GB2484141A

GB2484141A - Renewal of Drainage Infrastructure

Info

Publication number: GB2484141A
Application number: GB1016543.9A
Authority: GB
Inventors: Andrew Kibblewhite; David Green; Richard Swann
Original assignee: Dyno Rod Ltd
Current assignee: Dyno Rod Ltd
Priority date: 2010-10-01
Filing date: 2010-10-01
Publication date: 2012-04-04
Also published as: GB201016543D0

Abstract

The invention relates to a method of replacing an existing pipe section such as a water trap 10 of an interceptor which connects an opening into or out from a manhole with a replacement pipe 44. The method comprises providing an assembly of a driving tool 42 and a replacement pipe section 44 around the driving tool, the assembly being sufficiently short to fit into a manhole in alignment with its opening. The assembly is aligned with the opening and the assembly is driven into the existing pipe section, until the replacement pipe has reached an intended position. The driving tool is retracted leaving the replacement pipe in place. The water trap is thereby replaced by a straight section of pipe. The tool is preferably a powered unit having a fixed part and a movable part wherein the fixed part is a support 40 which supports the assembly against unwanted movement. The moving part is preferably a piston which projects through the replacement pipe, and has a generally conical bursting head (60, 62, 64, 66 figures 4-7) which allows the piston to break through the legs of the U trap.

Description

I

Renewal of Drainage Infrastructure This invention relates to the renewal of drainage infrastructure. It relates in particular to improvement measures concerning interceptor replacement, within drainage infrastructure.

An interceptor is a pipework section which extends between a manhole and a downstream pipe, which may be a downstream drainage pipe. A correctly functioning interceptor allows waste to flow from the manhole to a downstream pipe, but in such a way that odours and vermin are prevented from passing in the opposite direction, into the manhole.

One type of interceptor commonly used in the United Kingdom is shown, installed, in Figs. 1 and 2. The interceptor is shown as 2 and terminates at upstream and downstream end fittings, 4 and 6 respectively, and is thereby connected as part of a pipe or flow run 8, 8' which is slightly inclined in the downstream direction (from left to right as shown in Fig. 1). The interceptor has an enclosed (full-pipe) section which is generally U-shaped, downwardly installed so as to serve as a water trap 10. In Fig. I the interceptor is shown partially broken away to show the liquid in the trap. The interceptor also has an auxiliary pipe 12 (or rodding access point) providing alternative access into the main flow run through the interceptor. In the type of interceptor shown in Fig. 1 the auxiliary pipe 12 is in the form of a straight limb which is downwardly inclined in the downstream direction, and which has a first end 14 which terminates in a rodding access cap 16, which removably closes a rodding opening, and a second end 18 which connects to the main flow run downstream of the water trap, close to the downstream end fitting 6. The interceptor is built into and beyond (in the downstream direction) the base of a manhole 20.

The manhole is a cuboid well formed by a downstream brick wall 22A, an upstream brick wall 22B, two side brick walls, 22C, 22D, a concrete base and a manhole cover. As best shown in Fig. 2, the base has set into it an open channel 26, with concrete benching 28 each side of it.

The benching comprises benching surfaces 30, 32 which incline downwardly towards the open channel 26, thereby to assist drainage, should liquid-borne wastes (sewage) splash or rise in the manhole. The upstream end of the interceptor likewise has a short region in which it defines an open channel 34, leading to the closed-pipe water trap. This open channel 34 provides the outlet 36 from the manhole. The outlet from the manhole in this specification is part of the normal flow run of wastes through and out of the manhole. It is not to be confused with the rodding opening provided above it, as part of the auxiliary pipe 12. It will be seen that the outlet 36 and the rodding opening into the auxiliary pipe are accessible from the manhole, to permit maintenance and clearance work.

It will also be apparent that the liquid in the water trap 10, and the cap 16 over the rodding opening of the inclined section, should prevent odours and vermin from travelling upstream, into the manhole. However, problems frequently arise with such interceptors, many of which are decades old. They may simply degrade with age. The water traps may become blocked with debris causing back-up of foul water. The cap 16 may be broken or lost, and the auxiliary pipe left open -thereby defeating the purpose of the interceptor. When the water trap is blocked and no cap is present foul water may stand in the manhole, causing damage, and with the auxiliary pipe then functioning in a completely unintended way, as an overflow. Such failure rates are high.

It is a substantial and expensive task to replace an interceptor which cannot be restored by regular measures, such as rodding to remove a blockage. It requires the excavation of the interceptor, by removing material from within the manhole (including from its base, and the downstream wall), and outside, downstream of it). A new interceptor must be installed and the manhole restored, and material removed downstream of the manhole must be reinstated.

It would be desirable to have a better approach to the replacement of existing pipe sections from manholes, which could be used when failures occur or, given the likelihood of numerous failures to come as the drainage infrastructure ages, in a preventative program of replacement.

In accordance with a first aspect of the invention there is provided a method of replacing an existing pipe section which connects an opening into a manhole or from a manhole with a replacement pipe, the method comprising: -providing an assembly of a driving tool and a replacement pipe around the driving tool, the assembly being sufficiently short to fit into a manhole in alignment with its opening -aligning the assembly with the opening -driving the assembly into the existing pipe section, and -when the replacement pipe has reached an intended position, retracting the driving tool leaving the replacement pipe in place.

The word opening in the present invention denotes inlet as well as outlet. It is not unknown, though rare, for there to be an interceptor at the inlet to a manhole. Replacement of such an interceptor is not excluded in the present invention. However the specification will generally refer to an outlet from the manhole since provision of a replacement pipe from the outlet is the more common context of use.

The existing pipe section is preferably an interceptor, having means to prevent odours and vermin from passing into the manhole, from a pipe; generally a downstream drainage pipe.

The downstream drainage pipe could be for taking wastewater (sewage) and/or stormwater to a main, or it could be for delivery to a septic tank.

The existing pipe section may have an upstream end which provides the outlet for wastes from the downstream side of the manhole, a downstream end, and, between its upstream and downstream ends, a water trap formed by U-shaped pipe section which is a downward deviation from the flow run through the manhole and towards the downstream drainage pipe.

The existing pipe section may have an auxiliary pipe communicating with, and leading downwardly into, the general flow run through the manhole and towards the downstream drainage pipe. The auxiliary pipe preferably has a first or distal end which has (or once had) a removable cap, to open a rodding opening and provide access for the clearance rods, with the intention that clearance rods may be inserted into the existing pipe section via the auxiliary pipe, without breaking pipework.

The existing pipe section is typically downstream of the manhole and suitably has the features of the preceding two paragraphs, namely: -an upstream end which provides the outlet for wastes from the manhole, on the downstream side of the manhole, and -a downstream end connected to the downstream drainage pipe; and one or both of: -a water trap between its upstream and downstream ends, and -an auxiliary pipe communicating with, and leading downwardly into, the general flow run of wastes downstream of the U-section, the auxiliary pipe having a distal end which provides a rodding opening. Preferably the auxiliary pipe has (or once had) a removable cap.

In a preferred method the existing pipe section is an interceptor of the type shown in Fig. 1.

Preferably the replacement pipe is generally rigid such that it may be driven into place by the application of a force to its rear end.

Preferably the replacement pipe is not greater than 800 mm long, preferably not greater than 700 mm long, preferably not greater than 600 mm long, preferably not greater than 520 mm long. Preferably the replacement pipe is at least 200 mm long, preferably at least 300 mm long, preferably at least 400 mm long.

The method may comprise driving the replacement pipe until it has travelled the desired distance into the existing pipe section. The replacement pipe may be cut to the required length before it is advanced or its exposed portion may be removed in situ.

The method may comprise driving a first replacement pipe until it is fully within the existing pipe section which is being replaced; then driving a second replacement pipe which engages the rear end of the first pipe and thereby drives it. The driving tool preferably directly drives the first pipe until that is fully home, then directly drives the second pipe, indirectly also driving the first pipe. The second pipe may be cut to the required length before it is advanced or its exposed portion may be removed in situ, after insertion is complete.

Preferably the method replaces the existing pipe section by no more than three replacement pipes; and preferably by one pipe or by two replacement pipes only.

Replacement pipes preferably have means whereby they may be fixed to each other in an end to end arrangement. Preferably a replacement pipe has a male conformation at one end and a female conformation at the other end, so that a plurality of identical pipes can be joined together end to end. In some embodiments one end of a replacement pipe may have an external screw thread and one end of a replacement pipe (preferably the same pipe) may have a conforming internal screw thread, so that two replacement pipes may be screwed together.

Preferably one end of a replacement pipe has an external screw thread and the other end has a conforming internal screw thread. Preferably, therefore, the replacement pipe may be drawn from a supply of identical pipes.

Preferably the driving tool is a powered unit which has a fixed part (cylinder) and a movable part (piston, or ram). The power source is preferably in the immediate location of the manhole.

The operation may be achieved under electrical power or under hydraulic or pneumatic power.

When electrical power is used, gearing (for example a rack and pinion) may convert rotary motion into the required linear motion of the driving tool. When pneumatic or hydraulic power is used a pneumatic or hydraulic power pack may be used. Most preferably hydraulic power is used.

Preferably the method includes providing a support arrangement to support the assembly in such alignment. Preferably the support arrangement supports the assembly (the driving tool and replacement pipe) against unwanted movement. Preferably the support arrangement is provided within the manhole.

Preferably the support arrangement may be adjusted to locate the assembly in position to drive into the outlet from the manhole.

Preferably the support arrangement has provision for both horizontal and vertical adjustment within the manhole, and once the desired operating position has been achieved, for supporting the assembly against unwanted horizontal and vertical movement, whilst permitting advancing and retracting movement.

The support arrangement preferably supports the assembly against unwanted movement by providing load-bearing contact with the upstream and downstream walls of the manhole. In effect the support arrangement may be braced across the manhole, in alignment with the flow direction.

The support arrangement preferably supports the assembly by providing at least one resting point on the base of the manhole. Preferably both are between the upstream wall and the centre line of the manhole.

The support arrangement preferably comprises a brace member engaged between opposite walls of the manhole, preferably between the downstream and upstream walls of the manhole (i.e. having the outlet from the manhole) and the rear wall of the manhole. The assembly is mounted directly or indirectly to the brace member. The brace member preferably has a length-adjustable member to adapt to manholes of different sizes. The length adjustable member is preferably adjustable in length by provision of hydraulic or pneumatic power, or by manual means, for example by use of a turnbuckle.

The support arrangement may bear against the downstream wall of the manhole via a downstream wall plate which spreads the force. This downstream wall plate may be carried as part of the support arrangement. The downstream wall plate is designed so as to not obstruct the operation to replace the existing pipe section. Typically, in use, the downstream wall plate will be located above the outlet; preferably as high as possible above the outlet.

The apparatus used may include an upstream load plate which is to be used between the support arrangement, and the upstream wall of the manhole, to spread the force. This upstream wall plate is preferably not carried as part of the support arrangement, but is used with it. It may be a substantial plate and may have a lifting eye. Preferably the upstream load plate rests on the base of the manhole. The upstream wall plate may suitably have a projecting portion whose distal end is rounded and, in the method of the invention, fits within the open channel of the base of the manhole, and inclined shoulders, to each side of the projecting portion. The shoulders are sufficiently inclined as to not be obtruded by inclined benching at the base of the manhole.

In use the downstream wall plate and the upstream wall plate may have wood between them and the respective -downstream or upstream -wall. This is particularly useful if the wall is uneven.

The support arrangement suitably comprises a column on which the assembly, and the support arrangement, may be carried.

Preferably the support arrangement has means for adjusting the height of the assembly.

Preferably the support arrangement has means for adjusting the height of the support arrangement.

Preferably the support arrangement has means for adjusting the height of the assembly and means for adjusting the height of the support arrangement, the respective means being independent of each other.

Suitably the assembly of the driving tool and the replacement pipe section is cantilevered to the column.

Suitably the column has a lower end portion whose extremity is rounded and, in the method, rests within the open channel of the base of the manhole, without any need to excavate or remove or otherwise damage the open channel.

Preferably the column is generally upright in the manhole, in use, and the assembly is mounted to the column somewhat downwardly, suitably at an angle of approximately 70-90°, preferably 75-85°, and more preferably 77-83°, and most preferably approximately 80°. It is found that such angles are generally suitable in achieving good results. Although provision for the operator to adjust the angle of the assembly to the column may easily be designed into the arrangement this is not considered necessary.

Preferably the assembly is mounted to the column at a desired height by a peg and hole mounting. Suitably holes formed in a fitting at the rear end of the driving tool may be aligned with holes formed in the column, and peg(s) of sufficient length are slid through the respective aligned holes, to effect securement.

The column is preferably a U-section column whose U-opening preferably faces, in the method, the downstream wall of the manhole. It thus has side walls, preferably parallel to each other, and an intermediate or connecting wall. Its side walls suitably have an array of through-holes or eyes, aligned as pairs. Suitably there are enough pairs of though-holes to provide at least 8 locations for pegs, which are provided, and are sufficiently long to pass through a pair of aligned through-holes.

Preferably the rear end of the driving tool has a fitting of shape and size to fit inside or outside the U-opening (preferably inside a downstream-facing U-opening) and the body has enough holes or eyes to provide one, two, or more, locations for the peg(s), sufficiently long to extend from one side of the fitting to the other. The through hole(s) of the fitting are aligned with the selected through hole(s) of the column, thereby to mount the driving tool at the correct height, for alignment with the outlet, using peg(s) passing though respective through holes in the column and the fitting. Although in principle a single peg could be used if the design of the respective parts allowed for little play, use of two pegs is preferred. More than two pegs could be used, if sufficient holes are provided on both parts, but no particular advantage is believed to arise from using more than two pegs.

Preferably there is provided, above the assembly, a slider adjustably mounted on the column.

Suitably the upper part is a U-section column whose U-opening faces the upstream wall of the manhole. It thus has side walls, preferably parallel to each other, and an intermediate or connecting wall. Its side walls suitably have an array of through-holes or eyes. Suitably though-holes to provide at least 1 location for a peg, which is sufficiently long to span both side walls. The upper part may embrace the column or the column may embrace the upper part, but in either case at least one through-hole of each can be aligned, thereby to mount the upper part to the column, at a desired height, using a peg passing though respective through holes in the upper part and the fitting. Although in principle a single peg could be used if the design of the respective parts allowed for little play, holes to permit use of two pegs is preferred. More than two pegs could be used, if sufficient holes are provided on both parts, but no particular advantage is believed to arise in using more than two pegs.

The surface of the upper part which faces the downstream wall of the manhole may have a plate attached to it, so as to define a narrow spacing between the plate, and that surface of the upper part. The plate may have an upwardly open, blind, slot. The support arrangement may carry a plate-like or planar foot at its upstream end. In use the foot may be slid into the narrow spacing between the plate and the upper part and the shaft or body of the support arrangement may pass down the slot to a desired extent, up to a limit position determined by its blind end.

A said upstream load plate may be located between the column and the upstream wall of the manhole. Preferably the upstream load plate and the column both rest in the channel at the base of the manhole. Preferably they abut each other.

It will be appreciated, therefore, that preferred support arrangements defined and described in this specification allow the assembly of the driving tool and replacement pipe to be located at the right position, and with support against unwanted movement from that position, to drive into the outlet from the manhole, in a reliable manner, notwithstanding variations in shapes and sizes of manholes.

Preferably the replacement pipe is located over the piston of the driving tool and the connection between them is sufficiently free that when the piston is retraced the replacement pipe is left in place.

Preferably the piston has at its rear end a seating which is in contact with the rear end of the replacement pipe, and by means of the seating the piston pushes the replacement pipe, and thereby advances it.

1 5 Preferably the front (or distal) end of the piston projects through the pipe and makes the first connection with the existing pipe section.

Preferably the front end of the piston has a bursting head, suitably having a conical or part conical shape. Preferably the bursting head is ribbed. Ribs may suitably be radial or circumferential. Different bursting heads may be provided, each with means for releasable securement to the forward end of the driving tool. Thus there is preferably provision to replace a bursting head by a different bursting head better suited to the conditions.

Preferably the front end of the piston terminates in a spike. This assists in achieving accuracy and it providing a focussed impact force. These characteristics may be useful especially in initial phases of operation. Different spikes may be provided and there is provision to replace a spike by a different spike better suited to the conditions, for example of different material or shape.

In use in the method the support arrangement is installed in a manhole. For ease, the driving tool, with the replacement pipe around it, is preferably attached to the support arrangement once this has been done. The set-up is such that the assembly of the driving tool and replacement pipe is aligned with the outlet, and hence with the existing flow run.

The driving tool is operated and the piston advances, breaking the existing pipe section (probably at each end of a U-section defining a water trap, very likely to be present), and carrying the replacement pipe with it. Once the piston has advanced a sufficient distance to insert the replacement pipe, the piston is withdrawn. If a second replacement pipe, or portion thereof, is needed the second replacement pipe is put onto the driving tool, and secured to the first replacement pipe. The piston is again advanced, thereby to advance the second pipe or portion thereof, and the first replacement pipe is pushed forward as a consequence. When the required length of replacement pipe has been introduced the piston is withdrawn, the equipment is withdrawn from the manhole. If there is an exposed portion of the first replacement pipe, or of the second replacement pipe if used, this can now be cut off. In some embodiments the replacement pipe may have been cut to a desired length before being inserted but since it can be difficult to estimate the length of pipe required it is preferred to cut off the excess length of pipe in situ.

Jointing and restoration are now carried out. This is minor compared with the earlier prior method described above, involving extensive excavation and replacement of the failed interceptor by a new interceptor. At the manhole end the replacement pipe end is readily accessible and simple jointing and, if necessary, cement repair, can be carried out. To deal with the front end of the replacement pipe, and at the junction between replacement pipes when more than one is used, joints may be formed by remote means, or a liner method used, for example using a "sock" or "cylindrical bandage", impregnated with a curable resin, and supported in an extended, open, condition by an inflated "balloon" or "packer". Once the resin has cured sufficiently the "packer" may be deflated and removed, and withdrawn leaving the "sock" or "cylindrical bandage" in place, open at both ends and allowing for flow-though of liquids.

It will be apparent that the replacement pipe, being driven into place, is suitably a straight pipe, and preferably a circularly cylindrical pipe. It will be apparent also that the use of a straight pipe is advantageous in terms of rodding operations to clear any blockages downstream of the manhole; hence the loss of an auxiliary limb of an interceptor is not problematical. Blockages may be less likely to form than in interceptors having a water trap. The water trap was originally designed to isolate the sewers from dwellings, and keep sewer smells and vermin downstream of the manhole, but we have concluded that a water trap is not essential, or even particularly desirable. Sewer smells are not likely to reach a household even without a water trap being present. In terms of vermin, it must be borne in mind that this principle of isolation was already compromised by the absence of the rodding access caps on the auxiliary limb, in many cases, and by the proven ability of rats to negotiate water traps. Water traps frequently give rise to problems. It is the use of a straight pipe, without a water trap, which enables the replacement of defective or aged interceptors in the method of the invention, without substantial excavation.

Suitably a method of the first aspect employs the following steps: -the support arrangement is installed in a manhole, -the assembly of the driving tool with the replacement pipe around it is then attached to the support arrangement, -following positional adjustment if needed the driving tool is in alignment with the opening -the driving tool is operated and the piston advances, breaking the existing pipe section, and carrying the replacement pipe with it, -once the piston has advanced a sufficient distance to fully insert the replacement pipe, the piston is withdrawn leaving the replacement pipe in place, -if a second replacement pipe or portion thereof is needed the second replacement pipe or a portion thereof of suitably reduced length is put onto the driving tool, and the piston is again advanced, such that the second pipe or portion thereof is advanced, and the first replacement pipe is pushed forward as a consequence, -when the required length of replacement pipe has been introduced the piston is withdrawn, the equipment is withdrawn from the manhole and jointing and restoration is carried out.

In accordance with a second aspect of the invention there is provided a kit of parts for use in a method of replacing an existing pipe section which connects to an opening of a manhole, the kit of parts comprising: -a driving tool which is sufficiently short to fit into the manhole in alignment with the opening; -a replacement pipe which is sufficiently short to fit into the manhole in alignment with the opening, wherein the replacement pipe is adapted for fitment around the driving tool such that when the driving tool advances, it advances the replacement pipe but when the driving tool retracts, it does not retract the replacement pipe -a support arrangement to support the driving tool, with the replacement pipe around it, in such alignment in a manhole.

In accordance with a third aspect of the invention there is provided an assembly of parts, in use in replacing an existing pipe section which connects an opening of a manhole to a downstream pipe, the arrangement of parts comprising: -a driving tool which is sufficiently short to fit into the manhole in alignment with the opening; -a replacement pipe which is sufficiently short to fit into the manhole in alignment with the opening, the replacement pipe being fitted around the driving tool, the fitment being such that when the driving tool advances, it advances the replacement pipe but when the driving tool retracts, it does not retract the replacement pipe -a support arrangement which is capable of supporting the driving tool, with the replacement pipe around it, in such alignment in the manhole.

Preferred features of the first aspect of the invention (such features being as defined above, as described below with reference to Figs. 3 to 17, and in the accompanying claim) are preferred aspects of the second and third aspects of the invention.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a side/cross-sectional view of a manhole and of pipework including a known interceptor, as described above; Fig. 2 is cross-sectional view from a mid-line through the manhole of Fig. 1, showing the downstream wall, as described above; Fig. 3 is a perspective view of a driving tool used in the present invention; Figs. 4 to 7 are perspective views of alternative bursting heads for fitment onto the driving tool of Fig. 3; Fig. 8 is a perspective view of a spike for fitment to a bursting head of Figs. 4 to 7; Fig. 9 is a perspective view of a column which is part of a support assembly used in the present invention; Fig. 10 is a perspective view of a slider which is part of a support assembly used in the present invention; Fig. 11 is a perspective view of a brace member which is part of a support assembly used in the present invention; Fig. 12 is a side view of the slider, brace member and driving tool (bearing a replacement pipe) all mounted to the column; Fig. 13 is a view from above of a hydraulic compressor (hydraulic power pack); Fig. 14 is a perspective view of an upstream wall plate used in the present invention; Fig. 15 is a view substantially corresponding to that of Fig. 1, showing the parts of Figs. 3 to 14 in place in a manhole, at the commencement of an interceptor replacement operation; Fig. 16 is a view substantially corresponding to that of Fig. 1, looking down into the manhole; Fig. 17 is a view corresponding to that of Fig. 15 except that the design of interceptor is different.

The apparatus shown in Figs. 3 to 17 is for replacing an interceptor built into the ground at the base of a manhole, on its downstream or outlet side (although it could also be used in replacing an upstream interceptor. One common type of downstream interceptor is shown as 2 in Fig. 1 and the arrangement of manhole and interceptor is as already described, with reference to parts numbered 2 to 36, shown in Figs. I and 2.

Fig. I shows, for illustration purposes, a functioning interceptor. This is often not the case as the clayware degrades over time, or the U-bend becomes blocked. When there is a failure interceptor replacement may be very urgently required. Alternatively replacement may be undertaken as a preventive measure. The present invention allows this to be done without significant excavations at the base of the manhole. The replacement can be effected when there is a problem in the manhole, arising from the failure of the interceptor, or on a preventive basis.

As shown in Fig. 15, in broad terms the apparatus employed is shown fitted in a manhole and includes a support arrangement generally indicated as 40, and a driving tool, generally indicated as 42. The driving tool carries around it a circularly cylindrical replacement pipe 44 of a rigid plastics material. The pipe has an external male thread at one end and a mating internal female thread at the other end. There is a supply of a such replacement pipes. The pipe is 500 mm in length and 85 mm in internal diameter, and the assembly of the driving tool 42 and replacement pipe 44 is supported by the support arrangement 40. The assembly is sufficiently short to fit in the manhole, in alignment with the outlet 36 from the manhole, i.e. the opening into the interceptor. The piston of the driving tool is advanced to break through both limbs of the U-bend 10 and convey the pipe into place, in place of the existing interceptor.

The driving tool shown in Fig. 3 has a cylindrical piston 46 around which a replacement pipe is located, in use. At the very rear end of the driving tool there is provided an end fitting 50 with transverse through-holes 52, 54. These are provided in a block 56, and are the means by which the driving tool is attached to the support arrangement (as will be further described).

The block is somewhat wedge-shaped, tapering in depth in its downward direction (in use).

The block could in some embodiments be removed from the driving tool and replaced by a block with a different wedge angle (or no wedge shape).

Hydraulic connections 57, 58 are provided, also at the rear end of the driving tool.

The rear end of the circularly cylindrical replacement pipe is engaged by a forward facing seating 48 at the rear end of the piston. As the piston advances it pushes the pipe with it.

A bursting head is secured to the front end of the piston. Suitable bursting heads 60, 62, 64, 66 are shown in Figs. 4-7. Each has a generally conical or part-conical frontal region. In Fig. 4 two inclined ribs, defining a part-conical frontal shape, with the head material cut away between the ribs, are shown. In Fig. 5 four inclined ribs, defining a part-conical frontal shape, with the head material cut away between them, are shown. In Fig. 6 a conical arrangement of concentric ridges 72 are shown. In Fig. 7 the frontal end is of plain frusto-conical form 74.

Different bursting heads can be used in different situations but the design of Fig. 6 is often particularly effective.

Each bursting head has in its rear face a central, screw-threaded, blind bore (not shown) by means of which it can be screwed onto a threaded shank 59 at the front end of the driving tool.

Each bursting head has a central, screw-threaded, blind bore 76, into which a frontal impact spike 78, shown in Fig. 8, may be fitted.

The support arrangement will now be described with reference to Figs. 9-13.

The support arrangement comprises a column 80, a slider 82 for mounting to the upper part of the column, and a length-adjustable brace member 84.

The column is a U-section channel 86 having parallel side walls 88, 90, and a connecting wall 92. The lower end of the channel is rounded at 94, so as to fit in the open channel at the base of a manhole. Each side wall has a single row of through-holes respectively 96, 96', 96'.

Each row has eight such through-holes. The through-holes in one side wall 88 are aligned with the through holes in the other side wall 90. Two pegs 100, 102, each provided with a spring clip end stop member 104 may be passed through a respective pair of aligned through-holes, as shown in Fig. 9.

The driving tool is mounted to the column by means of such through-holes and pegs. The two through-holes at the rear end of the driving tool may be aligned with selected through-holes of the column, and the pegs inserted to effect securement. Due to the taper in the fitting at the rear of the driving tool the driving tool is angled approximately 100 down from the horizontal, as can be seen in Figs. 12 and 15.

With reference to Fig. 10, the slider 82 is of channel shape 110 with parallel side walls 112, 114, and a connecting wall 116. Each side wall has a single row of through-holes, respectively 118, 118', 118"..., and 120, 120', 120". Thechannelofthesliderislargerthanthechannelof the column and may embrace it in an opposed-U arrangement, with the side walls 112, 114 of the slider outside the side walls 88, 90 of the channel, and two pegs (not shown, but identical to pegs 100, 102) passed through the respective through-holes, to secure the slider on the column, at a desired height.

The slider has, on its side opposite to the channel 110, a narrow spacing 124. The narrow spacing is formed between the joining wall 116 and a face plate 126. The plate has a face region 128, and at its side edges and at its bottom edge, but not at its top edge, a step 130, by means of which the face region 128 is narrowly spaced from the joining wall 116. The face plate has formed in it a blind slot or cut-out 132, open to the top of the plate 126, arranged generally vertical in use, and having a rounded termination 134. The blind slot is arranged generally vertical in use.

The bracing member 84 has a front load plate 140, intended in use to locate against the downstream wall of the manhole, and carrying a threaded shaft 142. It also has a rear fixing plate 144, carrying a shaft which has a non-threaded region 146 directly adjacent to the fixing plate 144, then a threaded region 148. In use the fixing plate 144 is slid into the narrow spacing 124 of the slider, with the non-threaded region 146 thereby travelling into the blind slot 132. Between the two threaded regions there is a turnbuckle 150. A lever 154 is provided, on the turnbuckle, to assist the user in turning it.

In use the general arrangement is as shown in Fig. 12, with the driving tool cantilever mounted to the lower part of the column, at an angle downwards from the horizontal of about 10°, and the bracing member secured to the slide, which it itself secured to the column. The turnbuckle may be turned in order to adjust the length of the bracing member, to suit the dimensions of the particular manhole.

Fig. 13 shows a hydraulic power pack 160, which is a small-sized unit which can be lifted to a position close to the manhole. Its power source may be its own petrol or diesel engine, or an electrical supply, which can come from the operator's vehicle, or, if available, from a local mains power source.

A separate load plate 164 is shown in Fig. 14. This is intended to spread the load from the column, onto the upstream wall of the manhole. It is a substantial item having a lifting eye 166. To reduce weight it has several large through-openings 167. It has a rounded projecting portion 168 which, in use, fits within the open channel of the base of the manhole. To each side of the projecting portion there are inclined shoulders 170, 172. These are sufficiently inclined as to not be obtruded by inclined benching at the base of the manhole.

In use the column is located in place, with the slider on it, and the brace member extended, to brace between the upstream and downstream walls of the manhole. As can be seen in Fig. 15, wooden batten(s) 180 may be used between the column and the upstream wall. The wood accommodates any unevenness of the upstream wall. It may provide improved grip, and may help to spread the load equally. It may also allow the column to be located clear of any obstruction provided by the inflow pipe into the manhole. The load plate 144 against the downstream of the manhole is shown directly against it but it may also be advantageous to have wood between it and the downstream wall, to accommodate unevenness and/or to improve grip. It will be observed that the brace member is located at an intermediate height of the manhole, above any part of the interceptor, and above the assembly of the driving tool and the replacement pipe.

Once the brace member has been secured at a suitable height, and so as to achieve adequate bracing, the driving tool is lowered into the manhole. Hydraulic lines 184, 186 may already be attached, or may be attached later. The driving tool is mounted to the column using the pegs.

As shown in Fig. 16, interceptor replacement is about to commence with the driving tool mounted to the column with a replacement pipe around it, and aligned with the opening on the interceptor.

In operation the driving tool is operated and the piston advances. The spike 78 breaks the clayware of the upstream limb of the U-bend (if indeed that clayware were already unbroken) and continues, until contact is made with the downstream limb of the U-bend. It is likely that during this operation the circularly cylindrical replacement pipe carried by the driving tool will be fully inserted, but without being long enough on its own to bypass the interceptor.

Accordingly the piston is withdrawn. The replacement pipe stays in place. The driving tool is manoeuvred to allow a second circularly cylindrical replacement pipe of the same type and size as the first replacement pipe to be introduced onto it, and screwed firmly to the first replacement pipe. The assembly of driving tool and second replacement pipe is located in the correct position, and a second phase of piston extension started. The second pipe drives the first pipe further, with its front annular face in contact with the rear annular face of the first pipe, until the required destination is reached. The exposed portion of the second pipe is now cut off, preferably generally level with the outlet from the manhole. Alternatively if it is known with confidence how long the interceptor being replaced is, the second pipe could be cut to the required length and then introduced.

The embodiment which is described thus requires two replacement pipes, with the second one requiring shortening. In other embodiments interceptor replacement requires one replacement pipe, which may require shortening. Again, if it is known with confidence how long the interceptor being replaced is, it could be cut to the required length and then introduced.

Preferably, however, the replacement pipe is cut off in situ, generally level with the outlet from the manhole.

The repair is now completed in conventional manner. At the outlet from the manhole this may mean simple cutting of the pipe and cement repair, with everything being easily accessible.

For less accessible regions a pipe liner is used. This is a "bandage" (or open-ended "sock") impregnated with curable resin, which is inserted inside the replacement pipe(s) with the aid of a partially-inflated balloon. When the correct location is reached the balloon is fully inflated and the resin allowed to cure. The balloon is then deflated and withdrawn, leaving the liner in place, in a shape-stable condition.

The entire operation is straightforward, on average taking not more than one third of the time of a prior "excavation method" which would be required for the installing of a like-for-like interceptor.

The interceptor shown in Figs. I and 15 is thus replaced, not by a new interceptor, but by a pipe. This does not provide what earlier engineers wanted, in that it does not isolate the manhole from the sewers. However it represents a practical recognition that a) many existing interceptors have simply failed, and others will do so in the coming years, b) many existing interceptors have rodding openings which do not have their caps, and which therefore already provide direct communication between sewers and manholes, c) the inventors are aware of no particular detriment arising from the use of a cylindrical pipe, and d) interceptors have to be replaced, by some means or other. In the circumstances outlined above replacing a dysfunctional and/or aged interceptor of complex shape, whose like-for-like replacement would require significant excavation, by a pipe of simple design which can simply be pushed into place, without any excavation being needed, is an excellent solution.

The skilled person will be aware that there are different interceptor designs. The invention is not confined to replacement of the interceptor designs shown in Figs. 1-15. Another design is shown in Fig. 17. This has a simple auxiliary entrance, accessible from within the manhole, upstream of the U-bend. This can be replaced in exactly the same way as the interceptor of Figs. 1-15. The apparatus is shown in place at the commencement of a replacement operation.

Terminology and general comments The word replacement is not intended in this specification to denote like-for-like replacement.

Indeed, it will be apparent from the above that the invention may involve introducing an interceptor of complex design by simple cylindrical pipe.

The word interceptor is defined above. It may be substituted by interceptor trap without change of meaning.

The word manhole may be substituted by access chamber or access pit without change of meaning.

Claims

Claims 1. A method of replacing an existing pipe section which connects an opening into a manhole or from a manhole with a replacement pipe, the method comprising: -providing an assembly of a driving tool and a replacement pipe around the driving tool, the assembly being sufficiently short to fit into a manhole in alignment with its opening -aligning the assembly with the opening -driving the assembly into the existing pipe section, and -when the replacement pipe has reached an intended position, retracting the driving tool leaving the replacement pipe in place.
2. A method as claimed in claim 1, wherein the existing pipe section is downstream of the manhole and has: -an upstream end which provides the outlet for wastes from the manhole, on its downstream side, and -a downstream end connected to the downstream drainage pipe; and one or both of: -a water trap between its upstream and downstream ends, and -an auxiliary pipe communicating with, and leading downwardly into, the general flow run of wastes downstream of the U-section, the auxiliary pipe having a distal end which provides a rodding opening.
3. A method as claimed in claim 1 or 2, wherein the driving tool is a powered unit which has a fixed part and a movable part, wherein the movable part may be both advanced and retracted under the available power.
4. A method as claimed in any preceding claim, wherein the support arrangement permits the assembly of the driving tool and the replacement pipe to be aligned with the outlet from the manhole, and supports the assembly against unwanted horizontal and vertical movement, whilst permitting advancing and retracting movement.
5. A method as claimed in any preceding claim, wherein a support arrangement is provided to support the assembly in such alignment with the outlet.
6. A method as claimed in claim 5, the support arrangement provides load-bearing contact with the upstream and downstream walls of the manhole.
7. A method as claimed in claim 6, wherein the support arrangement comprises a brace member engaged between opposite walls of the manhole, the brace member having a length-adjustable member to adapt to manholes of different sizes.
8. A method as claimed in any preceding claim, wherein the support arrangement comprises a column on which the assembly and the support arrangement may be carried each at a desired height.
9. A method as claimed in claim 8, wherein the column has a lower end portion which is rounded and, in the method, locates within an open channel of the base of the manhole.
10. A method as claimed in claim 8 or 9, wherein the assembly is cantilevered to the column.
11. A method as claimed in claim 10, wherein the column is generally upright in the manhole, in use, and the assembly is mounted to the column somewhat downwardly, suitably at an angle of approximately 70-89°.
12. A method as claimed in any of claims 8 to 11, wherein the assembly is mounted to the column at a desired height by a peg and hole mounting, wherein holes formed in a fitting at the rear end of the driving tool may be aligned with holes formed in the column, and peg(s) of sufficient length slid through the respective aligned holes, to effect securement.
13. A method as claimed in any of claims 8 to 12, wherein an upper part in the form of a slider is adjustably mounted on the column by a peg and hole mounting, wherein holes formed in a fitting at the slider may be aligned with holes formed in the column, and peg(s) of sufficient length slid through the respective aligned holes, to effect securement; wherein the surface of the slider which faces the downstream wall of the manhole has a plate attached to it, so as to define a narrow spacing between the plate and the upper part; and wherein the plate has an upwardly open, blind, slot; wherein the support arrangement carries a plate-like foot at its upstream end, wherein in use the foot is slid into the narrow spacing between the plate, and the upper part and the shaft or body of the support arrangement passes down the slot up to a limit position determined by its blind end, thereby to anchor the support arrangement to the column.
14. A method as claimed in any preceding claim, wherein the replacement pipe is located over a piston of the driving tool and the connection between them is sufficiently free that when the piston is retraced the replacement pipe is left in place.
15. A method as claimed in any preceding claim in which the front end of the piston projects through the replacement pipe and makes the first connection with the existing pipe section.
16. A method as claimed in any of any preceding claim, wherein the front end of the piston has a generally conical or part-conical bursting head.
17. A method as claimed in claim 16, wherein the bursting head is ribbed and terminates in a frontal spike.
18. A method as claimed in any preceding claim, wherein: -the support arrangement is installed in a manhole, -the assembly of the driving tool with the replacement pipe around it is then attached to the support arrangement, -following positional adjustment if needed the driving tool is in alignment with the opening -the driving tool is operated and the piston advances, breaking the existing pipe section, and carrying the replacement pipe with it, -once the piston has advanced a sufficient distance to fully insert the replacement pipe, the piston is withdrawn leaving the replacement pipe in place, -if a second replacement pipe or portion thereof is needed the second replacement pipe or a portion thereof of suitably reduced length is put onto the driving tool, and the piston is again advanced, such that the second pipe or portion thereof is advanced, and the first replacement pipe is pushed forward as a consequence, -when the required length of replacement pipe has been introduced the piston is withdrawn, the equipment is withdrawn from the manhole and jointing and restoration is carried out.
19. A kit of parts for use in a method of replacing an existing pipe section which connects an opening of a manhole to a downstream pipe, the kit of parts comprising: -a driving tool which is sufficiently short to fit into the manhole in alignment with the opening; -a replacement pipe which is sufficiently short to fit into the manhole in alignment with the opening, wherein the replacement pipe is adapted for fitment around the driving tool such that when the driving tool advances, it advances the replacement pipe but when the driving tool retracts, it does not retract the replacement pipe -a support arrangement which is capable of supporting the driving tool, with the replacement pipe around it, in such alignment in a manhole.
20. An assembly of parts, in use in replacing an existing pipe section which connects an opening of a manhole to a downstream pipe, the arrangement of parts comprising: -a driving tool which is sufficiently short to fit into the manhole in alignment with the opening; -a replacement pipe which is sufficiently short to fit into the manhole in alignment with the opening, the replacement pipe being fitted around the driving tool, the fitment being such that when the driving tool advances, it advances the replacement pipe but when the driving tool retracts, it does not retract the replacement pipe -a support arrangement supporting the driving tool, with the replacement pipe around it, in such alignment in the manhole.
21. A method of replacing an existing pipe section, which connects alan opening of a manhole to a downstream drainage pipe, with a replacement pipe, or a kit of parts or assembly of parts for carrying out such a method, the method, kit or assembly being substantially as hereinbefore described with particular reference to Figs. 3 to 17 of the accompanying drawings.