPSCO also has a “FloStopII”™ cylindrical rubber plug which is inserted into a hot tap fitting through a full bore size window and bottomed out on the opposed cylindrical pipeline wall opposite the tee. Application of axial compression to the rubber cylinder by a hydraulic cylinder causes it to expand radially so that a seal is made with the pipe bore and the edge of the window. The disadvantages of this device are its low pressure rating and the need for an on-center window cut without major burrs.
IPSCO has a folding head line stop which is inserted into a line similarly to the pivoting head line stop, but is first hydraulically unfolded and then caused to move into the downstream portion of the pipe by shoving downwardly on a four-bar linkage. This mechanism will not slam open during deployment, but its seal still wipes across the pipe bore and it may be difficult in a flowing line to refold the head for retrieval.
IPSCO has two other line stops which require that the line be totally cut oversized on both sides on a transverse axis. These devices both require a sufficient connection to be provided between the cut ends of the pipe by the hot-tap fitting. For the first of these devices, the “Sure-Stop”™, a cylindrical rubber sleeve is axially compressed by conical nuts with opposed threads which are driven by rotation of a shaft coaxial with the rubber sleeve. The axial compression causes the sleeve to pack off against the arcuate cut ends of the pipe. This device is capable of handling only low pressures and is subject to seal cutting on the machined edges of the pipe. The second device, the “HTP Stop”™, uses semicylindrical metal shells which are expanded against the cut ends of the pipe by the same double conical nut method as for the “Sure-Stop”. Metal-to-metal sealing is provided on the upstream side of the cut; evidently elastomeric seals are used on the downstream side. The metal-to-metal seal has high pressure and temperature capability, but the necessary seal interface forces are very high, necessitating a particularly strong hot-tap fitting and very high actuation forces. The metal-to-metal seal may be temperature sensitive and is hard to make reliable. The arcuate cut face of the pipeline must also be sufficiently smooth and regular to permit sealing.
Thus, a need exists for a plug suitable for sealing a bore against high pressures that can easily be installed or removed by robots and remote manipulators.
A further need exists for a passive bi-directional seal having significant preloading contact with the bore, which is not scuffed during its installation.
SUMMARY OF THE INVENTION
This invention contemplates a resettable plug assembly suitable for insertion into a pipeline from a transverse tee connection in order that flow may be stopped and pressure retained by the plug. The stopper plug is inserted in the upstream direction and utilizes a bypass valve to aid installation when there is flow. The seal of the plug is expanded radially to contact the wall of the pipeline for sealing. Once in place the bypass valve is closed to stop the flow in the pipeline.
One aspect of the present invention is a line stopper apparatus comprising: (a) a substantially tubular housing having a pocket in a first side adjacent to a lower end of said housing; (b) a sealing plug assembly, said sealing plug assembly having a main plug movable between an extended position and a retracted position, wherein when said main plug is in said retracted position the main plug is housed within the pocket of the housing; and an elastomeric seal, wherein the elastomeric seal is decompressed during insertion into a bore of a pipeline; (c) means for moving said main plug between the extended position and the retracted position; and (d) means for compressing said elastomeric seal when emplaced in the bore of the pipeline; whereby the seal is sealingly biased against a bore of a pipeline to stop fluid flow past the line stopper apparatus.
Another aspect of the invention is a line stopper for selectably blocking a hot-tapped tubular flow line, said line stopper comprising: (a) a substantially tubular housing having a pocket in a first side adjacent to a lower end of said housing, said pocket located on a housing diameter transverse to a longitudinal axis of the housing; (b) a through bore at an interior end of the pocket aligned with the pocket and penetrating to a second side of the housing opposed to the first side, wherein the through bore has a counterbore on an external end of the throug
Hall Elizabeth R.
Hook James
LandOfFree
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