A polyurethane lined steel pipe monitoring sensor and preparation method thereof

Abstract

A polyurethane lined steel pipe monitoring sensor and a preparation method thereof belong to the field of new material technology. The sensor provides a polyurethane lined steel pipe monitoring sensor based on the principle of electromagnetic induction, which solves the problem of weak conductivity and poor sensing sensitivity when polymer-based conductive materials act on sensing conductive elements. The lack of connection between the coil and the magnetic powder-filled polyurethane circular film in the sensor reduces the stress concentration point in the sensor. The sensor uses the impact of the fluid on the inner lining layer, and there are no wires and sensing elements that penetrate the inner lining layer, which greatly reduces the risk of fatigue fracture of the sensing element and improves the reliability of monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and specifically relates to a polyurethane lined steel pipe monitoring sensor and a preparation method thereof, and in particular to a polyurethane lined steel pipe monitoring sensor based on the electromagnetic induction principle and a preparation method thereof. Background Art

[0002] Polyurethane lined steel pipes are widely used in the mining industry, mainly for high-pressure sand-carrying fluid transportation. As the use time increases, the polyurethane lining layer gradually wears out. At present, the wear degree of the lining layer is difficult to monitor outside the pipe, resulting in untimely replacement and leakage. In response to the above problems, the prior art solution with patent application number CN202311562941 discloses a method for preparing a service life alarm sensor for a polyurethane lined steel pipe, and a polyurethane-based high-conductivity sensor is made and buried in the lining layer. When the lining layer is worn to a certain height, the conductive part of the sensor is worn and broken, the loop resistance changes, and the alarm signal is triggered. However, during the use of this type of technology, due to the high resistance value of the polyurethane-based conductive sensor element, when the content of conductive substances (such as ions, etc.) in the conveying medium is high, the sensing sensitivity is low. At the same time, the height of the sensor element and the wire penetrating the lining layer is the set warning height, and the sensor element and the wire form a penetrating stress concentration point in the lining layer, forming a structural defect that is easily damaged. In addition, the inner lining of the polyurethane-lined steel pipe is constantly subjected to pressure and impact during transportation, and the polyurethane-based sensor elements embedded inside are prone to fatigue fracture, causing damage to the sensor. Summary of the invention

[0003] In order to address the defects in the prior art, the present invention proposes a polyurethane lined steel pipe monitoring sensor and a preparation method thereof, which solves the problems of low sensitivity, easy generation of stress concentration points and poor fatigue resistance of polyurethane-based conductive sensor elements.

[0004] The present invention utilizes the following technical solutions.

[0005] A method for preparing a sensor for monitoring a polyurethane lined steel pipe, comprising:

[0006] S01, first weigh the polyurethane resin, add 40-70% of the mass of magnetic powder filler relative to the mass of the polyurethane resin, and use a stirrer to mix the polyurethane resin with the magnetic powder filler for 5-10 minutes to obtain a mixture;

[0007] S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, pour into a mold to form a magnetic powder-filled polyurethane circular film with a thickness of 0.2-2 mm and a diameter of 5-10 mm, cure the circular film at 90° C. for 3-10 min, cool to 0-5° C. to slow down the curing of the circular film, and then demold;

[0008] S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, casting the coil with polyurethane without magnetic powder and with a curing agent to form a circular film containing the coil, the thickness of the circular film is 0.2-2 mm, curing the circular film at 90° C. for 3-10 minutes, cooling to 0-5° C. to slow down the curing of the circular film, and then demolding;

[0009] S04, bury the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pour the polyurethane without magnetic powder and added with curing agent, cure at 90℃ for 3-10min, and cool to 0-5℃ to slow down the demoulding after curing;

[0010] S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

[0011] Furthermore, the material of the magnetic powder filler is a mixture of one or more of manganese-zinc ferrite, nickel-zinc ferrite, neodymium-iron-boron, aluminum-iron-boron, iron-silicon, and iron-silicon-aluminum in equal amounts.

[0012] Furthermore, the magnetic powder filler is made of neodymium iron boron powder.

[0013] Furthermore, the particle size of the magnetic powder filler is 3-10 μm.

[0014] Furthermore, the particle size of the magnetic powder filler is 5 μm.

[0015] Furthermore, the outer diameter of the spiral coil is 1-1.5 mm, the number of turns is 10-20, the coil spacing is 0.1-0.54 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.05-0.4 mm.

[0016] Furthermore, the diameter of the thin-diameter insulating enameled wire is 0.1 mm.

[0017] Furthermore, the magnetization time for thickness direction magnetization is 2s, the magnetization current is 30KA, and the magnetization voltage is DC1500V.

[0018] Furthermore, the method for preparing the polyurethane lined steel pipe monitoring sensor further includes:

[0019] S06. Remove rust and oil from the inner wall of the steel pipe, and adhere several sensor wires for monitoring the polyurethane-lined steel pipe based on the principle of electromagnetic induction to the pipe wall at the same time. The sensors are evenly distributed in the circumferential direction with an interval of 360 / X°. In the length direction, each group of 4 sensors is distributed with an interval of 100-200mm, and all leg wires are led out from the flange. After adhesion, keep warm at 100-120℃ for 60-90min. Then, use the centrifugal method to process the polyurethane lining on the inner wall of the steel pipe. After being cross-linked at 120℃ for 12-14h and slowly cured at room temperature for 80-100 hours, the sensor can be buried.

[0020] A polyurethane lined steel pipe monitoring sensor, comprising:

[0021] A polyurethane lined steel pipe monitoring sensor is prepared according to the preparation method of the polyurethane lined steel pipe monitoring sensor.

[0022] The beneficial effects of the present invention are that, compared with the prior art, the technical effects of the present invention include:

[0023] 1. A polyurethane lined steel pipe monitoring sensor based on the principle of electromagnetic induction is provided to solve the problem of weak conductivity and poor sensing sensitivity when polymer-based conductive materials act as sensing conductive elements.

[0024] 2. No connection between the coil and the magnetic powder-filled polyurethane circular film in the sensor reduces stress concentration points in the sensor.

[0025] 3. The sensor uses the impact of the fluid on the inner lining layer, and there are no wires and sensing elements penetrating the inner lining layer, which greatly reduces the risk of fatigue fracture of the sensing element and improves the reliability of monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of a method for preparing a sensor for monitoring a polyurethane lined steel pipe. DETAILED DESCRIPTION

[0027] The prior art scheme with patent application number CN202311562941 discloses a method for preparing a service life alarm sensor for a polyurethane lined steel pipe, and a polyurethane-based high-conductivity sensor is made and buried in the inner lining. When the inner lining is worn to a certain height, the conductive part of the sensor is worn and broken, the loop resistance changes, and an alarm signal is triggered. However, during the use of this type of technology, due to the high resistance value of the polyurethane-based conductive sensor element, when the content of conductive substances (such as ions, etc.) in the conveying medium is high, the sensing sensitivity is low. At the same time, the height of the sensor element and the wire penetrating the inner lining is the set warning height, and the sensor element and the wire form a penetrating stress concentration point in the inner lining, forming a structural defect that is easily damaged. In addition, the inner lining of the polyurethane lined steel pipe is constantly subjected to pressure and impact during the transportation process, and the polyurethane-based sensor element buried inside is prone to fatigue fracture, causing damage to the sensor.

[0028] In view of the above problems, the present invention provides a polyurethane lined steel pipe monitoring sensor based on the principle of electromagnetic induction and a preparation method thereof, which solves the problems of low sensitivity, easy generation of stress concentration points and poor fatigue resistance of polyurethane-based conductive sensor elements.

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely express the technical solution of the present invention. The embodiments expressed in this application are only some embodiments of the present invention, not all embodiments. According to the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the protection scope of the present invention.

[0030] like Figure 1 As shown, the preparation method of a polyurethane lined steel pipe monitoring sensor according to the present invention comprises:

[0031] S01, first weigh the polyurethane resin, take the polyurethane resin as a base, add 40-70% of the magnetic powder filler relative to the base by mass, use a high-speed stirrer to mix the polyurethane resin with the magnetic powder filler for 5-10 minutes to obtain a mixture;

[0032] S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, pour into a mold to form a magnetic powder-filled polyurethane circular film with a thickness of 0.2-2 mm and a diameter of 5-10 mm, cure the circular film at 90° C. for 3-10 minutes, cool to 0-5° C. to slow down the curing of the circular film, and then demold; the curing agent can be isophorone diisocyanate with a mass of 20% of the polyurethane resin.

[0033] In a preferred but non-limiting embodiment of the present invention, the material of the magnetic powder filler is a mixture of one or more of manganese zinc ferrite, nickel zinc ferrite, neodymium iron boron, aluminum iron boron, iron silicon, and iron silicon aluminum in equal amounts.

[0034] In a preferred but non-limiting embodiment of the present invention, the magnetic powder filler is made of high temperature resistant neodymium iron boron powder.

[0035] In a preferred but non-limiting embodiment of the present invention, the particle size of the magnetic powder filler is 3-10 μm.

[0036] In a preferred but non-limiting embodiment of the present invention, the particle size of the magnetic powder filler is 5 μm.

[0037] S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, and casting the coil with polyurethane containing no magnetic powder and adding a curing agent according to the method of S01 to form a circular film containing the coil, the thickness of the circular film is 0.2-2 mm, and the circular film is cured at 90° C. for 3-10 minutes, and then the temperature is reduced to 0-5° C. to slow down the curing of the circular film and then demolding;

[0038] In a preferred but non-limiting embodiment of the present invention, the outer diameter of the spiral coil is 1-1.5 mm, the number of turns is 10-20, the coil spacing is 0.1-0.54 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.05-0.4 mm.

[0039] In a preferred but non-limiting embodiment of the present invention, the diameter of the thin-diameter insulating enameled wire is 0.1 mm. The method of casting the coil with polyurethane containing no magnetic powder and adding curing agent to form a circular film containing the coil according to the S01 method includes:

[0040] First, the same mass of polyurethane resin as that in S01 is weighed, and a spiral coil whose mass is 40-70% relative to the mass of the reference is added to the polyurethane resin as a base, and the polyurethane resin with the spiral coil is mixed with a high-speed stirrer for 5-10 minutes to obtain a mixture; after vacuum degassing the mixture, a curing agent is added, and vacuum degassing is continued after uniform stirring, and a circular film containing a coil with a thickness of 0.2-2 mm and a diameter of 5-10 mm is cast in a mold.

[0041] S04, burying the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pouring polyurethane without magnetic powder and added with curing agent (the amount of curing agent and polyurethane is the same as in S01), curing at 90°C for 3-10min, and cooling to 0-5°C to slow down demolding after curing;

[0042] S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

[0043] In a preferred but non-limiting embodiment of the present invention, the magnetization time for thickness direction magnetization is 2s, the magnetization current is 30KA, and the magnetization voltage is DC1500V.

[0044] In a preferred but non-limiting embodiment of the present invention, the method for preparing a sensor for monitoring a polyurethane lined steel pipe further comprises:

[0045] S06. Remove rust and oil from the inner wall of the steel pipe, and adhere the sensor wires for monitoring the polyurethane-lined steel pipe based on the electromagnetic induction principle to the pipe wall at the same time. The number is several (the specific number can be 4, 8, 16). The sensors are evenly distributed in the circumferential direction, and the interval angle is 360 / X°; in the length direction, every 4 sensors are grouped, and each group is distributed with an interval of 100-200mm, and all the foot wires are led out from the flange; after adhesion, keep warm at 100-120℃ for 60-90min; then use the centrifugal method to process the polyurethane lining on the inner wall of the steel pipe, and after being cross-linked at 120℃ for 12-14h, and slowly cured at room temperature for 80-100 hours, the sensor can be buried. The method of using the conductive sensor is: install a multi-channel micro-current monitoring device at the flange to monitor the current generated at the location of each sensor in real time. When the inner lining layer is under pressure or impact, relative movement occurs between the coil and the magnetic powder-filled polyurethane circular film, and a current signal is generated in the sensor coil, which can monitor whether a large impact or vibration occurs in the pipe. In addition, when the magnetic powder-filled polyurethane circular film disappears due to wear, the coil no longer generates a microcurrent signal, indicating that the polyurethane lining at a certain point has been worn to the preset thickness of the sensor. At this time, the corresponding line of the monitoring device sends an alarm, giving periodic reminders of the wear of the inner wall.

[0046] The polyurethane lined steel pipe monitoring sensor of the present invention comprises:

[0047] A polyurethane lined steel pipe monitoring sensor is prepared according to the preparation method of the polyurethane lined steel pipe monitoring sensor.

[0048] The beneficial effects of the present invention are that, compared with the prior art, the technical effects of the present invention include:

[0049] 1. A polyurethane lined steel pipe monitoring sensor based on the principle of electromagnetic induction is provided to solve the problem of weak conductivity and poor sensing sensitivity when polymer-based conductive materials act as sensing conductive elements.

[0050] 2. No connection between the coil and the magnetic powder-filled polyurethane circular film in the sensor reduces stress concentration points in the sensor.

[0051] 3. The sensor uses the impact of the fluid on the inner lining layer, and there are no wires and sensing elements penetrating the inner lining layer, which greatly reduces the risk of fatigue fracture of the sensing element and improves the reliability of monitoring.

[0052] The following are specific embodiments to further illustrate the present invention:

[0053] Embodiment 1:

[0054] A method for preparing a sensor for monitoring a polyurethane lined steel pipe comprises:

[0055] S01, first weighing a polyurethane resin, taking the polyurethane resin as a base, adding a magnetic powder filler in an amount of 40% by mass relative to the base, and mixing the polyurethane resin with the magnetic powder filler using a high-speed stirrer for 5 minutes to obtain a mixture;

[0056] S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, pour into a mold to form a magnetic powder-filled polyurethane circular film with a thickness of 0.2 mm and a diameter of 5 mm, cure the circular film at 90° C. for 3 minutes, cool to 0° C. to slow down the curing of the circular film, and then demold; the curing agent can be isophorone diisocyanate with a mass of 20% of the polyurethane resin.

[0057] The material of magnetic powder filler is manganese-zinc ferrite.

[0058] The particle size of the magnetic powder filler is 3 μm.

[0059] S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, and casting the coil with polyurethane containing no magnetic powder and adding a curing agent according to the method of S01 to form a circular film containing the coil, the thickness of the circular film is 0.2 mm, and the circular film is cured at 90° C. for 3 minutes, and then cooled to 0° C. to slow down the curing of the circular film and then demolded;

[0060] The outer diameter of the spiral coil is 1 mm, the number of turns is 10, the coil spacing is 0.1 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.05 mm.

[0061] The method of casting the coil with polyurethane containing no magnetic powder and adding curing agent to form a circular film containing the coil according to the S01 method includes:

[0062] First, weigh the same mass of polyurethane resin as that in S01, take the polyurethane resin as the base, add 40% of the mass of spiral coil relative to the base, use a high-speed stirrer to mix the polyurethane resin with the spiral coil for 5 minutes to obtain a mixture; after vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, and cast in a mold to form a circular film containing a coil with a thickness of 0.2 mm and a diameter of 5 mm.

[0063] S04, burying the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pouring polyurethane without magnetic powder and added with curing agent (the amount of curing agent and polyurethane is the same as in S01), curing at 90° C. for 3 minutes, and cooling to 0° C. to slow down the demolding after curing;

[0064] S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

[0065] The magnetization time for thickness direction magnetization is 2s, the magnetization current is 30KA, and the magnetization voltage is DC1500V. The preparation method of the sensor for monitoring polyurethane lined steel pipe also includes:

[0066] S06. The inner wall of the steel pipe is derusted and degreased, and the sensor wires for monitoring the polyurethane-lined steel pipe based on the principle of electromagnetic induction are adhered to the pipe wall at the same time. There are 4 sensors evenly distributed in the circumferential direction with an interval of 360 / X°. In the length direction, each group of 4 sensors is distributed with an interval of 100mm, and all the leg wires are led out from the flange. After adhesion, keep warm at 100℃ for 60min. Then, use the centrifugal method to process the polyurethane lining on the inner wall of the steel pipe. After cross-linking at 120℃ for 12h and slow curing at room temperature for 80 hours, the sensor can be buried.

[0067] The method of using the conductive sensor is as follows: a multi-channel micro-current monitoring device is installed at the flange to monitor the current generated at each sensor location in real time. When the inner lining layer is under pressure or impact, relative movement occurs between the coil and the magnetic powder-filled polyurethane circular film, and a current signal is generated in the sensor coil, which can monitor whether a large impact or vibration occurs in the pipe; in addition, when the magnetic powder-filled polyurethane circular film disappears due to wear, the coil no longer generates a micro-current signal, indicating that the polyurethane lining at a certain point has been worn to the preset thickness of the sensor. At this time, the corresponding line of the monitoring device sends an alarm to provide a periodic reminder of the wear of the inner wall.

[0068] Sensors for monitoring polyurethane lined steel pipes, including:

[0069] A polyurethane lined steel pipe monitoring sensor is prepared according to the preparation method of the polyurethane lined steel pipe monitoring sensor described in this embodiment.

[0070] Embodiment 2:

[0071] A method for preparing a sensor for monitoring a polyurethane lined steel pipe comprises:

[0072] S01, first weighing a polyurethane resin, taking the polyurethane resin as a base, adding a magnetic powder filler in an amount of 55% by mass relative to the base, and mixing the polyurethane resin with the magnetic powder filler using a high-speed stirrer for 7 minutes to obtain a mixture;

[0073] S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, cast in a mold to form a circular polyurethane film filled with magnetic powder with a thickness of 1.1 mm and a diameter of 7 mm, cure the circular film at 90°C for 6 minutes, cool to 3°C to slow down the curing of the circular film, and then demold; the curing agent can be isophorone diisocyanate with a mass of 20% of the polyurethane resin.

[0074] The magnetic powder filler is made of nickel-zinc ferrite.

[0075] The particle size of the magnetic powder filler is 6 μm.

[0076] S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, and casting the coil with polyurethane containing no magnetic powder and adding a curing agent according to the method of S01 to form a circular film containing the coil, the thickness of the circular film is 1.1 mm, and the circular film is cured at 90° C. for 6 minutes, and then the temperature is reduced to 3° C. to slow down the curing of the circular film and then demolded;

[0077] The outer diameter of the spiral coil is 1.2 mm, the number of turns is 15, the coil spacing is 0.32 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.22 mm.

[0078] The method of casting the coil with polyurethane containing no magnetic powder and adding curing agent to form a circular film containing the coil according to the S01 method includes:

[0079] First, weigh the same mass of polyurethane resin as that in S01, and add 55% of the mass of spiral coils relative to the mass of the benchmark to the polyurethane resin. Use a high-speed stirrer to mix the polyurethane resin with the spiral coils for 7 minutes to obtain a mixture. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, and cast it in a mold to form a circular film containing coils with a thickness of 1.1 mm and a diameter of 7 mm.

[0080] S04, burying the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pouring polyurethane without magnetic powder and added with curing agent (the amount of curing agent and polyurethane is the same as in S01), curing at 90° C. for 6 minutes, and cooling to 3° C. to slow down the demolding after curing;

[0081] S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

[0082] The magnetization time for thickness direction magnetization is 2s, the magnetization current is 30KA, and the magnetization voltage is DC1500V. The preparation method of the sensor for monitoring polyurethane lined steel pipe also includes:

[0083] S06. The inner wall of the steel pipe is derusted and degreased, and the sensor wires for monitoring the polyurethane-lined steel pipe based on the principle of electromagnetic induction are adhered to the pipe wall at the same time. There are 8 sensors evenly distributed in the circumferential direction with an interval of 360 / X°. In the length direction, 4 sensors are arranged in a group with an interval of 150mm between each group, and all the leg wires are led out from the flange. After adhesion, the sensors are kept warm at 110℃ for 75min. The polyurethane lining is then processed on the inner wall of the steel pipe by the centrifugal method. After being cross-linked at 120℃ for 13h and slowly cured at room temperature for 90 hours, the sensor embedding is completed.

[0084] The method of using the conductive sensor is as follows: a multi-channel micro-current monitoring device is installed at the flange to monitor the current generated at each sensor location in real time. When the inner lining layer is under pressure or impact, relative movement occurs between the coil and the magnetic powder-filled polyurethane circular film, and a current signal is generated in the sensor coil, which can monitor whether a large impact or vibration occurs in the pipe; in addition, when the magnetic powder-filled polyurethane circular film disappears due to wear, the coil no longer generates a micro-current signal, indicating that the polyurethane lining at a certain point has been worn to the preset thickness of the sensor. At this time, the corresponding line of the monitoring device sends an alarm to provide a periodic reminder of the wear of the inner wall.

[0085] Sensors for monitoring polyurethane lined steel pipes, including:

[0086] A polyurethane lined steel pipe monitoring sensor is prepared according to the preparation method of the polyurethane lined steel pipe monitoring sensor described in this embodiment.

[0087] Embodiment 3:

[0088] A method for preparing a sensor for monitoring a polyurethane lined steel pipe comprises:

[0089] S01, first weighing a polyurethane resin, taking the polyurethane resin as a base, adding a magnetic powder filler in an amount of 70% of the base mass, and mixing the polyurethane resin with the magnetic powder filler using a high-speed stirrer for 10 minutes to obtain a mixture;

[0090] S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, pour into a mold to form a 2 mm thick and 10 mm diameter magnetic powder filled polyurethane circular film, cure the circular film at 90°C for 10 minutes, cool to 5°C to slow down the curing of the circular film and then demold; the curing agent can be isophorone diisocyanate with a mass of 20% of the polyurethane resin.

[0091] In a preferred but non-limiting embodiment of the present invention, the magnetic powder filler is made of neodymium iron boron.

[0092] The particle size of the magnetic powder filler is 10 μm.

[0093] S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, and casting the coil with polyurethane containing no magnetic powder and adding a curing agent according to the method of S01 to form a circular film containing the coil, the thickness of the circular film is 2 mm, and the circular film is cured at 90° C. for 10 minutes, and then cooled to 5° C. to slow down the curing of the circular film and then demolded;

[0094] The outer diameter of the spiral coil is 1.5 mm, the number of turns is 20, the coil spacing is 0.54 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.4 mm.

[0095] The method of casting the coil with polyurethane containing no magnetic powder and adding curing agent to form a circular film containing the coil according to the S01 method includes:

[0096] First, weigh the same mass of polyurethane resin as that in S01, take the polyurethane resin as the base, add 70% of the mass of spiral coil relative to the base, use a high-speed stirrer to mix the polyurethane resin with the spiral coil for 10 minutes to obtain a mixture; after vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, and cast in a mold to form a circular film containing a coil with a thickness of 2 mm and a diameter of 10 mm.

[0097] S04, burying the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pouring polyurethane without magnetic powder and added with curing agent (the amount of curing agent and polyurethane is the same as in S01), curing at 90° C. for 10 minutes, and cooling to 5° C. to slow down the demolding after curing;

[0098] S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

[0099] The magnetization time for thickness direction magnetization is 2s, the magnetization current is 30KA, and the magnetization voltage is DC1500V. The preparation method of the sensor for monitoring polyurethane lined steel pipe also includes:

[0100] S06. The inner wall of the steel pipe is derusted and degreased, and the sensor wires for monitoring the polyurethane-lined steel pipe based on the principle of electromagnetic induction are adhered to the pipe wall at the same time. There are 16 sensors evenly distributed in the circumferential direction with an interval of 360 / X°. In the length direction, 4 sensors are arranged in a group with an interval of 200mm between each group, and all the leg wires are led out from the flange. After adhesion, the sensors are kept warm at 120℃ for 90min. The polyurethane lining is then processed on the inner wall of the steel pipe by the centrifugal method. After being kept warm and cross-linked at 120℃ for 14h and slowly cured at room temperature for 100h, the sensor embedding is completed.

[0101] The method of using the conductive sensor is as follows: a multi-channel micro-current monitoring device is installed at the flange to monitor the current generated at each sensor location in real time. When the inner lining layer is under pressure or impact, relative movement occurs between the coil and the magnetic powder-filled polyurethane circular film, and a current signal is generated in the sensor coil, which can monitor whether a large impact or vibration occurs in the pipe; in addition, when the magnetic powder-filled polyurethane circular film disappears due to wear, the coil no longer generates a micro-current signal, indicating that the polyurethane lining at a certain point has been worn to the preset thickness of the sensor. At this time, the corresponding line of the monitoring device sends an alarm to provide a periodic reminder of the wear of the inner wall.

[0102] A polyurethane lined steel pipe monitoring sensor, comprising:

[0103] A polyurethane lined steel pipe monitoring sensor is prepared according to the preparation method of the polyurethane lined steel pipe monitoring sensor described in this embodiment.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a sensor for monitoring a polyurethane lined steel pipe, characterized in that: include: S01, first weigh the polyurethane resin, add 40-70% of the mass of magnetic powder filler relative to the mass of the polyurethane resin, and use a stirrer to mix the polyurethane resin with the magnetic powder filler for 5-10 minutes to obtain a mixture; S02. After vacuum degassing the mixture, add a curing agent, stir evenly and continue vacuum degassing, pour into a mold to form a magnetic powder-filled polyurethane circular film with a thickness of 0.2-2 mm and a diameter of 5-10 mm, cure the circular film at 90° C. for 3-10 min, cool to 0-5° C. to slow down the curing of the circular film, and then demold; S03, winding a thin-diameter insulating enameled wire on a plane into a spiral coil, casting the coil with polyurethane without magnetic powder and with a curing agent to form a circular film containing the coil, the thickness of the circular film is 0.2-2 mm, curing the circular film at 90° C. for 3-10 minutes, cooling to 0-5° C. to slow down the curing of the circular film, and then demolding; S04, bury the circular film containing the coil and the circular polyurethane film filled with magnetic powder into the inductor component mold, pour the polyurethane without magnetic powder and added with curing agent, cure at 90℃ for 3-10min, and cool to 0-5℃ to slow down the demoulding after curing; S05. The circular film containing the coil and the circular film filled with magnetic powder after demolding are magnetized in the thickness direction in a magnetizing machine, so that a sensor for monitoring the polyurethane lined steel pipe based on the electromagnetic induction principle can be obtained.

2. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 1, characterized in that: The material of the magnetic powder filler is a mixture of one or more of manganese-zinc ferrite, nickel-zinc ferrite, neodymium-iron-boron, aluminum-iron-boron, iron-silicon, and iron-silicon-aluminum in equal amounts.

3. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 2, characterized in that: The magnetic powder filler is made of neodymium iron boron powder.

4. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 3, characterized in that: The particle size of the magnetic powder filler is 3-10 μm.

5. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 4, characterized in that: The particle size of the magnetic powder filler is 5 μm.

6. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 5, characterized in that: The outer diameter of the spiral coil is 1-1.5 mm, the number of turns is 10-20, the coil spacing is 0.1-0.54 mm, the spiral coils are on the same plane, and the diameter of the thin-diameter insulating enameled wire used is 0.05-0.4 mm.

7. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 6, characterized in that: The diameter of the thin-diameter insulating enameled wire is 0.1mm.

8. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 7, characterized in that: The magnetizing time for thickness direction magnetization is 2s, the magnetizing current is 30KA, and the magnetizing voltage is DC1500V.

9. The method for preparing a polyurethane lined steel pipe monitoring sensor according to claim 8, characterized in that: The preparation method of the sensor for monitoring the polyurethane lined steel pipe also includes: S06. Remove rust and oil from the inner wall of the steel pipe, and adhere several sensor wires for monitoring the polyurethane-lined steel pipe based on the principle of electromagnetic induction to the pipe wall at the same time. The sensors are evenly distributed in the circumferential direction with an interval of 360 / X°. In the length direction, each group of 4 sensors is distributed with an interval of 100-200mm, and all leg wires are led out from the flange. After adhesion, keep warm at 100-120℃ for 60-90min. Then, use the centrifugal method to process the polyurethane lining on the inner wall of the steel pipe. After being cross-linked at 120℃ for 12-14h and slowly cured at room temperature for 80-100 hours, the sensor can be buried.

10. A sensor for monitoring a polyurethane lined steel pipe, characterized in that: include: A polyurethane lined steel pipe monitoring sensor prepared by the preparation method of a polyurethane lined steel pipe monitoring sensor according to any one of claims 1 to 9.

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