GB2335247A

GB2335247A - Pipe lining

Info

Publication number: GB2335247A
Application number: GB9904212A
Authority: GB
Inventors: Eric Frederick Joseph Crisp; Samuel Colin Crisp
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-03-13
Filing date: 1999-02-25
Publication date: 1999-09-15
Also published as: GB9904212D0

Abstract

A resin-impregnated or -soaked hose 14 is used to line a pipe 10, whereby heated fluid, preferably compressed air, is introduced into the hose or a member 18 disposed within it, so that the hose is urged into intimate contact with the inner periphery of the pipe. A valve 24 is provided at a location spaced from the fluid inlet, and is used to regulate the flow of heated fluid through the pipe as the resin is cured in situ. The fluid is preferably heated by passing it through a heat exchanger 22, the fluid being passed through a plurality of narrow tubes (30, figure 2) being heated by a gas burner (32, figure 2). The temperature of the fluid is preferably at least 15‹C when it is introduced into the hose or member disposed within the hose, and more preferably lies in the range of 20‹C to 70‹C. The resin is preferably an epoxy resin, the hose being soaked in a cooled resin bath prior to its insertion into the pipe.

Description

2335247 1 1 TITLE: PIPE LINING DESCRIPTION is The present invention

relates to a method and apparatus for lining a pipe, particularly but not exclusively for repairing damaged pipes.

The repair of underground pipes presents special difficulties because of the limited access which is available. To avoid the inconvenience and expense of digging up and replacing damaged pipes, a system has been developed to line the interior periphery of pipes in situ, with the potential to repair up to one hundred metres in one go. In the system a polyester hose closed at one end and impregnated with styrene resins is dragged into position through the pipe so that it spans the damaged portion. Thereafter, the hose, or an inner tube placed within it, is inflated with air under pressure to urge the 2 hose into intimate contact with the inner periphery of the damaged pipe. The air pressure is maintained until the resin has cured, producing a hard, impervious lining.

In the system, the cure time of the resin is carefully selected; on the one hand, it must not be too short otherwise the resin may cure before the hose is in position. On the other hand, it must not too long since this would lead to an unacceptable increase in the time required to effect the repair. Curing may be activated by a chemical trigger, with a retarding agent used to delay curing until the hose is in position. However, chemical triggers are only suitable with relatively thin linings, meaning that thicker linings have inordinately long cure times.

is In an effort to reduce cure times with relatively thick linings once the hose is in its required position, warm water has been used in place of an ambient air cure. A water tower is employed to generate sufficient pressure to urge the hose into intimate contact with the pipe, and large thermal-capacity heaters are required to generate even a modest rise in water temperature. The heated water is introduced into the pipe through a tube inserted in the hose which has perforations at intervals along its length.

The heated water flows through the perforations towards 25 the hose and circulates in the annular spacing between the tube and the hose before flowing back towards the point where it was first introduced into the pipe. Warm water circulation is maintained for up to three days, and at 3 considerable expense.

Polyester resin linings for damaged pipes are not ideal. The lining does not adhere to the pipe and infact shrinks after installation giving rise to two serious problems. Firstly, material including bacteria is able to accumulate in the space between lining and pipe; and secondly, the lining may slip axially down the pipe causing re-exposure of the damaged position. In an effort to overcome these problems, the use of epoxy resins have been proposed. Although more expensive than polyester resins, epoxy resin linings offer the advantage of positively bonding to the inner periphery of the pipe being repaired.

An epoxy resin with a cure time of about six hours at 150C is typically used. However, when repairing pipes underground, where the temperature may be significantly below 150C, the cure time may extend to 12 hours or more.

Throughout this period, the pipeline is out of action, usually necessitating the use of tankers to transport material that would otherwise have flowed through the pipe. In certain instances, the cost of transporting waste material above ground is extremely high, so there is a strong desire to reduce the cure time as much as possible.

one proposal for reducing cure time is the use of warm water as hereinbefore described with reference to the polyester resin linings. However, problems have been 4 encountered caused by localised temperature fluctuations in the pipe. It has been found that "cool spots" lead to areas where the hose comes away from the pipe, possibly due to contraction of the water. In such areas, the resin cures leaving a gap between the lining and the pipe which is a potential weak spot and a potential home for harmful bacteria to accumulate.

According to a first aspect of the present invention, there is provided a method of lining a pipe, comprising; introducing into the pipe a hose soaked or impregnated with uncured resin; introducing heated fluid into the hose or a member disposed within it to urge the hose into intimate contact with the interior periphery of the pipe; curing the resin in situ; characterised by: providing a valve at a location spaced along the pipe from where heated fluid is introduced; and regulating the valve to establish during curing a flow of heated fluid in one direction along the pipe being lined.

By establishing a flow of heated fluid along the length of the pipe by having the fluid inlet and outlet at opposite ends of the hose, it has proved possible for the first time to cure the lining within two to four hours without introducing defects. Preferably, the resin is an epoxy resin.

Preferably, the fluid is gaseous, and is most preferably air. It has surprisingly been found by the present applicant that by using hot air it is possible to warm the resin-impregnated hose along its length to such a degree that the in situ cure time is reduced to barely two hours. By using air, it is possible and perfectly acceptable to authorities governing the pipe repair for the gas passing through the valve to be discharged direct into the portion of the pipe down stream of the section being repaired, or direct into the atmosphere.

The method may further comprise compressing the gaseous fluid with a compressor before it is heated. The gaseous fluid may be heated by passing it through a heat exchanger, which may be heated with gas burners. It is considered undesirable to introduce combustion products into the pipe itself because these will ultimately be vented at the valve.

In order to achieve as uniform a cure as possible, the method may further comprise maintaining the heated fluid in the pipe at a constant pressure by regulating the valve. In the case of a gaseous f luid, the pressure may be maintained at about two atmospheres by regulating the valve.

In accordance with a second aspect of the present invention, there is provided apparatus for lining a pipe, comprising; a hose impregnated with uncured resin; means for heating fluid; means for inflating with heated fluid the hose or a member disposed within it to urge the hose into intimate contact with the inner periphery of the pipe; and a valve for regulating the flow of the fluid through the pipe whilst the resin cures, the valve in use being disposed at a location spaced along the length of 6 the hose f rom where heated f luid f irst contacts the hose or the member disposed within it.

The fluid heating means may comprise a heat exchanger. The heat exchanger separates the f luid from the source of heat, e.g., a gas burner, in which case combustion products are prevented from being introduced into the pipe.

The inflating means may comprise an air compressor when the fluid being used is air. The valve may be regulated in dependence upon the pressure of heated fluid in the pipe. The hose may be impregnated with uncured resin by bathing it in resin prior to insertion in the pipe. The resin bath may be cooled, e. g., with an ice/water bath, to delay resin curing until after the hose is positioned in the pipe. The resin may be an epoxy resin. An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: 20 Figure 1 is a schematic of apparatus embodying the invention; Figure 2 is a schematic view showing a section through a heat exchanger forming part of the apparatus of Figure 1; and 25 Figure 3 is a graph showing experimentally determined temperature readings during resin cure. Figure 1 illustrates schematically the repair of a pipe 10 which has developed cracks 12 causing pipe 7 contents' seepage. After thoroughly cleaning the pipe 10 to remove debris, a hose 14 soaked with uncured resin is introduced into the pipe 10 so as to span the cracks 12; the hose being of sufficient length that ultimately both the leading and trailing ends extend above ground. Once in position, the hose 14 is urged into contact with the inner periphery 16 of the pipe 10 by inflating inner tube 18 with warm air generated by passing the output of compressor 20 through heat exchanger 22. Whilst maintaining the air pressure in inner tube 18, a steady flow of warm air along the inner tube 18 is established by regulating valve 24. The resin rapidly cures in situ, forming a hard, impervious lining. When the resin has cured, the inner tube 18 may be deflated and removed from the pipe 10. Any excess portions of cured resin either side of the repaired pipe may be cut off and discarded.

The hose 14 comprises a fibrous material such as polyester felt. (The hose may also include an air impermeable layer on its inner most surface, in which case there is no need for the inner tube 18). The f ibrous material is soaked in a bath of an epoxy resin (for example, as supplied under the trade name I'Konudur 160PLL" by MC-Bauchemie MUller GmbH & Co) immediately prior to introducing it into the pipe 10. Typically, the leading end 26 of the hose 14 is dragged into the pipe 10 with the aid of a winch (not shown) together with the inner tube 18. Alternatively, the hose 14 may be forced into the pipe 10 using an inverter which uses compressed gas to 8 blow one end of the hose through the other as the hose is introduced into the pipe. Once in position, the end of the inner tube 18 adjacent the leading end 26 is fitted with a regulating pressure valve 24 which is set at two atmospheres. A pressure gauge may be coupled to the pressure valve 24 to facilitate monitoring of exiting gas pressure.

The trailing end 28 of the hose 14 is coupled to the air compressor 20 through the heat exchanger 22. As shown in Figure 2, the heat exchanger 22 comprises an array of fine tubes 30 which are heated by gas burners 32. Air from the compressor 20 is received in an ante-chamber 34 where it is distributed amongst the array of fine tubes 30 before being recombined in receiving chamber 36. As the air passes through the array of fine tubes 30, heat from the gas burners is readily absorbed. From the receiving chamber 36, hot air is forced into inner tube 18 and along its length before being vented at valve 24.

The use of hot air flowing the inner tube 18 throughout the curing process speeds up the repair procedure considerably. The graph of Figure 3 compares the temperature of the resin with the temperature of the hot air leaving the heat exchanger 22, over the entire cure time, approximately two hours. The graph also records the ambient temperature and the temperature of a control resin which was unheated. The temperature of the unheated resin varied between 150C and 200C and took 1 9 approximately eighteen hours to cure.

Claims

1 A method of lining a pipe, comprising: introducing into the pipe a hose soaked or impregnated with uncured resin; introducing heated fluid into the hose or a member disposed within it to urge the hose into intimate contact with the interior periphery of the pipe; and curing the resin in situ; characterised by: providing a valve at a location spaced along the hose from where heated fluid is introduced; and regulating the valve to establish a flow of heated fluid in one direction along the pipe being lined as the resin cures.

2. A method according to claim 1, in which the heated fluid is gaseous.

3. A method according to claim 2, in which the heated 15 gaseous fluid is air.

4. A method according to claim 2 or 3, further comprising compressing the gaseous fluid with a compressor prior to introducing it into the hose or the member.

5. A method according to any one of claims 2 to further comprising maintaining the heated gaseous fluid in the pipe at a pressure of about two atmospheres by regulating the valve.

6. A method according to any one of the proceeding claims, in which the heated fluid is obtained by passing fluid through a heat exchanger.

7. A method according to any one of the preceding claims, in which the temperature of the heated fluid is at 11 least 150C when introduced into the hose or the member.

8. A method according to claim 7, in which the temperature of the heated fluid is in the range 200C to 700C.

9. A method according to any one of the preceding claims, in which the resin is an epoxy resin.

10. Apparatus for lining a pipe, comprising a hose impregnated with uncured resin; means for heating fluid; means for inflating with heated fluid the hose or a member 10 disposed within it to urge the hose into intimate contact with the inner periphery of the pipe; and a valve for regulating the flow of heated fluid through the pipe whilst the resin cures, the valve in use being disposed at a location spaced along the hose from where heated fluid is introduced.

11. Apparatus according to claim 10, in which the fluid heating means comprises a heat exchanger.

12. Apparatus according to claim 10 or 11, in which the inflating means comprises an air compressor.

13. Apparatus according to any one of claims 10 to 12, further comprising a resin bath for soaking the hose with resin.

14. Apparatus according to claim 13, further comprising means for cooling the resin bath.

15. Apparatus according to any one of claims 10 to 14, in which the resin is an epoxy resin.

16. A method of lining a pipe substantially as 12 hereinbefore described and as illustrated with reference to the accompanying figures.

17. Apparatus for lining a pipe substantially as hereinbefore described and as illustrated with reference 5 to the accompanying figures.