Pipeline structure with a lining material, an end structure of said pipeline and a method for applying a lining material to a pipeline

A pipeline structure with a lining material wherein a hermetic outer tube is disposed at the inner surface of a pipeline, and an inner lining material is disposed at the inner surface of the outer tube, said inner lining being made of a rigid fiber-reinforced plastic wherein a thermosetting resin is reinforced by a fiber reinforcement material.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates to a novel structure and method for applying 
a lining material to reinforce pipelines such as a gas conduit, a city 
water pipe, a sewage pipe, pipelines for laying telecommunication cables 
or electric cables, and particularly, pipelines embedded in the ground. 
More particularly, the present invention relates to a technical means 
suitable for applying a lining material to a gas conduit or intermediate 
line with a working pressure of approximately 3 to 10 kg/cm.sup.2. 
2. Background Art 
A conventional method for applying a lining material to an underground 
pipeline comprises the steps of depositing a hermetic film on the outer 
surface of a tubular fiber reinforcement material composed of a tubular 
woven or unwoven fabric, or a combination of tubular woven and unwoven 
fabrics superimposed one over the other to provide a lining material, 
applying a thermosetting resin liquid to the inner surface of the lining 
material and impregnating the thermosetting resin liquid into the tubular 
fiber reinforcement material, inserting the lining material into the 
pipeline while the lining material is being reversed under a fluid 
pressure, pressing the lining material against the inner surface of the 
pipeline under the fluid pressure, curing the thermosetting resin liquid 
so as to adhesively attach the lining material to the inner surface of the 
pipeline, and causing the thermosetting resin liquid and the tubular fiber 
reinforcement material to cooperate together to provide a rigid FRP 
(FIBER-REINFORCED PLASTICS) tube within the pipeline. 
This method attempts to reduce the adhesive force between the lining 
material and the inner surface of the pipeline so as to prevent the lining 
material from cracking as the pipeline is damaged, or the joints from 
detaching due to earthquake or the like. This method also utilizes high 
strength fiber such as a glass fiber or an aromatic polyamide fiber on the 
circumference of the lining material so as to withstand internal or 
external pressure and insure a fluid path if the lining material is 
exposed as a result of damage to the pipeline (see U.S. Pat. No. 
5,164,237). 
Such a lining method is effective in the case that the pipeline is composed 
of cast iron pipes or fume pipes, but is not sufficiently effective 
particularly when it is applied to a steel pipe such as a gas conduit with 
an intermediate working pressure of approximately 3 to 10 kg/cm.sup.2 
(hereinafter, referred to as an "intermediate pressure A line"). 
The intermediate pressure A line uses carbon steel pipes which have a high 
strength and tenacity. These pipes are welded together to form a long 
pipeline system. Bent pipes are welded to bent portions of the pipeline to 
provide an integral pipeline system. With such a pipeline system, if the 
ground is liquified or subjected to contraction due to earthquake, the 
resulting stress tends to be concentrated on the bent portions. 
FIG. 3 shows the manner in which the bent portion of the intermediate 
pressure A line fractures. FIG. 3(a) shows a bent portion 2 of a pipeline 
1. When the ground contracts due to an earthquake or the like, the 
pipeline 1 is repeatedly extended and contracted in a longitudinal 
direction. This results in a change in the angle of the bent portion 2. 
This change causes the bent portion 2 to be significantly deformed in the 
direction in which it is bent and extended. If the bent angle .alpha. of 
the bent portion 2 increases, the bent portion 2 is urged into the pipe. 
If the bent angle a of the bent portion 2 decreases when the bent portion 
2 is extended, a portion of the bent portion which has been urged into the 
pipe is subject to extension. When the bent portion 2 is locally deflected 
to a substantial extent, a large crack 3 occurs within the bent portion 2 
due to fatigue, as shown in FIG. 3(b). 
In the case that a lining material 4 is adhered to the inner surface of the 
pipeline 1, the edge of the crack 3 is bent inwardly to produce sharp 
burrs 5. These burrs 5 break the lining material 4 as shown in FIG. 3(c). 
Thus, damage to the pipeline 1 causes corresponding damage to the lining 
material 4. 
A cast iron pipe has a low tenacity. Thus, if a cast iron pipe fractures, 
burrs 5 are rarely produced. Thus, a fluid path can be maintained since 
the lining material 4 is free from damage. On the other hand, a steel pipe 
has a high tenacity. Thus if a shock load is applied to a steel pipe, it 
will not fracture as opposed to the cast iron pipe. However, a crack 3 is 
likely to occur when local stress is concentrated on the bent portion 2. 
The resulting burrs 5 will cause damage to the lining material 4. 
An adhesive or a seal is applied to the end of the lining material within 
the pipeline so as to prevent the entry of a fluid between the lining 
material and the pipeline. Normally, a metal ring is fit within the end of 
the lining material. The metal ring is extended to thereby press the end 
of the lining material against the inner surface of the pipeline (see JP, 
B, Sho. 60-41276). 
With this treatment, however, the pipeline and the lining material is 
subjected to displacement if significant damage to the pipeline occurs. If 
the end of the lining material is displaced relative to the pipeline, the 
seal is damaged. A fluid then enters between the lining material and the 
pipeline and may flow out of a portion of the pipeline thus damaged. 
SUMMARY OF THE INVENTION 
It is a principal object of the present invention to overcome the problems 
encountered in the prior art and to provide a structure and method for 
applying a lining material, which prevents the lining material from being 
damaged by burrs which may occur when the bent portion of a pipeline 
composed of steel pipes is subjected to a crack and which insures the 
maintenance of a fluid path. 
Another object of the present invention is to provide an improved end 
structure which maintains the sealing integrity in the end of a lining 
material if the lining material and a pipeline are displaced relative to 
each other, thereby preventing fluid leakage. 
The present invention provides a pipeline structure with a lining material, 
characterized in that a hermetic outer tube 6 is disposed at the inner 
surface of a pipeline 1, and an inner lining material 4 is disposed at the 
inner surface of the outer tube 6 and made of a rigid FRP wherein a 
thermosetting resin 17 is reinforced by a fiber reinforcement material 12. 
The present invention also provides a method for applying a lining material 
to a pipeline, characterized by inserting a hermetic outer tube 6 into a 
pipeline 1, then inserting into the outer tube 6 an inner lining material 
4 wherein a fiber reinforcement material 12 is impregnated with a 
thermosetting resin liquid, applying a fluid pressure within the inner 
lining material 4 so as to expand the inner lining material 4, and curing 
the thermosetting resin liquid. 
Preferably, the outer tube 6 is a tube made of polyethylene or nylon, or a 
tube to which a tubular unwoven fabric 9 is laminated. 
It is preferred that the fiber reinforcement material 12 is reinforced in 
its circumferential direction so as to retard expansion under internal 
pressure, and that the radial expansion of the fiber reinforcement 
material 12 is small under the internal or working pressure of the 
pipeline. 
The present invention further provides an end structure for a pipeline 
lining material, characterized in that a flexible sleeve 22 has one end 
which fits within the end of an inner lining material 4 disposed within 
the pipeline 1; a metal ring 23a is positioned within the flexible sleeve 
22 and expanded to press the sleeve 22 and the inner lining material 4 
against the inner surface of the pipeline 1; that the sleeve is slackened 
at its center; and that a metal ring 23b is fit to the other end of the 
sleeve 22 and expanded to press the sleeve 22 against the inner surface of 
the pipeline 1. 
The present invention will become more fully understood from the detailed 
description given hereinbelow and the accompanying drawings which are 
given by way of illustration only, and thus are not limitative of the 
present invention, and wherein:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described with reference to the drawings. 
FIG. 1 schematically shows, in transverse section, the wall structure of a 
pipeline with an associated lining material according to the present 
invention. 
Element 1 designates a pipeline which is made of steel. A hermetic outer 
tube 6 is provided within the pipeline 1, but is not adhesively attached 
to the inner surface of the pipeline 1. 
FIG. 2(a) shows one form of the outer tube 6 wherein a tube 7 is made of a 
plastic, such as polyethylene or nylon, which has a low gas permeability. 
The outer tube 6 is composed only of the plastic tube 7. 
FIG. 2(b) shows another form of the outer tube 6 wherein the plastic tube 7 
is laminated to the inner surface of a tubular unwoven fabric 9. FIG. 2(c) 
shows another form of the outer tube 6 wherein the plastic tube 7 is 
laminated to the inner surface of a tubular woven fabric 8. 
Referring next to FIGS. 1, 2(a), 2(b) and 2(c), 4 designates an inner 
lining material. In any of FIGS. 2(a), 2(b) and 2(c), the inner lining 
material 4 is composed of a FRP layer 10 wherein a thermosetting resin is 
reinforced by a fiber reinforcement material 12, and a hermetic film 11 
attached to the inner surface of the FRP layer 10. 
As shown in FIG. 2(a), the fiber reinforcement material 12 of the FRP layer 
10 includes a tubular woven fabric 15 composed of warps 13 and wefts 14, 
and high-strength filament yarns 16 extending around the outer surface of 
the tubular woven fabric 15 with high density. The high-strength filament 
yarns 16 are interconnected by the warps 13 of the tubular woven fabric 15 
so as to prevent undue expansion of the inner lining material due to 
internal pressure. 
If the inner lining material 4 is subjected to undue expansion under the 
working internal pressure, it is highly likely that the inner lining 
material 4 would be damaged by burrs 5 which may occur when the pipeline 1 
is damaged due to an earthquake or the like. This is because the inner 
lining material 4 is constantly pressed against the inner surface of the 
pipeline 1 during use. 
An unsaturated polyester resin or an epoxy resin is used as the 
thermosetting resin 17 which forms the FRP layer 10. 
The inner lining material 4 has a circular section within the outer tube 6. 
The inner lining material 4 is adhered to the inner surface of the outer 
tube 6 by the thermosetting resin 17. The outer tube 6 extends along the 
inner surface of the pipeline 1. 
Next, in order to provide the pipeline with the inner lining material, the 
outer tube 6 is first inserted into the pipeline 1. The outer tube 6 may 
be pulled into the pipe 1. Preferably, the reversible outer tube 6 is 
inserted into the pipeline 1 while it is being turned inside out under 
fluid pressure. 
After the outer tube 6 has been inserted into the pipeline 1, the inner 
lining material 4 wherein the fiber reinforcement material 12 is 
impregnated with the thermosetting resin liquid is inserted into the outer 
tube 6. It is also preferred that the reversible inner lining material 4 
is inserted into the outer tube 6 while it is being turned inside out 
under fluid pressure. 
The inner lining material 4 could be simply pulled into the outer tube 6. 
However, the fiber reinforcement material 12 which is impregnated with the 
thermosetting resin liquid is exposed to the outer tube 6. Thus, it is 
difficult to pull the inner lining material 4 into the outer tube 6 
because the adhesive force of the thermosetting resin liquid retards the 
sliding movement of the inner lining material 4 relative to the outer tube 
6. 
Reversion of the inner lining material 4 under fluid pressure during 
insertion eliminates the drag between the inner lining material 4 and the 
outer tube 6. Advantageously, fluid or external pressure allows for an 
even distribution of the thermosetting resin liquid which has been applied 
to the inner lining material 4 before the inner lining material 4 is 
reversed. Thus, the thermosetting resin liquid can be evenly impregnated 
into the entire inner lining material 4 when the inner lining material 4 
is applied. Also, the fluid pressure causes the inner lining material 4 
thus reversed to be expanded into a cylindrical shape. The cylindrical 
inner lining material 4 is then pressed against and applied to the inner 
surface of the pipeline 1 through the outer tube 6. 
First the outer tube 6 is inserted into the pipeline 1, and then, the inner 
lining material 4 is inserted into the outer tube 6. The thermosetting 
resin liquid is cured while the inner lining material 4 is expanded into a 
cylindrical shape under fluid pressure. 
FIG. 5 shows the end structure of the inner lining material within the 
pipeline according to the present invention. Element 1 designates the 
pipeline. Element 4 designates the inner lining material applied within 
the pipeline 1. As shown in FIGS. 2(a), 2(b) and 2(c), the outer tube 6 is 
disposed between the pipeline 1 and the inner lining material 4. 
In this case, the outer tube 6 may be absent at the end of the inner lining 
material 4. 
Element 22 designates a flexible sleeve. The sleeve element 22 is made of 
rubber or a flexible plastic in which a thin woven fabric may be embedded. 
As shown in FIG. 6, the sleeve 22 has a small diameter portion 22a at its 
one end which has a diameter substantially equal to the inner diameter of 
the inner lining material 4, a large diameter portion 22b at the other end 
which has a diameter substantially equal to the inner diameter of the 
pipeline 1, and a taper portion 22c disposed therebetween. 
The sleeve 22 is attached to the end of the inner lining material 4 with 
the taper portion 22c slackened as shown the broken line in FIG. 6. The 
small diameter portion 22a of the sleeve 22 is fit within the end of the 
inner lining material 1. A metal ring 23a is engaged with the small 
diameter portion 22a and then, expanded so as to press the small diameter 
portion 22a of the sleeve 22 and the end of the inner lining material 4 
against the inner surface of the pipeline 1. The large diameter portion 
22b of the sleeve 22 is engaged with the inner surface of the pipeline 1 
outside of the inner lining material 4. A metal ring 23b is fit within the 
pipeline 1 and then, expanded so as to press the large diameter portion 
22b of the sleeve 22 against the inner surface of the pipeline 1. 
OPERATION 
According to the present invention, the inner lining material 4 is composed 
of the rigid FRP layer wherein the fiber reinforcement material 12 is 
impregnated with the thermosetting resin 17. The inner lining material 4 
is not adhesively attached to the pipeline 1 since the outer tube 6 exists 
between the inner lining material 4 and the inner surface of the pipeline 
1. 
If a crack 3 occurs in the bent portion 2 of the pipeline 1 as stated 
earlier, the inner lining material 4 may be inwardly deformed due to the 
resulting burrs 5. However, the inner lining material 4 would not be 
broken by the burrs 5 since the inner lining material 4 is separated from 
the pipeline 1. The inner lining material 4 will in no way be damaged if 
the pipeline 1 is damaged. 
The inner lining material 4 can be swung within the pipeline 1 under a 
working pressure, particular when the inner lining material 4 has an outer 
diameter less than the inner diameter of the pipeline 1. If the crack 3 
occurs, the inner lining material 4 is easily moved away from the burrs 5 
and will in no way be damaged. 
The outer tube 6 is composed of the tubular unwoven fabric 9 or the tuber 
woven fabric 8 laminated with the tube 7. The tubular unwoven fabric 9 or 
the tubular woven fabric 8 protects the tube 7 as well as the inner lining 
material 4 from being damaged by the burrs 5. This effectively prevents 
fluid leakage. 
The tube 7 of the outer tube 6 is made of a material which has a low gas 
permeability, such as polyethylene or nylon. Thus, no gas will leak from 
the tube. 
As shown by the solid line in FIG. 5, the end of the inner lining material 
4 is hermetically sealed against the inner surface of the pipeline 1. The 
end of the inner lining material 4 is pressed between the metal ring 23a 
and the pipeline 1 so as to prevent the entry of a fluid between the inner 
lining material 4 and the pipeline 1. 
If the pipeline 1 is broken or opened due to an earthquake or the like, the 
inner lining material 4 is separated from the pipeline 1 without suffering 
damage and remains in the form of a rigid tube. As a result, the end of 
the inner lining material 4 is displaced relative to the pipeline 1 or 
moved to the left as shown by broken line in FIG. 5. 
The sealing integrity may be lost when displacement between the inner 
lining material 4 and the pipeline 1 takes place. The small diameter 
portion 22a of the sleeve 22 is moved with the inner lining material 4 
whereas the large diameter portion 22b is fixed to the pipeline 1. The 
slackened portion is thus extended as shown by broken line in FIG. 5. 
Under the circumstance, the sleeve 22 prevents the entry of a fluid 
between the pipeline 1 and the inner lining material 4 and the leakage of 
the fluid from the broken portion of the pipeline 1. 
Again, according to the present invention, the sleeve 22 is moved from its 
slackened condition to an extended condition to accommodate the relative 
displacement between the end of the inner lining material 4 and the 
pipeline 1 when the pipeline 1 is subject to fracture due to an earthquake 
or the like. Thus, the sleeve 22 maintains sealing integrity at the end of 
the inner lining material 4 and prevents fluid from entering between the 
pipeline 1 and the inner lining material 4 and from, flowing out of the 
pipeline 1 through its broken portion. 
EXAMPLE 
The pipeline 1 takes the form of an intermediate pressure A gas conduit 
(inner diameter of 204.7 mm and working pressure of 10 kg/cm.sup.2). 
Details of the outer tube 6 are as follows. 
Example 1 (polyethylene tube) 
A low density polyethylene tube having an outer diameter of 200.0 mm, a 
thickness of 0.45 mm, a tensile strength of 160 kg/cm.sup.2, and an 
elongation of 700% when broken. 
Example 2 (unwoven fabric) 
A tubular unwoven fabric having an inner diameter of 188.6 mm, a thickness 
of 4.9 mm when a load of 500 g/cm.sup.2 is applied, a density of 0.18, 
extension strength of 25 Kg/cm and an elongation of 120% when broken. The 
tubular unwoven fabric is made of polyester and laminated with the 
polyethylene tube of Example 1. 
Comparative Example (without outer tube) 
No outer tube 6 is employed. 
To make the fiber reinforcement material 12 which forms the FRP layer 10 of 
the inner lining material 4, there is provided 640 lengths of warps 13, 
each including three polyester filament yarns having a thickness of 1,100 
d and two polyester span-like filament yarns having a thickness of 1,000 
d. 30 lengths of wefts 14 each includes two polyester filament yarns 
having a thickness of 1,000 d and are picked up over a span of 10 cm so as 
to provide a tubular woven fabric 15. 15 lengths of yarns, each including 
aramide filament yarns having a thickness of 1,500 d, are picked up over a 
span of 10 cm and are wound around the outer surface of the tubular woven 
fabric 15. A plurality of polyester span-like filament yarns or fastening 
yarns have a thickness of 1,000 d and are used to interconnect the yarns 
at thirty-two points. 
The fiber reinforcement material 12 has a weight of 1,090 g/m, a width, in 
flattened state, of 290 mm, a thickness of 2.6 mm, a longitudinal strength 
of 330 kg/cm, and a breaking pressure of 23 kg/cm.sup.2. The outer 
diameter of each of the pipeline 1 used in Example 1, Example 2 and 
Comparative Example under a working pressure (10 kg/cm.sup.2) is as 
follows. 
Example 1 205.1 mm 
Example 2 197.1 mm 
Comparative Example 206.9 mm 
In the following tests, the thermosetting resin 17, which forms the FRP 
layer 10 of the inner lining material 4, is made of epoxy resin. 
DEFORMATION TEST 
The pipeline 1 used in Example, 1, Example 2, and Comparative Example has a 
length of approximately 2 m and is provided with a lining. The bent 
portion 2 has an angle of 22.5 degrees. The pipeline 1 is tested by a test 
machine shown in FIG. 4. 
In FIG. 4, 1 designates the pipeline with the bent portion 2. A lining 
material is applied to the inner surface of the pipeline used in Example 
1, Example 2, and Comparative Example. 18 designates a stationary fixture 
on which a movable fixture 19 is slidably mounted. The pipeline 1 extends 
between the stationary fixture 18 and the movable fixture 19. 20 
designates a center hole jack which includes an operating rod 21 adapted 
to move the movable fixture 19 along the stationary fixture. 
After the pipeline 1 is mounted to the machine, an air under a pressure of 
10 kg/cm.sup.2 is injected into the inner lining material 4. The center 
hole jack 20 is then operated to reciprocatingly move the movable fixture 
19 to the left and right by 50 mm and 100 mm from its initial position so 
as to bend the bent portion 2 of the pipeline 1. The movable fixture 19 is 
reciprocated until a crack occurs in the pipeline 1, and the air under 
pressure leaks from the pipeline 1. Measurement is taken at one-eighth of 
each reciprocating movement of the movable fixture 19. 
The result of the test is shown in Table 1. 
TABLE 1 
______________________________________ 
OUTER AIR 
TUBE MOVEMENT CRACK LEAKAGE 
______________________________________ 
EXAMPLE 1 
POLY- .+-.50 mm 25/8 55/8 
ETHYLENE .+-.100 mm 15/8 36/8 
TUBE 
EXAMPLE 2 
UNWOVEN .+-.50 mm 25/8 73/8 
.+-.100 mm 6/8 &gt;10 
COM- NONE .+-.50 mm 25/8 55/8 
ATIVE .+-.100 mm 15/8 15/8 
EXAMPLE 
______________________________________ 
TENSILE TEST 
Two straight pipes having a length of 900 mm are arranged in series and 
spaced 100 mm apart from each other. A lining material used respectively 
in Example 1, Example 2 and Comparative Example extends through the pipes. 
A pressure of 1 kg/cm.sup.2 is applied to cure the thermosetting resin 17. 
The ends of the inner lining material 4 within the pipes are treated 
according to the present invention. Thereafter, the ends of the pipes 
adjacent to opposite ends of the inner lining material 4 are closed. A 
water pressure of 10 kg/cm.sup.2 is applied within the inner lining 
material 4. One of the pipes is fixed, whereas the other pipe is pulled. 
Load is measured when the distance between the pipes increases by 10 mm. 
DAMAGE RESISTANCE TEST 
The pipes with the lining material used in the tensile test are spaced 110 
mm apart from each other with an internal pressure of 10 kg/cm.sup.2. A 
chisel is brought into contact with the surface of the inner lining 
material 4 between the pipes. The chisel includes a tip having an angle of 
45 degrees. The chisel is then urged into the inner lining material 4 by 3 
mm. In this state, the chisel is moved along the length of the inner 
lining material by 100 mm and reciprocated ten times. The number of 
movement of the chisel is measured until the inner lining material 4 is 
broken to thereby cause the water under pressure to be ejected from the 
inner lining material 4. 
In the event that the sealing integrity of the inner lining material 4 is 
still maintained after the chisel is reciprocated ten times, the same test 
continues, but the chisel is more deeply pressed into the inner lining 
material progressively by 2 mm. The test is repeated until the inner 
lining material 4 is broken to thereby cause ejection of the water under 
pressure. 
TEST FOR DETERMINING THE FOLLOWABILITY OF THE INNER LINING MATERIAL AS THE 
PIPES ARE DISPLACED 
Two pipes have a length of 900 mm and are serially arranged in an 
end-to-end fashion. A lining material used respectively in Example 1, 
Example 2 and Comparative Example is applied within the pipes. The two 
pipes are separated by 100 mm while a pressure of 10 kg/cm.sup.2 is being 
applied within the inner lining material. At this time, measurement is 
taken to determine a maximum load. Also, the extent of extension of the 
inner lining material 4 is measured when the inner lining material 4 
fractures. 
The results of the tensile test, damage resistance test, and followability 
test are shown in Table 2. 
TABLE 2 
______________________________________ 
COMP. 
ITEM EXAMPLE 1 EXAMPLE 2 EXAMPLE 
______________________________________ 
OUTER TUBE PE TUBE UNWOVEN NONE 
FABRIC 
TENSILE TEST 
5.10 t 3.14 t 8.54 t 
RESISTANCE TO 
DAMAGE 
CHISEL DEPTH 
3 mm 10th TIME 10th TIME 3rd TIME 
5 mm 10th TIME 10th TIME 
7 mm 5th TIME 10th TIME 
9 mm 10th TIME 
11 mm 10th TIME 
13 mm 9th TIME 
FOLLOW ABILITY 
MAX 100 mm 100 mm 41 mm 
ELONGATION 
FRACTURE NO NO YES 
MAX LOAD 10 t 11 t 18 t 
______________________________________ 
From the test for determining the followability of the inner lining 
material as the pipes are displaced, it is found that the inner lining 
material follows with displacement of the pipes. This is because according 
to the present invention, the inner lining material is not adhesively 
attached to the pipes. Thus, the inner lining material 4 will in no way 
fracture when the pipes fracture. 
From the damage resistance test, it is found that the inner lining material 
of the present invention has an excellent resistance to damage. Thus, the 
inner lining material 4 will in no way be damaged by burrs which may occur 
when the pipeline 1 is subject to fracture. It also prevents fluid 
leakage. 
It will readily be assumed that in Example 2, the unwoven fabric protects 
the inner lining material 4 to provide an improved resistance to damage. 
Also, in Example 1, the polyethylene tube or outer tube 6 per se is not 
related to the resistance to damage, but has significantly better 
resistance to damage than the comparative example. 
As is clear from the result of the tensile test, the lining material of the 
comparative example is tensed upon application of substantial loads to the 
lining material. This is due to the fact that the lining material can not 
readily be separated from the pipeline since the lining material is 
adhesively attached to the pipeline. Accordingly, the lining material is 
likely to be broken by the burrs 5 when the bent portion 2 of the pipeline 
1 is subject to fracture 3. 
Conversely, the lining material of Example 1 is not under tension since it 
is separated from the pipeline. Accordingly, the lining material will be 
inwardly deformed if the burrs 5 urges the lining material. The lining 
material will in no way be broken by the burrs 5. It will be understood 
that better resistance to damage is obtained when the lining material is 
not adhered to the pipeline. 
Deformation test is made to the pipeline 1 which has a bent portion 2 and a 
lining material. From this test, it is found that the number of movement 
until fluid leakage occurs after the pipeline 1 cracks is greater in 
Examples of the present invention. Thus, the lining material insures a 
fluid path if the steel pipe is damaged due to earthquake or the like. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.