FR2533998A1 - DEVICE FOR STOPPING A DUCTILE FRACTURE WHICH SPREADS IN AN OBJECT AND METHOD FOR ITS IMPLEMENTATION - Google Patents

Abstract

A.FRACTURE ARREST DEVICE 10 FOR STOPPING A DUCTILE FRACTURE THAT SPREADS IN AN OBJECT SUCH AS A PIPE 12. B. IT INCLUDES A BAND CONSTITUTED OF A PLURALITY OF NON-METALLIC, CONTINUOUS FIBERS AND HIGH TENSILE STRENGTH 16 WHICH ARE WOUND AROUND THE OBJECT 12 ACCORDING TO THE DIRECTION PERPENDICULAR TO THE DIRECTION OF PROPAGATION AND ARE EMBEDDED IN A RESINOUS SUPPORT 27 WHICH IS SUBJECT TO CURING. C. APPLICATION: PROTECTION OF PIPE-LINES.

Description

Objects made of metal or other materials that are subject to stress

  elevated tend to fail-in that they develop one or more ductile fractures capable of spreading, or fissures spreading freely Objects that may have such fractures are too numerous to list in the present application, but there may be mentioned compressed gas cylinders, fan blades and wind mills, vehicle axles, pipes, etc. One of the areas that currently seems to face the most important potential problems with ductile fracutres that are spreading is that of the pipes, and in particular

  large diameter pipes used in pipelines.

  Pipelines of relatively large diameter that consist of steel pipe or other metal play increasingly important roles in the transport of

  gases, such as natural gas, CO 2 and other volatile fluids.

  For example, due to the increase in domestic gas reserves and a corresponding increase in natural gas use, there will be a correspondingly greater need for pipelines to take gas to collection pipelines. and carry it by transmission lines

over great distances.

  These pipes, if they have defects or are damaged, and if they contain fluids under relatively high pressures, are susceptible to ductile fractures that propagate at speeds between 122 and 274 meters per second. that a fracture of this type appears to increase if the product in the pipeline is corrosive, either because of the gas itself or because of the humidity such a gas frequently contains.

  also increases in the case of steel pipes transport-

  natural gas with a significant amount of hydrogen sulphide

  gene, which can lead to embrittlement In addition, the moisture that the gas contains and C 02 that could be present will produce carbonic acid, which also attacks the steel pipes In addition, the problem of failures increase significantly When it comes to a cold climate In addition, a ductile fracture that spreads can be caused by a shock from an external force such as an earthmover accidentally crashing against the pipeline, earthquakes, etc. . The tendency of objects to fail due to the occurrence of a spreading ductile fracture is generally due to the nature of the material constituting the object and the manner in which the material is worked or shaped to

  realize the object For example, many pipes for pipe-

  lines are made from a metal block which is elongated more in one direction than in another by passing between pairs of cylinders or similar means. Such a method produces an elongate plate to which a U-shaped configuration is to be given. curving it around its longitudinal axis The U-shaped plate is then bent to give it a cylindrical configuration by bringing the branches of the U end-to-end and by securing the sides in the longitudinal direction, for example by welding, in order to perform a relatively straight longitudinal weld A

  such pipe is much stronger * in the longitudinal direction

  only in the circumferential direction or in a circle,

  which defines an inherent axis of weakness and, consequently,

  In this case, the pipe can withstand greater forces in the longitudinal direction than in the circumferential or circumferential direction. Consequently, when such a pipe is missing, it is due to the fracture of a circle of width. indeterminate whose ends are separated Next, the neighboring circles break as a result of the failure of the first circle and a line of ends of circles that separate move longitudinally the

  along the pipe to define a ductile fracture that

  age. If there have been many proposals to limit the

  propagation of a ductile fracture in objects, and in particular

  in pipelines, including the use of solid-wall pipes, cables, concrete abutments, valves and sleeves

  metallic, it 3 were all less than satisfactory.

  For example, U.S. Patent No. 4,195,669 to Ives et al proposes to stop the propagation of such a fracture by providing a mass of material surrounding the hose to these

  preselected intervals as a peripheral constraint.

  However, the steel collar, the steel cable windings and the reinforced concrete casting described in this patent all prove to be heavy and of manipulation and installation.

  In addition, the crevice between the surrounding masses

  and the pipe and crevices together with neighboring turns in the case of steel cables, allow dirt and moisture to penetrate them and the resulting corrosion of the crevices weakens the pipe. the surrounding masses themselves, especially in the case

of cables.

  US Pat. No. 4,148,127 and 4,224,966 to Somerville disclose a method of applying a band fracture arresting device to the outside diameter of a pipe and a radial force to the inside diameter of the pipe. The fracture arresting devices described are preferably strips or rings made of the same metal as the pipeline. Consequently, they have the same problems of significant weight and difficult handling and installation as the In addition, the close contact between the pipe and the edges of the stop devices tends to cause stress concentrations in the pipe where

  edges of the stop devices support Of course, -

  concentrations of effort can lead to a failure

  The Somerville patent further states that the tapes may be fiberglass, but no longer say anything about the fiberglass tapes. If the tapes consist of a typical molded fiberglass-oriented band random way, the thickness needed to stop a fracture would be such to make the band very

  bulky and difficult to handle.

  U.S. Patent No. 3,870,350 to Loncaric discloses a pipe having areas of higher fracture resistance through cylindrical steel members which

  surround the pipe, to which they are all at least partial-

  The steel members are heavy and

  difficult to handle and install, and they are

additionally subjects to corrosion.

  In addition to the need for fracture arresting devices, it is desirable to provide the pipes and other objects with anti-corrosion protection even if no fracture arresting device is involved. but achieving an anti-corrosion protection of a pipe in the region of a fracture arresting device so

  compatible with the presence of fracture arresting devices

  ures poses additional problems.

  It is an object of the present invention to provide an improved apparatus for stopping a ductile fracture that propagates in an object, such as a pipe, and a method for

its implementation.

  Another purpose of the invention is to provide a device of the above type to stop a ductile fracture that spreads with minimal work and additional equipment and for a relatively low cost, and a

process for its implementation.

  Another object of the present invention is to provide an apparatus of the above type which is lightweight, resistant to corrosion and able to protect the object from impact, as well as

process for its implementation.

  Another object of the present invention is to provide an apparatus of the above type, and a method for its implementation.

  which provides anti-corrosion protection for the object.

  To achieve these and other objects, a plurality of fracture arresting devices are placed around the object that surround and contact the object at spaced intervals, each fracture arresting device being constituted a band of non-metallic, high strength, light, unidirectional fibers etc.

  embedded in a resinous material.

  Some non-metallic fibers have resistance

  very high tensile strength, while being lightweight, corrosion resistant and very low cost Glass fibers, for example, have a tensile strength which is about four times that of steel. continuous glass fibers aligned in one direction, for example in a wire comprising a plurality of

  flexible and parallel glass filaments, possess a

  Thus, a plurality of unidirectional and continuous glass fibers constitute a plurality of parallel wires surrounding an object that tends to develop ductile fractures that propagate in a direction perpendicular to the fractures. , makes the peripheral resistance of the object equal to that in the longitudinal direction and makes it possible to significantly increase the forces to which the object can withstand without defect. In addition, glass fibers, surrounding an object, in the form of band in the circumferential direction can stop a failure in the form of a

  ductile fracture that spreads once it is primed.

  Strips made from such unidirectional and continuous glass fibers lend themselves well to

  application on pipes as a fracture arresting device

  and can be rolled up at selected locations on pipe sections at the factory or can be wrapped around a pipe already installed on a job site Glass fibers also find application in situations where there is a risk of concentration of 'efforts, for example at the level of pipe connections and at the angles or elbows In addition, these strips can be wound either

by machine either by hand.

  To produce fracture arresting devices, the unidirectional and continuous glass fibers are embedded in a support of a resinous material which is then subjected to hardening, such as an enamel-asphalt, a

  coal tar enamel polyethylene or epoxy.

  Glass fibers are lightweight and not prone to corrosion and, when embedded in a hardened resinous support, the resulting fracture arresting device is free from corrosion and other environmental problems that strike. the fracture arresting devices of art

  In addition, the fracture arresting device con-

  The present invention is embodied in the present invention by providing the pipe with anti-corrosion protection, eliminating the ingress of dirt and moisture and preventing corrosion of the crevices. fractures is elastic and absorbs energy, thus protecting the hose from external shocks and avoiding the induction of

  Concentrations of effort in the pipe.

  The fracture arresting devices according to the present invention may be wound on a bare pipe and may also be wound on a pipe completely coated with a corrosion resistant substance; and they can be wound on a pipe with a coating loaded with a corrosion-resistant material The glass fibers of the fracture arresting devices can be saturated with a resinous material by passing them through a resin bath. as they are wound on the pipe, or the fibers can be saturated with the resinous materials by means of coating rollers or spray heads once in place on the pipe. Alternatively, the fibers can be impregnated beforehand. resin, wound on the pipe in the dry state and then heated to allow the resin to flow The glass fibers can be removed from a plurality of coils and aligned in parallel as they wind around the pipe , or they can be pre-aligned and held by transverse filaments to form mats that are

then wrapped around the pipe.

  Once the fiberglass strip, encased in a resinous support, wrapped around the pipe to a desired thickness, the support is cured to achieve a light, hardened, energy-absorbing, corrosion-resistant mass and fluid-proof Curing is accomplished by suitable means such as the application of heat, ultraviolet radiation or a catalyst. When the pipe is previously treated by a process that requires the application of heat, if for example, to coat the pipe with a fusion-bonded epoxy, the glass fibers and the resinous support can be applied immediately according to the above method, and the residual heat of the process can be used to effect the hardening of the resinous support, thereby eliminating the need for an additional hardening step. The present invention also envisages the realization of a pipe-independent fracture arresting device, which consists in winding a strip of glass fibers in a resinous support on a mandrel, in hardening it, in removing it from the mandrel and then to put it on the pipe-at the right time and place The fracture stop devices according to the present invention are very light,

  so that a device of one meter or more -

  It can easily be lifted and installed by a single worker. No particular means of securing the device to the pipe is necessary. It is sufficient to prevent the stop device from moving along the pipe and, for this purpose, the space between the device and the pipe can be filled with a foam, such as a plastic foam, which spreads

  the possibility of crevice corrosion.

  Thanks to the mechanical strength of the glass fibers and the ability of the resin to absorb energy, the fracture arresting devices protect, against shocks of external origin, the sections of pipe that they cover and prevent or reduce fragmentation of the pipe in the vicinity of a fracture arresting device upon failure

of the pipe.

  An embodiment of the present invention is hereinafter described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a fracture arresting device according to the present invention; when wrapped around a pipe; Figure 2 is an elevational view of the fracture arresting device of Figure 1 in place on a bare pipe; FIG. 3 is an elevational view of an alternative embodiment of the fracture arresting device during its winding around a coated pipe; FIG. 4 is an elevational view of the fracture arresting device of FIG. 1 in place on a pipe with a corrosion resistant coating; Figure 5 is an elevational view of an alternative embodiment of the fracture arresting device according to the present invention; Figure 6 is an elevational view of another alternative embodiment of the fracture arresting device according to the present invention; Figure 7 is an elevational view of another embodiment of the fracture arresting device according to FIG. 8 is a cross-sectional view of another embodiment of the fracture arresting device according to the present invention; Fig. 9 is a cross-sectional view of another embodiment of the fracture arresting device according to the present invention; Fig. 10 is another embodiment of the fracture arresting device according to the present invention; and FIG. 11 is a cross-sectional view of a pipe on which is mounted a fracture arresting device separately made according to another embodiment.

of the invention.

  As seen in FIG. 1, the fracture arresting device according to the present invention, indicated generally by the reference numeral 10, is wound around an object such as a bare pipe 12, mounted on a rotating mandrel 14 Although a pipe shown in FIG. 1 is provided, the fracture arresting device may be similarly wound around a compressed gas cylinder, blade or wing of a windmill or other object susceptible to fractures

  ductile propagating or cracking spreading freely.

  The fracture arresting device comprises a band consisting of a plurality of wires 16, each comprising a large number of non-metallic, non-conductive, inorganic, high strength, light, unidirectional and continuous fibers, such as glass fibers. Although one

  take as an example in the present description the fibers

  of glass, one can also use similar fibers having a high tensile strength, such as Kevlar fibers The son 16 are removed from a plurality of coils 18 carried by a rack 20 and pass through gathering and alignment devices 22 and 24 before passing into a bath 26 containing a resin 27 such as an epoxide, an enamel asphalt, coal tar enamel or polyethylene, or they are saturated with the resin A out of the bath 26, the son 16 pass over a wire applicator 28 movably mounted on a bar 30 disposed parallel to the rotating mandrel 14, and a device is generally provided to remove the excess resin The wire applicator 28 can move in both directions along the bar 30 between predetermined limits for winding on the pipe 12 a band of desired width In addition, it is possible to wind on the pipe 12 additional layers of continuous fibers coated with resi until you get a band or

  fracture arresting device 10 of appropriate thickness.

  The apparatus shown for winding the fracture arresting device 10 onto a pipe 12 is given purely by way of example, the glass fibers contained in the wires 16 which can be wound on the pipe 12 without application of

  resin, the resin 27 is then applied to the coils

  However, the application of the resin 27 to the threads 16 before the winding of the threads 16 on an object provides the advantage that the viscosity of the glass fibers can be applied to the pipe 12 by applicator rollers, spray nozzles or other suitable devices. of the resin 27 allows the wires

  to attach to the object helping to kick the start of the roll-

  Whatever the method chosen, it is necessary to apply a quantity of resin sufficient for the fracture arresting device 10 to consist of continuous and unidirectional glass fibers embedded in a resin support 27, and for a continuous connection is formed with the object, leaving no space for the penetration of

  dirt or moisture likely to cause corrosion.

  Fracture arresting devices 10 may be non

M 53998

  only wound on a pipe 12 mounted on a rotary mandrel 14 shown in Figure 1, but can also be applied to stationary objects by other machines and they can be applied by hand on rotating or stationary objects Some machines allow to Apply the fracture arresting devices 10 on the construction site as well as in the factory When the fracture arresting devices 10 are in place, the curing of

  resin 27 by application of heat, ultraviolet radiation

  violet, catalyst or other suitable means to obtain a light cured, energy-absorbing, resistant to

  corrosion, and impervious to fluids.

  The glass fibers can be impregnated beforehand

  resin 27 and applied to the pipe 12 in the dry state.

  Once the pre-impregnated glass fibers are in place, the application of the heat to the fibers has the effect of pouring the resin 27 so as to obtain a single mass of glass fibers embedded in a resinous support A subsequent application of heat will cause hardening

  resin, as well as all other hardening processes

mentioned above.

  Before treating a pipe according to the method of the present invention, it is preferable to clean the pipe by sandblasting or mechanical scraping and brushing with a wire brush to rid the pipe surface of oil, grease, dust, Moisture and non-adhesive deposits resulting from manufacture As seen in Figure 2, the fracture arresting device 10 is shown in place connected to the bare pipe 12 Apart from this application on a bare pipe 12 shown in Figure 2 , the fracture arresting device 10 can also be applied to a pipe to

  coating such as a pipe having an anti-

  For example, a relatively viscous hot substance, such as coal tar enamel, or asphalt enamel may be applied to the prepared outer surface of the pipe, as described in detail in US Patent Application 312958. of October 20, 1981 in the name of the present applicant Alternatively, the pipe may be pre-coated with a fluidized epoxide powder which is

  sprayed onto the outer surface of the

  heated pipe according to an electrostatic or other method.

  Alternatively, an extruded polyethylene layer may be applied to the outer surface of the pipe in a known manner. As shown in FIG. 3, a fracture arresting device 10 'is partially wound on a coated pipe

  12 ', the continuous glass fibers of the device 10' constit-

  The mat 34 is saturated with resin 27 and wound on the pipe 12 'to obtain another embodiment of the stuffing stopper 10' in accordance with the invention. present

  It is also possible to use mats of other

  figurations. When a fracture arresting device according to the present invention is applied to a coated pipe, as in the case illustrated in FIG. 3, the fracture arresting device 101 is wound around the coated pipe 121, the In this case, the winding of the fracture arresting device 12 'can be carried out immediately after the coating so that the residual heat of the coating process can effect the hardening of the resinous support of the coating. device, thus eliminating the need for

  separate step of hardening the support.

  As seen in FIG. 4, the fracture arresting device 10 may be wound around a pipe 12 "already provided with a coating such as a strip of paper, fabric or other material treated with asphalt or other anti-corrosion substance to ensure the pipe 12 "against corrosion The coating may be further constituted by a

  polyethylene or polypropylene tape coated with an adhesive.

  The fracture arresting device 10 of FIGS. 1 and 2 is shown disposed on the covering 36, but the fracture arresting device 10 'of FIG. 3, consisting of the resin saturated mat 34, can also be used on coating-36, as well as other forms of the shut-off device

  of fractures according to the present invention which will be described below.

  253399 w after. The fracture arresting devices are generally wound-in width and thickness determined to stop the propagation of a fracture and are arranged at predetermined intervals along a pipeline. For example, a device 10 It can be provided for each section of the pipeline. In most cases, it has been found that a fracture arresting device according to the present invention, of a width smaller than the diameter of the pipe and of a smaller thickness. to the thickness of the pipe, suffices, alone, to stop a fracture during propagation Strips of a width equal to about two thirds of the diameter of the pipe and a thickness equal to 60% of the thickness of the

  pipe stopped a fracture successfully.

  The fracture arresting devices can further be applied so that a strip of glass fibers in a resinous support would be insufficient to stop a fracture by itself, but a series of such strips is provided so that, acting together, they detect and stop the propagation of a fracture For example, as shown in FIG. 5, a continuous helical band 36 of glass fibers arranged in a resinous support can be helically applied along the entire length of the pipe, being wound on the joints 38, normally in the form of welds, between the pipe sections 12a, 12b, 12c The helix has a pitch such that there is a space between the turns adjacent to the helix Alternatively, it is possible to apply a plurality of mini-strips 40 distributed at small intervals along the pipe 12 to decelerate and stop the propagation of a

  fracture, as shown in Figure 6.

  According to another arrangement, continuous glass fibers embedded in a resinous support can be wound on alternating or periodic sections of the pipe 12, for example the pipe sections 12b and 12d, to obtain a fracture arresting device. extending along the entire length of the pipe section, as shown in Figure 7 Of course, with such an arrangement, a single fracture arresting device 42 is sufficient to stop a fracture, and only half of the pipe sections at maximum need a

fracture stop treatment.

  In general, the windings of a fracture arresting device according to the invention have rectangular configurations in cross-section, but other configurations than the rectangular configuration can be envisaged. As shown in FIG. The cross-section of the fracture arresting device 46 has an arcuate section so that the device 46 is thicker at its center and is notched at the center of the fracture arresting device 44. As can be seen in FIG. The transverse sections of the fracture arresting devices 44 and 46 of FIGS. 8 and 9, respectively, are drawn in dashed lines to

  evidence the cross-sections of the glass fibers.

  However, there are thousands of fibers arranged in parallel, in the same direction, each fiber preferably having a diameter of less than 0.0254 mm. The fracture arresting devices according to the present invention are essentially non-tension-wound, tension permitting the winding of the glass fibers in a regular and orderly manner being sufficient.

  stop fractures do not transmit efforts to

  to the pipe they surround, and thus do not tend to cause stress concentrations in the pipe, especially along the edges of the fracture arresting device. However, both embodiments of the figures 8 and 9 also make it possible to reduce the forces between the fracture arresting device and the pipe 12 at the edges of the fracture arresting device, thereby eliminating the possibility of forming stress concentrations at these locations of the fracture arresting device. pipe 12 caused by the stop device

fractures.

  Since the fracture arresting devices according to the present invention can be mounted on the pipe on the site, they can be placed directly on the seals 38 of the pipe 12, between the pipe sections 12a, 12b and 12c. as shown by the fracture arresting device 10 in Fig. 10, providing both fracture arrestability and seal protection 38, which generally require a separate form of protection, although the figure represents the fracture arresting device 10 of FIGS. 1 and 2 in place on the seals 38, the other embodiments of the fracture arresting device according to the present invention, for example that 10 'of FIG. 3

  using the mat 34, can be placed on the seals 38.

  FIG. 11 is a cross-sectional view of the pipe 12 on which is mounted a stop device of

  separable fractures 38, which consists of the same materials

  the other embodiments of the stop device described in the present application, and which is performed independently of the object to be treated by being, for example, wound on a rotating mandrel, hardened and removed Because the glass fibers and the resin is of a very light weight, the fracture ridge device for a pipe one meter or more in diameter is light enough to be lifted and placed by a single worker. on the pipe 12 and secured thereto to prevent slipping along the pipe A suitable mechanism for holding the separable fracture arresting device 48 in place on the pipe 12 is a foam packing 50, for example a plastic foam, filling the space between the

  pipe 12 and the fracture arresting device 48

  Foam 50 not only binds the fracture arresting device 48 and the hose 12 to each other, but also fills the space to prevent the ingress of dirt and moisture, thus avoiding the possibility of a

crevice corrosion.

  It goes without saying that many modifications can be made to the device described and shown without

  as far out of the scope of the invention.

Claims (15)

  A fracture arresting device for arresting a ductile fracture propagated in an object, the ductile fracture tending to propagate in a predetermined direction, characterized in that it comprises a band (10) consisting of a plurality of fibers non-metallic, continuous and of high tensile strength, fibers which are oriented perpendicular to said direction and embedded in a resinous support (27), said strip (10) enveloping said object (12) in contact with it.   2 Device according to claim 1, characterized in   the fibers (16) are glass fibers.   Device according to claim 1, characterized in that   that the resin (27) is an epoxide.   4 Device according to claim 1, characterized in that the strip (10) comprises a plurality of layers of the fibers. Device according to claim 1, characterized in   the band (10) is linked to the object (12).   Device according to claim 1, characterized in that   the fibers are held by transverse filaments   saux (32) to form a mat (34).   Device according to claim 1, characterized in that   the strip (36) is helically arranged.   8. Device according to claim 1, characterized in that the strip consists of a plurality of spaced strips (36), each having a thickness and width insufficient to stop a fracture but together having sufficient strength to decelerate and stop a fracture. Apparatus according to claim 1, characterized in that   the strip (44) is beveled along its edges (45).   Device according to claim 1, characterized in that the strip (46) has an arcuate transverse section, being thicker at its center and bevelled at its level. edges (47).   1 Device according to claim 1, characterized in that it further comprises a layer of foam material   (50) disposed between the band (48) and the object (12).   In combination, a fracture arresting device and a pipe in which a ductile fracture tends to propagate in a direction parallel to the axis of the pipe, characterized in that the fracture arresting device comprises a band (10). consisting of a plurality of non-metallic fibers, continuous and of high tensile strength, which fibers are oriented perpendicularly to said direction and embedded in a resinous support (27),   said tape wrapping the pipe (12) in contact with it.   Combination according to Claim 12, characterized in that the width of the strip (10) is less than diameter of the pipe (12).   Combination according to Claim 12, characterized in that the thickness of the strip (10) is less than the thickness of the pipe (12).   Combination according to claim 12, characterized in that the pipe comprises a coating layer and the device   fracture arresting device (10) is arranged on this layer.   Combination according to claim 12, characterized in that the pipe (12 ") has a coiled coating, the fracture arresting device (48) being disposed thereon. pipe (12) comprises a plurality of sections, a strip (42) being disposed on some of the sections 12b, 12d) substantially along the length of the section, while   other sections do not include tape.   Combination according to Claim 12, characterized in that the pipe comprises a plurality of sections and joints (38) between the sections (12), a strip (10) being arranged on each joint.   19 A method for stopping a ductile fracture propagating in an object, the ductile fracture tending to propagate in a predetermined direction, characterized in that it consists in: winding a strip (10) of continuous non-metallic fibers, high tensile strength, embedded in   a resinous support (27) around the object according to a direct   ion perpendicular to said direction, and   to harden the support.   Process according to claim 19, characterized in that the fibers are coated with resin before winding. Method according to claim 19, characterized in   that the fibers are coated with resin after winding.   Process according to claim 20, characterized in that it further comprises drying the front garment   winding and apply heat after winding for the resin to flow.   Process according to claim 19 or 22, characterized in that the winding and hardening steps are carried out after the object has been treated to give it a   resistance to corrosion in a process involving the application   of heat, the heat of this process   to perform the hardening step of the support.   24, A method for stopping a ductile fracture that propagates in an object, ductile fracture tending to propagate in a predetermined direction, characterized in that it consists in winding a strip of non-metallic fibers, continuous, unidirectional and a high tensile strength, fibers embedded in a resinous support, around a mandrel, hardening the resinous support to obtain a cured strip, removing the hardened strip from the mandrel, mounting the cured strip in place on the object so as to that the fibers are perpendicular to said predetermined direction.