REPAIR CLAMP FOR PIPE LINES

This invention relates to repair clamps used in the repair of damaged, leaking pipelines, for example, but not strictly limited to, pipe lines used to convey water supplies or other utilities to residences.

Over time, pipes in outdoor pipelines become subject to corrosion, excessive ground forces and other external factors in their surrounding environment which can result in holes, cracks and other structural damage through which leakage of contents can occur.

In current practice, repair clamps are provided for application around the outside circumference of a damaged pipe. Typically, when applied, the clamp forms a fully circumferential envelope enclosing the damaged area of pipe. This envelope may be formed either from a rigid body comprising perimeter sealing gaskets, or a flexible, typically metal body such as in stainless steel, mild steel, or a malleable iron like MCI or SGI. These flexible body clamps use a full area contact mat seal to enclose the damaged area of pipe.

The latter type of clamp is now most commonly used and usually in two main construction groups stainless steel /mild steel or a malleable iron. The malleable iron product offers not only a permanent seal but can provide an element of structural support to a damaged area of pipe to assist in maintaining continuity of seal.

In use, the clamps are employed whilst the main supply of fluid to the damaged pipe is still pressurised, this helps to maintain a supply of the conveyed fluid throughout the repair.

A problem with the above repair clamps is that they require a large trench to be dug surrounding the damaged pipe in order to expose the damaged

area and allow freedom of movement for the operator to clean the pipe surface and assemble the clamp. The large excavation required to properly expose the damaged area for repair is costly and time consuming to undertake and can cause traffic and other above ground services some considerable disruption. Additionally, with most pipes running alongside public roadways, there is a continual safety risk to the clamp operator from passing traffic. Clamps of conventional design are typically supplied in 1, 2 or more multiple parts which have to be broken down into their component parts in order to allow them to be assembled to the pipe manually. Installation of such conventional designs of clamp requires a trench of a size sufficient to allow safe manoeuvrability of the operator to prepare the pipe and assemble the clamp with appropriate tooling such as spanners and torque wrenches.

The present invention aims to provide a repair clamp which will substantially overcome the aforementioned problems and allow more convenient fitting of a repair clamp whilst not compromising on structural or sealing integrity.

In accordance with the present invention, there is provided a repair clamp assembly for use in the repair of damaged pipelines, the assembly comprising; a clamp body or housing consisting of multiple, serially connected clamp portions configured, in use, to envelop an outer circumferential surface of a damaged pipe portion, the clamp being defined by first and second ends which can be drawn together across the circumferential surface of the pipe, a gasket for providing a seal between the clamp and a portion of damaged pipe when the clamp is in use, a bridging plate for providing structural support to the clamp and/or gasket and one or more securement means for drawing together the first and second ends of the clamp and securing the clamp assembly in a closed position around the damaged pipe portion, wherein the securement means are configured to remain in an open configuration when the clamp is being

arranged around a damaged pipe portion and to engage when the clamp fully envelops a damaged pipe portion.

The securement means may, optionally, comprise a pair of bolt lugs located on opposing edges of the two ends of the clamp, a bolt configured to sit in the bolt lugs when the two ends are drawn sufficiently close together around a damaged pipe circumference and a fastening nut associated with one end of the bolt for applying load to the bolt when it is engaged with the bolt lugs. A retainer may be associated with a second end of the bolt resisting the bolt from rotating radially outwardly of the clamp so that it is urged radially towards the clamp to ensure its correct location within the bolt lugs during the closure of the clamp. In addition or as an alternative, there may be provided an outwardly inclined surface of the opposing bolt lug which tends to push the fastening nut of the bolt away from the clamp and pipe until the lugs are separated by a distance which is shorter than the bolt. As the distance between the lugs reduces, the bolt can be located in the opposing bolt lug and the nut tightened. The bolt lugs may have associated with them, tangentially extending fingers which, when the clamp is drawn around the pipe, engage against a surface of the opposing bolt lug thereby stopping excessive rotation of the bolt lugs which improves the seating of the nut and bolt head and reduces the stress in the bolt lugs.

The two ends of the clamp may additionally be provided with castellations or similar, interengageable projections extending circumferentially.

Desirably the clamp comprises just two similarly proportioned clamp portions connected via a hinge. The clamp portions may be cast or fabricated. Optionally, an external surface of at least two of the clamp portions is provided with a connector configured for connecting to a tool which can be used to control the fitting of the clamp assembly about a below ground pipe from an above ground location.

Each cast half clamp may be provided with a boss which can be drilled and tapped to provide outlets for the connection of pressure gauges, stopping equipment, service connections, bleeding valves, under-pressure drilling and tapping and the like.

The following describes a gasket which may be used with the clamp of the invention but which equally has application with other clamp designs, including prior art clamp designs.

The gasket is desirably a wrap around gasket having a length no smaller than the outer circumference of the damaged pipe portion around which, in use, it is to be wrapped. Desirably, the length of the gasket is longer than the outer circumference of the damaged pipe such that, when wrapped around the pipe, a first end of the gasket overlaps a second end. The sealing surface of the gasket is preferably provided with a sculpted pattern of ridges. These ridges may run in any one, or a combination of directions, for example but without limitation, the ridges may extend circumferentially, axially, diagonally or radially relative to the pipe portion around which, in use, the gasket is wrapped. The chosen pattern of ridges is desirably designed to provide a barrier to the release of internal pressure in a circumferential or axial direction from the pipe.

In one preferred embodiment, the ridges run predominantly longitudinally along the gasket (i.e. when applied to the pipe, they run circumferentially around the pipe). A number of additional ridges run perpendicularly (or axially with respect to the pipe).

The gasket desirably includes one or more outlet holes located in the gasket body, most desirably near or at the middle of the gasket, coincident with the outlet position in the clamp.

Optionally, an end of the gasket is moulded to have a similar curvature to that of the pipe to which it is to be applied. Desirably, it is the overlapping

first end which is so moulded. On the reverse surface of the gasket, the overlapping first end of the gasket may be provided with a ridged profile which complements that of the second end of the gasket on the sealing surface of the gasket such that, when the gasket is wrapped around the damaged pipe, the two complementary profiled surfaces mate.

Optionally, the reverse surface of the gasket is engineered to be harder than the sealing surface, thereby improving rigidity and preventing unwanted axial extrusion between the clamp and pipe.

Optionally, the bridging plate may be moulded as an integral part of the gasket. In this arrangement, the bridging plate may be shaped to provide extended structural support adjacent the first end of the gasket.

The bridging plate may also be provided as a separate component and optionally secured to the gasket by mechanical means, use of adhesive or other bonding agents. In the latter case, the plate is desirably provided with dimples and holes at locations across its flat surface to allow the rubber to flow through the holes and create a mechanical binding.

If not moulded as an integral part of the gasket, the bridging plate may comprise steel, desirably a stainless steel.

Optionally, additionally there may be provided a second bridging plate of narrower proportions at the hinge location when the clamp is not fully closed, particularly when the clamp is on a pipe of maximum outside diameter.

The bolt lugs may be provided with suitable means to locate either the bolt head or nut to prevent rotation of the bolt head or nut during the tightening process. This may, for example, take the form of a shaped recess in the surface of the bolt lug or raised portions to shroud the nut or bolt head. In a preferred configuration, the nut is captured in the bolt lug

and the spanner is used on the bolt head. This allows a standard socket spanner to be used throughout the entire assembly process. When the socket spanner is used on the nut during the tightening process the bolt thread advances through the nut and eventually attempts to push the socket off the nut. By tightening the bolt head, this problem is eliminated. The bolt and nut assembly may be held in position by a bolt retainer which can either act on the bolt head or the nut. The retainer is configured so as to maintain a perpendicular alignment of the bolt with the bolt lug.

An embodiment of the invention will now be described by way of example with reference to the accompanying figures of which:

Figure 1 shows an embodiment of a novel repair clamp in accordance with the present invention.

Figure 2 shows the embodiment of Figure 1 fitted around a damaged portion of pipe.

Figure 3 shows a fastening arrangement for use in securing the embodiment of Figure 1 around a damaged portion of pipe.

Figure 4 shows a first embodiment of a gasket for use in sealing the embodiment of Figure 1 when installed around a damaged portion of pipe.

Figure 5 shows a second embodiment of a gasket for use in sealing the embodiment of Figure 1 when installed around a damaged portion of pipe.

Figure 6 shows the reverse side of the embodiments of gasket of Figures 4 and 5.

Figure 7 shows an alternative embodiment of a clamp body for use as part of a repair clamp in accordance with the invention

Clamp body

As can be seen from Figures 1 and 2, an embodiment of the repair clamp of the invention comprises a housing composed of two identical cast or fabricated clamp halves 1,2 (though optionally, the clamp can comprise of more than two sections or sections that are configured differently such as one section of plain housing and the other with an outlet boss) each with a hinge 7,8 at one end and a bolt lug arrangement 15,16 at the other. Each cast half clamp is provided with bosses 3, 4 which can be drilled and tapped to provide outlets for the connection of pressure gauges, stopping equipment, service connections, bleeding valves, under-pressure drilling and tapping and the like.

The hinge arrangement 7,8,28 can be a self-cast interlocking system or a standard type hinge 7, 8 complete with a central hinge pin 28.

As can be seen in Figure 3, each bolt lug 15, 16 arrangement includes fingers 12, 13 which provide structural support to the mating clamp half. In addition, the fingers assist in the location of one or more fasteners 14. In addition, the fasteners may be self-locating (not shown) when the two clamp halves are assembled together around the pipe.

To assist in the clamps closure around the pipe, the housing is optionally further provided with an extended arm (not shown) removably attached to one or both sides of each clamp half 1, 2 in close proximity to the hinge I ₁ 8. The arm may extend circumferentially and at least partially around the pipe adjacent the clamp half which opposes the clamp half to which the arm is attached.

At each bolt lug end 15,16 of the clamp halves, the end surface is provided with castellations 20,21 which interlock as the clamp halves are closed around the portion of damaged pipe 30. These interlocking

castellations make the clamp adaptable to different tolerances of pipe. For example, around bottom tolerance pipe the castellations may completely inter engage bringing the clamp half end surfaces into close contact, while for top tolerance pipe the maximum gap between the end surfaces is minimised by the presence of the castellations 20, 21 which extend across the gap. Comparing this with plain-ended clamp halves, with plain-ended clamp halves the gap may be around 40mm across the width of the clamp but with castellated ends the gap is interrupted reducing significantly the effective gap and the stresses on the bridging plates attempting to bridge the gap. This enables the dimensions of the bridging plate to be minimised.

Also at each bolt lug end 15, 16 of the clamp halves there are located tangentially extending fingers 12, 13 which are designed to be in early proximity to the mating bolt lug end so as to provide anti rotational support for each bolt lug. This prevents over-stressing both the bolt lug area and the fasteners.

Furthermore each clamp half is provided with connectors 5, 6 to which a tool may be attached to enable remote application of the clamp about a damaged portion of pipe revealed in a trench.

Gasket

Sealing of the pipe 30 is provided by a mat type gasket 9. In accordance with the present invention, the mat is configured to wrap around the damaged portion of pipe. The gasket 9 may be made up of a single piece or multiple adjoining pieces and has a length which is sufficient to wrap around the entire outside circumference of the damaged pipe portion. The gasket 9 terminates with complimentary ends; free end 11 and fixed end 29. Optionally one or both ends may be tapered or bolt lug ended so as to provide a fully circumferential and consistent contact with the external circumference of the pipe.

The sealing surface 31 of the gasket which contacts with the damaged pipe is sculpted with a pattern of ridges 25, 26, 27 which may run in any one or a combination of directions; for example, but without limitation, the ridges may extend circumferentially, axially, diagonally or radial relative to the damaged pipe portion around which the gasket 9 is wrapped. These ridges 25, 26, 27 provide areas of local high gasket pressures, forming a high-pressure seal on the damaged surface of the pipe 30 which may be heavily pitted.

The ridges 25, 26, 27 of the gasket 9 are desirably positioned such that, in use, the internal pipe pressure is prevented from being released circumferentially or axially.

In a preferred embodiment (Figure 3) the gasket ridges 25 run circumferentially with occasional axial ridges 26 and one or more outlet holes 24 which assist in allowing any medium leaking from the pipe 30 to run circumferentially to the centre of the gasket 9 where outlets can be provided for easing the trapped internal pressure during the tightening of the clamp. With such an arrangement, jets of escaping medium (typically water) can be safely directed.

When applying the clamp to a damaged pipe portion, the gasket 9 is first located within the clamp halves 1, 2 such that a fixed end of the gasket 29 is in the proximity of a clamp half end. The gasket is then laid down and affixed mechanically or adhered within the assembled clamp halves. The length of the gasket is such that the other, free end of the gasket 11 extends around the pipe circumference enabling it to be retained in or under the clamp half end and to abut against or overlap the fixed end 29 of the gasket to ensure continuity of the circumferential seal.

Optionally, the free end 11 of the gasket 9 may be moulded so as to be shaped to the circumferencial radius of the pipe to which it is to be

applied, thereby assisting in its entry within the clamp and preventing misplacement of the gasket in a blind assembly.

In conventional mat gaskets, the free end is tapered to a thin uniform cross section, which has been found to be vulnerable to folding back on itself impairing the achievement of a leak tight seal.

An important improvement provided in the gaskets of the invention serves to stiffen the area 23 adjacent the free end 11 by providing at least a partial increase in thickness and a profile which compliments the surface adjacent the fixed end 29 of the gasket 9 with which this area 23 mates when the gasket is applied around the pipe circumference.

Desirably, the gasket is provided with a higher hardness at its rear surface than on its front (which, in use, is in contact with the pipe). This allows for improved sealing at the damaged pipe surface whilst maintaining some rigidity to prevent unwanted axial extrusion of the gasket from the space between the pipe and the clamp.

Bridging Plate

Adjacent the abutting clamp half ends there is provided a bridging plate 10 which gives structural support to the gasket 9 when the clamp assembly is assembled around a damaged pipe portion 30. The bridging plate may comprise any rigid and strong material, for example steel, more desirably a stainless steel.

The bridging plate is desirably secured to the gasket 9 or either clamp half 1, 2 to avoid its accidental removal during application of the clamp assembly to the damaged pipe portion 30. When secured to the gasket, fixing can be mechanical or through the use of an adhesive or other bonding agent. Optionally, the bridging plate 10 may be moulded as a integral part of the gasket 9.

To assist in maintaining correct position of the gasket during assembly, the gasket at its free end 11 may further be assisted by the bridging plate 10 being shaped to provide extended structural support closer to the gasket end 11.

Fasteners

One or more fasteners are located in the bolt lugs 15, 16 with retaining means (not shown) to maintain, for example, a bolt 14 in an upright position when the clamp half 2 is offered to the pipe, but allow it to swing out of the way when the mating bolt lug 15 of the other clamp half 1 is in close proximity. As the clamp halves 1, 2 are closed around the pipe 30 into final position, the bolt 14 is allowed to swing back to its upright position where it can be located into a location 32 in the mating bolt lug 15.

Operation

The clamp assembly (comprising the clamp halves, bridging plate, gasket and fasteners) can be fitted by hand or remotely, by means of a dedicated tool.

The following describes the mode of assembly about a damaged pipe portion which is equally applicable for remote and manual fitting whether using a single or multi-fastener clamp.

The clamp 1, 2 is first presented to the fitter in a loosely pre-assembled state where the bolt 14 is positioned with its nut 18 in its outermost extended position.

The fastener 14 is then swung away out of location from bolt lug 15 and the clamp halves are separated by opening of the hinge to allow for the

free passage of the clamp halves over the outer circumference of the pipe 30.

The clamp 1, 2 is offered over the pipe 30 and as the clamp advances around the pipe surface the clamp halves 1,2 are closed to envelop the damaged portion of the pipe.

When the clamp is almost completely closed around the pipe 30, the free end 11 of the gasket can be located between the pipe 30 and the oppositely facing clamp half. The gasket continues to tighten around the pipe and to locate into its final position as the clamp halves close together applying pressure to the damaged pipe surface.

As the clamp halves 1, 2 close together, the bridging plate 10 begins to make contact with the castellations 21 on the clamp half 2. At this point, the bolt is being swung away from the clamp by an inclined contact surface 19 of the mating bolt lug 15. When the clamp is fully closed, the bolt 14 swings back to an upright position and locates in the locater 32 on the mating bolt lug 15.

The clamp assembly can now be rotated to allow access to the bolt 14, which can be torqued to a final assembly condition.

As the torque is applied to the bolt 14, the bolt lugs 15, 16 move closer across the circumferential surface of the pipe 30 until the fingers 12, 13 of each bolt lug 15, 16 make contact with the mating bolt lug 15, 16. In this way, the bolt lugs 15, 16 are prevented from rotation and the remaining torque applied to the bolt 14 serves to draw the clamp halves closer into contact with outer circumferential surface of the pipe 30.

The above method can be performed by hand by a fitter deposited in a suitably proportioned trench provided around the damaged pipe 30. For remote fitting, an appropriately designed tool can be connected with the

tool connectors 5, 6 deposited in a smaller trench and operated remotely by a fitter located above ground.

Clamp body (alternative embodiment)

As can be seen from Figure 7, an embodiment of the repair clamp of the invention is broadly similar to that as shown in Figure 1 in that it comprises a housing composed of two identical cast or fabricated clamp halves 71, 72 (though optionally, the clamp can comprise of more than two sections or sections that are configured differently such as one section of plain housing and the other with an outlet boss) connected via hinge 77 and each having a bolt lug arrangement 715, 716 at the other. Each cast half clamp is provided with bosses 73, 74 which can be drilled and tapped to provide outlets for the connection of pressure gauges, stopping equipment, service connections, bleeding valves, under-pressure drilling and tapping and the like.

The hinge arrangement 77 can be a self-cast interlocking system or a standard type hinge 77 complete with a central hinge pin (not shown)

At each bolt lug end 715, 716 of the clamp halves, the end surface is provided with castellations 720, 721 which interlock as the clamp halves are closed around the portion of damaged pipe (not shown). In this embodiment the castellations 720, 721 are longer by comparison to the castellations 20, 21 of the embodiment of Figure 1 and the fingers absent. The castellations 720, 721 in this embodiment serve the dual functions of the castellations and the fingers of the embodiment of Figure 1. Furthermore each clamp half is provided with a connector 75 to which a tool may be attached to enable remote application of the clamp about a damaged portion of pipe revealed in a trench.

Another distinction with the embodiment of Figure 1 is that hinge 77 is disposed radially further away from the circumferential surface of the

clamp body. This arrangement allows the clamp ends to be of a uniform gap axially across the clamp. This provides a smaller gap at the clamp ends and creates some rotation of the clamp ends at the hinge to assist in radially compressing the gasket onto the pipe surface, thereby improving sealing.