GB2206174A - Liner for tubular form - Google Patents

Abstract

A liner 67, (16, Fig 5), suitable for lining a generally tubular form such as a pipe, cable duct or vessel, comprises a collapsible tubular lamina of a self-supporting polymeric film, which has on its outer surface one or more continuous or discontinuous adhesive areas. One method of installing the liner in a tubular form comprises sealing at least one end of the tubular lamina and inflating it into adhesive engagement with the inner surface of the form. A carriage 40, 42 may be used to install the liner. Liners in socketted pipes (Fig 13) may form cuffs at the pipe joint. <IMAGE>

Description

Liner For Tubular Form This invention relates to a liner for a generally tubular form and, in particular, to a liner for a pipe or conduit.

The provision of a liner within a tubular form, such as a pipe or vessel, is necessary or desirable for a variety of reasons,for example to prolong the life of the form, to reduce or prevent leakage of contents from the form, to reduce or prevent ingress of contaminants into the form, to inhibit corrosion of the form, to improve or control internal flow by reducing or altering frictional contact between the form and its contents, or to provide a chemically inert barrier between the form and a potentially reactive or corrosive medium contained therein.

A liner according to the invention, although of utility in lining tubular forms of various shapes and dimensions, including reaction vessels and storage chambers, is for ease of discussion hereinafter described in relation to its use as a lining for a pipe.

Lining of a pipe is conventionally effected either by introducing a preformed lining tube into the pipe or by applying a lining medium directly onto the internal surface of the pipe, for example by spreading a flowable medium over the internal surface of the pipe and thereafter drying or curing the applied medium.

Problems associated with the use of a preformed lining tube, usually fabricated from a polymeric resin, include the inherent difficulty of manoeuvring a long, relatively inflexible tube into a rigid pipe, the need to dimension the lining tube to accommodate distortions and irregularities in the internal profile of the pipe, the significant reduction in pipe capacity occasioned by the introduction of a liner of finite dimensions and the required investment in facilities for storing and transporting multiple sections of the relatively massive lining tube.

Direct application of a lining medium requires the provision of complex and expensive equipment capable of being iotroduced into and travelling through the pipe to apply the lining medium, ~ for example by an applicator which spirally unwinds a preformed continuous tape or by an assembly of rotatable brushes or scrapers which apply a flowable protective paint medium onto the internal surface of the pipe. With such systems it is difficult to ensure complete coverage of the interZIsurface to provide a continuous protective skin, and any defects in the protective layer are likely to induce and promote decay of the lining or pipe.For example, it has been observed that epoxy resin protective coatings in ductile pipes experienoe degradation, and become ineffective, within a period of from 2 to 3 years from application.

We have not devised a lining technique which overcomes or substantially eliminates the aforementioned problems.

Accordingly, the invention provides a liner for a generally tubular form, which liner ocoprises a collapsible tubular lamina of a self-supSorting polymeric film, said tubular lamina having on its outer surface one or more continuous or discontinuous adhesive areas.

By a '#e1f-supporting" film is herein meant a film capable of an independent existence in the absence of a supporting substrate.

The invention also includes a method of lining a generally tubular form, mmprising introducing into the form a tubular lamina of the foregoing type in a flat condition, sealing at least one end of the lamina before or after introducing it into the form, and inflating the tubular lamina into cooperating engagement with the inner surface of the generally tubular form.

When a tubular lamina is to be installed by this inflation method, at least one end portion of the lamina is hermetically sealed, for example by a transverse heat seal, to facilitate inflation of the tubular liner. An inflation probe may then be inserted into the free, unsealed end of the liner, the loose liner film material being teeporarily secured about the probe to permit the required degree of inflation. Alternatively, and preferably, each end portion of the tubular liner is sealed, and the sealed lay-flat liner may comprise a valve or port through which inflating fluid may be introduced.

The longitudinal dimension of the liner should at least-equal that of the tubular form. Preferably, however, the longitudinal dimension of the liner exceeds that of the form to provide a cuff portion which may be inverted to form an external sleeve over an end portion of the form. The transverse dimension of the liner is determined by the corresponding dimension of the form and should be selected to ensure that a close fit of the liner within the form is achieved.

The nature of the polymeric film liner will depend, inter alia, on the nature and reactivity of the contents to be introduced into the form, and should be selected accordingly.

Suitable film-forming materials, depending on the proposed application, include polyesters, such as polyethylene terephthalate, vinyl polymers, such as polyvinylchloride, hato- and co-polymers of n#no-alpha-olefins, such as of ethylene, propylene and butene-l, and blends of such polymers.

Low density polyethylene (LDPE) is a so of utility, particularly when blended with linear low density polyethylene (TTnPE) to provide a film having desirably high tear resistance and tensile strength.

Such a film is conveniently produced by a conventional, tubular, blown-film technique, and may be a single-layer film or a multi-layer composite produced by lamination or coextrusion techniques. As appropriate, the film may be unoriented, or uni dr bi-axially oriented, or heat-set.

The thickness of the film will depend on the intended application, but generally will be in a range of from 50 to 400 microns ()in), and preferably from 200 to 250 Fm.

A film liner according to the invention, in its lay-flat condition is conveniently formed as a continuous roll of film wound longitudinally onto a reel fran which the desired length may be cut when required to line a form. Provision of film on a compact reel facilitates storage, transport and handling of the liner and thus promotes the practice of the invention.

The full capacity of a vessel or pipe is not always utilised and a liner according to the invention is therefore provided with one or more adhesive areas to prevent potential sag or crease defects, and possible developrent of snag points at which the liner may tear or debris may accumulate, when the lined form operates at less than full fluid capacity.

In one of its forms, the liner comprises at least two adhesive elements, a distal element at or adjacent one end portion, and a proximal element at or adjacent the other end portion, of the liner.

Preferably, however, at least one further, intermediate, adhesive element is provided between the proximal and distal elements. The total number of adhesive elements required will be governed, inter alia, by the dimensions of the form and the thickness (and thus mass) of the liner, but in general the elements may be axially spaced apart at a pitch not exceeding 1 metre and preferably within a range of from 0.15 to 0.75 metre.

Providing the pattern of adhesive elements permits effective bonding of the liner to the form, the nature or shape of an individual adhesive element is not important. Thus, an individual element may be in the form of a deposit - for example circular, square or rectangular, but preferably extends across substantially the entire width of the liner in a direction substantially normal to the longitudinal axis thereof, suitably as a linear pattern of individual deposits or, preferably, as a continuous adhesive strip. If desired, an, or each, adhesive strip may comprise a vent channel to permit axial discharge of air which otherwise would be trapped in the annul us between the form and liner when the latter is inflated as herein described.

An adhesive element may comprise any conventional adhesive material which will develop a bond of sufficient strength to secure the liner to the form. Thus, the adhesive material may be activatable by moisture, by heat, by contact or by pressure. A pressure-sensitive strip adhesive oamprising a synthetic rubber resin is particularly suitable.

In another form of the invention, the tubular liner has on its outer surface a continuous adhesive coating. The coating may be applied' at the factory before delivery to the site of use of the liner, or at the place of manufacture of the tubular form, or preferably at the site of installation of the piping itself. The application of the coating may be carried out on a batch-wise or continuous basis and may be by deposition from a solution, dispersion or melt, using spray, brush, scraper or like applicators as desired.

Depending on the nature of the adhesive material, and particularly in the case of a pressure-sensitive adhesive material, a removable, protective layer, such as a patch or strip, may be applied to the operative surface of the adhesive, to prevent inadvertent activation of the adhesive, the protective patch or strip being removed only wh n activation is desired. A peelable tape generally provides adequate protection.

The invention provides a sMmple, econanical, effective and practicable technique for lining a tubular form, such as a ductile metal or plastics pipe-line, pipe section, reaction vessel, storage chamber, light#;uide or any other form of conduit requiring protection against corrosion, decay, abrasion or chemical or physical attack.

Installation of a liner to provide an inert, impervious, continuous skin may be effected at the production or delivery point of the tubular form or at the point of use in the field.

Installation may be effected in new forms to provide protection or into usedor soiled forms to extend the useful life thereof.

The invention is illustrated by reference to the accompanying drawings in which: Figures 1 to 4 are schematic elevations (not to scale) of successive stages in the production of a tubular, lay-flat liner; Figures 5 to 10 illustrate successive stages in the installation of a liner within a pipe section, Figures 5 to 7, 9 and 10 being schematic side elevations and Figure 8 a schematic end elevation along the line VIII-VIII of Figure 7; Figures 11 to 13 are schematic plan views illustrating the final steps in liner installation and assembly of a pipe-line fran lined pipe sections; and Figure 14 illustrates, in schematic elevation, the production and installation of a liner "in the field".

Referring to Figures 1 to 4 of the drawings, a platen 10 has therein a plurality (five) of transverse recesses 11, each of which contains a retractable plunger (not shown). Onto each retracted plunger, in a recess, is placed an appropriately dimensioned strip 12 of double-sided adhesive tape having a releasable protective backing layer (not shown) on the underside thereof, the ends 13 of strips 12 hanging freely at the edges of the platen.

A lay-flat tubular polyolefin film 14 is unwound from a storage reel 15 and drawn longitudinally over the platen (Figure 2) where the film is transversely severed to leave on the platen a liner lamina 16 having longitudinal edges 17, 18 a distal transverse edge 19 and a proxnnal transverse edge 20 (Figure 3).

The plungers are then raised to bring the adhesive strips into bonding contact with the underside of liner 16 and the free ends 13 of adhesive strips 12 are folded into axially overlapping engagement on the upper surface of liner 16 to yield a plurality of axially spacedapart adhesive elements - a proximal element 21, three intermediate elements 22, 23, 24 and a distal element 25 (Figure 3).

As shown in Figure 4, each end of the lay-flat liner is transversely sealed, in turn, between the jaws 26, 27 of a heat sealer 28, and the sealed lamina is folded (if desired) for packing and'or storage.

Referring to Figures 5 to 10 of the drawings which illustrate the installation and bonding of a liner 16 within a ductile pipe section 30 having a flared or bell end 31 and a straight end 32, a liner 16, prepared as described in relation to Figures 1 to 4 and resting on a trolley platform 40, is prepared for installation by removal of the backing layer from intennediate adhesive elements 22, 23, 24 but not fran proximal and distal elements 21 and 25 (Figure 5).

The prepared liner is then uniformly draped over a longitudinal trolley support member 41 of triangular cross-section (Figure 6), which is introduced into and along pipe section 30 on castors 42 (Figures 7 and 8). If desired, trolley support member 41 may be provided with a release coating, for example of polytetrafluoroethylene, to inhibit sticking of an intermediate adhesive element thereto.

When the liner 16 has been positioned within pipe section 30 to leave an approximately equal overhang 43, 44 at each end, and securely held, support member 41 is withdrawn (Figure 9), the backing layer of proximal and distal adhesive strips 21 and 25 is removed, an inflation clamp 45 is attached, the liner is held under longitudinal tension and is inflated to pressurise the adhesive elements into engagement with the internal surface 46 of the pipe section (Figure 10). On completion of the operation the free ends of the liner may be tucked into the pipe section for transport, thereby preventing contamination of the pipe lumen and also protecting the liner ends against physical damage during transit.

Referring to Figures 11 to 13 of the drawings, to prepare two lined pipe sections 30, 30' for assembly, the hollow chuck 50 of an expander tool 51 is inserted into the proximal end of liner 16 from which the transverse end seal has been cut, and the liner is stretched to match the external diareter of pipe section 30 at straight end 32 (Figure 1), over which th expanded liner end is then rolled, with the aid of a lubricant if required, to form a protective cuff 52 (Figure 12).The transverse end seal is then cut from the distal end of liner 16' located in pipe section 30', expander tool 51 is introduced to spread liner 16' at the bell end 31' of pipe section 30', whereby straight end 32 may be introduced through the hollow expander tool and into mating engagement with bell end 31'. The resultant pipe joint, after withdrawal of the expander tool, is shown in Figure 13. If preferred, the liner end may be expanded and rolled to form a protective cuff on the bell end of the pipe section.

Repetition of the jointing procedure permits assembly of a pipeline having an effectively continuous, protective lining skin throughout its length.

Referring finally to Figure 14, a cast iron pipe 60 is shown in situ below ground level 61; a length of perhaps 100 metres between inspection and an s access ##s 62, 63 being represented. Within the chamber 63 a coating machine 64 is temporarily installed. Above ground level, reels 65 and 66 to supply a tubular liner 67 and a support film 68 respectively are set up adjacent to the chamber 63.

The tubular liner 67 is in the form of a collapsed, flat-lying tube of a polyolefine laminate. The support 68 is a film of nylon or polypropylene.

In order to instal the liner 67 in the pipe 60, the liner and support film 68 are threaded separately through the coating machine 64 and their respective free ends are attached to a draw-line 69 previously threaded through the pipe 60. By means of the line 69, the liner and support film are drawn through the coating machine and then through the pipe 60. In the coating machine 64, a coating of a bitumen-based adhesive is plied to the outer surface of the tubular liner 67. The support film 68 passes through the base of the coating machine without any coating being applied to it.

Frem the coating machine, in which it lies flat, the support# film 68 enters the pipe 60 and therein adopts a concave format of generally semicircular crosksection. The liner 67 passes through the pipe 60 in a similar format, supported by the film 68. When the liner 67 emerges from the end of the pipe, the support film 68 is detached from the line 69 and retracted on to the reel 66, leaving the liner resting on the lower half of the pipe. The liner is cut to length and sealed.

By means of a probe (not shown) inserted into the sealed length of liner, the latter is inflated with compressed air until it engages the inner face of the pipe. The air pressure is maintaine for sufficient time (about 12 hours) for the adhesive to set and thereby secure the lining to the pipe throughout their mutual length.

Claims (11)

as

1. A liner for a generally tubular form, vhich liner comprises a collapsible tubular lamina of a self-suçporting polymeric film, said tubular lamina having on its outer surface one or more continuous or discontinuous adhesive areas.

2. A liner as:claimed in claim 1, wherein said tubular lamina has on its outer surface a continuous adhesive coating.

3. A liner as claimed in claim 2, wherein said adhesive coating comprises a bitunen-based adhesive.

4. A liner as claimed in claim 1, wherein said tubular lamina has on its outer surface a plurality of spaced-apart adhesive elements.

5. A liner as claimed in claim 4, wherein said adhesive elements are spaced apart along the length of the tubular lamina at a pitch not exceeding 1 metre.

6. A liner as claimed in claim 4 or claim 5, wherein said adhesive elements each comprises a strip of pressure-sensitive adhesive, extending at least part of the distance around the circumference of the tubular lamina.

7. A liner as claimed in claim 6, wherein the adhesive comprises a synthetic rubber resin.

8. A liner as claimed in any of the preceding claims, wherein the film oamprises a polyester, a vinyl polymer or a homo- or co-polymer of a mono-a1pha#lefin, or a blend of two or more such polymers.

9. A method of lining a generally tubular form, canprising introducing into the farm a tubular lamina as claimed in any of the preceding claims in a flat condition, sealing at least one end of said tubular larnina before or after introducing it into the form, and inflating the tubular lamina into cooperating engagement with the inner surface of the generally tubular form.

10. A rrrethod of lining a generally tubular form, substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 to 10 of the accompanying drawings.

11. A method of lining a generally tubular form, substantially as hereinbefore described with reference to, and as illustrated in, Fig. 14 of the acoompanying drawings.