Pipes and tubular conduits – With closures and plugs – Laterally insertable
Reexamination Certificate
2002-07-08
2003-07-08
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
With closures and plugs
Laterally insertable
C138S094000, C138S093000, C137S318000
Reexamination Certificate
active
06588455
ABSTRACT:
The present invention relates to a method and apparatus for blocking the bore of a fluid conduit. Particularly, but not exclusively, the invention provides a method and apparatus for temporarily blocking the bore of a pipe such as, for instance, a gas or water mains pipe.
A variety of different methods are known for temporarily stopping flow through an in service pipe to enable maintenance work to be carried out on a particular section of pipe without removing the whole pipe from service. Most are designed to be inserted through one or more holes drilled in the pipe wall using well known drilling apparatus designed for operation under pressure. For instance, within the gas industry inflatable stopping bags are widely used. Such bags are designed to be inserted (in a deflated state) through a hole drilled in the pipe wall and then subsequently inflated to form a sealed blockage in the pipe.
Whilst simple stopping bag devices are suitable for use in relatively low pressure applications, such as in low pressure gas pipes, they are less suitable for higher pressure situations in which the bag might tend to be pushed along the length of the pipe. British patent number 1311017 discloses an apparatus which enables stopping bags to be used in relatively high pressure gas pipes and which has since become well established. Essentially, a mechanical support is inserted into the pipe to support the inflatable bag in position. The mechanical support is an iris structure which is inserted through a hole drilled in the pipe prior to insertion and inflation of the stopping bag. The iris comprises a number of slats (of a length marginally shorter than the bore of the pipe) which are centrally pivoted on a support rod. The slats are initially aligned with one another and with the support member so that the iris mechanism can be inserted through a relatively small hole in the pipe wall. Once in position in the pipe (with the pivot axis of the slats coinciding with the central axis of the pipe bore) the slats are rotated into an open configuration effectively forming a disk extending across the bore of the pipe. Once the iris is opened in position a stopping bag is inserted through a second hole drilled in the pipe and inflated in position adjacent the iris.
Although bagging off systems are widely used in the gas industry this technology has yet to be successfully used in, for instance, the water industry. One reason for this is that the relatively high density and pressure of water within water mains exerts much higher mechanical forces which can push the bag along the pipe and thereby damage the bag. Moreover, tests on the iris structure described above have shown that this is not particularly suitable for use in water mains for a number of reasons. Firstly, to strengthen the known iris structure sufficiently to withstand the increased forces (for instance by thickening the slats) necessarily increases the bulk of the device with a corresponding increase in the size of the hole which must be drilled in the pipe wall for insertion of the iris. This can greatly increase the complexity and cost of the equipment needed both to drill the hole and to seal the hole again when the maintenance work has been completed.
Secondly, whereas the bore of a typical gas main is generally relatively clean, the bore of a water pipe will typically suffer tuberculation in which thick deposits of calcium and iron salts adhere to the wall of the pipe. These deposits can inhibit rotation of the iris slats thereby preventing the iris from fully opening. With the known iris mechanism the various slats are interconnected (a pin of one slat locating in a slot of an adjacent slat) and only one of the slats is positively rotated by the installation apparatus (via a bevel gear arrangement). The iris is designed so that after the first slat is rotated through a given angle, further rotation will cause it to drag the second slat with it. Once the second slat has rotated through a given angle its further rotation will then drag the third slat with it and so on. Thus, if the first slat is prevented from rotating the second and subsequent slats will also be prevented form rotating. Even if it is possible to fully open the iris, the presence of dirt and turberculation may damage or distort the slats thereby preventing them from being rotated into the closed position and removed from the pipe after use. This would then necessitate a section of pipe being replaced entirely.
Thirdly, although British patent number 1311017 suggests that the iris mechanism and subsequent stopping bag may be inserted through a single hole drilled in the pipe, the preferred arrangement (which is the practical arrangement in fact used) is to insert the bag through a separate hole thus requiring two holes to be drilled in the pipe wall. The second hole is needed because the bulk of the iris mechanism, including the bevel gear arrangement required to rotate the iris slats, provides an obstacle to insertion of the stopping bag once the iris is in position and thus to avoid drilling an unacceptably large hole a second hole must be drilled for insertion of the bag.
Systems conventionally used in the water industry (and other industries such as the oil industry) tend to comprise rigid disks, or deformable rubber bungs, which as stoppers are inserted through a hole drilled in the wall of the pipe. A disadvantage of these systems is that in view of the size of the disk/bung etc, the hole required in the pipe must generally be substantially equal to the diameter of the bore of the pipe. Equipment associated with the drilling of such a large hole, inserting the stopper and then closing the aperture once the maintenance operation etc is complete, is relatively heavy and expensive (bearing in mind that the drilling of all these operations must be performed under pressure). In addition, existing systems tend to require valuable equipment to remain permanently installed on the pipe once the maintenance operation is complete.
It is an object of the present invention to obviate or mitigate the disadvantages mentioned above.
According to a first aspect of the present invention there is provided apparatus for blocking the bore of a pipe through which fluid flows, the apparatus comprising at least four elongate shutter members pivotably mounted to an elongate support member for insertion through a pre-drilled aperture in the pipe wall, actuating means for pivoting said shutter members from an insertion configuration in which they are substantially aligned with said support member and a deployed configuration in which they are fanned out across the bore of the pipe to at least partially block said bore, wherein each shutter member is pivoted about a point located towards one end thereof and towards the insertion end of the support member so as in use to lie between the axis of the bore of the pipe and the wall of the pipe opposite the location of said aperture.
Positioning of the pivot point of the shutter members both towards one end thereof and towards the insertion end of the support member (i.e. the end of the support member that is inserted through the aperture in the pipe) provides a number of advantages over the prior art which will be apparent from the following description. In particular, this design enables the construction of apparatus which can withstand the relatively large mechanical force as encountered in pipes in which the fluid is a liquid, such as water, without being particularly bulky thereby minimising the size of the hole required for insertion of the apparatus. In addition, construction of the device in accordance with the present invention leaves the aperture in the pipe substantially unobstructed so that the same aperture may be used for subsequent insertion of an inflatable stopping bag or the like. Apparatus according to the present invention is therefore particularly suited, although not limited, to use in industries such as the water industry in conjunction with essentially conventional stopping bag arrangements for temporarily blocking the flow
Akin Gump Strauss Hauer & Feld & LLP
Brinson Patrick
Glynwed Pipe Systems Ltd.
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