JPH08335493A - Explosion-proof device of electromagnetic induction heater - Google Patents

Abstract

PURPOSE: To suppress becoming large size and make easy to handle by closely arranging a coil set in the surrounding of a heating element in a fluid path and a high frequency current generator and housing them in an explosion-proof case, and preferably covering the coil with a magnetic shield. CONSTITUTION: A first unit U1 in which a coil 13 set in the surrounding of a heating element 12 made of conductive material and an inverter part 5 for generating high frequency current are closely arranged is covered with a first explosion protecting case 51, and further covered with a second explosion proof case 53 if necessary. Preferably, the coil 13 is covered with an electromagnetic shield plate 52, and thereby, since the high frequency magnetic field of the coil 13 is shut in, generation of an electric spark is prevented. Two tips 56a, 56b of a piping 56 used for nitrogen sealing are opened within the electromagnetic shield plate 52 and within the case 51. A second unit U2 in which a temperature control part 2 and a phase shift control part 3 are closely arranged and covered with a case 54 is arranged in the position capable of conducting remote control, and is preferable to be connected with the unit U1 and an optical fiber 55.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosion-proof device for an electromagnetic induction heating device which heats a heating element immersed in a fluid such as liquid or gas by electromagnetic induction heating and heats the fluid by direct heat transfer. , Especially those that can be integrated into pipelines in chemical plants and the like.

[0002]

2. Description of the Related Art For example, a distillation column is indispensable in a reaction / separation process in a chemical plant. This distillation column is
It is a device that separates the mixed liquids by the difference in the boiling points of the liquids that make up the distillate. A device for heating the distillate is attached to this distillation column. As this heating device, an indirect heating device such as a sheath heater system is used. In this sheath heater system, a power source is turned on to the sheath heater to heat the heat transfer oil, and heat is exchanged between the heat transfer oil and the distillate with a heat exchanger.

In the sheathed heater system by indirect heating, since the heat medium is first heated by the sheathed heater, the rise time is long and the heating device tends to be large-scaled. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 3-98286, the column or case through which the fluid passes is made of an insulator, and the heating element housed in the column or case and into which the fluid is immersed is heated by electromagnetic induction. It has been proposed to incorporate a direct heating electromagnetic induction heating device into the pipeline. According to the electromagnetic induction heating device based on the direct heating, the heat transfer efficiency from the heating element to the fluid can be improved up to about 90% by increasing the heat transfer area of the heating element in which the fluid is immersed. Can be shortened.

[0004]

However, although the electromagnetic induction heating device proposed in Japanese Patent Laid-Open No. 3-98286 is small in size and capable of local heating, it is electrically heated, so that it is used in a chemical plant. Explosion-proof specifications are required, but if you normally cover the coil part and the high-frequency current generator such as the inverter part that uses the power element in the explosion-proof case, the small equipment will be enlarged to prevent explosion, There is also a problem that it becomes difficult to operate.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an explosion-proof device for an electromagnetic induction heating device incorporated in a pipeline of a chemical plant or the like, which has a large size. It is to provide an explosion-proof device that is easy to use and that suppresses

[0006]

An explosion-proof device for an electromagnetic induction heating device according to the present invention which solves the above-mentioned problems is a heating element made of a conductive material provided in a fluid passage and a coil provided around the heating element. And an explosion-proof device provided for an electromagnetic induction fluid heating device including a high-frequency current generator for the coil, wherein the coil and the high-frequency current generator are arranged close to each other, and these are placed in an explosion-proof case. It is stored. It is preferable to provide a magnetic shield that covers at least the coil in the explosion-proof case.

Another explosion-proof device for an electromagnetic induction heating device is a heating element made of a conductive material provided in a fluid passage, a coil provided around the heating element, a high-frequency current generator for the coil, and An explosion-proof device provided for an electromagnetic induction fluid heating device comprising a control unit for a high-frequency current generator and a temperature control unit for the heating element, wherein the coil and the high-frequency current generator are arranged close to each other. And a second unit in which the control unit and the temperature control unit are disposed close to each other and which are installed in a position that can be remotely controlled apart from the explosion-proof case. is there. An optical fiber is preferably used for the signal line between the first unit and the second unit.

[0008]

[Function] The coil that may generate an electric spark and the high-frequency current generator such as the inverter are put together in an explosion-proof case. In particular, the magnetic shield is effective for shielding the surroundings from the influence of the magnetic flux from the coil.

If the power part in the explosion-proof case and the control part for controlling the power part are separated, remote operation becomes possible. In particular, an optical fiber that does not use electricity is effective as a signal line connecting the both.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a structural diagram of the explosion-proof device 50.

In FIG. 1, the explosion-proof device 50 includes a coil 1
An explosion-proof case 51 that covers the first unit U1 in which the inverter 3 (the high-frequency current generator) 5 and the inverter unit 5 are arranged close to each other; and an electromagnetic wave shield plate 52 that is disposed in the explosion-proof case 51 and particularly covers the coil 13. A second explosion-proof case 53 that double-encloses the first explosion-proof case 51 if necessary, a case 54 that covers the second unit U2 in which the temperature control unit 2 and the phase shift control unit 3 are arranged close to each other, It is composed of an optical fiber 55 as a signal line connecting one unit U1 and the second unit U2.

Further, a pipe 56 for enclosing nitrogen is provided in the first explosion-proof case 51, and one end 56a of the pipe 56 opens into the electromagnetic wave shield 52, and the pipe 56
The other tip 56 b of the above is open in the first explosion-proof case 51. Further, a discharge port with a valve (not shown) is also provided for the replacement of air and nitrogen at the time of the first filling. Then, with the discharge port closed, the inside of the first explosion-proof case 51 and the second explosion-proof case 53 is made to have a positive pressure of about 10 millimeters by hydraulic pressure, so that air does not enter even if nitrogen leaks out. ing. That is, the first explosion-proof case 51 and the second explosion-proof case 53 have a structure close to a perfect seal, and a sealing material is provided at the opening of a door or the like. In particular, if the double explosion-proof cases 51 and 53 are used, the sealed structure of each case is simpler than that of a single case.

The parts where electric sparks are most likely to occur are the inverter part (high frequency current generator) 5 and the coil 13.
Part of. The coil 13 is for generating a high frequency magnetic field, and the inverter unit 5 is for generating a high frequency current. Usually, the two are installed apart from each other. For example, the coil 13 is installed in an appropriate place on the pipeline, and the inverter unit 5 is installed on the ground where the maintenance is easy. However, in the present invention, the inverter unit 5 is disposed close to the coil 13 so as to be integrated, and these are combined and housed in one explosion-proof case 51, 53.

When the heating capacity is large, a large amount of electric power flows through the coil 13, so that a strong high-frequency magnetic field is generated around the coil 13. Therefore, an eddy current may be generated in the conductive metal arranged around the coil 13 and an electric spark may be generated. In particular, when the inverter unit 5 is placed close to the coil 13, the risk increases. Therefore, the coil 13 is covered with the magnetic shield plate 52. The magnetic shield plate 52 is made of a material such as conductive metal or reinforced plastic containing carbon fiber. The high frequency magnetic field of the coil 13 is confined by the magnetic shield plate 52 and does not leak out from the magnetic shield plate 52.
Since the magnetic shield plate 52 is for containing the magnetic flux, it is not necessary to have a closed structure.

Since the inverter section 5 turns on and off a large current by the switching operation of the power element, loss occurs as heat. Further, the coil 13 also generates heat due to copper loss, and the magnetic shield plate 52 may also generate some heat.
However, since the coil 13 and the inverter unit 5 are confined in the explosion-proof cases 51 and 53 as described above, the generated heat is trapped in the cases. Therefore, a cooling device that communicates with the inside and outside of the cases 51, 53 is provided. As a preferable example of this cooling device, a fluid to be heated is used as a medium, and a branch pipe 57 and a coil 1 to the inverter unit 5 are used.
There is one in which a branch pipe 58 to 3 is provided. There is an advantage that the heat loss of external emission is reduced.

The coil 3 and the inverter unit 5 described above are installed at the site of the chemical plant, but the temperature control unit 2 and the phase shift control unit 3 can be installed in, for example, a control room. In that case, the case 54 accommodating the temperature control unit 2 and the phase shift control unit 3 may be an ordinary control panel. When the temperature control unit 2 and the phase shift control unit 3 are also placed at the site, it is possible to use an explosion-proof case. Between the case 54 and the explosion-proof cases 51, 53,
It is connected by an optical fiber 55 which is a signal line for control. Since the optical fiber 55 does not use electricity, it is not necessary to have an explosion-proof specification, and the wire diameter is thin, which is preferable.

Next, specific configurations of the control unit 2, the phase shift control unit 3, and the inverter unit 5 will be described with reference to FIGS. In FIG. 2, 1 is the main body of the electromagnetic induction heating device, and 2
Is a two-degree-of-freedom PID temperature control unit, 3 is a phase shift control unit including a PWM control IC (3a) and a driver 3b, and 5 is a sensorless high power factor high frequency inverter unit.

The high frequency inverter section 5 comprises a rectifying section 22 for the AC power supply 21, a non-smoothing filter 23, and a high frequency inverter section 24. The output power and the frequency of the high frequency inverter section 24 are controlled by the phase shift control section 3, and the commercial AC power supply 21 is efficiently converted into a high frequency current to effectively use the electric energy.

The temperature control unit 2 is composed of a fuzzy + auto-tuning two-degree-of-freedom PID temperature controller, and outputs an output voltage control signal to the phase shift control unit 3. Here, since the temperature sensor 17 for output control is provided at the outlet of the pipe 11, the output can be controlled in consideration of the loss of the inverter unit 5 and the coil 13.

As shown in the figure, the inverter section 5 and the electromagnetic induction heating apparatus body 1 are covered with an explosion-proof case 51. Then, the temperature control unit 2 and the phase shift control unit 3 are housed in an ordinary case 54 and installed in an area where explosion protection is not required. An optical fiber 55 connects the explosion-proof case 51 and the case 54.

FIG. 3 shows a more detailed high frequency inverter unit 2
Four circuits are shown. A heating system composed of a non-metallic pipe 11 around which a coil 13 is wound and a heating element 12 of a conductive metal can be represented by a transformer circuit model having large leakage inductance, and is represented by a simple RL circuit consisting of L1 and R1. can do. By connecting the compensation capacitor C1 in series to this RL circuit, a time-varying circuit system in which the electric circuit constant hardly changes can be obtained. Therefore, the resonance capacitor C1 can be easily tuned to compensate for the L component of the RL load system, and an optimum design circuit for the operating frequency and the resonance capacitor C1 can be performed.

The high frequency inverter section 24 uses four switching elements Q1 to Q4, which are Q1 and Q2.
Are connected in series, and those in which Q3 and Q4 are connected in series are connected in parallel. The switching elements Q1 to Q4 include switches S1 to S4 and a diode D.
It is represented by a circuit in which 1 to D4 are connected in parallel, and SIT (S
static Induction Transisto
r), B-SIT, MOSFET (Metal-Oxi)
de Semiconductor FET), IGB
It is formed using a semiconductor power device such as T or MCT.

When the switches S1 and S4 are closed, current flows in the circuit from the point a through the loads L1 and R1 to the point b. When the switches S2 and S3 are closed, the loads L1 and R1 are supplied from the point b.
An electric current flows through the circuit through point A to point a. That is, when viewed from the loads L1 and R1, it means that a current flows in the forward or reverse direction. Each of the switches S1 to S4 is driven by a voltage pulse having a duty cycle of less than 50%. Switch S
The voltage drive pulses of 1 and S2 are the reference phase pulses, and the voltage drive pulses of the switches S3 and S4 are the control phase pulses.
The phase difference φ of the voltage drive pulse between the reference phase and the control phase is 0 to 1
The output voltage is changed to P by changing continuously up to 80 °.
WM (Pulse Width Modulatio)
n), and theoretically the output power can be continuously changed from 0 to the maximum output determined by the load circuit constant and the inverter operating frequency.

As described above, in order to satisfy the explosion-proof specifications, the device body 1 which can be represented by a transformer circuit model having a large leakage inductance and the inverter section 24 including the switching elements S1 to S4 must be housed in a predetermined explosion-proof case 51. is there.

Returning to FIG. 2, the apparatus body 1 has a heating element 12 housed in a non-metallic pipe 11 forming a fluid passage, and a working coil 13 wound around the pipe 11. The low temperature fluid 14 entering from the lower side of the pipe 11 passes through the fluid passage in the heating element 12 to be uniformly heated as the mixed fluid 15, and then flows out as the high temperature fluid 16 from the upper outlet of the pipe 11. . The temperature of the high temperature fluid is detected by the temperature sensor 17, and the temperature sensor 17 is connected to the temperature control unit 2. This part is the magnetic shield plate 52
Covered with.

A device body 1 that can be incorporated into a pipeline
The detailed structure of is shown in FIG. At both ends of the pipe 11,
The pipes 51 and 52, the short pipes 53 and 54, and the flanges 55 and 56 are sequentially connected.

The materials of the flanges 55, 56 and the short pipes 53, 54 are required to have corrosion resistance against various fluids handled in a chemical plant, and the coil 1 described later is used.
Austenitic stainless steel such as non-magnetic SUS316 is used so that it is not easily affected by the magnetic flux formed by No. 3. Although this austenitic stainless steel is generally considered to be non-magnetic, it is not completely non-magnetic and is somewhat affected by magnetic flux. The flange 55 and the short pipe 53 are formed into a flange with a short pipe by welding or the like, and the flange 56 and the short pipe 5 are
4 is also formed into a flange with a short pipe by welding or the like. In particular, the same SUS31 is used for the short pipe 54 located on the outlet side of the fluid 16.
The six socket 54a is fixed by welding or the like, and the fitting 17a for mounting the temperature sensor 17 can be screwed in. Then, by screwing the pressing metal fitting 17b into the fitting 17a, the tip of the temperature sensor 17 can be fixed in a state of being positioned near the center of the short tube 54.

Then, both ends of the pipe 11 and the short pipes 53, 5
4 is not directly joined, but is joined via pipes 51 and 52. The material of the tubes 51, 52 is Fe-Ni-
A high strength heat resistant alloy is selected, such as a Co alloy. Also,
Generally, ceramics have a small thermal expansion coefficient, and austenitic stainless steels have a large thermal expansion coefficient. Therefore, ceramic is used for the pipe 11, austenitic stainless steel is used for the short pipes 53 and 54, and the pipe 11 and the short pipe 5 are
A large thermal stress is generated by directly joining 3, 54.
Therefore, the thermal expansion coefficient of the pipes 51, 52 interposed between the pipe 11 and the short pipes 53, 54 is selected to be between the thermal expansion coefficients of ceramics and austenitic stainless steel. Further, the joining between the short pipes 53 and 54 and the pipes 51 and 52 and the joining between the pipes 51 and 52 and the pipe 11 are performed by fusion using silver brazing or nickel brazing.

The pipe 52 is straight, but the pipe 51 is corrugated and is expandable and contractable in the axial direction. When the fluid is heated by the device body 1, thermal expansion causes not only the device body 1 but also the pipeline to extend in the axial direction.
Therefore, when the apparatus main body 1 is incorporated into the pipeline by flange joining, unexpected thermal stress may be generated in the weakest part of the apparatus main body 1, and therefore, a corrugation for escape of thermal expansion is provided in the apparatus main body 1. A tubular tube 51 was provided.

The coil 13 is formed by twisting litz wires, and is wound around the outer periphery of the pipe 11 or embedded in the wall of the pipe 11 by winding. Pipe 11
Since it holds the coil 13, defines a fluid passage, and accommodates the heating element 12 in the passage, it is made of a non-magnetic material having corrosion resistance, heat resistance, and pressure resistance. Specifically, inorganic materials such as ceramics, FRP (fiber reinforced plastics), resin materials such as fluororesins, non-magnetic metals such as stainless steel are used, and ceramics are most preferable.

Even if the above-mentioned flanges 55 and 56 are austenitic stainless steel, they generate heat under the influence of magnetic flux. Therefore, it is desirable to provide the magnetic shield plate 52 before the flanges 55 and 56.

FIG. 5 shows the structure of the heating element 12 incorporated in the pipe 11. A first metal plate 22 and a flat second metal plate 21 bent in a zigzag chevron are alternately laminated to form a cylindrical laminated body 12 as a whole. As the material of the first metal plate 22 and the second metal plate 21, martensitic stainless steel such as SUS447J1 is used. The ridges (or valleys) of the first metal plate 22 are arranged so as to be inclined by the angle α with respect to the central axis 24, and the ridges (or valleys) of the first metal plates 22 adjacent to each other with the second metal plate 21 interposed therebetween. ) Are arranged to intersect. The first metal plate 22 and the second metal plate 21 are welded by spot welding at the intersections of the peaks (or valleys) in the adjacent first metal plates 22 so that they can be electrically conducted.

After all, the first small flow path 27 inclined by the angle α is formed between the second metal plate 21 and the first metal plate 22 on the front side, and the second metal plate 21 and the first metal plate 21 are formed next. A second small flow path 28 inclined by an angle -α is formed between the metal plate 22 and
The first small channel 27 and the second small channel 28 intersect at an angle of 2 × α. Further, on the surfaces of the first metal plate 22 and the second metal plate 21, holes 26 are provided as third small flow paths for causing turbulent flow of fluid. Further, the first metal plate 2
The surfaces of the second metal plate 21 and the second metal plate 21 are not smooth, and are finely textured by a satin finish or embossing. This unevenness is small enough to be ignored as compared with the height of the peak (or valley).

When a high frequency magnetic field is applied to the laminated body 12,
Eddy current is generated in the entire first metal plate 22 and the second metal plate 21, and the stacked body 12 generates heat. At this time, the temperature distribution is an eyeball shape extending in the longitudinal direction of the first metal plate 22 and the second metal plate 21, and the central portion generates heat rather than the peripheral portion, which is suitable for heating the fluid flowing in the central portion. It has an advantage.

Further, a first small flow path 27 and a second small flow path 28 intersecting each other are formed in the laminated body 12 to diffuse the periphery and the center, and in addition, to form a third small passage. Due to the presence of 26, diffusion in the thickness direction between the first small channel 27 and the second small channel 28 is also performed. Therefore, these small channels 2
7, 28, 29 cause macroscopic dispersion, diffusion, and volatilization of the fluid over the entire laminated body 12. In addition, minute unevenness on the surface causes microscopic diffusion, diffusion, and volatilization. As a result, the fluid passing through the stacked body 12 becomes a substantially uniform flow, and a uniform contact opportunity between the first metal plate 22 and the second metal plate 21 and the fluid is obtained.

As shown in FIG. 4, the heating element 12 has a diameter D so as to form an annular gap Rs between the outer peripheral surface of the heating element 12 and the inner peripheral surface of the pipe 11, and the axis of the heating element 12 is set in the pipe 11. The core and the heating element 12 are loosely fitted so that they coincide with each other, inserted into the pipe 11 and held by the holding member 30.
The diameter D of the heating element 12 is the fluid 16 in the device body 1.
Has an annular gap Rs between the heating element 12 and the pipe 11 which is equal to or larger than the difference in thermal expansion between the amount of thermal expansion of the pipe 11 in the radial direction and the amount of thermal expansion of the heating element 12 in the radial direction. Has been decided. Further, the holding member 30 has a metal bar 31 which is welded to the short pipe 53 on the inflow side A by welding or the like and extends in the radially inward direction, and the tip of the metal bar 31 is aligned with the axial center of the heating element 12. It is composed of a fixed non-magnetic holding rod 32. And this holding rod 32 is
It is made of non-magnetic, heat-resistant and corrosion-resistant ceramic or the like and extends from the inflow side A to the outflow side B, and the extremity thereof positions and holds the heating element 12 at a position relative to the coil 13. . Reference numeral 35 denotes a ring-shaped stopper, which is made of non-magnetic, heat-resistant and corrosion-resistant ceramic or the like, is fitted into the pipe 11 from the outflow side B of the fluid 16, and is disposed between the heat generating body 12 and the pipe. The heating element 12 is fixed with a gap Vs that is the same as or slightly smaller than the amount of axial thermal expansion of the heating element 12. Further, the ring-shaped stopper 35 crosses the annular gap Rs from the outflow side B in the radial direction, and the heating element 12 is provided.
It is located above, and the thermal expansion of the heating element 12 causes the heating element 1 to
The ring-shaped gap Rs is closed from the outflow side B by engaging with 2.

When the fluid 16 flows from the inflow side A to the outflow side B of the apparatus main body 1 and the fluid 16 is heated by the electromagnetic induction by the coil 13 via the pipe 11 and the heating element 12, the pipe 11 and the heating element 12 are heated. Although there is a difference in the thermal expansion in the radial direction between the pipe 11 and the heating element 12, an annular gap Rs larger than the difference in thermal expansion is formed between the pipe 11 and the heating element 12, so that the difference in thermal expansion is reduced while narrowing the annular gap Rs. Absorb and heat element 1
The action of stress caused by the contact of the pipe 2 with the pipe 11 and the pushing of the pipe 11 is prevented, and the heating element 12 also thermally expands in the axial direction. Absorbed by Vs.

At this time, from the pipeline 104 to the device 1
The fluid 16 that has flowed into the inflow side A flows into the heating element 12 and is heated and flows into the inflow side B. At the same time, a part of the fluid 16 flows directly from the inflow side A or from the heating element 12. Although it tries to flow into the gap Rs, pass through the annular gap Rs, and flow toward the inflow side B, the heat generating body 12 engages with the ring-shaped stopper 35 due to thermal expansion in the axial direction, so that the outflow side B of the annular gap Rs. Since the fluid 16 is blocked from directly flowing to the outflow side B by the flow of the fluid 16 from the inflow side A to the outflow side B, the fluid 16 is blocked from flowing directly to the outflow side B. The fluid 16 flowing into Rs can be caused to flow into the heating element 12 by this pressure.

As a result, even if the heating element 12 is heated by electromagnetic induction by the coil 13, damage to the pipe 11 due to thermal expansion of the heating element 12 can be prevented and the thermal expansion of the heating element 12 can be absorbed. Even if the annular gap Rs is formed, the heating element 12 thermally expands and engages with the ring-shaped stopper 35 to close the annular gap Rs from the outflow side B, and the fluid 16 flowing out into the annular gap Rs is heated. 12
Since the fluid 16 can be caused to flow in, the fluid 16 can be uniformly heated by the heating element 12.

[0040]

In the explosion-proof device for the electromagnetic induction heating device according to the present invention, the coil which may generate electric sparks and the high-frequency current generator such as the inverter are put together in an explosion-proof case. Therefore, the size of the device can be reduced compared to the case where the devices are separately housed in the explosion-proof case.

Further, by separately providing a control unit for the electric power portion housed in the explosion-proof case, the control unit can be installed in a control room and used safely.

[Brief description of drawings]

FIG. 1 is a structural diagram of an explosion-proof device of the present invention.

FIG. 2 is a device configuration diagram of a high frequency current generator.

FIG. 3 is a circuit diagram of an inverter unit.

FIG. 4 is a cross-sectional view of an electromagnetic induction heating device body.

FIG. 5 is a structural diagram of a heating element.

[Explanation of symbols]

 2 Temperature control unit 3 Phase shift control unit (control unit of inverter unit) 5 Inverter unit 11 Pipe (fluid passage) 12 Heating element 13 Coil 50 Explosion proof device 51 First explosion proof case 52 Magnetic shield plate 53 Second explosion proof case 54 Case 55 Optical fiber 56 Nitrogen filling pipe U1 1st unit U2 2nd unit

Claims (4)

[Claims] 1. An electromagnetic induction fluid heating device comprising a heating element made of a conductive material provided in a fluid passage, a coil provided around the heating element, and a high-frequency current generator for the coil. An explosion-proof device provided, wherein the coil and the high-frequency current generator are arranged close to each other,
An explosion-proof device for an electromagnetic induction heating device that stores these in an explosion-proof case. 2. The explosion-proof device for an electromagnetic induction heating device according to claim 1, wherein a magnetic shield that covers at least the coil is provided inside the explosion-proof case. 3. A heating element made of a conductive material provided in the fluid passage, a coil provided around the heating element, a high-frequency current generator for the coil, and a control unit for the high-frequency current generator. An explosion-proof device provided for an electromagnetic induction fluid heating device including a temperature control unit for the heating element, wherein the coil and the high-frequency current generator are arranged in proximity to each other,
An electromagnetic induction consisting of a first unit containing these in an explosion-proof case, and a second unit in which the control unit and the temperature control unit are arranged in proximity to each other and installed at a position remote from the explosion-proof case and capable of remote control. Explosion-proof device for heating device. 4. The explosion-proof device for an electromagnetic induction heating device according to claim 3, wherein an optical fiber is used for a signal line between the first unit and the second unit.