Method of sealing pipe

A method of lining a pipeline or passageway with a flexible tubular liner. The liner is caused to evert in the pipeline by a fluid under pressure, and a former is used to smooth out the everting face of the liner and evenly apply resin over the everting face.

This invention relates to the lining of pipelines and passageways. The 
lining may be for the purpose of curing leaks, cracks and fissures in such 
pipelines and passageways, or it may be for the purpose of simply 
providing an inner lining. 
In some usages of underground pipelines, in particular in gas pipelines, 
there are pipe joints which are a source of trouble because of the 
occurrence of leaks and cracks at those joints which allow the leakage of 
the gas from the pipeline. That leakage can lead to dangerous situations, 
and in extreme cases explosion and bodily harm or even fatalities. It is 
therefore of considerable benefit if such pipelines can be repaired, 
rather than having to be replaced when the pipeline becomes unusable 
because of leaks, cracks of fissures. 
Various methods have been proposed for curing leaks at pipeline joints, but 
those methods have by and large involved exposing the pipe joint by 
excavation and wrapping the joint externally with a sealing bandage or 
medium. That process whilst satisfactory has the disadvantage of requiring 
location of the leak and excavation of the ground at the site of the leak. 
The present invention pertains to the repairing of leaks and also the 
lining of pipelines and passageways by the eversion into the passageway or 
pipeline of a flexible tubular member. It is known to evert flexible 
tubular members into pipelines and passageways to line same, but 
heretofore the known methods have involved the sticking of tubes to 
pipeline surfaces by means of adhesive, which process requires that the 
pipeline be pre-cleaned before the lining process can take place. 
In the present invention, we envisage the use of a curable resin 
composition in order on the one hand to form a rigid pipelining and on the 
other hand to seal leaks and cracks in pipelines and passageways, by 
methods which do not of necessity require the pre-cleaning of the pipeline 
of passageway surface, and which envisage te application of the resin 
composition inside the pipeline or passageway. 
In accordance with the method of the present invention for lining a 
pipeline or passageway, a flexible tubular laminate comprising a resin 
absorbent material inside a flexible membrane material is everted into the 
pipeline or passageway so that the resin absorbent material is applied to 
the surface to be lined, an uncured synthetic resin composition is applied 
directly to the everting portion of the resin absorbent material whilst in 
the pipeline or passageway, and a vacuum is applied to the inside of the 
laminate whilst it is in the pipeline or passageway to extract air from 
the resin absorbent material in the region where it everts to draw resin 
into the resin absorbent material at the point of eversion so that the 
resin is absorbed by the said resin absorbent material and then the resin 
is cured to form a hard lining in which the absorbent material is 
embedded, and the everted laminate is held by fluid pressure against the 
pipeline or passageway until the composition cures. 
The membrane and composition may be such that the membrane bonds to the 
composition. The use of a vacuum inside the laminate is an extremely 
important aspect of this invention because the removal of the air from the 
resin absorbent material at the everting face places the resin absorbent 
material in the best condition to receive the resin presented thereto for 
the effective soaking or saturating of the resin absorbent material so 
that it will carry as much of the resin as possible without any air 
bubbles therein. Also, the resin absorbent material has only a short time 
to make contact with the resin and if it were full of air, this air would 
prevent effective penetration of the resin into the absorbent material. 
The resin can thus cure to a hard, homogeneous pipe wall having no voids 
and having the impact resisting resin absorbent material layer embedded 
therein. 
The resin absorbent reinforcing material may be a tube of felt laminated 
with the flexible membrane so that the membrane and absorbent tube evert 
together, the absorbent tube initially being inside the membrane whereat 
the vacuum is applied, and after eversion, being located outside the 
membrane and being impregnated and soaked with the resin. Preferably, a 
resin composition with a slow curing time is used to give the resin 
sufficient time thoroughly to soak through the absorbent material. 
The method of the invention may be applied in relation to long or short 
pipeline lengths and also to pipeline lengths which are disposed 
vertically as well as horizontally. Thus, it can be applied to the lining 
of a vertically disposed pipeline length, such as a precast concrete pipe, 
by causing the lining membrane and the absorbent material to be everted 
upwards through the pipe, the composition being applied by forming a pool 
of the composition on top of the everting laminate. 
This aspect of the invention provides, in pipelines and passageways, a hard 
lining which is resistant to abrasion experienced for example when 
abrasive objects pass along the pipeline or passageway, and which also 
forms an effective seal against the escape of gas or other fluids from the 
pipeline or passageway. The lining also forms a barrier against the 
ingress of liquid or gas into the interior of the pipelines or passageways 
from the outside thereof. 
According to a preferred feature of the invention, the curing of the resin 
composition is controlled by the employment of a catalyst. 
It is known that the inclusion of a catalyst in a synthetic thermosetting 
resin composition can accelerate the curing of the resin considerably, but 
clearly the resin must not be allowed to set too quickly in the methods of 
the invention, as otherwise there would not be be sufficient time to 
position the liner against the pipeline or passageway to be lined. In 
accordance with the preferred feature of the present invention, a catalyst 
for accelerating the cure of the resin composition is embodied in the 
absorbent material so that accelerated cure of the resin composition only 
commences upon said composition being applied to the absorbent material. 
The advantageous effects of this preferred method can readily be 
understood. The resin composition is presented to the absorbent material, 
is absorbed thereby and rapidly accelerates to curing by contacting the 
catalyst at the time of carrying out the installation process. 
The thermosetting resin composition may be an epoxy resin and the absorbent 
material may be a polyester felt. 
In order to ensure that the resin composition is applied evenly and 
effectively to the absorbent material, a further prefered feature of the 
present invention provides that a plug of the resin composition is pressed 
against the everting end of the everting member. By so pressing the plug 
there is applied a "back pressure" to the resin composition which ensures 
that the composition is fored as well as being pulled by the vacuum into 
the absorbent material effectively and evenly to impregnate the same, and 
also to ensure that the composition flows through the absorbent material 
if necessary into holes, recesses cracks and the like in the interior of 
the passageway or pipeline. The back pressure may be applied by a 
retaining shield which also serves to prevent the escape of resin 
composition into branch pipelines or passageways connecting with the 
pipeline or passageway being lined. 
By this aspect of the invention it is ensured that the composition fills 
cracks, recesses, hollows and the like in the pipeline but forms only a 
small thickness skin over other sections of the pipeline, ensuring that 
there is minimum usage of the resin composition. 
The invention also provides a pipeline or passageway which is lined in 
accordance with the method of either aspect of the present invention.

Referring to FIG. 1, there is shown a pipeline section 10 made up of 
portions 10A and 10B, the portion 10B being enlarged at the end shown, so 
as to overlap the adjacent end of the portion 10A, so as to define a pipe 
joint as shown. 
This pipe section 10 is to be lined with a relatively thick layer of hard 
thermosetting resin, so as to seal the interior of the pipe section from 
leaks, and to increase its internal resistance to wear. 
For this purpose, a laminate as shown in FIG. 2 is used. This is a tubular 
laminate, and comprises an outer skin 12 of a material, such as plastics 
material in the form of polyvinyl chloride or polyethylene, which is 
relatively impermeable to a gas such as air or a liquid such as water, by 
which the tube will be everted into and along the pipe section. Inside the 
tubular skin 12 is a tubular liner 14 of a resin absorbent material, such 
as felt or flexible porous plastics foam material, or even a mixture of 
these materials. Although it is not essential to all aspects of the 
invention, this absorbent tube may previously have been treated with a 
catalyst or accelerator, for example which "sets off" the particular resin 
which may be an epoxy or polyester resin is used in this example, name an 
epoxy resin. 
In order to evert the tubular laminate 12 into and along the pipe section 
10, one end of the laminate is anchored firmly, and then a liquid or a gas 
under pressure is used to force or blow the laminate into and along the 
tube length 10 as shown in FIGS. 3 and 4. Arrows 14' in these figures 
illustrate the application of the fluid pressure. 
Into the other end of the pipeline section is introduced a supply pipe 16 
from which is delivered a quantity 18 of the resin, so that this resin is 
presented to the everting face of the laminate, and comes into contact 
with the catalyst impregnated absorbent tube 14, immediately before such 
tube everts against the inner surface of the pipeline section 10. FIG. 4 
shows the operation in a more advanced stage, and FIG. 5 shows the pipe 
section after hardening of the lining in which is embedded the absorbent 
tube 14. In some cases the membrane 12 may bond to the resin and therefore 
will remain in place to form a smooth inner surface. It may be necessary 
to trim the ends of the hardened liner of resin. Indeed, the skin 12 may 
be a coating applied to tube 14 so as to be integral therewith. It will be 
seen, as a comparison between FIGS. 3 and 4, that the tube 16 
progressively is moved towards the right as the operation proceeds. It can 
be appreciated that the lining forms an effective seal even across the 
joint in the pipeline shown. 
In order to achieve effective penetration of the resin composition 18 into 
the resin absorbent layer 14, a vacuum is applied to the inside of the 
laminate before it everts in the passageway. This vacuum is applied 
through a vacuum pipe 20 shown in FIG. 4, and the vacuum may be drawn by 
means of a suitable vacuum pump. The vacuum may be drawn at any suitable 
location and FIG. 4 gives only one example of how it can be applied. The 
effect of the vacuum is to withdraw air from the inside of the laminate in 
the region prior to eversion. This means that in the very centre of the 
everting face, there will be a negative pressure and the resin will 
therefore be induced into the "eye" of the eversion. If reference is made 
to FIG. 6, the everting region is shown in detail. The arrows 22 indicate 
the negative pressure pull on the resin 18, and reference X indicates how 
the resin has in fact been induced into the centre of the everting 
portion, against the movement of the everting laminate in an outwardly 
folding direction as indicated by the arrows 24 in FIG. 6. The vacuum 
applied in this region removes air from all of the spaces in the resin 
absorbent material, and the vacuum thus created is filled by the resin 18 
which penetrates deeply and thoroughly into the resin absorbent material. 
By the use of this vacuum, in a short time the resin composition totally 
and completely impregnates the resin absorbent layer 14, without any 
voids, which results in an even homogeneous layer of resin, in which the 
absorbent and strengthening layer 14 is immersed, being applied to the 
wall of the passageway to be lined. This even and thorough impregnation is 
obtained in a very short space of time i.e. between the travel of each 
portion of the everting laminate from the eversion region to the inner 
surface of the pipeline which is being lined. 
Referring now to FIG. 7, in this FIG. reference numeral 140 represents a 
concrete pipe to be lined. It will be seen that the pipe 140 stands 
upright and it is lined from the bottom end by everting into the pipe 140 
a flexible lining tube membrane 142, which is laminated with a tube 144 of 
a resin absorbent material such as polyester felt material. The felt 144 
lies inside tube 142 before it everts as shown in FIG. 7 after which the 
absorbent tube 144 lies outside tube 142. The eversion is by means of air 
under pressure acting on the lining tube 142 as indicated by the arrows 
145 in FIG. 7 and the uncured synthetic resin is applied to the felt tube 
by being in the form of a pool 146 formed on the everting surface of the 
laminate 142, 144. The vacuum is applied to the inside of the laminate 
before it everts, for the purposes already explained herein, by vacuum 
pipe 147 and vacuum pump 149. The resin soaks thoroughly into the 
absorbent tube 144 and through it, leaving no voids so as to make contact 
with the inner tube 142. The process is continued until the whole of the 
pipe 140 has been lined with the resin impregnated tube 144, appropriate 
resin being added to the pool 146 as desired. The resin is either allowed 
to cure naturally with the passage of time or is forced cured by the 
application of heat and then the lining is trimmed to the pipe length as 
desired. In this example of the method of the invention the inner membrane 
142 either can remain with the cured resin or it may be such as to be 
strippable from the resin lining (containing the absorbent tube 144 
embedded therein) after the resin has cured. This embodiment of the 
invention is extremely useful for rendering pipe lengths suitable for 
carrying material for which they would otherwise be unsuited. For example, 
concrete pipe lengths can be made suitable for transporting corrosive 
materials which attack concrete but do not affect the resin lining. 
In the embodiment of FIG. 7 the felt can be provided with a catalyst as 
described in relation to the embodiment of FIGS. 1 to 6. 
Referring now to FIGS. 8 to 11 of the drawings, in FIG. 8 there is shown a 
pipline 210 which has two sections 210A and 210B and the section 210B is 
enlarged at the end shown so as to overlap the adjacent end of the section 
210A, and to form a pipe joint. The section 210A is shown as having bumps 
and recesses 212 which it can be assumed, arose as a result of use of the 
pipeline and the effluxion of time. Let it be assumed that the pipeline 
shown is a gas main, and that the joint between the sections 210A and 210B 
and the bumps or recesses 212 are sources of leakage, and it is desired to 
line the pipeline so as to seal these points of leakage. 
In accordance with the method of this embodiment of the invention a tubular 
laminate as illustrated in FIG. 2 is used in the process. In the drawings, 
the laminate is indicated by reference numeral 214. 
In order to line the pipeline the tubular laminate 214 is everted into the 
pipeline as shown in FIG. 9. To do this, one end of the tube is firmly 
fixed and sealed at one end of the pipeline, and then the tube 214 is 
everted by applying fluid under pressure such as air or gas, or steam or 
even a liquid, or a combination of such fluids, the pressure applied being 
indicated by the arrows 216 in FIG. 9. Also as described in relation to 
FIGS. 1 to 6, a vacuum is applied to the inside of the tubular laminate so 
that the vacuum is present at the everting face. In this example, the 
tubular laminate 214 is everted against a plug 218 of a fluent lining 
composition such as epoxy resin, which is located in the pipeline and at 
the other side of the plug there is in this example a pipeline pig 220 
which is a tube turned inside upon itself and having the ends sealed 
together. The pig 220 is inflated so as to bear against the inner wall of 
the pipeline as shown. The other side of the pig has fluid under pressure 
applied thereto, for example by pump 222, so as to force the pig against 
the plug 218 so that the plug 218 is trapped between the everting laminate 
214 and the pig 220. This arrangement provides for the application of 
pressure to each side of the plug 218, with the effect that the plug 
material is forced against the pipeline walls as well as the everting 
laminate as the lining operation proceeds. As the laminate 214 is everted 
into and along the inside of the pipeline 210, so the material of the plug 
218 is wiped against the inner wall of the pipeline, and the plug 218 and 
pig 220 move along the pipeline. FIG. 10 shows the process at a later 
stage, when the pig 220 has moved nearly to the end of the section of 
pipeline which is shown in the drawings. This figure also shows the vacuum 
pipe 219. During the movement along the pipeline the air under pressure 
supplied from pump 222 is relieved through a one way valve 224. 
At the completion of the lining operation, the inner surface of the 
pipeline 210 is provided with a skin of the lining material 218 as shown 
clearly in FIG. 11 moreover the lining material is forced into crevices or 
recesses, such as at 266 as shown in FIG. 11 in the region of the pipe 
joint, forming an effective seal at such recesses or crevices. 
It is appreciated that it is not necessary to use the pipeline pig 220 
shown in the drawings, and in some cases this may be omitted, the counter 
pressure on the plug being provided simply by a supply of air from the 
pump 222. 
Furthermore, any suitable medium may be used for pressurising the pipeline 
on the downstream side, to maintain the application of pressure on each 
side of the plug, but it will be appreciated that in order to achieve 
movement of the everting laminate along the inside of the pipeline, the 
pressure in the everting laminate must be greater than that in the 
downstream section of the pipeline. It is to be noted also that the lining 
medium fills the bumps and hollows 212, as shown in FIG. 10 effectively 
sealing such locations against leakage. 
In the arrangement shown in FIGS. 12, 13 and 14, an underground passageway 
50 with a branch connection pipe 51 is shown as being lined in accordance 
with the method described in relation to FIGS. 1 to 7. This is to say, the 
laminate 12/14 is being everted along the passageway 50 to line same, and 
a vacuum is applied to the interior of the laminate so that the vacuum is 
present at the everting face 52 drawing the resin 18 into the resin 
absorbent material 14 of the laminate at the everting face 52. 
Instead of the resin simply being sprayed from pipe 16 as in FIG. 4, the 
resin is retained in a retaining shield 53 in the form of a dished cup of 
which the outer edge 54 approximates to the diameter of the passageway 50 
and embraces the everting end of the laminate in order to prevent, as 
shown in FIG. 13, resin from escaping into the branch connection 51. The 
shield may be of thin sheet material such as plastics or metal so that it 
will slip along the passageway as eversion proceeds, but it is shaped so 
as to contain the everting face 52 and with such everting face, form a 
closed chamber for the resin 18 which is charged into the chamber along 
pipe 16; pipe 16 can also form the means for pulling the shield 53 along 
the passageway 50. The shield will also be pushed along the passageway by 
the everting laminate end therefore the back pressure to be provided by 
the resin end shield need only be quite small, but care should be taken to 
ensure that the everting laminate does not trap or jam the edge 54 of the 
shield 53 which could terminate the eversion process. 
FIG. 14 shows how the installed laminate lies over the branch connection 
opening 51 and bulges thereinto. Subsequently, it is necessary to 
re-establish the connection between the branch connection 51 and the 
passageway 50 by removing portion 55 of the lining hence the reason why it 
is desirable that the resin should be prevented from flowing into the 
branch connection 51 during eversion. 
Instead of using a dished cup 53 a cylindrical box as indicated by dotted 
lines 56, may be used. In another arrangement, a flat plate as indicated 
by dotted lines 57 may be applied to the everting face to retain the resin 
18 in a chamber extending from the eye of the everting face to where the 
everting face lies tangent to said plate. The plate will of course be 
provided with a hole through which the resin is supplied to said chamber. 
Referring to the arrangement of FIGS. 15 and 16, again the laminate 12/14 
is being everted along a passageway 60, to line same, in the method as 
described in relation to FIGS. 1 to 6, with vacuum applied to the interior 
of the laminate. However, a smoothing member 62 is engaged with the 
everting face 64 of the laminate as shown. The smoothing member 62 serves 
two purposes namely to shape the laminate around the smoothing member as 
shown in FIG. 16, and to distribute resin over the everting face of the 
laminate. The smoothing member has a tapered nose 66 which extends into 
the everting face 62, the tapered nose 66 leading to a cylindrical section 
68. The resin is fed along a bore 70 in the smooting member, and is 
distributed to the laminate along a plurality of passages 72 as shown in 
FIG. 16. 
The tapered nose 66 which engages with the everting face 64 has a lobed 
cross-section defining crests 74 and valleys 76 and the laminate is sucked 
onto the former to follow these crests and valleys by virtue of the 
existence of the vacuum in the interior of the laminate. The 
cross-sectional circumference of the tapered nose gradually increases 
until its periphery reaches a maximum cross-sectional circumference that 
is approximately equal to the inner circumference of the pipeline or 
passageway being lined. By this expansion, the laminate is kept smooth and 
free of creases as it everts, thereby enhancing the impregnation process. 
The smoothing member 62 moves along the passageway with the everting face 
64, and the laminate slips over the tapered nose 66 as it everts. This 
modification may be used in any of the embodiments described in relation 
to FIGS. 1 to 14. 
It is to be appreciated that the method of the invention can be applied to 
any pipeline or passageway, whether underground or not, and can be 
utilised in connection with the embodiments of the invention described in 
relation to FIGS. 1 to 7.