Explosion-proof machines

Abstract

To provide an explosion-proof device including a light powder explosion-proof structure.SOLUTION: An explosion-proof device 1 has an explosion-proof space 6 formed inside a device case 3 that accommodates electronic components. The explosion-proof device 1 is sealed to satisfy explosion-proof conditions. Particles 13 including spherical hollow bodies having nonflammability and electrical insulation properties are filled within the explosion-proof space 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an explosion-proof device in which an explosion-proof space formed inside the electronic device is filled with a non-flammable material. [Background technology]

[0002] Conventionally, explosion-proof devices such as those described in Patent Document 1 have been used to measure physical quantities or control controlled objects in explosive atmospheres such as petrochemical plants. In the explosion-proof device disclosed in Patent Document 1, an explosion-proof space is formed inside a device case that houses electronic components. The explosion-proof space is provided with a fire-extinguishing volume that covers the electronic components. The fire-extinguishing volume employs a so-called powder explosion-proof structure, and its interior is filled with sand or glass beads. The explosion-proof device also has an opening through which electric wires connected to the electronic components are pulled out of the device case. This opening is sealed to meet explosion-proof conditions.

[0003] According to IEC 60079-5:2015, the international standard for powder explosion-proof structures, the material must be quartz or solid glass particles. However, there are no detailed regulations regarding the composition or shape of the glass, and the only requirement is that the particles must be filled so that there are no voids. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-174463 Summary of the Invention [Problem to be solved by the invention]

[0005] The powder explosion-proof structure described in Patent Document 1 has the problem that it is difficult to apply to large explosion-proof equipment. The reason for this is that large explosion-proof equipment requires a larger equipment case volume, and the total weight of the glass balls packed inside the equipment case becomes heavier. The heavier the explosion-proof equipment, the more difficult it becomes to install and the more susceptible it is to the effects of vibration, so it is necessary to form a strong support structure for the explosion-proof equipment.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an explosion-proof device with a lightweight powder explosion-proof structure. [Means for solving the problem]

[0007] To achieve this objective, the explosion-proof device of the present invention has an explosion-proof space formed inside an equipment case that houses electronic components, and is sealed to meet explosion-proof conditions, with the explosion-proof space filled with spherical hollow bodies that are non-flammable and electrically insulating.

[0008] In the explosion-proof equipment of the present invention, the explosion-proof space may be formed in a partial space between the electronic components inside the equipment case and the sealing portion of the equipment case, and the explosion-proof conditions may be met simply by filling the spherical hollow body into the explosion-proof space.

[0009] The explosion-proof device according to the present invention may be a field device that is installed at a process site and measures a predetermined physical quantity in the process.

[0010] The explosion-proof device according to the present invention may be a field device that is installed at a process site and controls a predetermined control target in the process. [Effects of the Invention]

[0011] According to the present invention, an explosion-proof device having a lightweight powder explosion-proof structure can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of an explosion-proof device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a particle. [Figure 3] FIG. 3 is a cross-sectional view illustrating the procedure for filling the glass spheres. [Figure 4] FIG. 4 is a cross-sectional view showing a modified example of an explosion-proof device in which the configuration of the explosion-proof space is changed. [Figure 5] FIG. 5 is a cross-sectional view of an explosion-proof device according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view of an explosion-proof device according to the third embodiment. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing a sensor portion of the positioner. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) An embodiment of an explosion-proof device according to the present invention will be described in detail below with reference to FIGS. The explosion-proof device 1 shown in Fig. 1 is an electromagnetic flowmeter 2. The electromagnetic flowmeter 2 is a field device that is installed at a process site (not shown) and measures a predetermined physical quantity in the process. In this case, the predetermined physical quantity is the flow rate of the fluid to be measured. The electromagnetic flowmeter 2 is provided with a detection section 5 including a measurement tube 4 inside an equipment case 3. The equipment case 3 is formed of a pipe-shaped main body 3a and a cylindrical connecting section 3b welded to the main body 3a. The explosion-proof equipment 1 according to this embodiment is configured so that the inside of the equipment case 3 forms an explosion-proof space 6.

[0014] The connecting portion 3b serves as an opening for drawing out the electric wire 7 extending from the detection portion 5 to the outside of the device case 3. The measuring portion 8 of the electromagnetic flowmeter 2 is attached to the connecting portion 3b. The electric wire 7 extending from the detection portion 5 is connected to the measuring portion 8 through the connecting portion 3b. The detection unit 5 includes a measurement tube 4 through which a fluid to be measured (not shown) flows, a pair of electrodes 11 and a pair of coils 12 attached to the measurement tube 4. In this embodiment, the electrodes 11 and the coils 12 correspond to the "electronic components" of the present invention.

[0015] In the explosion-proof device 1 according to this embodiment, particles 13 containing non-flammable hollow spherical bodies are filled inside the device case 3. That is, the space between the measuring tube 4 and the device case 3 (explosion-proof space 6) is filled with particles 13 containing non-flammable hollow spherical bodies that are electrically insulating, and the connecting part 3b is sealed while satisfying the explosion-proof conditions, thereby realizing a powder explosion-proof structure 14. The connecting portion 3b is provided with a lid 15 (see FIG. 3) to prevent particles 13 from entering the measuring portion 8. The non-flammable and electrically insulating spherical hollow bodies contained in the particles 13 according to this embodiment are hollow glass spheres 13a (see FIG. 2(A)). There are two patterns for filling the above-described particles 13 into the device case 3. The first pattern is a pattern in which part of the particles 13 are hollow glass spheres 13a and the rest are solid glass spheres 13b (see FIG. 2(B)). The second pattern is a pattern in which all of the particles 13 are hollow glass spheres 13a.

[0016] The hollow glass spheres 13a filled in the device case 3 may be of one type with the same wall thickness, or a mixture of multiple types of hollow glass spheres 13a with different wall thicknesses may be used. The hollow glass spheres 13a used have a particle size of 1 mm or less, which is the explosion-proof standard. Furthermore, hollow glass spheres 13a formed so that the hollow portion is a vacuum, or hollow glass spheres 13a filled with a gas such as air, can be used.

[0017] When hollow glass spheres 13a are filled inside the device case 3 of the electromagnetic flowmeter 2, if the diameter of the measuring tube 4 is 25A and the density of the hollow glass spheres 13a is 0.06 g / cc, the weight increase is small, about 2.2 g, compared to when no particles 13 are filled. In the case of spherical glass spheres, when the radius of the sphere is R and the radius of the hollow part is r, and r / R is greater than 0.8, the specific gravity is less than half that of solid glass spheres 13b.

[0018] The thickness of the hollow glass spheres 13a must be thick enough to provide pressure resistance that will not be crushed or broken by the weight of the hollow glass spheres 13a when they are filled inside the equipment case 3. Typical commercially available hollow glass spheres 13a are thin, with an outer diameter of 60 to 100 μm and a wall thickness of 0.5 μm, but have a pressure resistance of 1.7 MPa, which is sufficient to withstand being filled inside the equipment case 3. When the diameter of the electromagnetic flowmeter 2 becomes medium, the amount of particles 13 filled increases, and the weight increase of the glass component becomes significant. In such a case, it may be possible to mix hollow glass spheres 13a and solid glass spheres 13b.

[0019] According to the following formula (1), the thickness t of hollow sphere 13a is smaller than one-tenth of the outer diameter so that the weight ratio of hollow glass sphere 13a (hereinafter referred to as hollow sphere 13a) to solid glass sphere 13b (hereinafter referred to as solid sphere 13b) is less than 0.5.

[0020]

number

[0021] In formula (1), V0 is the volume of the solid sphere 13b, and V is the volume of the hollow portion. The weight ratio of the hollow sphere 13a to the solid sphere 13b is (V0-V) / V0, assuming that the specific gravity of the hollow portion is 0. Also, in formula (1), D is the outer diameter of the glass sphere, the radius R is D / 2, d is the diameter of the hollow portion, and r is the radius of the hollow portion. If the wall thickness is t, then t = Rr. Volume of solid sphere 13b V0 = 4πR 3 / 3, the volume of the hollow part V=4πr 3 / 3. From the above formula (1), t<0.2R=0.1D. The density of glass is 2.2g / cm 3 Commercially available hollow spheres 13a have an outer diameter of 50 μm, a wall thickness of 0.5 μm, a true density of 0.13 g / cc, and a bulk density of 0.08 g / cc (filling rate of approximately 63%). The pressure resistance of these hollow spheres 13a is approximately 1.7 MPa. The wall thickness t of these hollow spheres 13a is 0.01 D.

[0022] As long as D<1 mm and t>0.01D, which are within the explosion-proof range, the weight of the glass spheres packed into the equipment case 3 will not crush the hollow spheres 13a. The wall thickness can be made even thinner, but this is not practical because of manufacturing constraints and the glass spheres will be more likely to break during handling. The outer diameter D of the glass spheres can be made even smaller, but it is better to make it large enough so that it does not leak through the gap between the lid 15 and the equipment case 3. Regarding the packing ratio mentioned above: The packing ratio of spheres of uniform diameter reaches a maximum of 74% when face-centered cubic or hexagonal close packing is used, and in reality it is around 64%. Regarding the bulk density above: Bulk density = glass density x weight ratio x filling rate However, the weight ratio is (V0-V) / V0.

[0023] Next, a method for filling glass spheres (particles 13 including non-combustible hollow spheres) will be described with reference to FIG. To fill the device case 3 of the electromagnetic flowmeter 2 with glass spheres (particles 13), the device case 3 is supported by the vibrating device 16 in a position where the connecting portion 3b opens upward, as shown in Fig. 3. The vibrating device 16 is configured to vibrate the device case 3 in the horizontal direction and the up-down direction. The glass beads (particles 13) are filled by using a hopper 17 to drop the glass beads (particles 13) into the opening of the connecting portion 3b while vibrating the device case 3. The hopper 17 is provided with a scale (not shown) that measures the amount of glass beads (particles 13) flowing. When the glass beads (particles 13) are poured into the device case 3, the glass beads (particles 13) are poured from the hopper 17 up to a predetermined amount relative to the predetermined capacity of the device case 3, while checking the filling amount based on the flow rate of the glass beads (particles 13). In addition to checking the filling amount based on the flow rate of the glass beads (particles 13), it is also possible to check the filling amount based on the weight of the glass beads (particles 13) that have been poured.

[0024] The glass spheres (particles 13) introduced into the device case 3 flow into the gaps as the vibration of the device case 3 is transmitted, and the inside of the device case 3 is filled without any gaps. Then, when the glass beads (particles 13) reach the opening of the connecting portion 3b, the introduction of the glass beads (particles 13) is stopped, and a lid 15 is attached to the connecting portion 3b. Although not shown, the lid 15 has a hole or slit formed therein for passing the electric wire 7 connecting the detection portion 5 and the instrument portion 8. By filling the glass beads (particles 13) up to the connecting portion 3b, an explosion-proof device 1 is realized in which the connecting portion 3b (opening) of the device case 3 is sealed and satisfies the explosion-proof conditions.

[0025] The explosion-proof device 1 according to this embodiment has an explosion-proof space 6 formed inside the device case 3, and has a connecting portion 3b (opening) through which electric wires 7 connected to electrodes 11 and coils 12 (electronic components) inside the device case 3 are drawn out to the outside of the device case 3. In addition, in this explosion-proof device 1, particles 13 including hollow glass spheres 13a are filled into the explosion-proof space 6, and the connecting portion 3b is sealed while satisfying the explosion-proof conditions. The sealed connecting portion 3b is referred to as a sealing portion. Therefore, a lighter powder explosion-proof structure 14 can be obtained compared to when the explosion-proof space 6 is filled only with solid particles 13. Therefore, according to this embodiment, an explosion-proof device equipped with a light powder explosion-proof structure can be provided.

[0026] (Modification of powder explosion-proof structure) In the explosion-proof device 1 shown in Fig. 1, the entire interior of the device case 3 is filled with glass spheres (particles 13). However, as shown in Fig. 4, a powder explosion-proof structure 14 can also be realized by filling only a portion of the device case 3 with glass spheres (particles 13). In Fig. 4, members that are the same as or equivalent to those described in Figs. 1 and 3 are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0027] The connecting portion 3b of the explosion-proof device 1 shown in Figure 4 has a partition wall 21 at the boundary with the main body portion 3a. The partition wall 21 separates the inside of the main body portion 3a from the inside of the connecting portion 3b, and forms an explosion-proof space 22 between the partition wall 21 and the cover 15 of the connecting portion 3b. That is, the explosion-proof space 22 is formed in a portion of the space between the electronic components, such as the electrodes 11 and coils 12, and the opening at the upper end of the connecting portion 3b (the opening of the device case 3). Glass spheres (particles 13) are filled in this explosion-proof space 22. The powder explosion-proof structure 14 of this explosion-proof device 1 is configured so that the explosion-proof conditions are met simply by filling the explosion-proof space 22 with glass spheres (particles 13). By configuring the powder explosion-proof structure 14 in this manner, the total weight of the glass spheres (particles 13) can be reduced compared to the embodiment shown in Figure 1, making it possible to provide explosion-proof equipment with an even lighter powder explosion-proof structure.

[0028] (Second embodiment) The explosion-proof device according to the present invention can be configured as shown in Fig. 5. The explosion-proof device 31 shown in Fig. 5 is a magnetic angle sensor 32, and includes a detection unit 34 inside a metal case 33 made of a non-magnetic material. The angle sensor 32 is a field device that is installed at a process site and used to measure the actual opening of a valve during the process. This angle sensor 32 is also used as a component of a positioner that controls the opening of a control valve, or a component of a liquid level gauge. The predetermined physical quantity measured by this angle sensor 32 is the rotation angle of a rotating part 36 to which a magnet 35 located near the angle sensor 32 is attached. The rotating part 36 rotates around a center line C that extends vertically in FIG. 5.

[0029] The metal case 33 is formed by a flat base portion 33a and a cap portion 33b that covers the base portion 33a. In this embodiment, the metal case 33 corresponds to the "device case" of the present invention. The base portion 33a is formed with first and second through holes 38, 39 for passing multiple lead wires 37, and a third through hole 40 that serves as an inlet for introducing explosion-proof particles 13 into the metal case 33. The first and second through holes 38, 39 are sealed by a hermetic seal 41 with the lead wires 37 inserted therethrough. In this embodiment, the first and second through holes 38, 39 correspond to the "opening." The third through hole 40 is closed by a sealing pipe 42. The closed opening is referred to as a sealing portion.

[0030] A substrate 43 is attached to the tip of the lead wire 37 inserted into the metal case 33. A support 44 is erected in the center of the substrate 43, and a sensor main body 45 is attached to the tip of this support 44. The sensor main body 45 detects the rotation angle of the rotating part 36 based on the strength of the magnetic field of the magnet 35, and is electrically connected to the lead wire 37 via a wire 46. In this embodiment, the lead wire 37 inserted into the metal case 33, the sensor main body 45, and the wire 46 correspond to the "electronic component" as defined in the present invention. In this embodiment, the metal case 33 corresponds to the "equipment case" as defined in the present invention, and the space inside the metal case 33 becomes the explosion-proof space 47.

[0031] The interior of the metal case 33 is filled with particles 13 including spherical hollow bodies that are non-flammable and electrically insulating. That is, the space within the metal case 33 (explosion-proof space 47) is filled with particles 13 including spherical hollow bodies that are non-flammable and electrically insulating, thereby realizing a powder explosion-proof structure 48. The spherical hollow bodies can be the hollow glass spheres 13a used in the first embodiment. When filling the metal case 33 with particles 13, there are cases where hollow glass spheres 13a and solid glass spheres 13b are mixed, and cases where only hollow glass spheres 13a are filled into the metal case 33.

[0032] To fill the interior of the metal case 33 with particles 13 including non-flammable, electrically insulating hollow spheres, the metal case 33 is held in a position where the base portion 33a is positioned upward, and the particles 13 are poured into the third through-holes 40 of the base portion 33a. At this time, the metal case 33 may be vibrated using the vibrating device 16 used when the first embodiment is adopted. After the metal case 33 is filled with particles 13 including spherical hollow bodies that are non-flammable and electrically insulating, a sealing pipe 42 is inserted into the third through hole 40, and the gap between the third through hole 40 and the sealing pipe 42 is sealed, for example, by welding. As shown in this embodiment, by filling a metal case 33 with particles 13 containing spherical hollow bodies that are non-flammable and electrically insulating, the weight of the angle sensor 32, which is an explosion-proof device 31, can be reduced.

[0033] (Third embodiment) The explosion-proof device according to the present invention can be configured as shown in FIGS. 6 is a valve positioner 52. The positioner 52 is a field device that is installed at a process site and controls the opening of a valve during the process.

[0034] The positioner 52 according to this embodiment is configured by rotatably attaching a feedback lever 55 to a housing 54 having an angle sensor 53. The angle sensor 53 is fixed to the housing 54. The feedback lever 55 is supported by the housing 54 via a support shaft 56 so as to be able to swing freely. A stem of a valve (not shown) is interlockingly connected to the swinging end of the feedback lever 55. The feedback lever 55 swings around the support shaft 56 as the stem moves parallel to the valve opening or closing direction.

[0035] The support shaft 56 is rotatably supported by a bearing 57 in the housing 54. The feedback lever 55 is coupled to one end of the support shaft 56. Therefore, when the feedback lever 55 swings, the support shaft 56 rotates integrally with the feedback lever 55. A cylindrical yoke 58 with a bottom is attached to the other end of the support shaft 56. As shown in FIG. 7 , the yoke 58 is formed so as to surround the periphery of the angle sensor 53, and has multiple magnets 59 on its inner circumferential surface facing the angle sensor 53.

[0036] The angle sensor 53 is equivalent to that shown when the second embodiment described above is adopted, and includes a base 61 fixed to the housing 54, a sensor body 63 provided in a holder 62 protruding from the base 61, and a cup-shaped case 64 attached to the base 61 in a state of accommodating the sensor body 63. Although not shown, the base 61 is formed with a through-hole through which wiring is passed and which is sealed, as well as a through-hole which serves as a filling port for filling particles 13 including non-flammable and electrically insulating spherical hollow bodies.

[0037] The case 64 is made of a non-magnetic material and is fixed to the base 61. The space formed between the case 64 and the base 61 serves as an explosion-proof space 65, which is filled with particles 13 including spherical hollow bodies that are non-flammable and electrically insulating. That is, an explosion-proof space 65 in a case 64 is filled with particles 13 including spherical hollow bodies that are non-flammable and electrically insulating, thereby realizing a powder explosion-proof structure 66. The spherical hollow bodies can be the hollow glass spheres 13a used in the first embodiment. When filling the case 64 with particles 13, there are cases where hollow glass spheres 13a and solid glass spheres 13b are mixed, and cases where only hollow glass spheres 13a are filled into the case 64.

[0038] According to this embodiment, an explosion-proof positioner 52 is realized in which the inside of the case 64 of the angle sensor 53 becomes an explosion-proof space 65. As shown in this embodiment, by filling the inside of the case 64 of the angle sensor 53 with particles 13 containing spherical hollow bodies that are non-flammable and electrically insulating, it is possible to reduce the weight of the positioner 52 that becomes the explosion-proof device 51. When filling the inside of the angle sensor 53 with particles 13 containing spherical hollow bodies, the base 61 and the case 64 may be vibrated using the vibration device 16 used when the above-mentioned first embodiment is adopted.

[0039] In the first to third embodiments described above, examples have been shown in which the non-flammable and electrically insulating spherical hollow bodies are formed of hollow glass spheres 13a. However, the non-flammable spherical hollow bodies are not limited to glass spheres, and may be hollow spheres made of ceramics or synthetic resin, for example. In addition, in the above-described embodiment, an example was shown in which vibration was applied when filling the glass beads to prevent gaps from forming in the explosion-proof spaces 6, 22, 47, and 65. However, if the interior of the case into which the glass beads are filled has a simple shape and the glass beads flow in smoothly, it is not necessary to apply vibration when filling.

[0040] In the above-described embodiment, the electromagnetic flowmeter 2 and angle sensor 53 have been described as field devices that are installed at a process site and measure predetermined physical quantities during the process. However, the present invention can be applied to various detection devices that measure the flow rate of a fluid, the pressure of a gas or liquid, the movement speed of a substance, etc., such as a mechanical flowmeter, a thermal flowmeter, a pressure sensor, and a vacuum gauge. In the above-described embodiment, the valve positioner 52 is described as an example of a field device that controls a predetermined control target in a process. However, the field device that controls the control target may also be a controller that controls the operation of a valve or other device. [Explanation of symbols]

[0041] 1, 31, 51... explosion-proof equipment, 2... electromagnetic flowmeter (field equipment), 3... equipment case, 3b... connection part (opening), 6, 22, 47, 65... explosion-proof space, 7... electric wire, 11... electrode (electronic component), 12... coil (electronic component), 13... particles including non-flammable hollow spherical bodies, 13a... hollow glass sphere, 13b... solid glass sphere, 32 angle sensor (field equipment), 33... metal case, 37... lead wire (electronic component), 45, 63... sensor body (electronic component), 46... wire (electronic component), 52... positioner (field equipment), 64... case.

Claims

1. In an explosion-proof device in which an explosion-proof space is formed inside a device case that houses electronic components and is sealed while satisfying explosion-proof conditions, The explosion-proof space is filled with non-flammable and electrically insulating spherical hollow bodies, The outer diameter D of the spherical hollow body is D<0.1 mm; The thickness t of the spherical hollow body is 0.01D<t<0.1D. Explosion-proof equipment characterized by:

2. An explosion-proof device in which an explosion-proof space is formed inside a device case that houses electronic components and is sealed while satisfying explosion-proof conditions, The explosion-proof space is filled with non-flammable and electrically insulating spherical hollow bodies, The explosion-proof space is formed in a partial space between the electronic component in the device case and the sealing portion of the device case, and the explosion-proof conditions are met simply by filling the spherical hollow body into the explosion-proof space. Explosion-proof equipment characterized by:

3. It is a field device that is installed at the process site and measures a specific physical quantity in the process.

3. The explosion-proof device according to claim 1 or 2,

4. It is a field device that is installed at the process site and controls a specific control target in the process.

3. The explosion-proof device according to claim 1 or 2,

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