JPH0159474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Pipes and the pipelines they constitute are playing an increasingly important role in transporting gas, oil, water and other fluids. Pipes have traditionally been treated in various ways to increase their durability. For example, pipelines laid underground may be coated with bituminous materials, fiberglass pine, or plastics to protect against electrolytic corrosion, biochemical corrosion, cyclic soil stress, cathodic debonding, and mechanical damage. Painted or coated with various materials such as tape. However, until now little attention has been paid to improvements in burst strength, fracture resistance, heat resistance, safety factor, weight, and the like. Moreover, the few attempts to do so have resulted in other problems. For example, it has been proposed to wrap a relatively thick wire around a pipe in order to increase its radial strength, that is, its hoop strength, but such a configuration is prone to crevice corrosion due to moisture adhesion. , resulting in corrosion in the spaces between adjacent turns of the wire and in the spaces between the wire and the pipe.

It is therefore an object of the present invention to provide an improved pipe which still enjoys the protection treatments of the conventional type, yet which is significantly improved in terms of ductile fracture resistance.

It is another object of the invention to provide a pipe of the above type with high strength and ductile fracture resistance with a minimum of additional effort and materials and without introducing additional problems such as crevice corrosion as mentioned above. The goal is to provide the following.

A further object of the invention is to provide a pipe of the above type which is endowed with the strength and fracture resistance described above in a manner similar to that conventionally used for providing corrosion protection to pipes. be.

Yet another object of the present invention is to provide a method of manufacturing the improved pipe described above.

According to the present invention, a plurality of continuous, generally unidirectional, high strength non-metallic fibers are wrapped around a pipe. These fibers may be coated with a viscous material such as enamel or epoxy to form a homogeneous matrix that bonds to the pipe, or they may be coated with an adhesive backing or pre-impregnated with enamel or epoxy. good.

These and other objects and advantages of the present invention will become more apparent from the following description of the embodiments, which are given with reference to the accompanying drawings.

By way of example, the method of the invention will be described in connection with the treatment of relatively large diameter steel or other metal pipes. This treatment includes electrolytic and biochemical corrosion, cathodic debonding,
The purpose is to provide protection against soil stress and mechanical damage, to significantly increase the circumferential strength of the pipe, and to increase the axial ductile fracture resistance of the pipe.

According to a preferred embodiment of the invention, metal pipes are removed from the pipe surface by sandblasting or gritblasting, or by scraping or wire brushing to remove oil and grease from the pipe surface.
Cleans by removing dust, moisture, and non-stick mill scale. A primer is then applied to the outer surface of the pipe as a bonding agent between the steel pipe and the viscous material to be coated later. The primer can be any material, such as AWWA Type B, which has very strong bonding strength and fast drying time, and is compatible with both asphalt and coal tar coatings. It is preferred because it is perfectly compatible.

After priming the pipe according to the procedure described above,
Applying a hot viscous substance such as coal tar enamel or asphalt enamel to the primed exterior surface. As shown in FIG. 1, hot enamel is applied to the surface of pipe 10 by discharge head 12. As shown in FIG. A head 12 is spaced apart from the pipe 10 and is adapted to spray enamel onto the outer surface of the pipe. The head 12 may be of conventional design, preferably a weir, overflow box, or flow coater that receives the enamel at temperatures as high as 500°C (260°C) and discharges it onto the external surface of the pipe. It shall be in the form of a machine or curtain coater.
In this coating process, the pipe 10 is attached to the head 1.
The enamel may be applied to the outer surface of the pipe by moving the head 12 longitudinally while rotating relative to the head 2, or by moving the head 12 from side to side over a fixed length of the pipe. .

The coal tar enamels described above are preferably produced from modified filled coke oven pits. Asphalt enamel can be made from certain crude oils with oxidized fillers.

While the enamel coating is still hot, ie, before it has completely dried and bonded, a plurality of continuous unidirectional high strength inorganic non-conductive fibers are wrapped around the pipe. More specifically, with reference to FIG. 2, the treated outer surface of the pipe 10 is coated with the continuous unidirectional continuous web or wrapping material 14 of high strength non-metallic fibers. The wrapping material 14 is wrapped in one or more layers as required with a minimum tension, ie, a minimum tension sufficient to adequately adhere to the pipe. That is, the fibers are wrapped around the pipe with sufficient tension to adhere the fibers containing the viscous substance to the pipe. This tension corresponds to just enough tension to keep the fibers wrapped around the pipe straight and parallel. Further, the fibers constituting the web are preferably glass or other materials having properties equivalent to glass, as described below.

After coating the pipe with the unidirectional fiber wrapping 14 and while the enamel is still in its hot viscous state, a protective jacket 16 is wrapped over the wrapping 14 as shown in FIG. Put on. The jacket 16 is any material that protects the pipe from damage during pipe transportation and pipeline burying operations, and protects the enamel and fibers against cyclic soil stress and rock damage. However, the most preferred material for the jacket 16 is a reinforced fiber fabric impregnated with coal tar or asphalt, or a reinforced asbestos felt impregnated with coal tar or asphalt. The outer cover 16 is
Since the previously applied enamel is coated while still in a hot, unbonded state, it bonds to the unidirectional fibers of the enveloping material and to the pipe as the enamel bonds and hardens.

The fibers and bonded enamel constitute a homogeneous matrix bonded to the pipe, providing additional strength to the pipe and preventing corrosion as discussed below.

The wrapping material 14 is such that its unidirectional fibers extend in a plane substantially perpendicular to the axis of the pipe and the degree of overlap between each adjacent turn is from 1% to approximately 1%.
It can be wrapped in such a manner that it has a range of up to 50%. The jacket 16 can also be wrapped within the same degree of overlap.

That is, the fibers are wrapped around the pipe at an angle of slightly less than 90° to the axis of the pipe. A wrap angle of 90° to the longitudinal direction of the pipe will show the greatest effect. However, this angle does not allow continuous wrapping of the fibers along the length of the pipe. Also, at winding angles significantly smaller than 90°, the axial winding of the pipe takes place quickly, but this angle does not result in a higher circumferential bursting strength of the pipe.
This angle increases the axial burst strength of the pipe, but since the axial burst strength of metal pipes is inherently higher than the circumferential burst strength, there is no need to increase the axial burst strength of the pipe. .

As in the case of applying a viscous substance, the coating material 14
and 16 may be covered by moving the pipe longitudinally with rotation, by means of fixed rollers, an unwinding head, etc., or the pipe may be left stationary and covered by a machine equipped with an unwinding head. The sheathing material 14, 16 can be wound around the pipe and advanced in the longitudinal direction. All of these techniques are well known in the industry and will not be discussed in further detail here.

FIG. 4 shows a detail of a piece of wrapping material 14. The individual continuous unidirectional fibers 18 making up the wrapping material 14 are separated into a plurality of rovings or bundles 20 by transversely extending strings 22. The string 22 extends so as to alternately sew these bundles 20 up and down.

FIG. 5 shows an alternative embodiment of a wrapper 14'. In this example, unidirectional fibers 18
is again separated into bundles 20', but the width of the bundles is narrower than that of the embodiment of FIG.
Although it is not clear from the figure, the string 22 is connected to the bundle 20'
may be braided or otherwise tied to hold them in place.

In the embodiment of FIG. 6, the wrapping material 14'' is comprised of a plurality of bundles 20'', each consisting of a plurality of unidirectional fibers 18;
The stitches are sewn in a Z-pattern using a thread 24 extending over the entire length of 0''.

In yet another embodiment, the use of strings or the like may be omitted and the fibers 18 may be wrapped around the pipe in the form of a bundle using a wrapping machine or the like.

Also, according to a variant embodiment of the invention, the application of high-temperature enamel is omitted, and instead an adhesive is applied to the unidirectional fibers, and the fibers are wound around the pipe and bonded. You can also do that. In that case, the textile wrapper 14 is formed by any of the techniques described above, with any conventional adhesive applied to both sides of the wrapper 14 and one side of the wrapper A backing material can be applied to the pipe and the other side wrapped around the pipe in a manner similar to that shown in FIG.

Alternatively, an adhesive coating may be applied to one side of the encapsulant 14, a backing material may be applied to the coated side, and another adhesive coating may be applied to the other (exposed) side of the backing material. The coating can be applied and the adhesive coating side wrapped around the pipe in the manner described above.

According to yet another embodiment of the invention, the fibers can be impregnated with a liquid substance such as epoxy, enamel, etc. before being wrapped around the pipe. In that case, the fibers are preferably bundled as described above and impregnated with the liquid substance in a bath or through application rollers or the like. The fibers impregnated or coated with a liquid substance in this manner can immediately be wrapped around a pipe as shown in Figure 2 while the liquid substance is still wet and allowed to dry and adhere to the pipe. can. Alternatively, after applying the liquid substance to the fibers as described above, the liquid substance is allowed to dry for a period of time until it becomes "sticky" and the fibers are then wrapped around the pipe in the manner described above.

In each of the embodiments described above, the diameter of each fiber constituting the wrapping material 14 is preferably smaller than 0.001 inch (0.0254 mm). The narrower diameter completely covers the individual fibers and forms a homogeneous mixture with no gaps between the individual fibers and between the fibers and the pipe when wrapped around the pipe. Thus, pipes coated according to the invention do not suffer from the crevice corrosion mentioned above.

Also, as a result of the above-described arrangement, the axial ductile fracture resistance of the pipe is considerably improved. Additionally, a portion of the circumferential or hoop stress of the pipe is absorbed by the web 14 of continuous unidirectional fibers. Thus, the circumferential burst strength imparted to the pipe by the unidirectional fibers can be controlled to be equal to the longitudinal burst strength of the pipe. Of course, it can be adjusted by the type, number and size of fibers used and the number of layers.

That is, high strength non-metallic fibers are wrapped around the pipe in an amount that increases the circumferential burst strength of the pipe until the circumferential burst strength of the pipe is equal to its axial burst strength. When such an amount of fiber is wrapped around a pipe, the pipe becomes as difficult to rupture circumferentially as it is axially. The amount of fiber required to equalize the circumferential burst strength to the axial burst strength for any size and type of pipe can be determined by experiment.

Pipes treated according to the method of the invention have several further uses. For example, the bursting pressure of the pipe and the safety factor for certain operating pressures are increased.
Also, the stress values in the pipe are reduced at the same working pressure, thereby considerably reducing the possibility of stress corrosion cracking. Of course, for a given design working pressure and in order to obtain a certain safety margin against the bursting pressure, the metal content and therefore the weight of the pipes required can be reduced. Also, if the pipe is coated with enough unidirectional fibers, it will "leak before bursting".
The following damage conditions are obtained. That is, if the pipe 10 suffers from internal or external corrosion, it will leak before it bursts. Coating a pipe with small amounts of fiber slows the propagation of ductile cracks and keeps them within a short distance from the point of initiation. Such increased puncture resistance properties are particularly important for pipes intended to convey high pressure gases or volatile liquids such as CO ₂ .

One of the major advantages of the present invention is that it can be easily transferred to current techniques for providing corrosion protection to pipes. Current techniques coat randomly placed (not unidirectional) fiberglass mats with high temperature adhesives and protective jackets, which have little strength properties.

Another advantage of the method of the invention is that the possibility of pipe damage due to external impacts is significantly reduced. The pipe of the present invention will only experience localized impressions or depressions when subjected to most external impacts that would rupture a bare pipe. Also,
Other impacts, such as impressions or dents in bare pipes, cause little damage to the pipes of the present invention.

Various modifications can be made to the method of the invention without departing from the scope of the invention.
For example, in addition to applying multiple layers of the wrapping material 14 of unidirectional fibers 18, multiple layers of the outer covering 16 may be applied to the wrapping material 14.
They can also be coated alternately or non-alternately. In addition, the viscous substance described in the first embodiment is not limited to the above-mentioned enamel, but may also be a resin, urethane, epoxy, paint, etc. that completely coats the fibers and leaches moisture and other corrosive solutions. Other viscous substances that prevent These materials harden by simply being left alone or by heating, cooling, chemical reaction, moisture, ultraviolet light, etc., and bond filaments together or between filaments and pipes.
It also holds or bonds the filament in place.

Additionally, the technique of the method of the present invention can be applied to any type of pipe of any diameter with properties comparable to metals such as stainless steel, aluminum, copper, brass, etc., imparting the improved properties mentioned above. , moreover, the individual characteristics of these pipes (for example high corrosion resistance in the case of copper pipes) can be preserved.

The method of the invention dramatically increases fracture resistance,
It therefore extends the service life of the pipe and is therefore particularly suitable for pipes used in harsh environments. For example, the strength and break resistance of the pipe is significantly increased so that the pipe does not need to be repaired or replaced.
If not completely eliminated, it is significantly reduced.

Furthermore, the principles of the method of the invention can also be applied to high stress points in pipes, such as seams and longitudinal welds, to provide the improvements described above.
The present invention can also be used to stop or slow the propagation of ductile cracks in pipes. In some cases, cracks may not propagate at all.

Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention can be implemented in various forms within the spirit and scope thereof.

[Brief explanation of drawings]

1-3 are perspective views of a pipe showing the sequential steps in treating the pipe according to the method of the present invention.
4-6 are partially enlarged views of various embodiments of unidirectional fiber wrapping materials that can be used in the method of the invention. In the figure, 10 is a pipe, 12 is a discharge head, 14
is the wrapping material (web), 16 is the outer cover, 18 is the fiber,
20 is a fiber bundle.

Claims (1)

[Claims] 1. A method of treating a metal pipe to increase axial ductile fracture resistance, comprising a wrapping step of wrapping a plurality of continuous unidirectional high strength non-metallic fibers around the metal pipe; The fibers are bonded to each other and to the metal pipe by applying to either or both the metal pipe and the fibers a viscous substance which together forms a homogeneous matrix that is bonded to the metal pipe. the fibers absorb some of the stress in the circumferential direction of the pipe, and the pipe itself absorbs stress in the longitudinal direction; The bursting strength in the circumferential direction is controlled to be equal to the bursting strength in the longitudinal direction, and the fibers are stretched with a minimum tension so that they have an angle of slightly less than 90° with respect to the axis of the pipe. A method for treating a pipe, characterized in that the fibers are wound around the pipe so that the fibers have a thickness that prevents the propagation of ductile cracks in the axial direction of the pipe.