JPH02629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a hot water leak detection device in an induction furnace.

[Prior art and its problems]

In crucible-type induction furnaces, a leakage detection device is installed on the inner circumferential surface of the coil provided on the periphery of the induction furnace, and detects any leakage that occurs on the periphery of the crucible. , prevent damage to the coil and yoke by taking appropriate measures. This method of detecting hot water leaks is performed between a first antenna provided on the inner surface of the bottom of the crucible so as to be in constant contact with the hot water, and a second antenna formed of metal foil stretched around the outer circumferential surface of the crucible. Apply voltage to
If hot water leaks in the refractory that forms the crucible and comes into contact with the second antenna, the first antenna and second
A leak is detected by the current flowing between the antenna and the antenna.

However, in the past, even though a hot water leak had occurred, its detection was delayed, resulting in burnout of the coil and yoke, or even on the verge of other major accidents. When investigating such accidents where the detection of hot water leaks was delayed, it was often found that the hot water leaked from the bottom of the crucible.

By the way, the above-mentioned second antenna of the conventional hot water leak detection device installed on the outer circumferential surface of the crucible is made of aluminum or stainless steel, for example, 0.05 mm thick and 50 mm wide, which is arranged in a mesh pattern over the entire length of the upper and lower sides of the coil and the entire inner periphery of the coil. It's foil. The reason why aluminum or stainless steel foil is used in the hot water leak detection device is that, as shown in detail in Figure 1b, section A in Figure 1a, the insulating part 102 has an insulating material and a thin sandwich structure, so that the coil and molten metal are as close to each other as possible. This is to increase the melting efficiency by bringing them closer together, and to provide flexibility to the irregularly shaped furnace construction materials used when constructing the crucible. However, it was difficult to wrap this aluminum or stainless steel foil around the circumferential side of the bottom of the crucible, for example, to a distance of 50 mm or less from the bottom surface. In other words, slack tends to occur in this area when wrapping the foil, and if this slack becomes large, it will come into contact with the yoke and ground, causing current to flow to the detection device and cause it to malfunction even if there is no leakage. Become. Therefore, the height of the lower end of the second antenna must be limited relative to the yoke or the like. Note that the location where the lower end of the second antenna may be grounded is
As shown in the figure, the lower end of the L-shaped yoke is the horizontally bent part, but in the case of a bar-shaped yoke that does not have a horizontal part, it may be attached to a member that supports the yoke below, or a sagging antenna. The coil may bend from the bottom end and ground to the bottom end of the yoke.

However, after a detailed investigation into the hot water leak accident, it was discovered that the bottom of the crucible was the area where hot water often leaked. As shown in FIG. 1a, when forming the crucible 101, a refractory material such as SiO ₂
After placing the powder on the bottom of the crucible and stamping it, a corresponding mold is placed to form the cylindrical part. For this reason, the bottom and the cylindrical part form a joint, making it difficult to maintain the uniformity and denseness of the refractory material, and there are many leaks from this part. In other words, a foil-like material suitable as an antenna for detecting hot water leaks cannot be applied to the lowest part of the coil, and moreover, hot water often leaks from this area.

In other words, in the past, if the lower end of the second antenna was too slack, it would malfunction, and if you paid attention to the slack and raised the antenna a little too much, it would work even if there was a joint in the fireproof material where there was a lot of leakage. However, there was a drawback that detection was poor and there was a risk of serious accidents.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and its purpose is to solve the problem of melt leakage in induction furnaces by focusing on the bottom circumference of the crucible where melt leakage occurs frequently, and by eliminating detection failures and malfunctions and not relying on skilled work. The present invention aims to provide a detection device.

[Key points of the invention]

To achieve the above object, the present invention provides a conventional detection device for an induction furnace in which the lower end of the flexible second antenna at the height of the lower end of the coil is limited so as to prevent the lower end from being grounded downward. a third antenna that extends all around the crucible and is fixed to the inner circumferential surface of a coil insulating stand that supports the coil from below or to the inner circumferential surface of a coil reinforcing member that is at the same height inside the coil insulating stand; and configure it.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIG. 2, in the induction furnace 1, a coil 4 is wound into a cylindrical shape in contact with the inner circumferential surface of a plurality of yokes 3 fixed to an outer frame 2, and the inner circumferential surface of the coil 4 is coated with mica. A second antenna made of an insulating material such as a Teflon glass sheet and aluminum or stainless steel foil for detecting hot water leakage is wound around an insulating part 5 having a sandwich structure. The inner peripheral surface of this insulating part 5 and the crucible 6
The outer peripheral surfaces of the two are in contact with each other.

The crucible 6 is a refractory material 7 which is a basic member of the induction furnace 1.
constructed on top. A first antenna 8 is provided at the bottom 6a of the crucible 6 so that it passes through the bottom 6a of the crucible 6 from below, and the upper end 8a of the first antenna 8 is in contact with the hot water 9 stored in the crucible 6 on the surface of the bottom 6a. It will be done. A lead wire 10 is connected to the first antenna 8 , and this lead wire 10 passes through the refractory material 7 and is connected to one terminal of a power source 11 provided outside the induction furnace 1 . The other terminal of this power supply 11 is connected to one terminal of an ammeter 12, and the other terminal of the ammeter 12 is connected to a lead wire 13. This lead wire 13 passes through the refractory material 7 and is connected to a third antenna 14, which will be described below.

A coil insulating stand 15 that supports the lowest coil 4a of the coils 4 from below at a position on the outer periphery of the bottom 6a of the crucible 6 is provided on the upper surface of the horizontally curved portion at the lower end of the L-shaped yoke 3. 3a and 3b show the B part in FIG.
A third antenna 14 is embedded in the. Recessed portion 15b
is provided all around the inner circumferential surface 15a of the coil insulating stand 15, and therefore, the antenna 14 is provided all around the inner circumferential surface 15a of the coil insulating stand 15. Both ends or one end of the third antenna 14 are led out by a lead wire 13. Note that the third antenna 14 uses, for example, a Canthal wire.

By the way, when the insulating part 5 is made of aluminum foil or the like and has a sandwich structure, and the peripheral part is not provided with aluminum foil by a sufficient width, the insulating part 5 is replaced by the coil insulating stand 15 as shown in FIG. 3a. Even if it is applied up to the lower end surface of the yoke 3, that is, the upper surface of the horizontal part of the yoke 3, it will be at a sufficient position that it will not touch the ground. Further, when using the insulating part 5 in which aluminum foil is sandwiched up to the periphery, the lower end of the insulating part 5 is positioned slightly higher than in FIG. 3a to prevent the aluminum foil etc. from being grounded. The limited height is determined depending on the degree of sagging of the antenna, that is, the insulating portion 5.

The above explanation describes the configuration of the third antenna 14 in the case of molding the crucible 6 through the insulating part 5 in which the second antenna is installed inside the coil 4. In cases where the third antenna 14 is reinforced with cement or the like over the entire length and circumference of the coil insulating base 15 as described above, as shown in FIG. If it is provided in the recess 16b provided in the inner circumferential surface 16a of the lower end of the cylindrical cement reinforcing member 16, it can be detected more quickly. In addition, in any of the embodiments, in order to prevent the third antenna 14 from falling off even if it is attached to a surface without a groove,
The third antenna 14 may be held down with an adhesive Teflon tape 17.

If a hot water leak occurs at the bottom 6a of the crucible 6, if the hot water penetrates the refractory material forming the crucible 6 and comes into contact with the third antenna 14, the first antenna 8, hot water 9, third antenna 14, and lead will be damaged. A circuit is formed by the wire 13, the ammeter 12, the power source 11, and the lead wire 10, and current flows through it. By this, ammeter 1
The pointer 2 moves and it is detected that a hot water leak has occurred.

〔Effect of the invention〕

As explained above, in the present invention, the lower end of the second antenna, which is easily sagging and whose position cannot be fixed, is set to a sufficiently limited height without fear of being grounded downward, and the lower end of the second antenna is placed at the bottom of the lower end of the coil along its circumferential surface. By providing an independent third antenna with no risk of sagging on the coil insulating stand or reinforcing member, which is installed in a stable position, water leakage can be detected. It is now possible to detect leaks even at the bottom of the crucible, where it was previously impossible to detect leaks because it was difficult to install with a foil antenna. It is possible to prevent damage to the yoke,
It also has the effect of not requiring skilled work. Further, if independent detection circuits are provided for the second antenna and the third antenna, there is an effect that the location of the hot water leak can also be determined.

[Brief explanation of drawings]

Fig. 1a is a sectional view showing a conventional example, Fig. 1b is a partial sectional view of Fig. 1a, Fig. 2 is a sectional view showing an embodiment of the present invention, Fig. 3a is a partial sectional view of Fig. 2,
FIG. 3b is a front view of FIG. 3a, and FIG. 4 is a partial sectional view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Induction furnace, 4... Coil, 6... Crucible, 8... First antenna, 9... Hot water, 11... Power supply, 14... Third antenna, 15... Coil insulation stand, 15b, 16b... Recessed part, 16... Reinforcement material.

Claims (1)

[Claims] 1. A crucible-type induction furnace comprising a crucible made of a refractory material and a coil provided on the circumferential side of the crucible, the upper end of which is in contact with the hot water in the crucible on the bottom surface of the crucible. a first antenna provided as shown in FIG.
A flexible second antenna provided over almost the entire area facing the coil in the vertical direction of the outer peripheral surface of the crucible, and a power source connected between the second antenna and the first antenna. The lower end of the second antenna has a height that is limited to the height of the lower end of the coil so that there is no risk of it being grounded downward, and the inner circumferential surface of a coil insulating stand that supports the coil from below or the coil insulator A third antenna is provided that is fixed to the inner circumferential surface of the coil reinforcing member located at the same height inside the stand and covers the entire circumference of the crucible. A hot water leak detection device for an induction furnace, characterized in that when hot water leaks near the bottom surface, the occurrence of hot water leakage is detected by detecting that current flows through a path of a first antenna, a third antenna, and a power source.