Optical fiber sensing cable for fuel leak detection and preparation method thereof

Abstract

The present invention discloses an optical fiber sensing cable for detecting fuel leaks and a preparation method thereof. The optical fiber sensing cable for detecting fuel leaks comprises an oil sensing unit, an optical fiber and a protective sleeve. The oil sensing unit is used for absorbing oil and expanding; the optical fiber is spirally wound around the outer periphery of the oil sensing unit, and a plurality of gratings arranged at intervals along the length direction of the optical fiber are arranged inside the optical fiber; the protective sleeve is sleeved on the outer periphery of the oil sensing unit and the optical fiber. The application can be applied to harsh environments and long-distance oil pipelines, can quickly detect oil leaks, has high detection efficiency, and has very good prospects in oil leak monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to an optical fiber sensing cable for fuel leak detection and a preparation method thereof. Background Art

[0002] Pipeline corrosion, natural disasters, and human factors often lead to leakage accidents in buried oil pipelines. Leakage in oil pipelines not only causes energy waste and economic losses, but also causes serious environmental pollution.

[0003] Patent CN112762274A discloses a crude oil pipeline leakage detection robot, comprising: a supporting body, wherein a cylindrical cavity is provided inside the supporting body along the axial direction, and a plurality of strip grooves are evenly provided on the outer side of the supporting body along the circumferential direction, wherein a guide rail is fixedly installed in each strip groove, and two adjacent strip grooves are staggered; a plurality of caster assemblies, wherein the plurality of caster assemblies are opened to form an umbrella-shaped structure and contact the inner wall of the crude oil pipeline, or closed and retracted; a rotary drive assembly for driving the caster assemblies to rotate; and a plurality of axial propulsion assemblies, wherein the axial propulsion assemblies are shaftless propellers, and the plurality of shaftless propellers are evenly installed on the supporting body along the circumferential direction for driving the supporting body to actively advance.

[0004] However, long-distance oil pipelines are often buried underground or located in remote areas. The above-mentioned existing technologies are difficult to quickly reach the oil leak point for detection when dealing with long-distance oil pipelines, and the detection efficiency is low. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and propose an optical fiber sensing cable for fuel leak detection to solve the technical problems in the prior art that it is difficult to quickly travel to the oil leak point for detection when facing long-distance oil pipelines, resulting in low detection efficiency.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] The present invention provides an optical fiber sensing cable for fuel leak detection, comprising:

[0008] An oil sensing unit, the oil sensing unit being used for oil absorption and expansion;

[0009] an optical fiber, wherein the optical fiber is spirally wound around the outer periphery of the oil-sensing unit, and a plurality of gratings are provided in the optical fiber and spaced apart along the length thereof; and

[0010] The protective cover is sleeved on the outer periphery of the oil-sensing unit and the optical fiber.

[0011] In some embodiments, a plurality of optical fibers are provided, the plurality of optical fibers are arranged at intervals along the circumference of the oil sensing unit, and the gratings of the plurality of optical fibers are arranged in an interlaced manner.

[0012] In some embodiments, a side wall of the oil sensing unit is provided with a mounting groove, the mounting groove is arranged in a spiral shape, and the optical fiber is arranged in the mounting groove.

[0013] In some embodiments, the mounting groove is an arc-shaped groove or a V-shaped groove.

[0014] In some embodiments, the mounting groove is arranged in a spiral shape.

[0015] In some embodiments, the mounting groove is a V-shaped groove, the height of the V-shaped groove is one third of the radius of the oil sensing unit, and the angle of the V-shaped groove is in the range of 30°-45°; or

[0016] The installation groove is an arc-shaped groove, the depth of the arc-shaped groove is one fifth of the radius of the oil-sensing unit, and the radius of the arc-shaped groove is the same as the radius of the optical fiber.

[0017] In some embodiments, the oil-sensing unit is made of thermoplastic elastomer or anti-aging EPDM rubber.

[0018] In some embodiments, the protective cover includes a spiral armor tube and a braided layer. The spiral armor tube is sleeved on the outer periphery of the oil-sensing unit and the optical fiber, and the braided layer is arranged on the outer periphery of the spiral armor tube.

[0019] In some embodiments, the optical fiber sensing cable for fuel leak detection further includes a steel wire, which is disposed in the middle of the oil sensing unit and extends in the same direction as the oil sensing unit.

[0020] In some embodiments, the braided layer is made of nylon.

[0021] In some embodiments, the diameter of the oil sensing unit ranges from 5 mm to 20 mm.

[0022] In some embodiments, the distance between two adjacent gratings is 100 mm-2000 mm.

[0023] In addition, the present invention also provides a method for preparing an optical fiber sensing cable for fuel leak detection, comprising the following steps:

[0024] preparing optical fibers;

[0025] Extrusion molding oil-sensitive unit through extrusion equipment;

[0026] Lay the optical fiber on the side wall of the oil-sensing unit and fix the optical fiber to the oil-sensing unit;

[0027] The fixed optical fiber and oil-sensing unit are placed into a tubular protective sheath through packaging equipment and packaged into a cable.

[0028] Compared with the prior art, the optical fiber sensing cable for fuel leak detection provided by the present invention has an oil sensing unit for absorbing and expanding oil; the optical fiber is spirally wound around the outer periphery of the oil sensing unit, and a plurality of gratings arranged at intervals along its length are provided inside the optical fiber; the protective sleeve is sleeved on the outer periphery of the oil sensing unit and the optical fiber. When in use, the device is placed under the oil pipeline and kept consistent with the extension direction of the oil pipeline. When a leak occurs somewhere in the oil pipeline, hydrocarbon oil flows downward along the pipe wall, drips onto the protective sleeve, and contacts the oil sensing unit through the protective sleeve. The reaction of the hydrocarbon oil with the oil sensing unit causes the oil sensing unit to swell and expand. The oil-sensing unit expands to both sides, squeezing and driving the optical fiber to stretch along the axial and radial directions of the oil-sensing unit at the same time, thereby driving the grating to stretch, causing the stress field around the grating to change. Under the action of stress, its refractive index modulation period will change. Therefore, the wavelength change of the grating can be demodulated by a demodulator, thereby realizing the monitoring of oil leakage. The optical fiber is small in size, low in loss, high in sensitivity, anti-electromagnetic interference, good in insulation, corrosion resistance, and good in safety. It is easy to multiplex into a network, low in cost, and can be applied to harsh environments and long-distance oil pipelines. It can quickly detect oil leakage points and has high detection efficiency. It has very good prospects in oil leakage monitoring.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the description, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural schematic diagram of an embodiment of an optical fiber sensing cable for fuel leak detection provided by the present invention;

[0031] Figure 2 yes Figure 1 Cross-sectional view of a fiber optic sensing cable for fuel leak detection;

[0032] Figure 3 yes Figure 1 A cross-sectional view of the optical fiber;

[0033] Figure 4 yes Figure 1 Cross-sectional view of a fiber optic sensing cable for fuel leak detection at a central oil leak site.

[0034] Description of reference numerals:

[0035] 1- oil sensing unit, 12- arc groove;

[0036] 2-optical fiber, 21-fiber core, 22-grating, 23-tight sheath;

[0037] 3-protective sleeve, 31-spiral armor tube, 32-braided layer;

[0038] 4-Steel wire. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] In order to solve the technical problems in the prior art that it is difficult to quickly reach the oil leak point for detection in long-distance oil pipelines and the detection efficiency is low, the present invention provides a fiber optic sensing cable for fuel leak detection, which can be used in harsh environments and long-distance oil pipelines, can quickly detect the oil leak point, has high detection efficiency, and has very good prospects in oil leak monitoring.

[0041] See also Figure 1 , Figure 1 FIG. 1 is a schematic structural diagram of an optical fiber sensing cable for fuel leak detection according to an embodiment of the present invention.

[0042] The present invention provides an optical fiber sensing cable for fuel leak detection, comprising an oil sensing unit 1, an optical fiber 2, and a protective sleeve 3. The oil sensing unit 1 is used to absorb oil and expand; the optical fiber 2 is spirally wound around the outer circumference of the oil sensing unit 1, and a plurality of gratings 22 are provided in the optical fiber 2 and arranged at intervals along its length; the protective sleeve 3 is sleeved on the outer circumferences of the oil sensing unit 1 and the optical fiber 2.

[0043] In this example, see Figure 1The oil-sensing unit 1 is used to absorb oil and expand; the optical fiber 2 is spirally wound around the outer periphery of the oil-sensing unit 1, and a plurality of gratings 22 are arranged at intervals along the length direction of the optical fiber 2; the protective cover 3 is sleeved on the outer periphery of the oil-sensing unit 1 and the optical fiber 2. When in use, the device is placed under the oil pipeline and kept consistent with the extension direction of the oil pipeline. When a leak occurs somewhere in the oil pipeline, hydrocarbon oil flows down along the pipe wall and drips onto the protective cover 3, and contacts the oil-sensing unit 1 through the protective cover 3. The hydrocarbon oil reacts with the oil-sensing unit 1 to cause the oil-sensing unit 1 to swell and expand, and the oil-sensing unit 1 moves to both sides. After expansion, the optical fiber 2 is squeezed and driven to stretch in the axial and radial directions of the oil-sensing unit at the same time, thereby driving the grating 22 to stretch, causing the stress field around the grating 22 to change. Under the action of stress, its refractive index modulation period will change. Therefore, the wavelength change of the grating 22 can be demodulated by a demodulator, thereby realizing oil leakage monitoring. The optical fiber 2 is small in size, low in loss, high in sensitivity, anti-electromagnetic interference, good in insulation, corrosion resistance, and good in safety. It is easy to multiplex into a network, low in cost, and can be applied to harsh environments and long-distance oil pipelines. It can quickly detect oil leakage points and has high detection efficiency. It has very good prospects in oil leakage monitoring.

[0044] In one embodiment, a plurality of optical fibers 2 are provided, and the plurality of optical fibers 2 are arranged at intervals along the circumference of the oil sensing unit 1 , and the gratings 22 of the plurality of optical fibers 2 are arranged in an interlaced manner.

[0045] In this embodiment, since the spacing between the gratings 22 should not be too dense, the spacing between two adjacent gratings 22 is large. If the oil leakage point is between the two gratings 22, it is difficult to detect. Therefore, a plurality of optical fibers 2 can be provided, and the plurality of gratings 22 are evenly spaced around the circumference of the oil-sensing unit 1, and the gratings 22 in the plurality of optical fibers 2 are staggered. When arranged in the radial direction of the oil-sensing unit, the spacing between two adjacent gratings 22 in different optical fibers 2 is small, which not only improves the sensing accuracy, but also avoids the technical difficulties in the preparation process and the demodulation process, and can achieve long-distance and precise monitoring.

[0046] In one embodiment, see Figure 2 and Figure 4 The side wall of the oil sensing unit 1 is provided with a mounting groove, the mounting groove is arranged in a spiral shape, and the optical fiber 2 is arranged in the mounting groove.

[0047] In order to facilitate the installation and fixation of the optical fiber 2, the mounting groove is provided on the circumference of the oil sensing unit 1, and the mounting groove is adapted to the optical fiber 2, so that the optical fiber 2 can be placed in the mounting groove. The optical fiber 2 is limited by the mounting groove, which facilitates the fixation of the optical fiber 2 on the oil sensing unit 1.

[0048] In one embodiment, see Figure 2 , the mounting groove is an arc groove 12 or a V-shaped groove.

[0049] Specifically, the form of the installation groove is not limited, and the installation groove can be arranged in an arc shape or in a V shape, and can be arranged according to specific circumstances.

[0050] In one embodiment, the mounting groove is a V-shaped groove, the height of the V-shaped groove 11 is one third of the radius of the oil sensing unit 1 , and the angle of the V-shaped groove is in the range of 30°-45°.

[0051] Specifically, in order to adapt to the optical fiber 2, the height of the V-groove 11 is one-third of the radius of the oil-sensing unit 1, and the angle of the V-groove is in the range of 30°-45°. Such a setting can accommodate the optical fiber 2 so that the optical fiber 2 is stuck in the V-groove, thereby achieving the purpose of fixing the optical fiber 2.

[0052] In one embodiment, the installation groove is an arc-shaped groove 12 , the depth of the arc-shaped groove 12 is one fifth of the radius of the oil-sensing unit 1 , and the radius of the arc-shaped groove 12 is the same as the radius of the optical fiber 2 .

[0053] In this embodiment, the optical fiber 2 and the oil sensing unit 1 are connected by gluing, that is, they are fixed by gluing at a certain distance.

[0054] In this example, see Figure 3 The optical fiber 2 includes a core 21 and a tight sheath 23 arranged in sequence from the inside to the outside, wherein the grating 22 is arranged on the core 21, and multiple gratings 22 form a grating 22 array, and the tight sheath 23 is covered on the outer periphery of the core 21 for protecting the core 21.

[0055] In this embodiment, the tight sheath 23 is made of thermoplastic elastomer or nylon.

[0056] In one embodiment, the oil sensing unit 1 is made of thermoplastic elastomer or anti-aging EPDM rubber. Thermoplastic elastomer and anti-aging EPDM rubber have the property of swelling upon absorbing oil, thereby deforming at the oil leak site, thereby causing changes in the optical signal in the optical fiber at that site.

[0057] In one embodiment, the protective cover 3 includes a spiral armor tube 31 and a braided layer 32 . The spiral armor tube 31 is sleeved on the outer periphery of the oil-sensing unit and the optical fiber, and the braided layer 32 is arranged on the outer periphery of the spiral armor tube 31 .

[0058] In this embodiment, the spiral armor tube 31 is formed by a steel belt spirally wound around the oil-sensitive unit. The pitch of the spiral armor tube 31 is greater than the width of the steel belt, so that a gap is formed in the spiral armor tube 31 to facilitate oil infiltration into the oil-sensitive unit. The spiral armor tube 31 and the braided layer are used together to provide better protection and prevent the entire optical cable from being damaged.

[0059] In one embodiment, the braided layer 32 is made of nylon.

[0060] In this embodiment, the braided layer 32 is formed by weaving, and the material of the braided layer 32 is nylon. The braided layer 32 made of nylon can not only provide mechanical protection for the overall structure but also facilitate the penetration of hydrocarbon oil.

[0061] Specifically, the thickness of the braided layer 32 is 0.8 mm-1 mm.

[0062] In this embodiment, the steel strip is made of 304 stainless steel with a thickness of 0.4 mm. When the diameter of the oil sensing unit is 5 mm, the outer diameter of the spiral armor tube 31 is 10 mm.

[0063] In one embodiment, the optical fiber sensing cable for fuel leak detection further includes a steel wire 4, which is disposed in the middle of the oil sensing unit and extends in the same direction as the oil sensing unit.

[0064] In this embodiment, since the oil-sensitive unit will expand in the axial and radial directions after the oil penetrates, in order to prevent the oil-sensitive unit from excessively expanding in the axial direction and causing the entire optical cable to break, a steel wire 4 can be arranged inside the oil-sensitive unit. The steel wire 4 extends in the same direction as the oil-sensitive unit, that is, the steel wire 4 passes through the entire oil-sensitive unit in the axial direction of the oil-sensitive unit. Such an arrangement can enhance the tensile strength of the entire optical cable.

[0065] Specifically, the diameter of the steel wire 4 is 0.6 mm.

[0066] In one embodiment, the diameter of the oil sensing unit 1 ranges from 5 mm to 20 mm.

[0067] In one embodiment, the distance between two adjacent gratings 22 is 100 mm-2000 mm.

[0068] Since the preparation of the grating 22 is limited by the preparation process of the optical fiber 2 grating 22 array, the spacing between the gratings 22 should not be too dense. Too dense gratings 22 will cause attenuation of the optical signal, increase the difficulty of signal demodulation, and be unfavorable for long-distance sensing and monitoring. Therefore, in this embodiment, the spacing between two adjacent gratings 22 is 100mm-2000mm. Such a setting can achieve a better monitoring effect and avoid the gratings 22 being too dense.

[0069] In this embodiment, the length of the grating 22 is 1 mm-5 mm.

[0070] In this embodiment, the diameter of the fiber core 21 is 0.25 mm, and the diameter of the optical fiber 2 is 0.8 mm-1.5 mm.

[0071] In order to better understand the present invention, the following Figures 1 to 4 The technical solution of the present invention is described in detail:

[0072] During specific use, the device is placed below the oil pipeline, aligned with its extension direction. When a leak occurs somewhere in the pipeline, hydrocarbon oil flows down the pipeline wall, drips onto the protective sheath 3, and then penetrates the protective sheath 3 to contact the oil-sensing unit 1. The hydrocarbon oil reacts with the oil-sensing unit 1, causing it to swell. The oil-sensing unit 1 expands in both directions, squeezing and driving the optical fiber 2 to stretch axially and radially, thereby stretching the grating 22. The stress field around the grating 22 changes, and its refractive index modulation period changes under the action of stress. Therefore, the wavelength change of the grating 22 can be demodulated by a demodulator, thereby enabling oil leak monitoring. The optical fiber 2 is compact, low-loss, highly sensitive, resistant to electromagnetic interference, excellent insulative properties, corrosion-resistant, and safe. It is easy to reuse into a network, is low-cost, and is suitable for harsh environments and long-distance oil pipelines. It can quickly detect oil leaks with high detection efficiency, and has a very promising prospect in oil leak monitoring.

[0073] In addition, the present invention also provides a method for preparing an optical fiber sensing cable for fuel leak detection, comprising the following steps:

[0074] S1, preparing optical fiber 2;

[0075] Specifically, the large-scale grating 22 array technology is prepared online using an optical fiber 2 drawing tower, and the grating 22 array is engraved on the fiber core 21. The length of the grating 22 is 1mm-5mm, the interval between two adjacent gratings 22 is 100mm-2000mm, and the diameter of the fiber core 21 is 0.25mm.

[0076] A layer of tight nylon sheath 23 is extruded on the surface of the fiber core 21 to form the optical fiber 2. The diameter of the optical fiber 2 is 0.8 mm to 1.5 mm.

[0077] S2, extruding the oil-sensing unit 1 through an extrusion device;

[0078] Specifically, a steel wire 4 having a diameter of 0.6 mm is prepared, and then the oil-sensitive unit 1 is extrusion-molded on the outer periphery of the steel wire 4 using an extrusion device.

[0079] Specifically, a material having a swelling property for hydrocarbon oil is extruded by an extrusion device to form an oil-sensing unit 1 having a V-shaped groove on its surface. The V-shaped groove is arranged in a spiral shape, and the diameter of the oil-sensing unit 1 is 5 mm to 20 mm.

[0080] Specifically, a material having a swelling property for hydrocarbon oil is extruded by an extrusion device to form an oil-sensing unit 1 having an arc groove 12 on its surface. The arc groove 12 is arranged in a spiral shape, and the diameter of the oil-sensing unit 1 is 5 mm to 20 mm.

[0081] S3, attaching the optical fiber 2 to the side wall of the oil sensing unit 1, and fixing the optical fiber 2 to the oil sensing unit 1;

[0082] Specifically, based on the embodiment of the oil-sensitive unit 1 without grooves on the surface, the optical fiber is spirally wound around the circumference of the oil-sensitive unit, and then the optical fiber 2 and the oil-sensitive unit 1 are fixed using an automatic dispensing machine with UV curing function and a dispensing loading platform, and the glue point of the UV curing glue is located in the middle position of two adjacent gratings 22.

[0083] Specifically, based on the embodiment of the oil-sensitive unit 1 having a V-groove on the surface, the optical fiber 2 is fitted into the V-groove, and then the optical fiber 2 and the oil-sensitive unit 1 are fixed using an automatic dispensing machine with UV curing function and a dispensing loading platform, and the glue point of the UV curing glue is located in the middle position of two adjacent gratings 22.

[0084] Specifically, based on an embodiment of an oil-sensitive unit 1 having an arc-shaped groove 12 on its surface, a twisting machine is used to place the optical fiber 2 in the arc-shaped groove 12, and then an automatic dispensing machine with UV curing function and a dispensing loading platform are used to fix the optical fiber 2 and the oil-sensitive unit 1, and the glue point of the UV curing glue is located in the middle position of two adjacent gratings 22.

[0085] S4. Place the fixed optical fiber 2 and the oil sensing unit 1 into a tubular protective sheath 3 through a packaging device and package them into a cable.

[0086] Specifically, a steel strip is spirally wound to form a spiral armor tube 31 and a nylon material is braided to form a braided layer, which are then arranged inside and outside the outer layer. Then, the fixed optical fiber 2 and the oil sensing unit 1 are placed in a tubular protective sheath 3 and packaged into a cable.

[0087] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. An optical fiber sensing cable for fuel leak detection, characterized in that: It includes: An oil sensing unit, the oil sensing unit is used for oil absorption and expansion; An optical fiber, wherein the optical fiber is spirally wound around the outer circumference of the oil sensing unit, and the optical fiber is provided with a plurality of gratings arranged at intervals along the length direction thereof; and A protective sleeve, sleeved on the outer circumference of the oil sensing unit and the optical fiber; The side wall of the oil sensing unit is provided with a mounting groove, the mounting groove is arranged in a spiral shape, and the optical fiber is arranged in the mounting groove; The mounting groove is an arc groove or a V-shaped groove; A steel wire is arranged in the middle of the oil-sensitive unit and is consistent with the extending direction of the oil-sensitive unit.

2. The optical fiber sensing cable for fuel leak detection according to claim 1, characterized in that: A plurality of optical fibers are provided, and the plurality of optical fibers are arranged at intervals along the circumference of the oil sensing unit, and the gratings of the plurality of optical fibers are arranged in an interlaced manner.

3. The optical fiber sensing cable for fuel leak detection according to claim 1, characterized in that: The mounting groove is a V-shaped groove, the height of the V-shaped groove is one third of the radius of the oil sensing unit, and the angle of the V-shaped groove is in the range of 30°-45°; or The installation groove is an arc-shaped groove, the depth of the arc-shaped groove is one fifth of the radius of the oil-sensing unit, and the radius of the arc-shaped groove is the same as the radius of the optical fiber.

4. The optical fiber sensing cable for fuel leak detection according to claim 1, characterized in that: The material of the oil-sensing unit is thermoplastic elastomer or anti-aging EPDM rubber.

5. The optical fiber sensing cable for fuel leak detection according to claim 1, characterized in that: The protective sleeve comprises a spiral armor tube and a braided layer. The spiral armor tube is sleeved on the outer periphery of the oil sensing unit and the optical fiber, and the braided layer is arranged on the outer periphery of the spiral armor tube.

6. The optical fiber sensing cable for fuel leak detection according to claim 1, characterized in that: The diameter of the oil-sensing unit ranges from 5 mm to 20 mm, and the spacing between two adjacent gratings ranges from 100 mm to 2000 mm.

7. A method for preparing an optical fiber sensing cable for fuel leak detection, used for preparing the optical fiber sensing cable for fuel leak detection according to any one of claims 1 to 6, characterized in that: The following steps are involved: preparing optical fiber; Extrusion molding oil-sensitive unit through extrusion equipment; Lay the optical fiber on the side wall of the oil-sensitive unit and fix the optical fiber to the oil-sensitive unit; The fixed optical fiber and oil-sensing unit are placed into a tubular protective sheath through packaging equipment and packaged into a cable.

Images