GB2466772A

GB2466772A - Apparatus and method for cleaning the interior of a pipe

Info

Publication number: GB2466772A
Application number: GB0823634A
Authority: GB
Inventors: Kevin James Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-12-30
Filing date: 2008-12-30
Publication date: 2010-07-07
Anticipated expiration: 2028-12-30
Also published as: GB2466772B; GB0823634D0

Abstract

A cleaning assembly for cleaning an internal surface of a pipe, such as a section of water main, has a flexible hose fitted with a cleaning head 3 at one end, the cleaning head 3 having a sealing member or bladder 3 configured or configurable to form a sliding seal across said pipe. Flowing fluid through the hose is used to set up a pressure difference across the sealing member 3 to urge the cleaning head 3 along the pipe section so that the cleaning head 3 can wipe deposited material from the pipes inner face. Methods for the use of the assembly allow cleaning with reduced risk of removed material re-depositing downstream and the water originally in the pipe section may be used for the cleaning process and replaced during or after cleaning.

Description

Apparatus and method for cleaning a main

Field

The present invention relates to methods and apparatus for cleaning the interiors of pipes in fluid distribution networks, especially water distribution networks, known as water mains, used for industrial and domestic water supply. The invention is also of use for cleaning other fluid distribution networks such as gas mains and sewerage systems. More specifically, the invention relates to the cleaning of sections of pipe work without the need to excavate sections of main from buried locations underground.

Background

Water distribution networks comprise pipe work, typically buried beneath the ground. The pipe work is typically interconnected and separable into different sections by shut-off valves, each of these sections may comprise a plurality of hydrants or washouts (defined by purpose or ownership) along its length or at its ends.

The pipes used for water distribution networks may be formed from any suitable material such as iron or polymer and in some cases the pipe interiors may have been internally lined to extend the lifetime of the pipe and to improve the quality of the water that passes through the pipe.

Over time due to corrosion or due to ingress of particulate matter which may form sediments or coatings on the inside of the pipe work, it may become necessary to clean the pipe's interiors. Known methods have associated disadvantages. If a section of pipe is removed from the water distribution network for it to be cleaned, excavation of sections of the pipe from the ground may be required, taking the water main out of service for a long period of time with subsequent loss of supply to the customers and possible disruption to transport networks (depending on the location of the buried pipe section, which may be under a road or pavement). Such excavations may also result in the loss of large volumes of water to waste, which in turn leads to potential environmental problems. Costly treatment of waste arising from the cleaning process may be needed before the waste may be discharged to rivers and/or land drains or transported to a treatment site.

Another known cleaning method involves the injection of air into the main which then has to be removed by venting in order to prevent discolouration of the water supply. This method also gives the risk of secondary bursts if the air is compressed and subsequently tries to escape through joints and seals. This method also involves the loss of large volumes of water.

Another method involves spraying large quantities of water into the pipe at a high pressure so as to "jet wash" deposits of material from the inner surface of the pipe. This is a costly and troublesome exercise because of the volumes of water involved and the need to provide appropriate drainage and/or recycling for the water used. One method for dealing with the waste-water is to recycle it using a return hose provided outside the pipe being cleaned, which collects the waste water downstream and carries it back upstream for reuse in the cleaning process.

This presents problems in that a route must be found through which the return hose may pass; this is not always possible. In particular, when the pipe being cleaned is buried underground the return hose must travel above ground, disrupting the area under which the pipe to be cleaned is buried.

Another cleaning method involves placing a tethered ball inside the pipe so that the ball travels down the pipe and dislodges deposited material. A problem of this approach, however, is that the ball does not always dislodge all of the deposits and the material dislodged may remain in the pipe leading to risk of re-deposition of the material downstream of the cleaned region.

Hence, there is a need for a method for cleaning the interiors of water main pipes, which overcomes some, or all of the disadvantages of the prior art. It is a first object of the invention, amongst others, to provide such a cleaning method, which provides good cleaning of pipe interiors without the need for excavation of pipe sections and preferably without requiring excessive waste of water.

It is an object of the present invention to provide methods and apparatus which obviate or mitigate at least some of the problems outlined above.

Summary

A first aspect of the invention provides a cleaning assembly for cleaning an internal surface of a pipe, the cleaning assembly comprising a flexible hose having a proximal end adapted for connection to a pump and a distal end having a fluid port, wherein a cleaning head is provided towards the distal end of the hose, the cleaning head comprising a sealing member configured or configurable to form a sliding seal across said pipe whereby the sealing member may support a pressure difference between distal and proximal faces of the sealing member.

A second aspect of the invention provides an attachment configured to form the sealing member of the cleaning assembly of the first aspect of the invention, wherein the attachment is constructed and arranged to be fixed towards said distal end of said hose.

A third aspect of the invention provides a method for cleaning an internal surface of a section of pipe comprising: i) closing proximal and distal ends of the section of pipe to substantially prevent flow through the section of pipe, ii) inserting the distal end the flexible hose and the cleaning head of a cleaning assemb'y according to any one of claims I to 10 into the section of pipe through an inlet valve of the pipe at its proximal end, iii) attaching a fluid pumping means to the proximal end of the flexible hose, iv) providing a pressure difference between the distal and proximal faces of the sealing member by pumping a fluid through the hose and fluid port such that the pressure on the distal face is lower than the pressure on the proximal face and such that a sliding seal is formed between the sealing member and the internal surface of the pipe, v) drawing the cleaning head from the proximal end towards the distal end of the section of pipe by means of the pressure difference whereby the wiping means wipes the internal surface of the pipe.

Although the invention is described below in the context of a water main, the invention is not limited to use with water mains and may be used for cleaning any

suitable pipe-work.

The flexible hose will be a hose of smaller diameter than the pipe to be cleaned, usually of much smaller diameter such as less than % the diameter or even less than 115th Typically hoses for use with the invention may be commercially available flexible hoses of elastomeric material such as rubber or PVC, usually reinforced to prevent collapse when the external pressure exceeds the internal pressure.

The fluid port of the hose at its distal end may be used for passing fluid out of the hose or for drawing fluid into the hose, and the term "outlet" or nIet" is not to be considered as limiting in the context of this specification.

The cleaning head is situated towards the distal end of the hose, preferably as close as possible to the distal end of the hose without interfering with the port, such that as much of the pipe section as possible can be cleaned by the cleaning head. Typically, the hose will only extend a few centimetres, such as 10 cm or less past the cleaning head.

The sealing member is configured or configurable to form a sliding seal against the internal surface of the pipe. By a sliding seal is meant a seal that fully extends across the cross section of the pipe such that a substantial flow of fluid between the distal and proximal sides of the seal is not permitted and such that a pressure difference can be established between the distal and proximal faces of the seal, whereby a force may be applied to urge the seal along the pipe slidably (whilst substantially maintaining the seal against leakage of fluid across the seal). For instance the seal could be in the form of a flexible washer (e.g. of rubber or leather) having a fluid-tight connection to the outer surface of the hose and configured to fit the internal cross-section of the pipe.

In forming the sliding seal, the sealing member will wipe the internal surface of a pipe section to be cleaned, thus effecting cleaning by wiping deposited material from an internal surface of the pipe. The cleaning head of the assembly may comprise a further wiping means configured or configurable to wipe the internal surface of the pipe, or the sealing means may act solely as the wiping means.

Preferably, the sealing member is deformable between first and second configurations such that in the first configuration the sealing member has a cross section insufficient to form said sliding seal and in the second configuration it has a cross section sufficient to form said sliding seal. This allows the distal end of the cleaning assembly to be inserted easily into the pipe to be cleaned.

Preferably, the sealing member is maintainable in the second configuration, in use, by means of a pressure difference applied across the seal, typically established by pumping fluid into or out of the port at the distal end of the hose.

The sealing member wifl typically have two second configurations in which t has a cross section sufficient to form a sliding seal when it is maintainable in the second configuration by means of a pressure difference applied across the seal -one of the second configurations will arise when the distal side of the sealing means is at a lower pressure than the proximal side, and the other second configuration (i.e. a third configuration) may arise when the distal side of the sealing means s at a higher pressure than the proximal side.

The sealing member may comprise a flexible wall enclosing a volume of fluid to form a bladder. An outer surface of the hose may, for instance, be used to form a wall of the bladder. For instance, the second aspect of the invention may be an attachment adapted to be attached to a distal end of a hose to form a bladder.

Such an attachment may comprise a tube of flexible material extending between distal and proximal openings, wherein the openings are configured to be sealable against the outer surface of said hose, whereby the tube and said outer surface of said hose may be configured to form a bladder enclosing a volume of fluid.

Suitably, the volume of fluid is such that the bladder has a flaccid state providing the first configuration of the sealing member having a cross section insufficient to form said sliding seal and a turgid state providing the second configurations of the sealing member having a cross section sufficient to form said sliding seal.

Typically, for any particular pipe to be cleaned, the bladder, in its flaccid state, whilst enclosing the volume of fluid, will have a cross sectional area less than that of the pipe to be cleaned, preferably only marginally less, such that the bladder, when in its flaccid state, allows the cleaning head to be easily inserted into the section of pipe, but such that initiating a flow of fluid through the hose can result in a pressure difference across the proximal and distal faces of the bladder, providing a sliding seal against the internal surface of the pipe.

The fluid enclosed by the bladder is preferably a liquid, more preferably the same liquid that the pipe usually carries, such that any leakage of liquid from the bladder does not lead to undue contamination. Also, the use of the same liquid prevents buoyancy arising from density differences causing the bladder to float in the liquid in the pipe. Usually, the cleaning method of the invention will be put into effect with the section of pipe still substantially filled with liquid, typically the liquid as normally carried by the pipe (when the pipe is intended for conveying liquids).

When the sealing member is a bladder, different sizes of bladder may be used configured for use with pipes having different internal diameters. The bladder may be provided with instructions concerning the volume of liquid to be enclosed, or may be designed to have sufficient firmness to hold the correct amount of liquid when filled under ambient pressure.

As explained above, the sealing member may form all or at least part of the wiping means at the sliding seal formed with the pipes internal surface.

Preferably, the sealing member, when acting also as a wiping means, comprises an abrasive means arranged to abrasively clean said internal surface. Any further wiping means also preferably comprises an abrasive means arranged to abrasively clean said internal surface.

For instance, the sealing member may be provided with a roughened or ribbed outer surface where the sliding seal is to be formed such that the surface forming the sliding seal may abrade deposits on the inner surface of the pipe to assist with the cleaning process. In other words, the abrasive means may be an outer surface of the sealing member configured or configurable to form said sliding seal.

When the fluid port is used for drawing fluid out from a section of pipe, there is a risk that the port may become attached to an inner surface of the pipe, particularly to the valve face terminating the section of pipe at its distal end, through suction. To prevent this, the fluid port is preferably configured to maintain a fluid flow into or out of the hose when the distal end of the hose is contacted against a shut off valve in said pipe. For instance, the port may be covered by a structure, such as a cap with laterally placed apertures so that flow is normal to the long axis of the hose; this allows flow of liquid when the port is pressed towards a surface. Other suitable configurations can be envisaged, such as the use of a grid or mesh partially covering the fluid port.

The second aspect of the invention provides an attachment configured to form the sealing member of the cleaning assembly of the invention. The attachment is constructed and arranged to be fixed towards said distal end of a hose, allowing a conventional hose to be configured for use as the sealing member of the invention.

The attachment of the second aspect of the invention may comprise a tube of flexible material extending between distal and proximal openings, wherein the openings are configured to be sealable against said outer surface of said hose, whereby the tube and said outer surface of said hose may be configured to form a bladder enclosing a volume of fluid.

The preferred features detailed above for the sealing member of the cleaning assembly of the first aspect of the invention are also applicable to the attachment of the second aspect of the invention. For instance, the attachment, as well as acting as a sealing member, may form at least part of the wiping means at the sliding seal. Preferably, the sealing member, also acting as a wiping means, comprises an abrasive means arranged to abrasively clean said internal surface as well as forming a sliding seal at said inner surface.

A third aspect of the invention provides a method for cleaning an internal surface of a section of pipe using the cleaning assembly of the first aspect of the invention.

The method requires (i) closing proximal and distal ends of the section of pipe to substantially prevent flow through the section of pipe. This is typically achieved by use of mains closure valves normally placed in-line in mains systems.

Next, (ii) the distal end the flexible hose and the cleaning head of a cleaning assembly according to the first aspect of the invention is inserted into the section of pipe through an inlet valve of the pipe at the proximal end of the section of pipe. This may be achieved by use of a gate valve. Again, these are typically fitted to mains at suitable junctions or may be fitted as needed.

Next, (iii) a fluid pumping means is attached to the proximal end of the flexible hose. This may be a pump for drawing fluid out through the hose or for pumping fluid into the hose, or, for instance, a high pressure hydrant (such as a fire hydrant) may be connected to the hose to pump fluid into the hose).

(iv) A pressure difference between the distal and proximal faces of the sealing member in the pipe section is provided by pumping a fluid through the hose and fluid port such that the pressure on the distal face is lower than the pressure on the proximal face and such that a sliding seal is formed between the sealing member and the internal surface of the pipe. Typically, the fluid will be water and the section of pipe will be filled with the fluid (typically water) as the method of the invention is carried out.

The cleaning head is then (v) drawn from the proximal end towards the distal end of the section of pipe by means of the pressure difference whereby the wiping means wipes the internal surface of the pipe.

The method of the invention may further comprise; (vi) withdrawing the cleaning head to the proximal end of the section of pipe after step (v) and then repeating step (v), This can be repeated as necessary in order to ensure good cleaning of the section of pipe.

In step (v), as the cleaning head is drawn towards the distal end of the section of pipe by the pressure difference, fluid is drawn from the section of pipe and when the fluid is a liquid, the liquid will contain the material cleaned from the inner surface of the pipe. This liquid can be monitored to see whether further repetition of the method is needed to clean the section of pipe.

Liquid drawn from the pipe may be filtered and returned into the inlet valve of the pipe section, filling or partially filling the pipe behind the sealing member as it is drawn a'ong the section of pipe towards the distal end. This may serve to provide lubrication for the sliding seal and may also provide buoyant support for the hose within the pipe. Feeding the filtered liquid back into the pipe during this step removes the need for a storage cistern or tanker to hold the water removed from the pipe by the pumping means during step (v).

During step (vi) a pressure difference between the distal and proximal faces of the sealing member may provided by pumping a fluid through the hose and fluid port such that the pressure on the distal face of the sealing member is higher than the pressure on the proximal face of the sealing member and such that a sliding seal is formed between the sealing member and the internal surface of the pipe, whereby the pressure difference urges the cleaning head towards the proximal end of the section of pipe.

In this case, the section of pipe will be refilled with fluid. This may be fresh fluid, or, preferably, in order to prevent wastage when the fluid is a liquid, the liquid withdrawn during step (v) may be cleaned and recycled for use in step (vi). For instance, if the liquid has been returned to the pipe behind the sealing member as the sealing member progressed to the distal end of the section of pipe, then liquid for use in step (v) may be withdrawn from the proximal end of the pipe by the pumping means (e.g. using a feed hose for the pumping means inserted into the inlet valve of the pipe. Preferably, fluid extracted from the section of pipe in step (v) is cleaned and recycled for refilling the section of pipe during or after cleaning. Once again, this reduces wastage of liquid and minimises the need for any additional liquid storage container or tanker.

The method is particularly useful when the pipe is a water main as it allows for cleaning of sections of main with minimal disruption to over-ground traffic and with minimal water wastage. As water may be used for cleaning, and as the section of pipe may be refilled with clean water at the end of the cleaning method by step (vi) it also leads to minimal contamination and low risk of removed deposited material being re-deposited downstream. The removed material is suitably extracted from the water and transported to landfill or otherwise disposed of.

As explained above, the method is preferably carried out whilst the pipe is substantially filled with the fluid, preferably water.

Brief Description of the Drawings

Embodiments of the present invention are now described by way of example only with reference to the figures, in which: Figure 1 shows a schematic cross-sectional side view through a pipe holding a cleaning assembly according to a first embodiment of the invention. The sealing member 3 of the cleaning assembly is in a flaccid state; Figure 2 shows an enlarged view of figure 1 showing more detail of the distal end of the cleaning assembly; Figure 3 is a schematic cross-sectional view through Figure 2 on the line X-X; Figure 4 shows a schematic cross-sectional side view through a pipe holding a cleaning assembly according to a first embodiment of the invention. The sealing member 3 of the cleaning assembly is in a first turgid state as liquid is drawn out through the hose 2; Figure 5 shows an enlarged view of figure 4 showing more detail of the distal end of the cleaning assembly; Figure 6 is a schematic cross-sectional view through Figure 5 on the line X-X; Figure 7 shows a schematic cross-sectional side view through a pipe holding a cleaning assembly according to a first embodiment of the invention. The sealing member 3 of the cleaning assembly is in a second turgid state as liquid is forced into the pipe section through the hose 2; Figure 8 shows an enlarged view of figure 7 showing more detail of the distal end of the cleaning assembly; Figure 9 is a schematic cross-sectional view through Figure 8 on the line X-X;

Detailed Description

Turning to figure 1, a section of underground water main I has been isolated from the rest of the water main network by shut off valves 6,13 at its distal and proximal ends respectively. The sealing member is in the form of a bladder 3 enclosing a liquid 7 (water) attached to hose 2 by clips 8,9 at openings 16,17 and forms the cleaning assembly of the first embodiment of the invention. The outer surface of the hose 2 forms part of the inner wall of the bladder 3.

The volume of liquid 7 is such that the bladder 3 is in a flaccid state when no pressure difference is present across distal and proximal faces of the bladder 3.

The outer surface 14 of the bladder 3 is ribbed to improve its abrasivity.

The distal end of the hose 2 holding the bladder sealing member 3 in its flaccid state has been inserted into the pipe section 1 through an open gate valve (not shown) at a hydrant 12 at the proximal end of the pipe section 1. The pipe I remains filled with water 4 and material 5 is deposited on the inner surface of the pipe 1.

In order to fit the bladder 3 to the hose 2 prior to insertion of the resulting cleaning assembly into the section of pipe 1, the bladder 3 is initially in an inverted configuration, inside-out, and the opening 16 is offered up to the distal end 10 of the hose 2 and slid onto the hose 2 past the fluid port I land then fastened to the hose 2 outer wall using a jubilee clip 8 to form a fluid-tight seal.

The attached bladder 3 is then inverted over the hose 2 through the other opening 17, whilst held under water, such that the required volume of water 7 is enclosed within the bladder 3. The opening 17 is then sealed to the hose 2 by means of a second jubilee clip 9.

Turning to figures 4 to 6, the embodiment is shown in use for cleaning the section of pipe. The proximal end of the hose 2 is connected to a pump (not shown) and water is drawn through the hose 2 from the distal end 4 of the pipe 1 through the fluid port 11 (acting as a fluid inlet port). This is driven by the pressure at A and B being lower than the pressure at C, and this pressure difference leads to the bladder 3 deforming to a turgid state forming a sliding seal against the inner surface of the pipe 1 at location D. Without wishing to be bound by theory, it is thought that this phenomenon arises because the force arising from the pressure difference across the bladder is partially balanced by the wall tension in the flexible walls of the turgid bladder 3. A residual force will exist because of the pressure difference between B and C, and this force will urge the sliding seal at D along the pipe 1 towards the distal end 6, pulling the cleaning assembly with it.

The movement may be controlled by an operator paying out the hose 2 in a controlled manner to limit the rate of progress of the sealing member 3 along the pipe 1. As the sliding seal D progresses along the pipe I the ribbed outer surface 14 of the bladder 3 scrapes material 5 from the inner surface of the pipe 1. Water is taken up through the hose from the distal side of the sealing member 3 through the fluid port 11 carrying released material. The proximal side 15 of the sealing member 3, may left relatively free of water (save for any water that might already be present on the proximal side in the pipe before the pumping commences, and any water which may leak past the sliding seal as the pressure difference is established and as the seal slides along the pipe 1. Alternatively, the water, containing displaced material, may be filtered to remove the material ready for disposal and the cleaned water returned to the pipe I through the hydrant 12, refilling the pipe with water behind the sealing member 3 as it progresses along the pipe 1 towards the distal end 6.

Pumping continues until the end of the hose 10 reaches the distal end of the pipe section at the shut-off va've 6. The configuration of the end of the hose 10 relative to the fluid port 11 means that the port will not attach to the face of the shut-off valve 6 by suction.

The hose and cleaning assembly could be simply recovered by turning off the pump and filling the pipe with water such that the bladder 3 returns to its flaccid state as the pressure difference across its distal and proximal faces is lost. An operator can then simply pull the cleaning assembly from the cleaned section of pipe.

However, a preferred method is shown in Figures 7 to 9. A pump or high-pressure water line is attached to the proximal end of the hose 2 and clean water pushed out through the hose and fluid port 11 (acting as a fluid outlet port) into the distal end 4 of the pipe section 1. This leads to a pressure difference between distal B and proximal C sides of the bladder 3 forcing it to adopt a second turgid configuration giving a sliding seal 0 against the inner face of the pipe 1.

The resulting force urges the sealing member 3 back towards the proximal end of the pipe section 1 whilst refilling the distal part 4 with clean or cleaned water (which may be recycled from the first cleaning operation). This avoids the need for an operator to pull the cleaning assembly along the pipe section. Once at the proximal end of the pipe section, the distal end of the cleaning assembly can be removed by allowing it to adopt a flaccid state by allowing the pressures on either side of the sealing member bladder 3 to equalise. Alternatively, the cleaning process as shown in figures 4 to 6 may be repeated by changing the flow direction in the hose 2 so that water is pulled out of the pipe section 1 through the hose 2.

The cleaning assembly may be passed to and fro along the pipe section as many times as needed to give adequate cleaning, by means of the methods detailed above, prior to its removal through the hydrant 12. After removal of the cleaning assembly, the pipe section is left filled with clean water, and the hydrant 12 closed prior to opening the shut-off valves 6,13 to reconnect the cleaned section to the remainder of the main. The removed material, filtered from the recycled water, is transported for disposal elsewhere.

Although the above embodiment relates to the cleaning of a water mains pipe, it will be appreciated that the invention may readily be applied to any fluid conduit including drainage and waste systems. Although the pipe of the above embodiment is circular, it will be appreciated that the invention is readily applicable to pipes and fluid conduits of other shapes. It will be appreciated that the present invention may be used to clean other conduits, such as gas conduits, or indeed any suitable bore provided that the conduit or bore is filled with fluid, preferably liquid, such as water, prior to the commencement of the cleaning process.

In addition to the advantages already mentioned hereinbefore, the invention may also provide the following benefits: The use of a conformable seal such as a bladder allows small variations in pipe cross section to be automatically compensated; The inlet hydrant can be smaller than the pipe cross section when the sealing means is a bladder having a flaccid state; Different sealing members having differing sizes and differing outer surfaces can be employed for cleaning different pipes; Only one inlet point is needed at a proximal end to give cleaning access to an entire section of pipe, and no second over-ground return hose is needed; The pressure difference can be used to drive the cleaning assembly to and fro along a section of pipe without the need for further mechanical assistance; From any particular access point, the cleaning head can be sent either up-or downstream (relative to the conventional flow in the pipe) and the cleaning head can easily pass around bends in the pipe; The apparatus and method, using a flexible hose, does not lead to wear into the pipe at bends, as would tethered cleaning systems using a rope or cable to tether a cleaning ball; Piping installed under highways can be cleaned from a single entry point off the highway thus reducing traffic management costs.

It will be appreciated that numerous modifications to the above described embodiment may be made without departing from the scope of the invention as defined in the appended claims. For example, the sealing member may be some other cleaning member. In some embodiments, the bladder may be replaced by a substantially solid, yet resilient, cleaning member.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that while the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

CLAIMS1. A cleaning assembly for cleaning an internal surface of a pipe, the cleaning assembly comprising a flexible hose having a proximal end adapted for connection to a pump and a distal end having a fluid port, wherein a cleaning head is provided towards the distal end of the hose, the cleaning head comprising a sealing member configured or configurable to form a sliding seal across said pipe whereby the sealing member may support a pressure difference between distal and proximal faces of the sealing member.
2. A cleaning assembly according to claim 1 wherein the cleaning head comprises a wiping means configured or configurable to wipe the internal surface of the pipe.
3. A cleaning assembly according to claim 1 or claim 2 wherein the sealing member is deformable between first and second configurations such that in the first configuration the sealing member has a cross section insufficient to form said sliding seal and in the second configuration it has a cross section sufficient to form said sliding seal.
4. A cleaning assembly according to claim 3 wherein the sealing member is maintainable in the second configuration, in use, by said pressure difference.
5. A cleaning assembly according to any preceding claim wherein the sealing member comprises a flexible wall enclosing a volume of fluid to form a bladder.
6. A cleaning assembly according to claim 5 wherein an outer surface of the hose forms a wall of the bladder.
7. A cleaning assembly according to claim 5 or claim 6 wherein the volume of fluid is such that the bladder has a flaccid state providing the first configuration of the sealing member having a cross section insufficient to form said sliding seal and a turgid state providing the second configuration of the sealing member having a cross section sufficient to form said sliding seal.
8. A cleaning assembly according to any one of claims 5 to 7 wherein the fluid is a liquid.
9. A cleaning assembly according to any preceding claim wherein the sealing member forms at least part of the wiping means at said sliding seal.
10. A cleaning assembly according to any preceding claim wherein the wiping means comprises an abrasive means arranged to abrasively clean said internal surface.
11. A cleaning assembly according to claim 10 wherein the abrasive means is an outer surface of the sealing member configured or configurable to form said sliding seal.
12. A cleaning assembly according to any preceding claim wherein the fluid port is configured to maintain a fluid flow into or out of the hose when the distal end of the hose is contacted against a shut off valve in said pipe.
13. An attachment configured to form the sealing member of a cleaning assembly according to any preceding claim, wherein the attachment is constructed and arranged to be fixed towards said distal end of said hose.
14. An attachment according to claim 13 comprising a tube of flexible material extending between distal and proximal openings, wherein the openings are configured to be sealable against said outer surface of said hose, whereby the tube and said outer surface of said hose may be configured to form a bladder enclosing a volume of fluid.
15. A method for cleaning an internal surface of a section of pipe comprising: i) closing proximal and distal ends of the section of pipe to substantially prevent flow through the section of pipe, ii) inserting the distal end of the flexible hose and the cleaning head of a cleaning assembly according to any one of claims 1 to 12 into the section of pipe through an inlet valve of the pipe at its proximal end, iii) attaching a fluid pumping means to the proximal end of the flexible hose, iv) providing a pressure difference between the distal and proximal faces of the sealing member by pumping a fluid through the hose and fluid port such that the pressure on the distal face is lower than the pressure on the proximal face and such that a sliding seal is formed between the sealing member and the internal surface of the pipe, v) drawing the cleaning head from the proximal end towards the distal end of the section of pipe by means of the pressure difference whereby the wiping means wipes the internal surface of the pipe.
16. A method according to claim 15 further comprising; vi) withdrawing the cleaning head to the proximal end of the section of pipe after step (v) and then repeating step (v), vii) optionally repeating step (vi).
17. A method according to claim 16 wherein during step (vi) a pressure difference between the distal and proximal faces of the sealing member is provided by pumping a fluid through the hose and fluid port such that the pressure on the distal face of the sealing member is higher than the pressure on the proximal face of the sealing member and such that a sliding seal is formed between the sealing member and the internal surface of the pipe, whereby the pressure difference urges the cleaning head towards the proximal end of the section of pipe.
18. A method according to any one of claims l5to 17 wherein the pipe is a water main.
19. A method according to any one of claims 15 to 18 wherein the method is carried out whilst the pipe is substantially filled with the fluid, preferably water.
20. A method according to claim 19 wherein fluid extracted from the section of pipe in step (v) is cleaned and recycled for refilling the section of pipe during or after cleaning 21 A cleaning assembly, attachment and method substantially as hereinbefore described with reference to the accompanying drawings.